A6262

A6262_V01 ALLEGRO

Document overview

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Technical content

DESCRIPTION

The A6262 is a linear, programmable current regulator providing up to 100 mA from each of four outputs to drive arrays of high brightness LEDs. The regulated LED current from each output, accurate to 5%, is set by a single reference resistor. Current matching in each string is better than 10% without the use of ballast resistors. Driving LEDs with constant current ensures safe operation with maximum possible light output. Output control is provided by an enable input, giving direct control for PWM applications, and by a debounced switch input, proving an on/off toggle action. Optimum performance is achieved driving 1 to 3 LEDs in each string: up to 4 strings at 100 mA each. Outputs can be connected in parallel or left unused as required. Short detection is provided to protect the LEDs and the A6262 during a short-to-ground at any LED output pin. The output will automatically resume the regulated current when the short is removed. A temperature monitor is included to reduce the LED drive current if the chip temperature exceeds an adjustable thermal threshold. The device packages are a 10-pin MSOP (suffix LY), and a 16-pin TSSOP (LP), both with exposed pad for enhanced thermal dissipation. They are lead (Pb) free, with 100% matte tin leadframe plating. A6262-DS, Rev. 10 MCO-0000875 FEATURES AND BENEFITS ▪ AEC-Q100 qualified ▪ Total LED drive current up to 400 mA ▪ Current shared equally up to 100 mA by 4 strings ▪ 6 to 50 V supply ▪ Low dropout voltage ▪ LED output short-to-ground and thermal protection ▪ On/off toggle switch input ▪ Enable input for PWM control ▪ Current slew rate limit during PWM ▪ Current set by reference resistor ▪ Automotive temperature range APPLICATIONS : Typical Application Diagram A6262 Automotive LED Array Driver ▪ Dome light, map light, space lighting, mood lighting A6262 LA1 VIN Automotive

12 V power net

PACKAGES: Not to scale 10-pin MSOP with exposed thermal pad (suffix LY) 16-pin TSSOP with exposed thermal pad (suffix LP) June 3, 2022

Automotive LED Array DriverA6262 Allegro MicroSystems

955 Perimeter Road

Manchester, NH 03103-3353 U.S.A. www.allegromicro.com Absolute Maximum Ratings1 Characteristic Symbol Notes Rating Unit Load Supply Voltage VIN –0.3 to 50 V Pin EN –0.3 to 50 V Pins LA[1:4] –0.3 to 50 V Pins IREF, THTH, SW –0.3 to 6.5 V Ambient Operating Temperature Range2 TA K temperature range –40 to 125 °C Maximum Continuous Junction Temperature TJ(max) 150 °C Transient Junction Temperature TtJ Over temperature event not exceeding 10 s, lifetime duration not exceeding 10 h, guaranteed by design characterization 175 °C Storage Temperature Range Tstg –55 to 150 °C 1With respect to GND. 2Limited by power dissipation. Selection Guide Part Number Ambient Operating Temperature, TA (°C) Packing Package A6262KLPTR-T –40 to 125 4000 pieces per 13-in. reel 16-pin TSSOP with exposed thermal pad, 4.4 × 5 mm case A6262KLYTR-T 10-pin MSOP with exposed thermal pad, 3 × 3 mm case Thermal Characteristics*may require derating at maximum conditions, see application information Characteristic Symbol Test Conditions* Value Unit Package Thermal Resistance (Junction to Ambient) RθJA LP package On 4-layer PCB based on JEDEC standard 34 ºC/W On 2-layer PCB with 3.8 in.2 of copper area each side 43 ºC/W LY package On 4-layer PCB based on JEDEC standard 48 ºC/W On 2-layer PCB with 2.5 in.2 of copper area each side 48 ºC/W Package Thermal Resistance (Junction to Pad) RθJP 2 ºC/W *To be verified by characterization. Additional thermal information available on the Allegro™ website.

Automotive LED Array DriverA6262 Allegro MicroSystems Manchester, NH 03103-3353 U.S.A. www.allegromicro.com LA1 VIN VBAT Current Regulators GNDPAD Temp Comp Temp Monitor Slew Limit Current Reference Control Logic LA2 LA3 LA4 EN SW IREF RREF RTH THTH Deglitch D Q C Q R Functional Block Diagram Pinout Diagrams THTH IREF GND LA1 LA2 SW EN VIN LA4 LA3 PAD NC NC THTH IREF GND LA1 LA2 NC NC NC SW EN VIN LA4 LA3 NC PAD Terminal List Table Name Number FunctionLP LY EN 13 9 Enable SW 14 10 Switch input GND 5 3 Ground reference IREF 4 2 Current reference LA1 6 4 LED anode (+) connection 1 LA2 7 5 LED anode (+) connection 2 LA3 10 6 LED anode (+) connection 3 LA4 11 7 LED anode (+) connection 4 NC 1,2,8, 9,15,16 n.a. No connection; connect to GND PAD – – Exposed thermal pad THTH 3 1 Thermal threshold VIN 12 8 Supply

Automotive LED Array DriverA6262 Allegro MicroSystems Manchester, NH 03103-3353 U.S.A. www.allegromicro.com Supply and Reference VIN Functional Operating Range2 6 – 50 V VIN Quiescent Current IINQ LA[1:4] connected to VIN – – 10 mA VIN Sleep Current IINS EN = GND, VIN = 16 V – – 15 µA Startup Time tON VIN > 7 V to ILA1 < –5 mA, RREF = 125 Ω 5 15 30 µs Current Regulation Reference Current Ratio GH ILAx / IREF – 12.5 – – Current Accuracy3 EILAx –10 mA > ILAx > –100 mA –5 ±4 5 % Current Matching4 EIMLAx –20 mA > ILAx > –100 mA, VLAx match to within 1 V – 5 10 % Output Current, High Level ILAx EN = high – GH × IREF – – IREF = 8 mA, EN = high –105 –100 –95 mA Maximum Output Current ILAxmax IREF = 9.2 mA, EN = high – – –110 mA Minimum Drop-out Voltage VDO VIN – VLAx , ILAx = –100 mA – – 800 mV VIN – VLAx , ILAx = –40 mA – – 660 mV Current Slew Time Current rising or falling between 10% and 90% 50 80 110 µs Logic Inputs EN and SW Input Low Voltage VIL – – 0.8 V Input High Voltage VIH 2 – – V Input Hysteresis (EN pin) VIhys 150 350 – mV Pull-Down Resistor (EN pin) RPD – 50 – kΩ Pull-Up Current (SW pin) IPU – 100 – µA SW Input Debounce Time tSW 10 – 50 ms Protection Short Detect Voltage VSCD Measured at LAx 1.2 – 1.8 V Short Circuit Source Current ISCS Short present LAx to GND –2 –0.8 –0.5 mA Short Release Voltage VSCR Measured at LAx – – 1.9 V Short Release Voltage Hysteresis VSChys VSCR – VSCD 200 – 500 mV Thermal Monitor Activation Temperature TJM TJ with ISEN = 90%, THTH open 95 115 130 °C Thermal Monitor Slope dISEN/dTJ ISEN = 50%, THTH open –3.5 –2.5 –1.5 %/°C Thermal Monitor Low Current Temperature TJL TJ at ISEN = 25%, THTH open 120 135 150 °C Overtemperature Shutdown TJF Temperature increasing – 170 – °C Overtemperature Hysteresis TJhys Recovery = TJF – TJhys – 15 – °C 1For input and output current specifications, negative current is defined as coming out of (sourcing) the specified device pin. 2Function is correct but parameters are not guaranteed outside the general limits (7 to 40 V). 3When EN = high, EILAx = 100 × [( | ILAx | × RREF / 15 ) –1], with ILAx in mA and RREF in kΩ. 4EIMLA = 100 × [ max ( | ILAx– ILA(AV) | ) / ILA(AV) ] , where ILA(AV) is the average current of all active outputs. ELECTRICAL CHARACTERISTICS1 Valid at TJ = –40°C to 150°C, VIN = 7 to 40 ; unless otherwise noted Characteristics Symbol Test Conditions Min. Typ. Max. Unit

Automotive LED Array DriverA6262 Allegro MicroSystems Manchester, NH 03103-3353 U.S.A. www.allegromicro.com Functional Description The A6262 is a linear current regulator that is designed to pro- vide drive current and protection for parallel strings of series- connected high brightness LEDs in automotive applications. It provides up to four matched programmable current outputs at up to 100 mA, with low minimum dropout voltages below the main supply voltage. For 12 V power net applications, optimum performance is achieved when driving 4 strings of 1 to 3 LEDs, at current up to 100 mA per string. The A6262 is specifically designed for use in internal illumina- tion applications where the LED activity is controlled by a PWM signal, by a logic signal, or by a push-to-make, ground-connected switch. Current regulation is maintained and the LEDs protected during a short to ground at any point in the LED string. A short to ground on any regulator output terminal will disable that output until the short is removed. Open load on any output will be ignored. Integrated thermal management reduces the regulated current level at high internal junction temperatures to limit power dis- sipation. Pin Functions VIN Supply to the control circuit and current regulators. A small value ceramic bypass capacitor, typically 100 nF, should be con- nected from close to this pin to the GND pin. GND Ground reference connection. Should be connected directly to the negative supply. EN Logic input to enable LED current output. This provides a direct on/off action and can be used for direct PWM control. The EN input overrides the SW input when EN is high. When EN transitions from high to low, SW input logic is reset to off. SW Logic input to toggle LED current output on and off. A single push-to-make switch between SW and GND will provide push-to-make/push-to-break, on/off toggle action. The SW input is debounced by typically 30 ms and is internally pulled to typi- cally 3 V, with approximately 100 µA. IREF 1.2 V reference to set current reference. Connect resistor, RREF , to GND to set reference current. THTH Sets the thermal monitor threshold, TJM , where the output current starts to reduce with increasing temperature. Connecting THTH directly to GND will disable the thermal monitor function. LA[1:4] Current source connected to the anode of the first LED in each string. Connect directly to VIN to disable the respective output. In this document “LAx” indicates any one of the outputs. LED Current Level The LED current is controlled by a matching linear current regu- lator between the VIN pin and each of the LAx outputs. The basic equation that determines the nominal output current at each LAx pin is: Given EN = high, ILAx = RREF K (1) where ILAx is in mA and RREF is in kΩ; K is 15. The output current may be reduced from the set level by the ther- mal monitor circuit. Conversely the reference resistors may be calculated from: ILAx =RREF K (2) where ILAx is in mA and RREF is in kΩ. For example, where the required current is 90 mA for all four channels the resistor value will be: = =RREF 167 Ω15 It is important to note that because the A6262 is a linear regu- lator, the maximum regulated current is limited by the power dissipation and the thermal management in the application. All current calculations assume adequate heatsinking for the dissi- pated power. Thermal management is at least as important as the electrical design in all applications. In high current high ambient temperature applications, the thermal management is the most important aspect of the systems design. The application section below provides further detail on thermal management and the associated limitations. Operation with Fewer LED Strings or Higher Currents The A6262 may be configured to use fewer than the maximum quantity of LED strings: by connecting outputs together for higher currents, by leaving the outputs open, or by connecting the output directly to VIN to disable the regulator for that output.

Manchester, NH 03103-3353 U.S.A.

• The current regulators between VIN and each LAx output pro- vide a natural current limit due to the regulation.
• Each LAx output includes a short-to-ground detector that will disable the output to limit the dissipation.
• The thermal monitor reduces the regulated current as the tem- perature rises.
• Thermal shutdown completely disables the outputs under ex- treme overtemperature conditions. Short Circuit Detection A short to ground on any LED cathode (figure 1A) will not result in a short fault condition. The current through the remaining LEDs will remain in regulation and the LEDs will be protected. Due to the difference in the voltage drop across the LEDs, as a result of the short, the current match- ing in the A6262 may exceed the specified limits. Any LAx output that is pulled below the short detect voltage (fig- ure 1B) will disable the regulator on that output. A small current will be sourced from the disabled output to monitor the short and detect when it is removed. When the voltage at LAx rises above the short detect voltage, the regulator will be re-enabled. A shorted LED (figure 1C) will not result in a short fault condi- tion. The current through the remaining LEDs will remain in regulation and the LEDs will be protected. Due to the difference in the voltage drop across the LEDs, as a result of the short, the current matching in the A6262 may exceed the specified limits. A short between LEDs in different strings (figure 1D) will not result in a short fault condition. The current through the remain- ing LEDs will remain in regulation and the LEDs will be pro- tected. The current will be summed and shared by the affected strings. Current matching in the strings will then depend on the LED forward voltage differences. Temperature Monitor A temperature monitor function, included in the A6262, reduces the LED current as the silicon junction temperature of the A6262 increases (see figure 2). By mounting the A6262 on the same thermal substrate as the LEDs, this feature can also be used to limit the dissipation of the LEDs. A6262 VIN GND LA2 LA1 LA3 LA4 A6262 VIN GND LA2 LA1 LA3 LA4 A6262 VIN GND LA2 LA1 LA3 LA4 A6262 VIN GND LA2 LA1 LA3 LA4 A. Any LED cathode short to ground. Current remains regulated in non-shorted LEDs. Matching may be affected. B. Any LAx output short to ground. Shorted output is disabled. Other outputs remain active. C. Current remains regulated. Matching may be affected. Only the shorted LED is inactive. D. Short between LEDs in different strings. Current remains regulated. Current is summed and shared by affected strings. Intensity match dependent on voltage binning.

Figure 1. Short circuit conditions.

Manchester, NH 03103-3353 U.S.A. is specified, in the characteristics table, at the 90% current level. value, the THTH pin resistor can be decided from Figure 3b. up voltage is 3 V, use a 100 kΩ resistor. small and TJM is increased to close to the shutdown temperature. Figure 2. Temperature monitor current reduction. Figure 3a. Relationship between TJM and VTHTH. Figure 3b. Typical Resistor Values to Set Voltage on THTH Pin.

Automotive LED Array DriverA6262 Allegro MicroSystems Manchester, NH 03103-3353 U.S.A. www.allegromicro.com

Application Information

The most critical design considerations when using a linear regu- lator such as the A6262 are the power produced internally as heat and the rate at which that heat can be dissipated. There are three sources of power dissipation in the A6262:

• The quiescent power to run the control circuits
• The power in the reference circuit
• The power due to the regulator voltage drop The elements relating to these dissipation sources are illustrated in figure 4. Quiescent Power The quiescent power is the product of the quiescent current, IINQ , and the supply voltage, VIN , and is not related to the regulated current. The quiescent power, PQ, is there- fore defined as: PQ = VIN × IINQ (3) Reference Power The reference circuit draws the reference current from the supply and passes it through the reference resis- tor to ground. The reference current is 8% of the output current on any one active output. The reference circuit power is the prod- uct of the reference current and the difference between the supply voltage and the reference voltage, typically 1.2 V. The reference power, PREF , is therefore defined as: PREF = RREF (VIN – VREF) × VREF (4) Regulator Power In most application circuits the largest dis- sipation will be produced by the output current regulators. The power dissipated in each current regulator is simply the product of the output current and the voltage drop across the regulator. The total current regulator dissipation is the sum of the dissipa- tion in each output regulator. The regulator power for each output is defined as: PREGx = (VIN – VLEDx ) × ILEDx (5) where x is 1, 2, 3, or 4. Note that the voltage drop across the regulator, VREG , is always greater than the specified minimum drop-out voltage, VDO . The output current is regulated by making this voltage large enough to provide the voltage drop from the supply voltage to the total forward voltage of all LEDs in series, VLED . The total power dissipated in the A6262 is the sum of the quies- cent power, the reference power, and the power in each of the our regulators: PDIS = PQ + PREF + PREGA + PREGB + PREGC + PREGD (6) The power that is dissipated in each string of LEDs is: PLEDx = VLEDx × ILEDx (7) where x is A, B, C, or D, and VLEDx is the voltage across all LEDs in the string.

Figure 4. Internal power dissipation sources.

Manchester, NH 03103-3353 U.S.A. by the A6262: thermal shutdown and thermal foldback. a few milliseconds to a few seconds. A6262, then the thermal foldback feature will have time to act. current and therefore the dissipation. as the thermal foldback feature acts. Figure 5. Power Dissipation versus Supply Voltage Figure 6. LED current versus Supply Voltage Figure 7. Junction Temperature versus Supply Voltage

4 Strings

Manchester, NH 03103-3353 U.S.A. resistance from the silicon to the ambient temperature is 40°C/W. cant amount of thermal vias as described below. substrate or by adding a heatsink. targets over a specified voltage range.

• For maximum supply voltage the limiting factor is the power that can be dissipated from the regulator without exceeding the temperature at which the thermal foldback starts to reduce the output current below an acceptable level.
• For minimum supply voltage the limiting factor is the maximum drop-out voltage of the regulator, where the difference between the load voltage and the supply is insufficient for the regulator to maintain control over the output current. Minimum Supply Limit: Regulator Saturation Voltage The supply voltage, VIN , is always the sum of the voltage drop across the high-side regulator, VREG , and the forward voltage of the LEDs in the string, VLED, as shown in figure 4. VLED is constant for a given current and does not vary with supply voltage. Therefore VREG provides the variable difference between VLED and VIN . VREG has a minimum value below which the regulator can no longer be guaranteed to maintain the output current within the specified accuracy. This level is defined as the regulator drop-out voltage, VDO. The minimum supply voltage, below which the LED current does not meet the specified accuracy, is therefore determined by the sum of the minimum drop-out voltage, VDO , and the forward voltage of the LEDs in the string, VLED . The supply voltage must

Figure 8. Board via layout for thermal dissipation: (top) LP package and (bottom) LY package.

Automotive LED Array DriverA6262 Allegro MicroSystems Manchester, NH 03103-3353 U.S.A. www.allegromicro.com always be greater than this value and the minimum specified sup- ply voltage, that is: VIN > VDO + VLED, and VIN > VIN (min) (9) As an example, consider the configuration used in figures 6 and 7 above, namely 4 strings of 3 red LEDs, each string running at 50 mA, with each LED forward voltage at 2.3 V. The minimum supply voltage will be approximately: Maximum Supply Limit: Thermal Limitation As described above, when the thermal monitor reaches the activation tempera- ture, TJM (due to increased power dissipation as the supply volt- age rises), the thermal foldback feature causes the output current to decrease. The maximum supply voltage is therefore defined as the voltage above which the LED current drops below the accept- able minimum. This can be estimated by determining the maximum power that can be dissipated before the internal (junction) temperature of the A6262 reaches TJM. Note that, if the thermal monitor circuit is disabled (by connect- ing the THTH pin to GND), then the maximum supply limit will be the specified maximum continuous operating temperature, 150°C. The maximum power dissipation is therefore defined as: PD(max) = RθJA ∆T(max) (10) where ΔT(max) is difference between the thermal monitor activa- tion temperature, TJM , of the A6262 and the maximum ambient temperature, TA(max), and RθJA is the thermal resistance from the internal junctions in the silicon to the ambient environment. If minimum LED current is not a critical factor, then the maxi- mum voltage is simply the absolute maximum specified in the parameter tables above. Application Examples Operation with High-Side PWM Supply In some filament bulb replacement applications the supply may be provided by a PWM-driven high-side switch. The A6262 can be used in this application by simply connecting EN to VIN. The toggle action of the SW input will be reset to off at each power-up. In addition, in all cases when EN is high, the EN input will override the SW toggle status and enable the outputs. At the high-to-low transition of EN, the SW toggle will always be reset to the off state. When power is applied, there will be a short startup delay, tON , before the current starts to rise. The rise time of the current will be limited by the internal current slew rate control. Figures 9a to 9c show application circuit options, including a higher voltage supply, and combinations of outputs tied together and disabled. Operation with both EN and SW In some applications it may be required to utilize the functionality of both the EN input and the SW input. For example, in dome lighting, where a manual switch may be used to turn the light on and the lighting control unit may dim the light to off (see figure 10). In these cases, it is important to understand the interaction of the two control inputs.

• In all cases, when EN is high the EN input will override the SW toggle status and enable the outputs.
• When EN is low the SW input can be used to toggle the outputs on and off.
• The only time there is any interaction between the EN input and the SW toggle is the high-to-low transition of EN, where the SW toggle will always be reset to the off state.
• The SW toggle will also be reset to the off state at power-up.

Manchester, NH 03103-3353 U.S.A.

12 V PWM

24 V power net

Figure 10. Typical applications using SW and EN together Figure 9. Typical applications with various supply and output options.

Manchester, NH 03103-3353 U.S.A. IREF pin to set appropriate current through various LED batches. Figure 11. Application Circuit for Binning – Current-setting resistor (RREF2)

Automotive LED Array DriverA6262 Allegro MicroSystems Manchester, NH 03103-3353 U.S.A. www.allegromicro.com Package LP, 16-Pin TSSOP with Exposed Thermal Pad C SEATING PLANE C0.10 16× 6.10 0.65 0.45 1.70 3.00 5.00 ±0.10 3.00 3.00 3.00

1.20 MAX

0.15 0.025

0.65 BSC

0.25 BSC

1.00 REF

0.60 ±0.15 0.30 0.19 0.22 0.09 GAUGE PLANE SEATING PLANE B A A Terminal #1 mark area B Reference land pattern layout (reference IPC7351 SOP65P640X110-17M); All pads a minimum of 0.20 mm from all adjacent pads; adjust as necessary to meet application process requirements and PCB layout tolerances; when mounting on a multilayer PCB, thermal vias at the exposed thermal pad land can improve thermal dissipation (reference EIA/JEDEC Standard JESD51-5) PCB Layout Reference View Exposed thermal pad (bottom surface) C C D Standard Branding Reference View XXXXXXX Date Code Lot Number Line 1, 2 = 7 characters Line 3 = 5 characters Line 1: Part Number Line 2: Logo A, 4 digit Date Code Line 3: Characters 5, 6, 7, 8 of Assembly Lot Number Branding scale and appearance at supplier discretionD For Reference Only – Not for Tooling Use (Reference JEDEC MO-153 ABT; Allegro DWG-0000379, Rev. 3) Dimensions in millimeters – NOT TO SCALE Dimensions exclusive of mold flash, gate burrs, and dambar protrusions Exact case and lead configuration at supplier discretion within limits shown

Automotive LED Array DriverA6262 Allegro MicroSystems Manchester, NH 03103-3353 U.S.A. www.allegromicro.com Package LY, 10-Pin MSOP with Exposed Thermal Pad For Reference Only – Not for Tooling Use (Reference Allegro DWG-0000390, Rev. 2 and JEDEC MO-187) Dimensions in millimeters– NOT TO SCALE Dimensions exclusive of moldfl ash, gate burrs, and dambar protrusions Exact case and lead configuration at supplier discretion within limits shown A 3.00 ±0.10 +0.20 0.25 0.53 0.15 ±0.05 0° to 6° Seating Plane Gauge Plane –0.10 +0.11

2.00 BSC

1.60 BSC

B 0.96 SEATING PLANE 0.50 REF 0.05 0.15 0.27 0.18 –0.15 +0.10 Date Code Lot Number XXXXX C Lines 1, 2 = 5 characters. Line 3 = 3 characters. Line 1: Part Number Line 2: 4-digit Date Code Line 3: Characters 5, 6, 7 of Asembly Lot Number Right Align Standard Branding Reference View A B Exposed thermal pad (bottom surface) Terminal #1 mark area C Branding scale and appearance at supplier discretion 0.10

Automotive LED Array DriverA6262 Allegro MicroSystems Manchester, NH 03103-3353 U.S.A. www.allegromicro.com For the latest version of this document, visit our website: www.allegromicro.com

Revision History

6 June 24, 2013 Update Features List, figure 5

7 June 25, 2015 Temperature Monitor text on page 7 updated to match EC table: derating slope is -2.5% per °C 8 July 26, 2016 Revised Temperature Monitor section (page 7) and added Binning Resistor Arrangement section (page 13)

9 May 28, 2020 Minor editorial updates

10 June 3, 2022 Updated package drawings (pages 14-15)

Copyright 2022, Allegro MicroSystems. Allegro MicroSystems reserves the right to make, from time to time, such departures from the detail specifications as may be required to permit improvements in the performance, reliability, or manufacturability of its products. Before placing an order, the user is cautioned to verify that the information being relied upon is current. Allegro’s products are not to be used in any devices or systems, including but not limited to life support devices or systems, in which a failure of Allegro’s product can reasonably be expected to cause bodily harm. The information included herein is believed to be accurate and reliable. However, Allegro MicroSystems assumes no responsibility for its use; nor for any infringement of patents or other rights of third parties which may result from its use. Copies of this document are considered uncontrolled documents.