AN8041S

AN8041S PANASONIC | Alldatasheet

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Liquid crystal backlight control IC n Overview The AN8041S is an inverter control IC for liquid crystal backlight using PWM method. The output voltage of DC-DC converter and the current of cath- ode-ray tube can be controlled by using two error amplifiers, so that the system is designed easily. Since the n-channel MOSFET can be directly driven, it is possible to construct a highly effective power supply. n Features

• Operating supply voltage: 3.6 V to 34 V *
• Totem pole output circuit: Output current of –500 mA
• Built-in bootstrap circuit
• N-channel power MOSFET can be directly driven
• Built-in two error amplifier circuits allow both the voltage and current control
• Incorporating on/off functions (active-high control input, standby mode current is 5 mA or less)
• Built-in timer latch short-circuit protection circuit
• Maximum oscillation frequency: 500 kHz Note) *: The voltage is limited to the range of 3.6 V to 17 V if used in a step-down circuit. n Applications
• LCD displays, digital still cameras, and PDAs n Block Diagram SOP016-P-0225A Unit: mm 0.3 (0° to 10°) (0.15) Seating plane 10.1±0.3 4.2±0.3 6.5±0.3 16 9 1.27(0.605) Seating plane 0.40±0.25 0.1±0.1 1.5±0.2 CB14 Out13 FB18 IN+16 IN-17 S.C.P. 5 Off 16 DTC4 V REF GND 12 S.C.P. comp. Q Q R S V CC Bootstrap CT3 Constant current source RT2 OSC V REF 2.57 V On/off active-high PWM comp. Error amp. 2 U.V .L.O. QR S Latch Error amp. 1 FB29 IN+211 IN-210

AN8041S Voltage Regulators n Pin Descriptions n Absolute Maximum Ratings Parameter Symbol Rating Unit Supply voltage V CC 35 V Off terminal application voltage V OFF 35 V Error amplifier input voltage V I - 0.3 to VREF V DTC terminal application voltage V DTC - 0.3 to VREF V Out terminal application voltage V OUT 35 V CB terminal application voltage V CB 35 V Out terminal constant output current IO –100 mA Out terminal peak output current IO(PEAK) –500 mA Power dissipation * PD 143 mW Operating ambient temperature * T opr -30 to +85 °C Storage temperature * Tstg -40 to +125 °C n Recommended Operating Range Parameter Symbol Range Unit Supply voltage (when using step-down circuit) VCC 3.6 to 17 V Supply voltage (when using step-up circuit) VCC 3.6 to 34 V Oscillation frequency f OUT 5 to 500 kHz Oscillator timing resistance R T 5.1 to 30 k W Oscillator timing capacitance C T 100 to 10 000 pF Error amplifier input voltage V IN - 0.1 to +0.8 V Reference voltage output current I REF -1 to 0 mA Pin No. Symbol Description 1V REF Reference voltage output pin

2 RT Pin for connecting oscillator

3 CT Pin for connecting oscillator

4 DTC Dead-time control pin

5 S.C.P. Pin for connecting the time constant setting capacitor for short-circuit protection 6I N +1 Error amplifier 1 noninverted input pin Pin No. Symbol Description 7I N -1 Error amplifier 1 inverted input pin

8 FB1 Error amplifier 1 output pin

9 FB2 Error amplifier 2 output pin

10 IN -2 Error amplifier 2 inverted input pin

11 IN +2 Error amplifier 2 noninverted input pin

12 GND Grounding pin

13 Out Output pin

14 CB Bootstrap output circuit

15 V CC Power supply voltage application pin

16 Off On/off control pin

Note) *: Expect for the operating ambient temperature and storage temperature, all ratings are for Ta = 25°C.

Voltage Regulators AN8041S n Electrical Characteristics at VCC = 12 V, RT = 15 kW , CT = 120 pF, Ta = 25°C Parameter Symbol Conditions Min Typ Max Unit Reference voltage block Output voltage V REF IREF = -1 mA 2.483 2.57 2.647 V Input regulation with input fluctuation Line VCC = 3.6 V to 34 V ¾ 72 5 m V Load regulation Load I REF = - 0.1 mA to -1 mA ¾ 11 0 m V Output voltage V TC1 Ta = -30°C to +25°C ¾– 1 ¾ % temperature characteristics 1 Output voltage V TC2 Ta = 25°C to 85°C ¾– 1 ¾ % temperature characteristics 2 Output short-circuit current I OS ¾- 10 ¾ mA U.V.L.O. block Circuit operation start voltage V UON 2.8 3.1 3.4 V Hysteresis width V HYS 60 140 220 mV Error amplifier block Input offset voltage V IO -6 ¾ 6m V Input bias current I B -500 -25 ¾ nA Common-mode input voltage range V ICR - 0.1 ¾ 0.8 V High-level output voltage 1 V EH V REF - 0.3 VREF - 0.1 ¾ V Low-level output voltage 1 V EL ¾ 0.1 0.3 V Output sink current I SINK V FB = 0.9 V ¾ 8 ¾ mA Output source current I SOURCE V FB = 0.9 V ¾- 110 ¾m A Open-loop gain A G ¾ 70 ¾ dB Dead-time control circuit block Input current I DTC R T = 15 kW- 14.8 -12.3 -9.8 mA Low-level input threshold voltage VDT-L Duty = 0% ¾ 0.45 0.65 V High-level input threshold voltage VDT-H Duty = 100% 1.2 1.4 ¾ V Output block Oscillation frequency f OUT R T = 15 kW , 180 200 220 kHz C T = 120 pF Output duty ratio Du R DTC = 75 kW 45 50 55 % Low-level output voltage V OL IO = 70 mA ¾ 1.0 1.3 V High-level output voltage V OH IO = -70 mA V CB -2.0 VCB -1.0 ¾ V Frequency f dV fOUT = 200 kHz, ¾– 3 ¾ V supply voltage characteristics V CC = 3.6 V to 34 V Frequency f dT1 fOUT = 200 kHz, ¾– 9 ¾ V temperature characteristics 1 T a = -30°C to +25°C Frequency f dT2 fOUT = 200 kHz, ¾– 9 ¾ V temperature characteristics 2 T a = 25°C to 85°C

AN8041S Voltage Regulators n Electrical Characteristics at VCC = 12 V, RT = 15 kW , CT = 120 pF, Ta = 25°C (continued) Parameter Symbol Conditions Min Typ Max Unit Bootstrap circuit block Input standby voltage V INCB ICB = -70 mA V CC -1.2 VCC -1.0 VCC - 0.8 V Oscillator block RT terminal voltage V RT ¾ 0.37 ¾ V Short-circuit protection block Input threshold voltage V THPC 0.70 0.75 0.80 V Input standby voltage V STBY ¾ 30 120 mV Input latch voltage V IN ¾ 30 120 mV Charge current I CHG -2.76 -2.3 -1.84 mA Comparator threshold voltage V THL ¾ 1.82 ¾ V On/off control block Threshold voltage V TH 0.8 ¾ 2.0 V Whole device Total consumption current I CC ¾ 3.9 5.0 mA Standby current I CC(SB) ¾¾ 5 mA Pin No. Equivalent circuit Description I/O 1V REF :O The reference voltage output terminal (2.57 V (allowance: –3%)). Incorporating short-circuit protection against GND.

2 RT: ¾

The terminal used for connecting a timing resis- tor to set oscillator's frequency. Use a resistance value within the range of 5.1 kW to 30 kW . The terminal voltage is approx. 0.37 V.

3 CT: ¾

The terminal used for connecting a timing ca- pacitor to set oscillator's frequency. Use a capacitance value within the range of 100 pF to 10 000 pF. For frequency setting method, refer to the " Application Notes, [3] Function descriptions " section. Use an oscillation frequency in the range of 5 kHz to 500 kHz. n Terminal Equivalent Circuits V CC V REF RT (» 0.37 V) 100 W DTC S.C.P. V REF OSC comp. To PWM input IO 2IO

Voltage Regulators AN8041S Pin No. Equivalent circuit Description I/O

4 DTC: ¾

The terminal for connecting a resistor and ca- pacitor to set the dead-time and soft start period of PWM output. Input current IDTC is determined by the timing resistor RT , so that dispersion and fluctuation with temperature are suppressed. It is approx. -12.3 mA when RT = 15 kW . IDTC = V RT · 1 [A]R T 2 5 S.C.P.: ¾ The terminal for connecting a capacitor to set the time constant of soft start and timer latch short- circuit protection circuit. Use a capacitance value in the range of more than 1 000 pF. The charge current I CHG is determined by the timing resistor RT , so that dispersion and fluc- tuation with temperature are suppressed. It is approx. -1.3 mA when RT = 15 kW . ICHG = V RT · 1 [A]R T 11 6I N +1: I The noninverted input terminal of the error am- plifier 1. For common-mode input, use in the range of - 0.1 V to +0.8 V. 7I N -1: I The inverted input terminal of the error ampli- fier 1. For common-mode input, use in the range of - 0.1 V to +0.8 V.

8 FB1: O

The output terminal of the error amplifier 1. Source current: approx. -120 mA Sink current : approx. 8 mA Correct the frequency characteristics of the gain and the phase by connecting a resistor and a ca- pacitor between this terminal and IN-1 terminal.

9 FB2: O

The output terminal of the error amplifier 2. Source current: approx. -120 mA Sink current : approx. 8 mA Correct the frequency characteristics of the gain and the phase by connecting a resistor and a ca- pacitor between this terminal and IN-2 terminal. n Terminal Equivalent Circuits (continued) QS Latch

0.75 V R

To U.V .L.O. V REF V REF Source current Sink current V REF Source current Sink current V REF PWM comparator input I DTC C DTC R DTC RT

AN8041S Voltage Regulators Pin No. Equivalent circuit Description I/O

10 IN -2: I

The inverted input terminal of the error ampli- fier 2. For common-mode input, use in the range of - 0.1 V to +0.8 V.

11 IN +2: I

The noninverted input terminal of the error am- plifier 2. For common-mode input, use in the range of - 0.1 V to +0.8 V.

12 GND: ¾

Grounding terminal.

13 Out: O

Totem pole type output terminal. A constant output current of –100 mA and a peak output current of –1 A can be obtained.

14 CB: O

Bootstrap output terminal. When using step-down circuit, connect the ca- pacitor for boost between this terminal and the n-channel MOSFET source side of the switching device. When using step-up circuit, short circuit this terminal with VCC terminal.

15 V CC :I

Power supply application terminal.

16 Off: I

On/off control terminal. High-level input: normal operation (VOFF > 2.0 V) Low-level input: standby condition (VOFF < 0.8 V) The total consumption current can be suppressed to 10 mA or less. n Terminal Equivalent Circuits (continued) V REF 1110 V CC 17 kW Internal circuit Start/Stop 13 kW

Voltage Regulators AN8041S n Application Notes [1] Main characteristics PD ¾ Ta Oscillation frequency ¾ Timing capacitance Oscillation frequency temperature characteristics Output duty ratio temperature characteristics Internal reference voltage temperature characteristics Output duty ratio ¾ DTC terminal voltage 100 600 0 25 150 Ambient temperature Ta (°C) Power dissipation PD (mW) 200 143 207 300 360 400 500 518 50 75 85 100 125 Glass epoxy board (50 · 50 · 0.8t mm3) R th(j-a) = 263°C/W PD = 380 mW (25°C) Independent IC without a heat sink R th( j-a) = 278°C/W PD = 360 mW (25°C) 500 100 1 000 10 000 Timing capacitance CT (pF) Oscillation frequency fOUT (kHz) 100 R T = 5.1 kW R T = 15 kW 185 -50 -25 100 Ambient temperature Ta (°C) Oscillation frequency fOUT (kHz) 190 195 200 205 0 25 50 75 V CC = 12 V -50 -25 100 Ambient temperature Ta (°C) Output duty ratio Du (%) 0 25 50 75 V CC = 12 V 2.53 -50 -25 100 Ambient temperature Ta (°C) Internal reference voltage VREF (V) 2.54 2.55 2.56 2.57 0 25 50 75 V CC = 12 V 0.2 0.4 1.4 DTC terminal voltage (V) Output duty ratio Du (%) 100 0.6 0.8 1.0 1.2 V CC = 12 V

AN8041S Voltage Regulators n Application Notes (continued) [2] Timing chart 1. PWM comparator operation waveform 2. Short-ciruit protection operation waveform Off terminal voltage DTC terminal voltage High Low High Low 3.6 V 2.57 V 1.82 V 1.32 V 0.44 V 0.03 V Supply voltage (VCC ) Triangular wave (CT) Error amplifier 1 output (FB 1) Error amplifier 2 output (FB 2)Internal reference voltage (VREF ) S.C.P. terminal voltage Out terminal waveform Power supply on Soft start operation Maximum duty tPE Low 0.75 V S.C.P. terminal voltage 0.03 V High Low High 1.32 V 0.44 V 1.82 V 2.57 V Out terminal waveform Triangular wave (CT) Error amplifier output (FB2) Error amplifier output (FB1) Internal reference voltage DTC terminal voltage Short-circuit protection comparator threshold level Short-circuit protection comparator output

1. Timer latch short-circuit protection circuit

prevents the parts such as external main switch device, flywheel diode, the choke coil from destruction or deterioration. comparator also maintains balance. output terminal to low-level and sets the dead-time to 100%. the latch circuit is set, it is not reset unless the power supply is turned off. Figure 4. Short-circuit protection circuit circuit protects the system from destruction or deterioration due to the malfunction of the control circuit.

2.0 V, the internal reference voltage rises, and starts the control operation. level so that the switching device (n-channel MOSFET) turns on . connecting the external resistor RDTC between the DTC terminal and GND terminal. and 100% when VDTC = 1.32 V typical. overshoot and undershoot amount differ depending on the oscillation frequency. Figure 5. Setting the dead-time

• 100 [%] I DTC = V RT
• 1 [A]tON + tOFF R T 2 = V DTC - VCTL
• 100 [%] V DTC = IDTC · R DTC V CTH - VCTL = VRT · R DTC
• 1 [A]R T 2 Example) When f OSC = 200 [kHz] (RT = 15 kW , CT = 150 pF), RDTC = 75 [kW ] V CTH » 1.32 [V], VCTL » 0.44 [V], VDTC » 0.37 [V] Therefore IDTC » 12.3 [mA] V DTC » 0.925 [V] Du » 55.1 [%] In addition, the operation delay of the PWM comparator, the deviation of the peak and trough triangular oscillation value may cause the deviation of the actual measurements value from the theoretical value. So, regu- lation on IC-mounted PCB should be required. By adding the external resistor R DTC and capacitor CDTC , the soft start function can be installed, which gradually broadens the on-period of the output pulse at the time of the power supply operation start. The soft start operation prevents the overshoot of DC-DC comparator output.

AN8041S Voltage Regulators n Application Notes (continued) [3] Function descriptions (continued) 8. Output block, bootstrap circuit (continued) 2) N-channel MOSFET (M1) turn-on time: t2 When the PWM comparator output reverses, the Out terminal (pin 13) is switched over to high-level. The Out terminal voltage VO rises toward the CB terminal voltage. V O = VCB -V CE (sat) At that time, M1 voltage between the gate and source becomes: V GS = VO +V F When the Out terminal voltage VO rises to the gate threshold voltage, the M1 is turned on. The M1 source- side voltage after the turn-on rises to the value expressed in the following equation: V S = VCC -V DS(ON) Since the bootstrap capacitor CB is connected between the M1 source-side and the CB terminal, the CB terminal voltage is capacitance-coupled, and rises according to the M1 source-side voltage. It is expressed in the following equation: V CB = VS +V CC -V D1 +V F = 2 · VCC -V D1 +V DS(ON) +V F 3) N-channel MOSFET (M1) turn-off time: t3 The Out terminal voltage drops to the saturation voltage of the transistor Q1 and it is turned off. The M1 source side voltage decreases to -V F , and in the same way the CB terminal voltage is capacitance- coupled, and drops to VCC -V D1 volt, and returns to the condition described in a).

• Bootstrap circuit usage notes (1) Operating supply voltage range when the step-down circuit is used When the step-down circuit is used for the DC-DC converter control : As described in the above, when the n-channel MOSFET of the switching device turns on, the voltage of CB terminal (pin 14) rises to the voltage about two times higher than the V CC . Since the allowable applied voltage for the CB terminal is 35 V, use the boost circuit at an operating supply voltage of 3.6 V or more. V CB = 2 · VCC - VD1 - VDS(ON) + VF < 35 [V] V CC < 35 + VD1 + VDS(ON) - VF [V]2 < 17 [V] (2) Value setting for bootstrap capacitor The bootstrap capacitor is capacitors-coupled with the n-channel MOSFET source-side at its turn-on time to increase the CB terminal voltage over the VCC . At this time, the bootstrap capacitor is discharged by the n-channel MOSFET gate drive current. If the capacitance value of the bootstrap capacitor is set at too low value, it causes the efficiency decrease due to increase in switching loss. Therefore, set the capacitance at a sufficiently high value compared with the n-channel MOSFET gate input capacitance. CB >> Ciss Study with the actual mounting board and set the optimum value. (3) CB terminal connection when the booster circuit is used In the case of using the step-up type DC-DC converter control, the bootstrap circuit is not required since the n-channel MOSFET source side is grounded. Therefore, use it by short-circuiting the CB terminal (pin 14) to the V CC terminal (pin 15). For that reason, the operating supply voltage range is 3.6 V to 34 V in the case of using the step-up circuit type.

Voltage Regulators AN8041S n Application Circuit Examples

• Inverter control for liquid crystal backlight
• DC-DC converter control (step-up circuit example) CB14 Out13 FB18 IN+16 IN-17 S.C.P. 104 pF 3.3 kW In 8.2 kW 18 kW 3 kW5 Off 16 DTC4 V REF1 GND 12 S.C.P. comp. Q Q R S V CC15 Bootstrap CT3 Constant current source RT2 OSCV REF 2.57 V On/Off active-high PWM comp. Error amp. 2 U.V .L.O. QR S Latch Error amp. 1 FB29 IN+211 IN-210 12 mA 2.3 mA 1.82 V V 1 0.72 V V 1 0.1 mF kW 15 kW SBD SBD 0.01 mF 120 pF L A M P CB14 Out13 FB18 IN+16 IN-17 S.C.P. In Off 16 DTC4 V REF1 GND 12 S.C.P. comp. Q Q R S V CC15 Bootstrap CT3 RT2 OSCV REF 2.57 V On/Off active-high PWM comp. Error amp. 2 U.V .L.O. QR S Latch Error amp. 1 FB29 IN+211 IN-210 1.82 V V 1 V 1 SBD Out Constant current source