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www.rohm.com 2011.07 - Rev. A © 2011 ROHM Co., Ltd. All rights reserved. LED Drivers for LCD Backlights White Backlight LED Driver for Medium to Large LCD Panels (Switching Regulator Type) BD6142AMUV
- Description This IC is white LED driver IC with PWM step-up DC/DC converter that can boost max 41V and current driver that can drive max 30mA. The wide and precision brightness can be controlled by external PWM pulse. This IC has very accurate current drivers, and it has few current errors between each strings. So, it will be helpful to reduce brightness spots on the LCD panel. Small package is suited for saving space.
- Features 1) High efficiency PWM step-up DC/DC conver ter (fsw=typ 1.25MHz, 0.60MHz ~ 1.6MHz) 2) High accuracy & good matching current drivers 8ch (MAX30mA/ch) 3) Integrated 50V power Nch MOSFET 4) Soft Start function 5) Drive up to 11 LEDs in series, 8 strings in parallel 6) Wide input voltage range (4.2V ~ 27V) 7) Rich safety functions ・Over-voltage protection ・External SBD open detect / Output Short protection ・Over current limit ・CH Terminal open / GND short protect ・CH over voltage protect / LED short protect ・hermal shutdown ・UVLO 8) Analog Brightness Control 9) Small & thin package (VQFN024V4040) 4.0 × 4.0 × 1.0mm
- Applications All medium sized LCD equipments, Backlight of Notebook PC, net book, monitor, light, Portable DVD player, light source etc. No.11040EAT11
www.rohm.com 2011.07 - Rev. A © 2011 ROHM Co., Ltd. All rights reserved.
- Absolute maximum ratings (Ta=25℃) Parameter Symbol Ratings Unit Condition Maximum applied voltage 1 VMAX1 7 V VDC, ISET, ABC, COMP, FSET, TEST, FAULT Maximum applied voltage 2 VMAX2 45 V CH1 ~ CH8, LX, OVP Maximum applied voltage 3 VMAX3 30.5 V VIN, Enable Maximum applied voltage 4 VMAX4 15 V PWM Power dissipation 1 Pd1 500 *1 mW Power dissipation 2 Pd2 780 *2 mW Power dissipation 3 Pd3 1510 *3 mW Operating temperature range Topr -40 ~ +85 ℃ Storage temperature range Tstg -55 ~ +150 ℃ *1 Reduced 4.0mW/ ℃ With Ta>25℃ when not mounted on a heat radiation Board. *2 1 layer (ROHM Standard board) has been mounted. Copper foil area 0mm 2, When it’s used by more than Ta=25 ℃, it’s reduced by 6.2mW/ ℃. *3 4 layer (JEDEC Compliant board) has been mounted. Copper foil area 1layer 6.28mm 2, Copper foil area 2~4layers 5655.04mm2, When it’s used by more than Ta=25 ℃, it’s reduced by 12.1mW/℃.
- Operating conditions (Ta=-40℃ ~ +85 ℃) Parameter Symbol Limits Unit Conditions Min. Typ. Max. Power supply voltage VIN 4.2 12.0 27.0 V
www.rohm.com 2011.07 - Rev. A © 2011 ROHM Co., Ltd. All rights reserved.
- Electrical characteristics (Unless otherwise specified, VIN=12V, Ta = +25℃) Parameter Symbol Limits Unit Conditions Min. Typ. Max. [General] Quiescent Current Iq - 1.6 4.4 µA Enable=0V Current Consumption Idd - 3.6 5.4 mA OVP=0V,ISET=36k Ω Max. Output Voltage MOV - - 41 V Under Voltage Lock Out UVLO 3. 1 3.7 4.1 V VIN falling edge [Enable Terminal] Low Input Voltage range EnL 0.0 - 0.8 V High Input Voltage range1 EnH 2.0 - VIN V Pull down resistor EnR 100 300 500 k Ω Enable=3V Output Current ENIout - 0 2 µA Enable=0V [PWM Terminal] Low Input Voltage range PWML 0.0 - 0.8 V High Input Voltage range2 PWMH 1.3 - 12.0 V Pull down resistor PWMR 100 300 500 k Ω PWM=3V Output Current PWMIout - 0 2 µA PWM=0V [FAULT] Nch RON FFCR - - 3 k Ω Enable=PWM=3V, OVP=2V [Regulator] VDC Voltage VREG 4.2 5.0 6.0 V No load, VIN > 6V [Switching Regulator] LED Control voltage VLED 0.64 0.80 0.96 V Switching frequency accuracy Fs w 1.00 1.25 1.50 MHz FSET=56k Ω Duty cycle limit Duty 91.0 95.0 99.0 % CH1-8=0.3V, FSET=56k Ω LX Nch FET RON RON - 0.48 0.58 Ω ILX=80mA [Protection] Over Current Limit Ocp 1.5 2.5 - A *1 Over voltage limit Input OVP 1.16 1.20 1.24 V Detect voltage of OVP pin Output Short Protect OVPfault 0.02 0.05 0.08 V Detect voltage of OVP pin OVP leak current OVIL - 0.1 1.0 µA CH Terminal Over Voltage Protect accuracy VSC -15 0 +15 % VSC=5V [Current driver] LED maximum current ILMAX - - 30 mA LED current accuracy ILA CCU - - ±2.5 % ILED=20mA (36kΩ) LED current matching ILMAT - - 2.5 % (Max LED current – Min LED current)/ Ideal current (20mA) ILED=20mA LED current matching2 ILMAT2 - - 1.5 % ▪Each LED current/Average (CH1- 8) ▪ILED=20mA LED current limiter ILOCP - 0 0.1 mA Current limit value at ISET Resistance 1kΩ setting ISET voltage Iset - 0.733 - V LED current accuracy2 ILACCU2 - ±3.0 - % ILED=20mA, ABC=0.733V *1 This parameter is tested with DC measurement.
www.rohm.com 2011.07 - Rev. A © 2011 ROHM Co., Ltd. All rights reserved.
- Reference data Fig. 1 LED current characteristics PWM dimming Fig. 2 LED current characteristics PWM dimming Fig. 3 LED current characteristics Analog dimming Fig. 4 LED maximum current F i g . 5 E f f i c i e n c y F i g . 6 E f f i c i e n c y LED Current vs PWM duty 0.010 0.100 1.000 10.000 100.000 1 10 100 PWM Duty [%] LED Current [mA] VIN=6V VIN=12V VIN=27V LED current vs PWM Duty 0.01 0.1 100 0.1 1 10 100 duty[%] LED current[mA] VIN=6V VIN=12V VIN=27V Efficiency vs VIN (10serials and 8strings) 80.0% 82.0% 84.0% 86.0% 88.0% 90.0% 92.0% 94.0% 96.0% 98.0% 100.0% Frequency [MHz] Efficiency[%] VIN=7V VIN=12V VIN=27V Efficiency vs VIN (10serials and 6strings) 80.0% 82.0% 84.0% 86.0% 88.0% 90.0% 92.0% 94.0% 96.0% 98.0% 100.0% Frequency [MHz] Efficiency[%] VIN=7V VIN=12V VIN=27V <Condition> ■Ta = 25℃ ■ISET = 36kΩ ■CH1 = 0.8V <Condition> ■10serial×8parallel ■Ta = 25℃ ■LED Current = 20mA ■PWM frequency = 200Hz ■Frequency = 1.25MHz(FSET=56kΩ) ■Coil = 10µH <Condition> ■10 serial×8parallel ■Ta = 25℃ ■LED Current = 20mA ■PWM frequency = 30kHz ■Frequency = 1.25MHz(FSET=56kΩ) ■Coil = 4.7µH <Condition> ■Ta = 25℃ ■10 serial×8parallel ■LED Current = 20mA ■Coil = TDK, LTF5022T-100M1R4-LC <Condition> ■Ta = 25℃ ■10 serial×6parallel ■LED Current = 20mA ■Coil = TDK, LTF5022T-100M1R4-LC LED current vs ISET current 0 1 02 03 04 05 0 ISET current [uA] LED current [mA] 25℃ 85℃ -40℃ <Condition> ■VIN = 12V ■CH1 = 0.8V LED current vs ABC voltage 0.000 5.000 10.000 15.000 20.000 25.000 30.000 35.000 ABC Voltage [V] LED current [mA] VIN=4.2V VIN=12V VIN=27V
www.rohm.com 2011.07 - Rev. A © 2011 ROHM Co., Ltd. All rights reserved. PIN VDC GND A PIN VIN PGND B PIN GND C PIN VIN GND D PIN GND E 5.5V Clump PIN PGND F PIN PGND G GND
- Block diagram and pin configuration Fig. 7 Block diagram
- Pin assignment table Pin No. Pin Name IO Function Terminal diagram
1 Enable In PWM input pin for power ON/OFF or Power control E
2 TEST In TEST signal (Pull down 100k Ω within IC) E
3 FSET In Resister connection for frequency setting A
4 ABC In Analog Brightness Control C
5 GND - GND for Switching Regulator B
6 PWM In PWM input pin for power ON/OFF only driver E
7 CH8 In Current sink for CH8 C
8 CH7 In Current sink for CH7 C
9 CH6 In Current sink for CH6 C
10 CH5 In Current sink for CH5 C
11 ISET In Resister connection for LED current setting A
12 CH4 In Current sink for CH4 C
13 CH3 In Current sink for CH3 C
14 CH2 In Current sink for CH2 C
15 CH1 In Current sink for CH1 C
16 OVP In Detect input for SBD open and OVP C
17 PGND - PGND for switching Tr D
19 LX Out Switching Tr drive terminal F
20 Out Switching Tr drive terminal F
21 FAULT Out Fault signal C
22 COMP Out ERRAMP output A
23 VIN In Battery input G
24 VDC Out Regulator output / Internal power-supply C
Output Over Voltage PROTECT LED TERMINAL OPEN/SHORT DETECTOR LED RETURN SELECT CH1 CH 2 CH 3 CH 4 CH 5 CH 6 CH 7 CH 8 OVP Current SENCE Over Current Protect Soft start Control SENCE OSC + ERRAMP PWM COMP 8ch GND Current Driver PWM ISET ISET Resistor driver COMP TEST FSET ABC Clamp
www.rohm.com 2011.07 - Rev. A © 2011 ROHM Co., Ltd. All rights reserved.
- Application example and Layout are shown in Page. 21. Fig. 8 BD6142A Application example (8 parallel) Fig. 9 BD6142A Application example (6 parallel) BD6142AMUV CH1 CH2 CH3 CH4 CH5 CH6 CH7 CH8 OVP 10 serial x 8 par allel (80pcs) 20mA ABC LX LX 2.2µF/50V FAULT VIN 10µH 10µF Enable PWM 2.1V to VI N CO MP 1kΩ ISET 36k Ω GND PGND PWM fPWM=100Hz~25kHz VDC PGND 22nF 2.2MΩ 68k Ω VOUT 2.2µF GND PGND FSETTEST 56kΩ 1nF 7V to 27V RESET BD6142AMUV CH1 CH2 CH3 CH4 CH5 CH6 CH7 CH8 OVP 9 serial x 6 parallel (54pcs) 20mA ABC LX LX 2.2µF/50V FAULT VIN 10µH 10µF 7V to 27V Enable RE SE T PWM 2.1V to VIN CO MP 1kΩ ISET 36kΩ GNDPGND PW M fPWM=100Hz~25kHz VDC PGND 22nF 2.2MΩ 73.2kΩ VOU T 2. 2µF GND PGND FSETTEST 56kΩ 1nF
www.rohm.com 2011.07 - Rev. A © 2011 ROHM Co., Ltd. All rights reserved. Fig. 10 BD6142A Application example (3 parallel) BD6142AMUV CH1 CH2 CH3 CH4 CH5 CH6 CH7 CH8 OVP 10 serial x 3 parallel (30pcs) 20mA ABC LX LX 2.2µF/50V FAULT VIN 10µH 10µF 4.2V to 27V Enable RESET PWM 2.1V to VIN CO MP 1kΩ ISET 36kΩ GNDPGND PWM fPW M=100Hz~25kHz VDC PGND 22nF 2.2MΩ 68kΩ VOUT 2. 2µF GND PGND FSETTEST 110kΩ 1nF
www.rohm.com 2011.07 - Rev. A © 2011 ROHM Co., Ltd. All rights reserved.
- Functional descriptions 1) PWM current mode DC/DC converter While this IC is power ON, the lowest voltage of CH1, 2, 3, 4, 5, 6,7, 8 is detected, PWM duty is decided to be 0.8V and output voltage is kept invariably. As for the inputs of the PWM comparator as the feature of the PWM current mode, one is overlapped with error components from the error amplifier, and the other is overlapped with a current sense signal that controls the inductor current into Slope waveform to prevent s ub harmonic oscillation. This output controls internal Nch Tr via the RS latch. In the period where inte rnal Nch Tr gate is ON, energy is accumulated in the external inductor, and in the period where internal Nch Tr gate is OFF, energy is transferred to the output capacitor via external SBD. This IC has many safety functions, and their detection signals stop switching operation at once. 2) Pulse skip control This IC regulates the output voltage usi ng an improved pulse-skip. In “pulse-ski p” mode the error amplifier disables “switching” of the power stages when it detects low outpu t voltage and high input voltage. The oscillator halts and the controller skip switching cycles. The error amplifier reactivate s the oscillator and starts swit ching of the power stages again when this IC detects low input voltage. At light loads a conventional “pulse-skip” regulation mode is used. The “pulse- skip” regulation minimizes the operating current because this IC does not switch continuously and hence the losses of t he switching are reduced. When the error amplifier disables “switching”, the load is also isolated from the input. This improved “pulse-skip” control is also referred t o as active-cycle control. Fig. 11 Pulse-skip 3) Soft start This IC has soft start function. The soft start function prevents large coil current. Rush current at turning on is prevented by the soft start function. After Enable, PWM is changed ‘L’ ‘H’, and UVLO is detected, soft start becomes effective for within typ 4.3ms and soft start doesn't become effective even if Enable is changed ‘L’ ‘H’ after that. Fig. 12 Soft start 4) FAULT When the error condition occurs, boost operating is stopped by the protection function, and the error condition is outputted from FAULT. After power ON, when the protection function is operating under about 4.3ms(typ.) have passed. Once enable change to ‘L’, FAULT status is reset Object of protect function is as shown below. - Over-voltage protection (OVP) - Thermal shut down (OTP) - Over current limit (OCP) - Output short protect - LED Short (Latch) - LED Open (Latch) Fig. 13 FAULT operating description off normal boost stop normal off normal un-detection detect un-detect Typ4.3 ms FAULT Protection function(OVP, TSD, OCP) Boost operating Enable VDC PWM Mask un-detectProtection function(LED open, LED short) detect un-detect Latch Typ100us PWM VOUT LED current LX 20mA duty 20% @1.25MHz(typ) Pulse skip Enable Max 1ms Typ 4.3ms OFF ON OFF ON VDC Soft start PWM UVLO Enable Max 1ms OFF ON OFF ON VDC Soft start PWM UVLO OFF T1 T2 Soft Start Time=T1+T2=4.3ms typ
www.rohm.com 2011.07 - Rev. A © 2011 ROHM Co., Ltd. All rights reserved.
- Protection PROTECTION TABLE CASE FAILURE MODE DETECTION MODE FAIL CHANNEL GOOD CHANNEL VOUT REGULATED BY FAULT Terminal LED Short connected CH1 CH1 > VSC(5V) LED current stop and DC/DC feedback doesn’t return CH2 to CH8 Normal Highest VF of CH2 to CH8 ‘H’ ‘ (Latch) LED OPEN connected CH1 CH1 < 0.2V and VOUT > VOVP LED current stop and DC/DC feedback doesn’t return CH2 to CH8 Normal Highest VF of CH2 to CH8 ‘H’ ‘ (Latch) VOUT/LX GND SHORT OVP < 50mV FAULT change from L to H, and switching is stopped. When OVP>50mV, FAULT return L ‘H’ ‘L’ Output LED stack voltage too high VOUT > VOVP FAULT change from L to H, and switching is stopped. Even if OVP<1.2V, FAULT don’t return L ‘H’ ‘L’ LX current too high OCP > 2.5A or OTP > 130C FAULT change from L to H, and switching is stopped. Even if IC return normal status, FAULT don’t return L ‘H’ ‘L’ ・Over voltage protection (OVP) At such an error of output op en as the output DC/DC and the LED is not connected to IC, the DC/DC will boost too much and the OVP terminal exceed the absolute maximum ratings, and may destruct the IC. Therefore, when OVP terminal becomes sensing voltage or hi gher, the over voltage limit protection works, and turns off the swit ching Tr, and DC/DC will be stopped. At this moment, the IC changes from activation into non-activation, and the output voltage goes down slowly. And, when the Feedback of CH1 isn’t returned, so that VOUT will return normal voltage. Fig. 14 OVP operating description VOUT CH1 voltage CH1 connection CH2 connection Feedback Enable, PWM normal CH1 CH1CH2 normal open CH1 current 20mA 0mA CH2 current 20mA 0mA O V P S i g n a l Hysteresis(typ 2.5%)
www.rohm.com 2011.07 - Rev. A © 2011 ROHM Co., Ltd. All rights reserved. This section is especially mentioned here because the spec shown electrical charac teristic is necessary to explain this section. Over voltage limit min 1.16V typ 1.20V max 1.24V LED control voltage min 0.64V typ 0.80V max 0.96V LED terminal over voltage protect min 4.25V typ 5.00 V max 5.75V 1. Calculate the conditions that the total value of LED VF is MAX. Example) In the case of serial 8 LEDs with VF=2.9V(min), 3.2V(typ), 3.5V(max) => 3.5V x 8=28V 2. Then calculate the biggest value of output with the following formula. The biggest value of output = the biggest value calculated for 1 + the biggest value of LED terminal voltage. (0.96V) Example) The biggest value of output = 28V + 0.96V =28.96V 3. Set the smallest value of over voltage larger than the biggest value of output. If over voltage is closer to the total value of VF, it could be occurred to detect over voltage by ripple, noise, and so on. It is recommended that some margins should be left on the difference between over voltage and the total value of VF. This time around 6% margin is placed. Example) Against the biggest value of output = 28.96V, the smallest value of over voltage = 28.96V x 1.06 = 30.70V Ic over voltage limit min=1.16V, typ=1.20V, max=1.24V 4. The below shows how to control resistor setting over voltage Please fix resistor high between OVP terminal and output and then set over voltage after changing resistor between OVP terminal and GND. While PWM is off, output voltage decreases by minimizing this resistor. Due to the decrease of output voltage, ripple of output voltage increases, and singing of output condenser also becomes bigger. Example) Selecting OVP resistor. ・OVP resistor selection (Example. 1) VF=3.5V max, serial = 7 LED OVP = 1.2V, R1 = 2.2MΩ, R2 = 95.3kΩ (Example. 2) VF=3.5V max, serial = 8 LED OVP = 1.2V, R1 = 2.2MΩ, R2 = 82kΩ VOUT = 1.2 × (2.2MΩ + 82kΩ)/ 82kΩ = 33.40V (Example. 3) VF=3.5V max, serial = 9 LED OVP = 1.2V, R1 = 2.2MΩ, R2 = 73.2kΩ (Example. 4) VF=3.5V max, serial = 10 LED OVP = 1.2V, R1 = 2.2MΩ, R2 = 68kΩ VOUT = 1.2 × (2.2MΩ + 68kΩ)/ 68kΩ = 40.02V ・External SBD open detect / Output Short protection In the case of external SBD is not connected to IC, or VOUT is shorted to GND, the coil or internal Tr may be destructed. Therefore, at such an error as OVP bec oming 50mV(typ.) or below, turns off the output Tr, and prevents the coil and the IC from being destructed. And the IC changes from activation into non-activation, and current does not flow to the coil (0mA). ・Thermal shut down This IC has thermal shut down function. The thermal shut down works at 130C (typ.) or higher, and the IC changes from activation into non-activation. OVP terminal VOUT
www.rohm.com 2011.07 - Rev. A © 2011 ROHM Co., Ltd. All rights reserved.
- Operating of the application deficiency 1)When 1 LED or 1string OPEN during the operating The LED string which became OPEN isn't lighting, but other LED strings are lighting. Then LED terminal is 0V , output boosts up to the over voltage protection voltage. When over voltage is detected, the feedback of open string isn’t returned, so that VOUT will return normal voltage. 2)When LED short-circuited in the plural All LED strings is turned on unless CH1~8 terminal voltage is more than 5V(typ.). When it was more than 5V only the strings which short-circuited is turned off normally and LED current of other lines continue to turn on. Short line(CH1) current is changed from 20mA to 0.05mA(typ), so CH1 terminal don’t heat. 3)When Schottky diode remove All LED strings aren’t turned on. Also, IC and a switching tr ansistor aren't destroyed because boost operating stops by the Schottky diode open protected function. CH 1 CH 2 CH 1 CH 2 Fig. 15 LED open protect Fig. 16 LED short protect VOUT CH1 voltage CH1 connection CH2 connection Feedback Enable, PWM CH1 current normal CH1 OFFCH2 normal open 20mA 0mA CH2 current 20mA 0mA CH1 OVP CH1 enable 100µs CH1terminal FeedBack CH1 curren t CH1 CH2 CH2 curren t 20mA 20mA 0.05mA(typ) Vout 0.8V LED short CH2 terminal 0.8V Typ 5V CH1>CH2 100us(typ)
www.rohm.com 2011.07 - Rev. A © 2011 ROHM Co., Ltd. All rights reserved.
- Control Signal input timing Timing sequence1 Referring to Fig.17, the recommended turn “on” sequence is VIN followed by ENABLE and PWM. The recommended turn ”off” sequence is ENABLE and PWM followed by VIN. This sequence is recommendation. Timing sequence2 Referring to Fig.18, the recommended turn “on” sequence is VIN, ENABLE followed by PWM. The recommended turn “off” sequence is PWM followed by ENABLE and VIN. ENABLE, PWM VIN Power ON Power OFF LED IC Timing Sequence for PWM Control Turn-on VIN 2 ~ 5VMin 0µs PWM ENABLE Min 0µs 4.2 ~ 27V 2 ~ 5V 0 ~ 0.8V 0 ~ 0.8V LED IC Timing Sequence for PWM Control Turn-off PWM 2 ~ 5V Min 0µs VIN ENABLE Min 0µs 4.2 ~ 27V 2 ~ 5V 0 ~ 0.8V 0 ~ 0.8V Fig. 17 Timing sequence1 PWM VIN, ENABLE Power ON Power OFF ENABLE 2 ~ 5V Min 0µs VIN PWM Min 0µs 4.2 ~ 27V 2 ~ 5V 0 ~ 0.8V 0 ~ 0.8V VIN 2 ~ 5V Min 0µs ENABLE PWM Min 0µs 4.2 ~ 27V 2 ~ 5V 0 ~ 0.8V 0 ~ 0.8V LED IC Timing Sequence for PWM Control Turn-on Fig. 18 Timing sequence2 LED IC Timing Sequence for PWM Control Turn-off *other signal is input after a signal turned on. *other signal is input after a signal turned off. *Other signal is input after a signal turned off. *other signal is input after a signal turned on.
www.rohm.com 2011.07 - Rev. A © 2011 ROHM Co., Ltd. All rights reserved. Timing sequence3 Referring to Fig.19, the recommended turn “on” sequence is VIN, PWM followed by ENABLE. The recommended turn “off” sequence is ENABLE followed by PWM and VIN. VIN wake up speed Fig. 20 control Signal timing In case, there is PWM OFF status (min: 10ms) during operation as Fig. 21, ENABLE should turn from ‘H’ to ‘L’ as Fig.21. If PWM stops and VOUT voltage is dropped, this IC will be condition of current limiter when PWM starts (no soft start). If soft start isn’t needed, reset is no need. VIN Min. 100µs 4.1 V 1 2 Fig. 21 PWM stop and ENABLE turn “off” PWM OFF VIN ENABLE Min 10ms PWM PWM reset ENABLE VIN, PWM Power ON Power OFF PWM 2 ~ 5V Min 0µs VIN ENABLE Min 0µs 4.2 ~ 27V 2 ~ 5V 0 ~ 0.8V 0 ~ 0.8V VIN 2 ~ 5V Min 0µs PWM ENABLE Min 0µs 4.2 ~ 27V 2 ~ 5V 0 ~ 0.8V 0 ~ 0.8V LED IC Timing Sequence for PWM Control Turn-on Fig. 19 Timing sequence3 LED IC Timing Sequence for PWM Control Turn-off *other signal is input after a signal turned on. *other signal is input after a signal turned off.
www.rohm.com 2011.07 - Rev. A © 2011 ROHM Co., Ltd. All rights reserved.
- How to activate Please be careful about the following when being activated. - Regulator (VDC) operates after ENABLE=H. Inside circui t operates after releasing UVLO. When IC boosts after releasing UVLO, soft start function operates. (Refer to Fig.12, 7th page). Soft start circuit needs t15 (more than 15µs) as Fig. 22 shows. Soft start operates for Tsoft time. Please make H width of PWM more than 15µs until soft start finishes. - Please input PWM signal according to Fig. 23 after soft start finishes. Fig. 22 Soft start Example) Time until soft start finishes at PWM frequency 25kHz and PWM=H time16µs According to soft start time typ4.3ms tsoft = 16µs – 15µs = 1µs Soft start time/ tsoft /PWM frequency = 4300µs / 1µs /25kHz = 4300 / 25kHz = 172ms Fig. 23 Input timing (after soft start) Name Unit Min. Typ. Max. t1 Power supply rising time µs 100 - - t2 Power supply-ENABLE time µs 0 - - t3 ENABLE rising time µs 0 - 100 t4 ENABLE falling time µs 0 - 100 t5 ENABLE low width µs 50 - - t6 Power supply-PWM time µs 0 - - t7 PWM rising time µs 0 - 100 t8 PWM high width µs 5 - - t9 PWM falling time µs 0 - 100 t10 PWM low width µs 5 - - t11 PWM frequency µs 40 5000 10000 t12 ENABLE (H)->PWM (H) time µs 0 - - t13 ENABLE (L)->PWM (L) time µs 0 - - t14 PWM (L)->ENABLE (L) time µs 0 - - t15 PWM high width (while soft start) µs 15 - - H Operating voltage V 4.2 12 27 L Non operating voltage V - - 4.2 L[V]VIN VDC ENABLE H[V] t2 t3 t14 t10 t11 t7 t9t8 t4 t5 H[V] PWM t14 At light dimming of PWM terminal (after soft start finishes) VIN VDC ENABLE UVLO PWM SOFT START Over current value increases.. t15 tsoft tsoft tsoft
www.rohm.com 2011.07 - Rev. A © 2011 ROHM Co., Ltd. All rights reserved.
- How to select the number of LED strings of the current driver When the number of LED strings of the current driver is reduced, the un-select can be set the matter that the unnecessary CH1 ~ 8 terminal is opened. When it uses with 6 lines and so on, it can correspond to it by becoming 2 unnecessary lines to open. When VOUT wake up, VOUT boost up until OVP voltage. Once IC detect OVP , VOUT don’t boost up until OVP from next start up. To set PWM and Enable to L, IC reset CH7, 8 status as Fig. 24. When VOUT wake up, CH8 (open terminal) and CH1 are selected as Fig. 25. Fig. 24 Select the number of CH lines 1 Fig. 25 Select the number of CH lines 2 (wake up) CH 1 CH 2 CH 3 CH 4 CH 5 CH 7 CH 6 CH 8 PWM Enable VOUT CH1~6 CH7~8 OVP Normal voltage 0.8V(typ) 0V Reset Mask open CH1 Current CH8 Terminal CH8 Current 20mA Vout Soft start: typ 4.3ms ENABLE Stable PWM CH1 Terminal 0mA 0mA Feedback terminal Typ 0.8V Over voltage protect signal “Unmask Terminal select (LED open protect) CH1CH8 Normal condition Over Voltage Protect 100µs(typ)
www.rohm.com 2011.07 - Rev. A © 2011 ROHM Co., Ltd. All rights reserved.
- Start control (Enable) and select LED current driver (PWM) This IC can control the IC system by Enable, and IC can power off compulsory by setting 0.8V or below. Also, It powers on Enable is at more than 2.0V. After it’s selected to Enable=H, When it is selected at PWM=H, LED current decided with ISET resistance flow. Next, When it is selected at PWM=L, LED current stop to flow. Enable PWM IC LED current 0 0 Off OFF 1 0 On OFF 0 1 Off OFF 1 1 On Current decided with ISET
- LED current setting range LED current can set up Normal current by resistance value (RISET) connecting to ISET voltage. Setting of each LED current is given as shown below. RISET = 720/ILEDmax Also, Normal current setting range is 10mA~30mA. LED current becomes a leak current MAX 2µA at OFF setting. ISET Normal current setting example RISET LED current 24kΩ (E24) 30.0mA 30kΩ (E24) 24.0mA 36kΩ (E24) 20.0mA 43kΩ (E24) 16.7mA 68kΩ (E12) 10.6mA
- Frequency setting range Switching frequency can be set up by resistance value (RFSET) connecting to FSET port. Setting of frequency is given as shown below. Also, Frequency setting range is 0.60MHz~1.60MHz. FSET frequency setting example RFSET frequency 130kΩ (E96) 0.57MHz 56kΩ (E24) 1.25MHz 43kΩ (E24) 1.59MHz Max Duty example Frequency Max Duty[%] Min Typ Max 0.57MHz - 96.0 - 1.25MHz 91.0 95.0 99.0 1.59MHz - 92.0 - Min Duty example Frequency Min Duty[%] Min Typ Max 1.25MHz - 20 - Frequency [MHz] 1.25 56kΩ 130 k Ω FSET[kΩ] 0.57 1.59 43 kΩ
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- PWM dimming Current driver PWM control is controlled by providing PWM signal to PWM port, as it is show in Fig. 26. The current set up with ISET is chosen as the H section of PWM and the current is off as the L section. Therefore, the average LED current is increasing in proportion to duty cycle of PWM signal. This method that it lets internal circuit and DC/DC to work, because it becomes to switch the driver, the current tolerance is a few when the PWM brightness is adjusted, it makes it possible to brightness control until 5µs (Min 0.1% at 200Hz). And, don't use for the brightness control, because effect of ISET changeover is big under 1µs ON time and under 1µs OFF time. Typical PWM frequency is 100Hz~25kHz. Conditions: 8serial 6parallel, LED current=20mA/ch, VIN=7V, Ta=25℃, Output capacitor=2.2μF(50V/B3)
- Analog dimming BD6142 control LED current according analog input (ABC terminal). For ABC voltage = typ 0.733V, LED current can set up Normal current by resistance value (RISET) connecting to ISET voltage. To decrease ABC voltage, LED current decrease, and to increase ABC voltage, LED current increase. Please set max LED current to check LED current setting range of P.12 Please care that ABC voltage of max LED current is 0.733V ABC input range is 0.05V~0.9V(Target). This dimming is effected by ISET tolerance as follows. When you don’t use analog dimming, please set condenser to ABC terminal. Until the condenser of ABC terminal is finished to charge, LED current increase with that speed. The resister between 1.2V and ABC terminal is 120.9kΩ. Please select the capacitor to care charge time. PWM LED current Coil current IC’s active current ON OFF ON OFF ON OFF ON Fig. 26 PWM sequence ISET ISET Resistor driver ABC 1.2V 0.733V DC Input 120.9kΩ 36kΩ 180kΩ ISET ISET Resistor driver ABC 1.2V 0.733V 120.9kΩ 180kΩ 36kΩ Fig. 27 Analog dimming application Fig. 28 PWM dimming application ILED [mA] 20mA 0.733V 0.9V ABC[V] Fig. 29 ILED vs ABC voltage PWM VOUT LED current VOUT PWM 400ns/div 10mA/div LED current 40ns/div 10mA/div
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- Coil selection The DC/DC is designed by more than 4.7µH. When L value sets to a lower value, it is possibility t hat the specific sub-harmonic oscillation of current mode DC / DC will be happened. Please do not let L value to 3.3µH or below. And, L value increases, the phase margin of DC / DC becomes to zero. Please enlarge the output capacitor value when you increase L value. Please select lower DC resistance (DCR) type, efficiency still relies on the DCR of Inductor. Please estimate Peak Current of Coil. Peak current can be calculated as following. Peak Current calculation <The estimate of the current value which need for the normal operation> As over current detector of this IC is detected the peak current, it have to estimate peak current to flow to the coil by operating condition. In case of, - Supply voltage of coil = V In - Inductance value of coil = L - Switching frequency = fsw (Min=1.0MHz, Typ = 1.25MHz, Max = 1.5MHz) - O u t p u t v o l t a g e = V OUT - Total LED current = I LED - Average current of co il = Iave - Peak current of coil = Ipeak - Cycle of Switching = T - Efficiency = eff (Please set up having margin) - ON time of switching transistor = Ton - ON Duty = D CCM: Ipeak = (VIn / L) × (1 / fsw) × (1-( VIn / VOUT)), DCM: Ipeak = (VIn / L) × Ton Iave=( VOUT × IOUT / VIn) / eff Ton=(Iave × (1- VIn / VOUT) × (1/fsw) × (L/ VIn) × 2)1/2 Each current is calculated. As peak current varies according to whether there is the direct current superposed, the next is decided. CCM: (1- V In / VOUT) × (1/fsw) < Ton peak current = Ipeak /2 + Iave DCM: (1- V In / VOUT) × (1/fsw) > Ton peak current = VIn / L × Ton (Example 1) In case of, VIn = 7.0V, L = 10µH, fsw = 1.2MHz, VOUT = 32V, ILED = 120mA, Efficiency = 88% Iave = (32 × 120m / 7) / 88% = 0.62A (1- V In / VOUT) × (1 / fsw) = 0.65µs < Ton(1.07µs) CCM Peak current = 0.46A / 2 + 0.62A = 0.85A (Example 2) In case of, VIn = 16.0V, L = 10µH, fsw = 1.2MHz, VOUT = 32V, ILED = 120mA, Efficiency = 88% 1/2 = 0.37µs (1- VIn / VOUT) × (1 / fsw)=0.41µs > Ton(0.37µs) DCM Ipeak = VIn / L x Ton = 16 / 10µ x 0.37µs = 0.59A Peak current = 0.59A *When too large current is set, output oversh oot is caused, be careful enough because it is led to break down of the IC in case of the worst. DCM/CCM calculation Discontinuous Condition Mode (DCM) and Continuous Condition Mode (CCM) are calculated as following. CCM: L > V OUT × D × (1 - D)2 × T / (2 × ILED) DCM: L < V OUT × D × (1 - D)2 × T / (2 × ILED) *D = 1- V In / VOUT (Example 1) In case of, VIn = 7.0V, L = 10µH, fsw = 1.2MHz, VOUT = 32V, ILED = 120mA CCM (Example 2) In case of, VIn = 12.0V, L = 10µH, fsw = 1.2MHz, VOUT = 32V, ILED = 60mA DCM
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- OUTPUT Capacitor selection Output Capacitor smoothly keeps output voltage and supplies LE D current. Output Voltage consists of Charge (FET ON) and Discharge (LED current). So Output voltage has Output ripple Voltage every FET switching. Output ripple voltage is calculated as following. Output ripple Voltage - Switching cycle = T - Total LED current = I LED - Switching ON duty = D - Output ripple Voltage = V ripple - Output Capacitor = COUT - Output Capacitor (real value) = C real - Decreasing ratio of Capacitor = Cerror C real = COUT × Cerror (Capacitor value is decreased by Bias, so) Creal = ILED × (1-D) × T / Vripple COUT = ILED × (1-D) × T / Vripple / Cerror (Example 1) In case of, VIN=12.0V, fsw = 1.2MHz, VOUT =32V, ILED =120mA, COUT = 8.8µF, Cerror = 50% T = 1 / 1.2MHz D = 1 – VIN / VOUT = 1 – 12/32 Vripple = I LED × (1-D) × T / (COUT×Cerror) = 120mA × (12/32) / 1.2MHz / (8.8µF×0.5) = 8.5mV 0V 35V 50V Output voltage Capa [ µF] Cout Creal Fig. 30 Bias Characteristics of Capacitor
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- The separations of the IC Power supply and coil Power supply This IC can work in separating the power source in both IC power supply and coil power supply. With this application, it can obtain that decrease of IC power consumption, and the applied voltage exceeds IC rating 27V. That application is shown in below Fig.31. The higher voltage source is applied to the power source of coil that is connected from an adapter etc. Next, the IC powe r supply is connected with a different coil power supply. Under the conditions for inputting from 4.2V to 5.5V into IC VIN, please follow th e recommend design in Fig.31. It connects VIN terminal and VDC terminal together at IC outside. When the coil power supply is applied, it is no any problem ev en though IC power supply is the state of 0V. Although IC power supply is set to 0V, pull-down resistance is arranged fo r the power off which cuts off the leak route from coil power supply in IC inside, the leak route is cut off. And, ther e is no power on-off sequence of coil power supply and IC power supply. Separate VIN and Coil power supply Connect VIN and VDC terminals Fig. 31 Application at the time of power supply isolation BD6142AMUV CH1 CH2 CH3 CH4 CH5 CH6 CH7 CH8 OVP 10 serial x 6 parallel (60pcs) 20mA ABC LX LX 2.2µF/50V FAULT VI N 10µH 10µF 7V to 27V Enable RESET PWM 2.1V to VIN CO MP 1kΩ ISET 36kΩ GNDPGND PWM fPWM=100Hz~25kHz VDC PGN D 22nF 2. 2MΩ 68kΩ VOU T 2.2µF GND PGND FSET 4.2V to 30V TEST 1nF56 kΩ BD6142AMUV CH1 CH2 CH3 CH4 CH5 CH6 CH7 CH8 OVP 10 serial x 6 parallel (60pcs) 20mA ABC LX LX 2.2µF/50V FAULT VI N 10µH 10µF 4.2V to 5.5V Enable RESET PWM 2.1V to VIN COMP 1kΩ ISET 36kΩ GNDPGND PWM fPW M=100Hz~25kHz VD C PGN D 22nF 2.2MΩ 68kΩ VOUT 2.2µF GND PGND FSET 4.2V to 30V TEST 56kΩ
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- Layout In order to make the most of the performance of this IC, its PC B layout is very important. Characteristics such as efficiency and ripple and the likes change greatly with layout patterns, which please note carefully. Fig. 32 Schematic <Input bypath capacitor CIN (10μF)> Put input bypath capacitor CIN (10μF) as close as possible between coilL1 and PGND pin. <Smoothing capacitor CVDC1(2.2µF) of the regulator> Connect smoothing capacitor CVDC1(2.2μF) as close as possible between VDC pin and GND. <Schottky barrier diode SBD> Connect schottky barrier diode SBD as close as possible between coil1and SW pin. <Output capacitor COUT1> Connect output capacitor COUT1 between cathode of SBD and PGND. Make both PGND sides of CVIN and COUT1 as close as possible. <LED current setting resistor RISET(36kΩ)>> Connect LED current setting resistor RISET(36kΩ) as close as possible between ISET pin and GND. There is possibility to oscillate when capacity is added to ISET terminal, so pay attention that capacity isn’t added. <Analog dimming pin smoothing capacitor CABC (1nF)> Put analog dimming pin smoothing capacitor CABC (1nF) close to ABC pin and do not extend the wiring to prevent noise increasing and also LED current waving. <Frequency setting resistor(56KΩ)> Put frequency setting resistor(56KΩ) as close as possible between FSET pin and GND. <Over voltage limit setting resistor ROVP1(2.2MΩ) and ROVP2(68KΩ) Put over voltage limit setting resistor ROVP1(2.2M Ω) and ROVP2(68K Ω) as close as possible to OVP pin and do not extend the wiring to prevent noise increasing and also detecting over voltage protection in error. <GMAMP setting resistor RCMP(1kΩ) and CCMP(1nF) for phase compensation > Put GMAMP setting resistor RCMP(1K Ω) and CCMP(22nF) as close as possible to COMP pin and do not extend the wiring to prevent noise increasing and also oscillating. <Connect to GND and PGND> GND is analog ground, and PGND is power ground. PGND might cause a lot of noise due to the coil current of PGND. Try to connect with analog ground, after smoothing with input bypath capacitor CVIN and output capacitor COUT1. <Heat radiation of back side PAD> PAD is used for improving the efficiency of IC heat radiation. Solder PAD to GND pin (analog ground). Moreover, connect ground plane of board using via as shown in the patterns of next page. The efficiency of heat radiation improves according to the area of ground plane. <Others> When those pins are not connected direct ly near the chip, influence is give to the performance of BD6142AMUV, and may limit the current drive performance. As for the wire to the inductor, make its resistan ce component small so as to reduce electric power consumption and increase the entire efficiency. BD6142AMUV CH1 CH2 CH3 CH4 CH5 CH6 CH7 CH8 OVP 10 serial x 8 parallel (80pcs) 20mA ABC LX LX COUT1(2.2µF/50V) FAULT VIN L1(10µH) CIN(10µF) 7V to 27V Enable RESET PWM 2.1V to VIN CO MP RCMP(1 kΩ) ISET RIS ET(36kΩ) GN DPGND PWM fPWM=100Hz~25kHz VDC PGND CCMP(22nF) RO VP 1 (2.2MΩ) RO VP 2 (68kΩ) VOUT CV DC1 (2.2µF) GND PGND FSETTEST SBD RFSET(56kΩ) CABC(1nF)
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- Recommended PCB layout Fig. 33 Top Copper trace layer Fig. 34 Middle1 Copper trace layer Fig. 35 Middle2 Copper trace layer Fig. 36 Bottom Copper trace layer COUT1 SBD PGND GND RISET ROVP2ROVP1 RCMPCCMP CIN CVDC1 D6142 GND PGND Input Voltage VOUT RFSET CABC
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- Selection of external parts Recommended external parts are as shown below. When to use other parts than these, select the following equivalent parts. ・Coil Value Manufacturer Product number Size (mm) DC current (mA) DCR (Ω) L W H (MAX) 10µH TOKO A915AY-100M 5.2 5.2 3.0 1400 0.140 10µH TDK LTF5022T-100M1R4-LC 5.0 5.2 2.2 1400 0.140 10µH TOKO B1047AS-100M 7.6 7.6 5.0 2700 0.053 ・Capacitor Value Pressure Manufacturer Product number Size L W H 10µF 25V MURATA GRM31CB31E106KA75 3.2 1.6 1.6 2.2µF 50V MURATA GRM 31CB31H225K 3.2 1.6 1.6 2.2µF 50V Panasonic ECJHVB1H225K 3.2 1.6 0.85 2.2µF 10V MURATA GRM 188B31A225K 1.6 0.8 0.8 0.1µF 50V MURATA GRM 188B31H104K 1.6 0.8 0.8 0.1µF 10V MURATA GRM 188B31A104K 1.6 0.8 0.8 0.022µF 10V MURATA GR M155B31H223K 1.0 0.5 0.5 470pF 50V MURATA GRM155B11H471K 1.0 0.5 0.5 ・Resistor Value Tolerance Manufacturer Product number Size (mm) L W H 91kΩ ±0.5% ROHM MCR03PZPZD9102 1.6 0.8 0.45 75kΩ ±0.5% ROHM MCR03PZPZD7502 1.6 0.8 0.45 68kΩ ±0.5% ROHM MCR03PZPZD6802 1.6 0.8 0.45 56kΩ ±0.5% ROHM MCR03PZPZD5602 1.6 0.8 0.45 36kΩ ±0.5% ROHM MCR03PZPZD3602 1.6 0.8 0.45 10kΩ ±1.0% ROHM MCR03PZPZF103 1.6 0.8 0.45 1kΩ ±0.5% ROHM MCR03PZPZD1002 1.6 0.8 0.45 330Ω ±0.5% ROHM MCR03PZPZD3300 1.6 0.8 0.45 ・SBD Pressure Manufacturer Product number Size (mm) L W H 60V ROHM RB160M-60 3.5 1.6 0.8 The coil is the part that is mo st influential to efficiency. Select the coil wh ose direct current resist or (DCR) and current - inductance characteristic is excellent. BD6142A is design ed for the inductance value of 10µH. Don’t use the inductance value less than 3.3µH. Select a capacitor of ceramic type with excellent frequency and temperature characteristics. Further, select Capacitor to be used with small direct current resistance.
- About heat loss In heat design, operate the DC/DC converter in the following condition. (The following temperature is a guarantee temperature, so consider the margin.) 1. Ambient temperature Ta must be less than 85℃. 2. The loss of IC must be less than dissipation Pd.
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- Application example 1. ESD & Flicker (wakeup (duty 5%@200Hz)) LED current: 20mA (ISET = 36kΩ) LED: 10 LEDs in series, 3 strings in parallel Fig. 37 Application example of 10inch panel D6142 CCaappaa 447700ppFF RReessiissttoorr 2200ΩΩ IICC CCaappaa 11µµFF Fig. 38 Layout example for ESD protection BD6142AMUV CH1 CH2 CH3 CH4 CH5 CH6 CH7 CH8 OVP 10 serial x 3 parallel (30pcs) 20mA ABC LX LX 2.2µF/50V FAULT VIN 10µH 10µF 4.2V to 27V Enable RESET PWM 2.1V to VIN CO MP 1kΩ ISET 36kΩ GNDPGND PWM fPW M=100Hz~25kHz VDC PGND 22nF 560kΩ 18kΩ VOUT 2. 2µF GND PGND FSETTEST 56kΩ 1nF 470pF 470pF 470pF 1uF 20Ω For ESD protection 0.1uF
www.rohm.com 2011.07 - Rev. A © 2011 ROHM Co., Ltd. All rights reserved. 2. Analog Dimming and monitoring FAULT terminal LED current: 20mA (ISET = 36kΩ) LED: 10 LEDs in series, 8 strings in parallel Fig. 39 Application example of Analog dimming BD6142AMUV CH1 CH2 CH3 CH4 CH5 CH6 CH7 CH8 OVP 10 serial x 8 parallel (80pcs) 20mA ABC LX LX 2.2µF/50V FA ULT VIN 10µH 10µF 7V to 27V Enable RESET PWM 2.1V to VIN CO MP 1kΩ ISET 36kΩ GN DPGND VDC PGN D 22nF 2.2MΩ 68kΩ VOUT 2.2µF GN D PGND FSETTEST 3V to 5V monitor D/AMax 0.9 V 30kΩ 1nF 56kΩ
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- Notes for use (1) Absolute Maximum Ratings An excess in the absolute maximum ratings, such as supply voltage, temperature range of operating conditions, etc., can break down devices, thus making impossible to identify breaking mode such as a short circuit or an open circuit. If any special mode exceeding the absolute maximum ratings is assumed, consideration should be given to take physical safety measures including the use of fuses, etc. (2) Operating conditions These conditions represent a range within which characteri stics can be provided approx imately as expected. The electrical characteristics are guaranteed under the conditions of each parameter. (3) Reverse connection of power supply connector The reverse connection of power supply connector can br eak down ICs. Take protec tive measures against the breakdown due to the reverse connection, such as mounting an external diode between the power supply and the IC’s power supply terminal. (4) Power supply line Design PCB pattern to provide low impedance for the wiring between the power supply and the GND lines. In this regard, for the digital block power supply and the analog block power supply, even though these power supplies has the same level of potential, separate t he power supply pattern for the digital blo ck from that for the analog block, thus suppressing the diffraction of digital noises to the analog block power supply resulting from impedance common to the wiring patterns. For the GND line, give consideration to design the patterns in a similar manner. Furthermore, for all power supply terminals to ICs, mount a capacitor between the power supply and the GND terminal. At the same time, in order to use an electrolytic capacito r, thoroughly check to be sure the characteristics of the capacitor to be used present no problem including the occu rrence of capacity dropout at a low temperature, thus determining the constant. (5) GND voltage Make setting of the potential of the GND terminal so that it will be maintained at the minimum in any operating state. Furthermore, check to be sure no terminals are at a potential lower than the GND voltage including an actual electric transient. (6) Short circuit between terminals and erroneous mounting In order to mount ICs on a set PCB, pay thorough attention to the direction and offset of the ICs. Erroneous mounting can break down the ICs. Furthermore, if a short circuit occurs due to foreign matters entering between terminals or between the terminal and the power supply or the GND terminal, the ICs can break down. (7) Operation in strong electromagnetic field Be noted that using ICs in the strong electromagnetic field can malfunction them. (8) Inspection with set PCB On the inspection with the set PCB, if a capacitor is connected to a low-impedance IC terminal, the IC can suffer stress. Therefore, be sure to discharge from the set PCB by each process. Furthermore, in order to mount or dismount the set PCB to/from the jig for the inspection process, be sure to turn OFF the power supply and then mount the set PCB to the jig. After the completion of the inspection, be sure to turn OFF the power supply and then dismount it from the jig. In addition, for protection against static electricity, establish a ground for the assembly process and pay thorough attention to the transportation and the storage of the set PCB. (9) Input terminals In terms of the construction of IC, parasitic elements are in evitably formed in relation to potential. The operation of the parasitic element can cause interference with circuit operati on, thus resulting in a malf unction and then breakdown of the input terminal. Therefore, pay thorou gh attention not to handle the input te rminals, such as to apply to the input terminals a voltage lower than the GND respectively, so t hat any parasitic element wi ll operate. Furthermore, do not apply a voltage to the input terminals when no power supply voltage is applied to the IC. In addition, even if the power supply voltage is applied, apply to the input terminals a voltage lower than the power supply voltage or within the guaranteed value of electrical characteristics. (10) Ground wiring pattern If small-signal GND and large-current GND are provided, It will be recommended to separate the large-current GND pattern from the small-signal GND pattern and establish a si ngle ground at the reference poi nt of the set PCB so that resistance to the wiring pattern and voltage fluctuations due to a large current will cause no fluctuations in voltages of the small-signal GND. Pay attention not to cause fluctuations in the GND wiring pattern of external parts as well. (11) External capacitor In order to use a ceramic capacitor as the external capacitor, determine the c onstant with consideration given to a degradation in the nominal capacitance due to DC bias and changes in the capacitance due to temperature, etc. (12) Thermal shutdown circuit (TSD) When junction temperatures become 130 ℃ (typ) or higher, the thermal shutdown circuit operates and turns a switch OFF. The thermal shutdown circuit, which is aimed at isolat ing the LSI from thermal runaway as much as possible, is not aimed at the protection or guarantee of the LSI. Therefor e, do not continuously use the LSI with this circuit operating or use the LSI assuming its operation. (13) Thermal design Perform thermal design in which there ar e adequate margins by taking into account the permissible dissipation (Pd) in actual states of use. (14) Selection of coil Select the low DCR inductors to decrease power loss for DC/DC converter.
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- Ordering part number B D 6 1 4 2 A M U V - E 2 Part No. Part No. Package MUV: VQFN024V4040 Packaging and forming specification E2: Embossed tape and reel (Unit : mm) VQFN024V4040 0.08 S S 1219 1318 0.4±0.1 0.02+0.03-0.02 1PIN MARK 2.4±0.1 C0.2 0.5 4.0±0.1 0.75 2.4±0.1 4.0±0.1 1.0MAX (0.22) 0.25+0.05 -0.04 ∗ Order quantity needs to be multiple of the minimum quantity. <Tape and Reel information> Embossed carrier tapeTape Quantity Direction of feed The direction is the 1pin of product is at the upper left when you hold reel on the left hand and you pull out the tape on the right hand 2500pcs Direction of feed Reel 1pin
R1120Awww.rohm.com © 2011 ROHM Co., Ltd. All rights reserved. Notice ROHM Customer Support System http://www.rohm.com/contact/ Thank you for your accessing to ROHM product informations. More detail product informations and catalogs are available, please contact us. Notes No copying or reproduction of this document, in part or in whole, is permitted without the consent of ROHM Co.,Ltd. The content specified herein is subject to change for improvement without notice. The content specified herein is for the purpose of introducing ROHM's products (hereinafter "Products"). If you wish to use any such Product, please be sure to refer to the specifications, which can be obtained from ROHM upon request. Examples of application circuits, circuit constants and any other information contained herein illustrate the standard usage and operations of the Products. The peripheral conditions must be taken into account when designing circuits for mass production. Great care was taken in ensuring the accuracy of the information specified in this document. However, should you incur any damage arising from any inaccuracy or misprint of such information, ROHM shall bear no responsibility for such damage. The technical information specified herein is intended only to show the typical functions of and examples of application circuits for the Produc ts. ROHM does not grant you, explicitly or implicitly, any license to use or exercise intellectual property or other rights held by ROHM and other parties. ROHM shall bear no responsibility whatsoever for any dispute arising from the use of such technical information. The Products specified in this document are intended to be used with general-use electronic equipment or devices (such as audio visual equipment, office-automation equipment, commu- nication devices, electronic appliances and amusement devices). The Products specified in this document are not designed to be radiation tolerant. While ROHM always makes efforts to enhance the quality and reliability of its Products, a Product may fail or malfunction for a variety of reasons. Please be sure to implement in your equipment using the Products safety measures to guard against the possibility of physical injury, fire or any other damage caused in the event of the failure of any Product, such as derating, redundancy, fire control and fail-safe designs. ROHM shall bear no responsibility whatsoever for your use of any Product outside of the prescribed scope or not in accordance with the instruction manual. T h e P r o d u c t s a r e n o t d e s i g n e d o r m a n u f a c t u r e d t o b e u s e d w i t h a n y e q u i p m e n t , d e v i c e o r system which requires an extremely high level of reliability the failure or malfunction of which may result in a direct threat to human life or create a risk of human injury (such as a medical instrument, transportation equipment, aerospace machinery, nuclear-reactor controller, fuel- controller or other safety device). ROHM shall bear no responsibility in any way for use of any of the Products for the above special purposes. If a Product is intended to be used for any such special purpose, please contact a ROHM sales representative before purchasing. If you intend to export or ship overseas any Product or technology specified herein that may be controlled under the Foreign Exchange and the Foreign Trade Law, you will be required to obtain a license or permit under the Law.