AL8843Q
Document overview
- Manufacturer or author: Diodes Incorporated
- PDF pages: 18
Technical content
Features
- Qualified to AEC-Q100 Grade 1
- Wide Input Voltage Range: 4.5V to 40V
- Output Current up to 3A
- Internal 40V NDMOS Switch
- Typical 4% Output Current Accuracy
- Single Pin for On/Off and Brightness Control by DC Voltage or PWM Signal
- Recommended Analog Dimming Range: 10% to 100%
- Soft-Start
- High Efficiency (Up to 97%)
- LED Short Protection
- Inherent Open-Circuit LED Protection
- Over Temperature Protection (OTP)
- Up to 1MHz Switching Frequency
- SO-8EP Package Available in Green Molding Compound (No Br, Sb)
- Totally Lead-Free & Fully RoHS Compliant (Notes 1 & 2)
- Halogen and Antimony Free. “Green” Device (Note 3)
- The AL8843Q suitable for automotive applications requiring specific change control; this part is AEC-Q100 qualified, PPAP capable, and manufactured in IATF 16949 certified facilities. https://www.diodes.com/quality/product-definitions/ Pin Assignments (Top View) GND GND NC SET CTRL VIN SW SW EP SO-8EP
Applications
- Automotive Daytime Running Lights
- Automotive Front and Rear Fog Lights
- Automotive Turn/Stop Lights
- Automotive Dimmable Interior Lights Notes: 1. No purposely added lead. Fully EU Directive 2002/95/EC (RoHS), 2011/65/EU (RoHS 2) & 2015/863/EU (RoHS 3) compliant. 2. See https://www.diodes.com/quality/lead-free/ for more information about Diodes Incorporated’s definitions of Halogen - and Antimony-free, "Green" and Lead-free. 3. Halogen- and Antimony-free "Green” products are defined as those which contain <900ppm bromine, <900ppm chlorine (<1500ppm total Br + Cl) and <1000ppm antimony compounds. AL8843Q Document number: DS41943 Rev. 2 - 2 1 of 18 www.diodes.com October 2019 © Diodes Incorporated
Typical Applications Circuit VIN SET CTRL GND SW RSET D1AL8843Q VIN: 4.5V to 40V Pin Descriptions Pin Number Pin Name Function 1, 2 GND Ground of IC 3 SET Set Nominal Output Current Pin. Connect resistor R SET from this pin to V IN pin to define nominal average output current.
4 NC No Connection
5 CTRL
Multi-Function On/Off and brightness control pin: Leave floating for normal operation. Drive to voltage below 0.3V to turn off output current. Drive with DC voltage (0.4V < VCTRL < 2.5V) to adjust output current from 10% to 100% of IOUT_NOM. Drive with an analog voltage > 2.6V output current will be 100% of IOUT_NOM. A PWM signal (Low level voltage < 0.3V, High level voltage > 2.6V, transition time less than 1µs) allows the output current to be adjusted over a wide range up to 100%. Connect a capacitor from this pin to ground to increase soft-start time. (Default soft-start time = 0.1ms. Additional soft-start time is approximate 1.5ms/1nF). 6 VIN Input Voltage (4.5V to 40V). Decouple to ground with 10μF or higher X7R ceramic capacitor close to device. 7, 8 SW Switch Pin. Connect inductor/freewheeling diode here, minimizing track length at this pin to reduce EMI. EP EP Exposed pad/TAB. Connect to GND and thermal mass for enhanced thermal impedance. AL8843Q Document number: DS41943 Rev. 2 - 2 2 of 18 www.diodes.com October 2019 © Diodes Incorporated
BG & Reference PWM/DC Dimming Current Monitor Hysteresis Control OTP Logic & Driver VIN CTRL SET SW GND PWM 4.5V 4.5V_Drv PWM OTP Ref Comp AL8843Q 7, 86 1, 2 Absolute Maximum Ratings (Note 5) Symbol Parameter Rating Unit VIN Input Voltage -0.3 to +42 V VSW, VSET Voltage at SW pin and SET Pin -0.3 to +42 V VCTRL CTRL Pin Input Voltage -0.3 to +6 V TJ Operating Junction Temperature -40 to +150 °C TSTG Storage Temperature Range -65 to +150 °C TLEAD Lead Temperature (Soldering, 10s) +300 °C Note: 5. Stresses greater than those listed under Absolute Maximum Ratings can cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated under Recommended Operating Conditions is not implied. Exposure to Absolute Maximum Ratings for extended periods can affect device reliability. ESD Ratings Symbol Parameter Rating Unit VESD Human Body Model (HBM), Per AEC Q100-002 ( Note 6) ±2000 V Charged Device Model (CDM), Per AEC Q100-011 ±1000 Note: 6. AEC-Q100-002 indicates that HBM stressing shall be accordance with the ANSI/ESDA/JEDEC JS- 001 specification. AL8843Q Document number: DS41943 Rev. 2 - 2 3 of 18 www.diodes.com October 2019 © Diodes Incorporated
Recommended Operating Conditions Symbol Parameter Min Max Unit VIN Input Voltage 4.5 40 V fSW Switching Frequency — 1 MHz IOUT Continuous Output Current — 3 A VCTRL Voltage Range from 10% to 100% DC Dimming Relative to GND 0.4 2.5 V VCTRL_HIGH Voltage High for PWM Dimming Relative to GND 2.6 5.5 V VCTRL_LOW Voltage Low for PWM Dimming Relative to GND 0 0.3 V TA Operating Ambient Temperature -40 +125 °C Thermal Information (Note 7) Symbol Parameter Rating Unit θJA Junction-To-Ambient Thermal Resistance 45 °C/W θJC Junction-To-Case (Top) Thermal Resistance 5 °C/W Note: 7. Device mounted on 2″×2″ FR-4 substrate PCB, 2oz copper, with minimum recommended pad layout. AL8843Q Document number: DS41943 Rev. 2 - 2 4 of 18 www.diodes.com October 2019 © Diodes Incorporated
Electrical Characteristics (@VIN = 16V, TA = -40°C to +125°C. Typical values are at TA = +25°C, unless otherwise specified.) Symbol Parameter Condition Min Typ Max Unit SUPPLY VOLTAGE VIN Input Voltage — 4.5 — 40 V IQ Quiescent Current CTRL Pin Floating, VIN = 16V — 0.35 — mA VUVLO Under Voltage Lockout VIN Rising — 3.9 — V VUVLO_HYS Under Voltage Lockout Hysteresis — — 250 — mV HYSTERESTIC CONTROL VSET Mean Current Sense Threshold Voltage Measured on SET Pin with Respect to VIN 96 100 104 mV VSET_HYS Sense Threshold Hysteresis — — ±13 — % ISET SET Pin Input Current VSET = VIN -0.1V — 8 — µA ENABLE AND DIMMING VCTRL Voltage Range from 10% to 100% DC Dimming Relative to GND For Analog Dimming 0.4 — 2.5 V — Analog Dimming Range — 10 — 100 % VCTRL_ON DC Voltage on CTRL Pin for Analog Dimming On VCTRL Rising — 0.45 — V VCTRL_OFF DC Voltage on CTRL Pin for Analog Dimming Off VCTRL Falling — 0.40 — V SWITCHING OPERATION RON SW Switch On Resistance @ISW = 100mA — 0.2 — Ω ISW_LEAK SW Switch Leakage Current — — — 8 μA tSS Soft Start Time VIN = 16V, CCTRL = 1nF — 1.5 — ms fSW Switching Frequency VIN = 16V, VO = 9.6V (3 LEDs) L= 47μH, ILED =1A — 250 — kHz fSW_MAX Recommended Maximum Switch Frequency — — — 1 MHz tON_REC Recommended Minimum Switch ON Time For 4% Accuracy — 500 — ns tPD Internal Comparator Propagation Delay (Note 8) — — 100 — ns THERMAL SHUTDOWN TOTP Over Temperature Protection — — +150 — °C TOTP_HYS Temperature Protection Hysteresis — — +30 — °C Note: 8. Guaranteed by design. AL8843Q Document number: DS41943 Rev. 2 - 2 5 of 18 www.diodes.com October 2019 © Diodes Incorporated
4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 200 220 240 260 280 300 320 340 360 380 400 420 440 Quiescent Current (µA) Input Voltage (V) Typical Performance Characteristics (@TA = +25°C, VIN = 16V, unless otherwise specified.) Quiescent Current vs. Input Voltage Quiescent Current vs. Temperature SET Threshold Voltage vs. Input voltage SET Threshold Voltage vs. Temperature 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 100 105 110 115 120 SET Threshold Voltage (mV) Input Voltage (V) VSET_H VSET_MEAN VSET_L -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 100110120130 200 220 240 260 280 300 320 340 360 380 400 420 440 VIN=16V Quiecent Current (µA) Temperature ( o -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 100110120130 100 105 110 115 120 SET Threshold Voltage (mV) Temperature ( o VSET_H VSET_MEAN VSET_L 120 150 180 210 240 270 300 330 360 LED Current (mA) CTRL Pin Voltage (V) 0 10 20 30 40 50 60 70 80 90 100 100 120 140 160 180 200 220 240 260 280 300 320 340 LED Current (mA) Duty Cycle (%) L=47µH,freq=680kHz fPWM=100Hz fPWM=200Hz fPWM=500Hz fPWM=1kHz PWM Dimming (VIN=16V, 3 LEDs, 47μH, RSET =0.3Ω) LED Current vs. Duty Cycle Analog Dimming (VIN=16V, 3LEDs, 47μH, RSET =0.3Ω) LED Current vs. CTRL Pin Voltage AL8843Q Document number: DS41943 Rev. 2 - 2 6 of 18 www.diodes.com October 2019 © Diodes Incorporated
4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 100 Efficiency (%) Input Voltage (V) VO=3.3V VO=6.6V VO=9.9V VO=13.2V VO=16.5V VO=19.8V VO=23.1V VO=26.4V VO=29.7V VO=33V 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 100 Efficiency (%) Input Voltage (V) VO=3.3V VO=6.6V VO=9.9V VO=13.2V VO=16.5V VO=19.8V VO=23.1V VO=26.4V VO=29.7V VO=33V Typical Performance Characteristics (continued) (@TA = +25°C, VIN = 16V, unless otherwise specified.) Efficiency vs. Input Voltage (RSET =0.1Ω, L=33μH) Efficiency vs. Input Voltage (RSET =0.067Ω, L=47μH) Efficiency vs. Input Voltage (RSET =0.05Ω, L=47μH) LED Current vs. Input Voltage (RSET =0.3Ω, L=100μH) 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 100 Efficiency (%) Input Voltage (V) VO=3.3V VO=6.6V VO=9.9V VO=13.2V VO=16.5V VO=19.8V VO=23.1V VO=26.4V VO=29.7V VO=33V 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 100 Efficiency (%) Input Voltage (V) VO=3.3V VO=6.6V VO=9.9V VO=13.2V VO=16.5V VO=19.8V VO=23.1V VO=26.4V VO=29.7V VO=33V 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 100 Efficiency (%) Input Voltage (V) Vo=3.3V Vo=6.6V Vo=9.9V Vo=13.2V Vo=16.5V Vo=19.8V Vo=23.1V Vo=26.4V Vo=29.7V Vo=33V 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 320 322 324 326 328 330 332 334 336 338 340 342 344 346 348 350 LED Current (mA) Input Voltage (V) VO=3.3V VO=6.6V VO=9.9V VO=13.2V VO=16.5V VO=19.8V VO=23.1V VO=26.4V VO=29.7V VO=33V Efficiency vs. Input Voltage (RSET =0.15Ω, L=47μH) Efficiency vs. Input Voltage (RSET =0.3Ω, L=100μH) AL8843Q Document number: DS41943 Rev. 2 - 2 7 of 18 www.diodes.com October 2019 © Diodes Incorporated
4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 640 645 650 655 660 665 670 675 680 685 690 695 700 LED Current (mA) Input Voltage (V) VO=3.3V VO=6.6V VO=9.9V VO=13.2V VO=16.5V VO=19.8V VO=23.1V VO=26.4V VO=29.7V VO=33V 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 970 975 980 985 990 995 1000 1005 1010 1015 1020 1025 1030 LED Current (mA) Input Voltage (V) VO=3.3V VO=6.6V VO=9.9V VO=13.2V VO=16.5V VO=19.8V VO=23.1V VO=26.4V VO=29.7V VO=33V 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 100 150 200 250 300 350 400 450 500 550 600 650 700 750 800 Frequency (kHz) Input Voltage (V) VO=3.3V VO=6.6V VO=9.9V VO=13.2V VO=16.5V VO=19.8V VO=23.1V VO=26.4V VO=29.7V VO=33V 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 100 150 200 250 300 350 400 450 500 550 600 650 700 750 800 850 Frequency (kHz) Input Voltage (V) VO=3.3V VO=6.6V VO=9.9V VO=13.2V VO=16.5V VO=19.8V VO=23.1V VO=26.4V VO=29.7V VO=33V 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 1.48 1.49 1.50 1.51 1.52 1.53 1.54 1.55 1.56 LED Current (A) Input Voltage (V) VO=3.3V VO=6.6V VO=9.9V VO=13.2V VO=16.5V VO=19.8V VO=23.1V VO=26.4V VO=29.7V VO=33V Typical Performance Characteristics (continued) (@TA = +25°C, VIN = 16V, unless otherwise specified.) 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 1.98 1.99 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 Vo=3.3V Vo=6.6V Vo=9.9V Vo=13.2V Vo=16.5V Vo=19.8V Vo=23.1V Vo=26.4V Vo=29.7V Vo=33V LED Current (A) Input Voltage (V) LED Current vs. Input Voltage (RSET =0.1Ω, L=33μH) LED Current vs. Input Voltage (RSET =0.15Ω, L=47μH) LED Current vs. Input Voltage (RSET =0.05Ω, L=47μH) LED Current vs. Input Voltage (RSET =0.067Ω, L=47μH) Operating Frequency vs. Input Voltage (RSET =0.15Ω, L=47μH) Operating Frequency vs. Input Voltage (RSET =0.3Ω, L=100μH) AL8843Q Document number: DS41943 Rev. 2 - 2 8 of 18 www.diodes.com October 2019 © Diodes Incorporated
4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 100 150 200 250 300 350 400 450 500 550 600 650 700 750 800 850 900 Frequency (kHz) Input Voltage (V) VO=3.3V VO=6.6V VO=9.9V VO=13.2V VO=16.5V VO=19.8V VO=23.1V VO=26.4V VO=29.7V VO=33V 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 100 150 200 250 300 350 400 450 500 Frequency (kHz) Input Voltage (V) VO=3.3V VO=6.6V VO=9.9V VO=13.2V VO=16.5V VO=19.8V VO=23.1V VO=26.4V VO=29.7V VO=33V Typical Performance Characteristics (continued) (@TA = +25°C, VIN = 16V, unless otherwise specified.) LED Current vs. Output Voltage (RSET =0.15Ω, L=47μH) LED Current vs. Output Voltage (RSET =0.1Ω, L=33μH) 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 100 150 200 250 300 350 Vo=3.3V Vo=6.6V Vo=9.9V Vo=13.2V Vo=16.5V Vo=19.8V Vo=23.1V Vo=26.4V Vo=29.7V Vo=33V fSW (kHz) Input Voltage (V) 3 6 9 12 15 18 21 24 27 30 33 320 322 324 326 328 330 332 334 336 338 340 342 344 346 348 350 LED Current (mA) Output Voltage (V) VIN=10V VIN=12V VIN=16V VIN=20V VIN=24V VIN=28V VIN=32V VIN=36V VIN=40V 3 6 9 12 15 18 21 24 27 30 33 640 645 650 655 660 665 670 675 680 685 690 695 700 VIN=10V VIN=12V VIN=16V VIN=20V VIN=24V VIN=28V VIN=32V VIN=36V VIN=40V LED Current (mA) Output Voltage (V) 3 6 9 12 15 18 21 24 27 30 33 970 975 980 985 990 995 1000 1005 1010 1015 1020 1025 1030 LED Current (mA) Output Voltage (V) VIN=10V VIN=12V VIN=16V VIN=20V VIN=24V VIN=28V VIN=32V VIN=36V VIN=40V Operating Frequency vs. Input Voltage (RSET =0.067Ω, L=47μH) Operating Frequency vs. Input Voltage (RSET =0.1Ω, L=33μH) LED Current vs. Output Voltage (RSET =0.3Ω, L=100μH)) Operating Frequency vs. Input Voltage (RSET =0.05Ω, L=47μH) AL8843Q Document number: DS41943 Rev. 2 - 2 9 of 18 www.diodes.com October 2019 © Diodes Incorporated
Typical Performance Characteristics (continued) (@TA = +25°C, VIN = 16V, unless otherwise specified.) LED Current vs. Output Voltage (RSET =0.067Ω, L=47μH) LED Current vs. Output Voltage (RSET=0.05Ω, L=47μH) Performance Characteristics (@VIN = 16V, 3 LEDs, RSET = 0.3Ω, L = 47μH, TA = +25°C, unless otherwise specified.) Steady State Start Up PWM Dimming (100Hz, Duty=50%) LED Open Protection IL 100mA/div VSW 5V/div Time 1μs/div Time 20μs/div Time 5ms/div Time 1ms/div VSW 10V/div VIN 10V/div IL 200mA/div VSW 10V/div VCTRL 2V/div IL 200mA/div VLED 5V/div VSW 10V/div IL 200mA/div VCTRL 2V/div 3 6 9 12 15 18 21 24 27 30 33 1.99 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 2.11 LED Current (A) Output Voltage (V) VIN=10V VIN=12V VIN=16V VIN=20V VIN=24V VIN=28V VIN=32V VIN=36V VIN=40V 3 6 9 12 15 18 21 24 27 30 33 1.48 1.49 1.50 1.51 1.52 1.53 1.54 1.55 1.56 LED Current (A) Output Voltage (V) VIN=10V VIN=12V VIN=16V VIN=20V VIN=24V VIN=28V VIN=32V VIN=36V VIN=40V AL8843Q Document number: DS41943 Rev. 2 - 2 10 of 18 www.diodes.com October 2019 © Diodes Incorporated
Application Information
In normal operation, when normal input voltage is applied at V IN, the AL8843Q internal switch will turn on. Current starts to flow through sense resistor RSET, inductor L1, and the LEDs. The current ramps up linearly, and the ramp-up rate is determined by VIN, VOUT and the inductor L1. This rising current produces a voltage ramp across RSET. The internal circuit of the AL8843Q senses the voltage across R SET and applies a proportional voltage to the input of the internal comparator. When this voltage reaches an internally set upper threshold, the internal switch will be turned off. The inductor current continues to flow through RSET, L1, LEDs and diode D1, and back to the supply rail, but then it decays with the rate determined by the forward voltage drop of LEDs and the diode D1. This decaying current produces a falling voltage on RSET, which is sensed by the AL8843Q. A voltage proportional to the sense voltage across RSET will be applied at the input of internal comparator. When this voltage falls to the internally set lower threshold, the internal swit ch will be turned on again. This switch-on-and-off cycle continues to provide the average LED current, set by the sense resistor RSET. LED Current Configuration The nominal average output current in the LED(s) is determined by the value of the external current sense resistor ( RSET), which is connected between VIN and SET pins, and is given by: ( ) SET NOMOUT R 0.1I = The table below gives values of nominal average output current for several preferred values of current setting resistor ( RSET) in the Typical Application Circuit shown on Page 2. RSET (Ω) Nominal Average Output Current (mA) 0.033 3,000 0.05 2,000 0.067 1,500 0.1 1,000 0.15 667 0.3 333 The above values assume that the CTRL pin is floating and at a nominal reference voltage for internal comparator. It is possible to use different values of RSET if the CTRL pin is driven by an external dimming signal. Analog Dimming Applying a DC voltage from 0.4V to 2.5V on the CTRL pin can adjust output current from 1 0% to 100% of I OUT_NOM, as shown in Figure 1. If the CTRL pin is brought higher than 2.5V, the LED current will be clamped to 100% of IOUT_NOM while if the CTRL voltage falls below the threshold of 0.3V, the output switch will turn off. PWM Dimming The LED current can be adjusted digitally, by applying a low frequency Pulse-Width-Modulated (PWM) logic signal to the CTRL pin to turn the device on and off. This will produce an average output current proportional to the duty cycle of the control signal. To achieve a high resolution, the PWM frequency is recommended to be lower than 500Hz, however higher dimming frequencies can be used at the expense of dimming dynamic range and accuracy. Typically, for a PWM frequency of 500Hz, the accuracy is better than 1% for PWM ranging from 1% to 100%. The accuracy of the low duty cycle dimming is affected by both the PWM frequency and the switching frequency of the AL 8843Q. For best accuracy/resolution, the switching frequency should be increased while the PWM frequency should be reduced. AL8843Q Document number: DS41943 Rev. 2 - 2 11 of 18 www.diodes.com October 2019 © Diodes Incorporated
Figure 1. Analog Dimming Curve The default soft-start time for AL88 43Q is only 0.1ms , and this provides very fast turn-on of the output , improving the PWM dimming accuracy . comparator. The additional soft-start time is related to the capacitance between CTRL and GND, the typical value will be 1.5ms/nF. lower the overall efficiency. This capacitor has to supply the relatively high peak current to the coil and smooth the ripple on the input current. should be placed as close as possible to the IC. dielectric are not suitable for decoupling in this application and should NOT be used. leakage current. It also provides better efficiency than silicon diodes, due to lower forward voltage and reduced recovery time.
The higher forward voltage and overshoot due to reverse recovery time in silicon diodes will increase the peak voltage on the SW output. If a silicon diode is used, more care should be taken to ensure that the total voltage appearing on the SW pin including supply ripple , won’t exceed the specified maximum value. Application Information (continued) Inductor Selection Recommended inductor values for the AL8843Q are in the range 33μH to 100μH. Higher inductance are recommended at higher supply voltages in order to minimize output current tolerance due to switching delays, which will result in increased ripple and lower efficiency. Higher inductance also results in a better line regulation. The inductor should be mounted as close to the device as possible with low resistance connections to SW pins. The chosen coil should have saturation current higher than the peak output current and a continuous current rating above the required mean output current. The inductor value should be chosen to maintain operating duty cycle and switch on/off times within the specified limits over the supply voltage and load current range. The following equations can be used as a guide. SW Switch ‘On’ Time 𝒕𝑶𝑵 = 𝑳∆𝑰 𝑽𝑰𝑵 −𝑽𝑳𝑬𝑫 −𝑰𝑳𝑬𝑫(𝑹𝑺𝑬𝑻 + 𝑹𝑳 + 𝑹𝐒𝐖) SW Switch ‘Off’ Time 𝒕𝑶𝑭𝑭 = 𝑳∆𝑰 𝑽𝑳𝑬𝑫 + 𝑽𝑫 + 𝑰𝑳𝑬𝑫(𝑹𝑺𝑬𝑻 + 𝑹𝑳) Where: L is the coil inductance; RL is the coil resistance; RSET is the current sense resistance; ILED is the required LED current; ΔI is the coil peak - peak ripple current (internally set to 0.26 × ILED); VIN is the supply voltage; VLED is the total LED forward voltage; RSW is the switch resistance (0.2Ω nominal); VD is the diode forward voltage at the required load current. Thermal Protection The AL8843Q includes Over Temperature Protection (OTP) circuitry that will turn off the device if its junction temperature gets too high. This is to protect the device from excessive heat damage. The OTP circuitry includes thermal hysteresis that will cause the device to restart normal operation once its junction temperature has cooled down by approximately +30°C. Open Circuit LEDs The AL8843Q has by default open LED protection. If the LEDs become open circuit , the AL8843Q will stop oscillating; the voltage at the SET pin will rise to VIN and the SW pin will then fall to GND. No excessive voltages will be seen by the AL8843Q. LED Chain Shorted Together If the LED chain becomes shorted together (the anode of the top LED becomes shorted with the cathode of the bottom LED) , the AL8843Q will continue to switch and the current through the AL8843Q’s internal switch will still be at the expected current, so no excessive heat will be generated within the AL8843Q . However, the duty cycle will change dramatically and the switching frequency will most likely decrease. See Figure 2 for an example of this operation at 24V input voltage driving 3 LEDs. The on-time of the internal power MOSFET switch is significantly reduced because almost all of the input voltages are now developed across the inductor. The off-time is significantly increased because the reverse voltage across the inductor is now just the Schottky diode voltage (See Figure 2) causing a much slower decay in inductor current. AL8843Q Document number: DS41943 Rev. 2 - 2 13 of 18 www.diodes.com October 2019 © Diodes Incorporated
Application Information (continued) Recommendations for minimizing radiated EMI and other transients and thermal considerations are: 1. The decoupling capacitor (C1) has to be placed as close as possible to the VIN pin and D1 Cathode. 2. The freewheeling diode’s (D1) anode, the SW pin and the inductor have to be placed as close as possible to each other to avoid ringing. 3. The Ground return path from C1 must be a low impedance path with the ground plane as large as possible. 4. The LED current sense resistor (RSET) has to be placed as close as possible to the VIN and SET pins. 5. The majority of the conducted heat from the AL8843Q is through the GND pin 2. A maximum earth plane with thermal vias into a second earth plane will minimise self-heating. 6. To reduce emissions via long leads on the supply input and LEDs , low RF impedance capacitors should be used at the point where the wires are joined to the PCB.
Ordering Information
AL8843Q X–X Package SP: SO-8EP PackingProduct Name 13: Tape and Reel Compliance Q: Automotive Part Number Package Code Package 13” Tape and Reel Quantity Part Number Suffix AL8843QSP-13 SP SO-8EP 2500/Tape & Reel -13 Marking Information AL8843Q (Top View) YY WW X X E Logo WW : Week : 01~52; 52 YY : Year : 19, 20, 21~ X X : Internal Code 8 7 6 5 1 2 3 4 represents 52 and 53 week Marking ID E : SO-8EP AL8843Q Document number: DS41943 Rev. 2 - 2 15 of 18 www.diodes.com October 2019 © Diodes Incorporated
Package Outline Dimensions (All dimensions in mm (inch).) Please see http://www.diodes.com/package-outlines.html for the latest version. Package Type: SO-8EP 5.800(0.228) 6.200(0.244) 1.270(0.050) 0.400(0.016) 3.800(0.150) 4.000(0.157) 0.150(0.006) TYP 0.250(0.010) 0.150(0.006) 1.350(0.053) 1.550(0.061) 2.110(0.083) 2.710(0.107) 2.750(0.108) 3.402(0.134) 5.100(0.201) Note: Eject hole, oriented hole and mold mark is optional. 0.300(0.012) AL8843Q Document number: DS41943 Rev. 2 - 2 16 of 18 www.diodes.com October 2019 © Diodes Incorporated
Please see http://www.diodes.com/package-outlines.html for the latest version. Package Type: SO-8EP G E X Y Y1 Z Dimensions Z (mm)/(inch) G (mm)/(inch) X (mm)/(inch) Y (mm)/(inch) (mm)/(inch) (mm)/(inch) E (mm)/(inch) AL8843Q Document number: DS41943 Rev. 2 - 2 17 of 18 www.diodes.com October 2019 © Diodes Incorporated
DIODES INCORPORATED MAKES NO WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, WITH REGARDS TO THIS DOCUMENT, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE (AND THEIR EQUIVALENTS UNDER THE LAWS OF ANY JURISDICTION). Diodes Incorporated and its subsidiaries reserve the right to make modifications, enhancements, improvements, corrections or other changes without further notice to this document and any product described herein. Diodes Incorporated does not assume any liability arising out of the application or use of this document or any product described herein; neither does Diodes Incorporated convey any license under its patent or trademark rights, nor the rights of others. Any Customer or user of this document or products described herein in such applications shall assume all risks of such use and will agree to hold Diodes Incorporated and all the companies whose products are represented on Diodes Incorporated website, harmless against all damages. Diodes Incorporated does not warrant or accept any liability whatsoever in respect of any products purchased through unauthorized sales channel. Should Customers purchase or use Diodes Incorporated products for any unintended or unauthorized application, Customers shall indemnify and hold Diodes Incorporated and its representatives harmless against all claims, damages, expenses, and attorney fees arising out of, directly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized application. Products described herein may be covered by one or more United States, international or foreign patents pending. Product names and markings noted herein may also be covered by one or more United States, international or foreign trademarks. This document is written in English but may be translated into multiple languages for reference. Only the English version of this document is the final and determinative format released by Diodes Incorporated. LIFE SUPPORT Diodes Incorporated products are specifically not authorized for use as critical components in life support devices or systems without the express written approval of the Chief Executive Officer of Diodes Incorporated. As used herein: A. Life support devices or systems are devices or systems which: 1. are intended to implant into the body, or 2. support or sustain life and whose failure to perform when properly used in accordance with instructions for use provided i n the labeling can be reasonably expected to result in significant injury to the user. B. A critical component is any component in a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or to affect its safety or effectiveness. Customers represent that they have all necessary expertise in the safety and regulatory ramifications of their life support devices or systems, and acknowledge and agree that they are solely responsible for all legal, regulatory and safety-related requirements concerning their products and any use of Diodes Incorporated products in such safety -critical, life support devices or systems, notwithstanding any devices - or systems -related information or support that may be provided by Diodes Incorporated. F urther, Customers must fully indemnify Diodes Incorporated and its representatives against any damages arising out of the use of Diodes Incorporated products in such safety-critical, life support devices or systems. Copyright © 2019, Diodes Incorporated www.diodes.com AL8843Q Document number: DS41943 Rev. 2 - 2 18 of 18 www.diodes.com October 2019 © Diodes Incorporated