A6260

A6260 ALLEGRO

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Description

The A6260 is a linear, programmable current regulator providing up to 350 mA for driving high-brightness LEDs. The LED current, accurate to 4%, is set by a single low-power sense resistor. Driving LEDs with constant current ensures safe operation with maximum possible light output. For automotive applications, optimum performance is achieved when driving between 1 and 3 LEDs at cur- rents up to 350 mA. The low dropout voltage of the A6260 allows a single white LED to be driven safely, at full current, with a supply voltage down to 6 V . An enable input allows PWM dimming and can be used to enable low-current sleep mode. The rate of change of current during PWM switching is limited to reduce EMI. Overcurrent detection is provided to protect the LEDs and the A6260 during short-to-supply or short-to-ground at any LED terminal. The integrated temperature monitor can be used to reduce the LED drive current if the chip temperature exceeds the thermal limit. The device is available in an 8-pin SOIC package with exposed thermal pad (suffix LJ). The device is lead (Pb) free with 100% matte-tin leadframe plating. 6260-DS Features and Benefits ▪ Automotive grade ▪ LED drive current up to 350 mA ▪ 6 to 40 V supply ▪ Reverse battery protection ▪ Low drop-out voltage ▪ LED short circuit and thermal protection ▪ 10 μA maximum shutdown current ▪ PWM dimming control input ▪ Current slew rate limiting High Brightness LED Current Regulator Package: 8-pin SOIC with exposed thermal pad (suffix LJ) Typical Application Not to scale A6260 7 to 20 V (–14 V min, 40 V max) LA PWM Dimming and On-Off Control EN VIN SENSE GND Automotive

12 V Power Net

High Brightness LED Current RegulatorA6260 2Allegro MicroSystems, Inc.

115 Northeast Cutoff

Worcester, Massachusetts 01615-0036 U.S.A. Selection Guide Part Number Packing A6260KLJTR-T 3000 pieces per reel THERMAL CHARACTERISTICS may require derating at maximum conditions Characteristic Symbol Test Conditions* Value Units Package Thermal Resistance RθJA 4-layer PCB based on JEDEC standard 35 ºC/W 2-layer PCB with 0.8 in.2 of copper area each side 62 ºC/W RθJP 2 ºC/W *Additional thermal information available on Allegro website. Absolute Maximum Ratings* Characteristic Symbol Notes Rating Units Load Supply Voltage V IN –14 to 40 V EN Pin Voltage V EN –14 to 40 V LA and LC Pins Voltage V Lx –0.3 to 40 V LSS Pin Voltage V LSS –0.3 to 0.3 V SENSE Pin Voltage V SENSE –0.3 to 0.3 V THTH Pin Voltage V THTH –0.3 to 7 V Ambient Operating Temperature Range T A Range K –40 to 125 ºC Junction Operating Temperature Range T J –40 to 150 ºC Storage Temperature Range T stg –55 to 150 ºC ESD Rating, Human Body Model AEC-Q100-002, all pins 2000 V ESD Rating, Charged Device Model AEC-Q100-011, all pins 1050 V *With respect to GND.

High Brightness LED Current RegulatorA6260 3Allegro MicroSystems, Inc. Worcester, Massachusetts 01615-0036 U.S.A. Functional Block Diagram LA VIN SENSE Reg GND Reference Generator EN VBATT R S Current Regulator Current Limited Switch Slew Limit LSS Output Monitor Temp Monitor Temp Comp LC Control Logic THTH RTH Terminal List Table Number Name Description

1 SENSE Current sense input

2 GND Ground reference

3 THTH Thermal threshold input

4 EN Enable input

5 VIN Main supply

6 LA LED anode (+) connection

7 LC LED cathode (-) connection

8 LSS Low-side sense connection

High Brightness LED Current RegulatorA6260 4Allegro MicroSystems, Inc. Worcester, Massachusetts 01615-0036 U.S.A. Characteristics Symbol Test Conditions Min. Typ. Max. Units Supply and Reference V IN Functional Operating Range1 VIN 6 – 40 V VIN Quiescent Current I INQ LA, LC unconnected – – 4 mA VIN Shutdown Current I INS EN < 400 mV – 1 10 μA Startup Time t ON EN 2 V to 35 mA ILC 91 8 2 7 μs Current Regulation Maximum Current Sink I LCmax RS = 250 mW, VIN – VLA > 2 V 350 – – mA Current Sink I LC RS = 286 mW, VIN – VLA > 2 V 333 350 367 mA Current Sink Accuracy err ILC 100 mA < ILC < 350 mA –5 ±4 5 % SENSE Reference Voltage V SENREF 260 mΩ < RS < 1Ω 97 102 107 mV Switch Dropout Voltage V DO VIN – VLA , ILOAD = 350 mA – 2.25 2.35 V VIN – VLA , ILOAD = 150 mA – 1.35 1.4 V Regulator Saturation Voltage V SAT VLC – VSENSE, ILOAD = 350 mA – 500 550 mV VLC – VSENSE, ILOAD = 150 mA – 250 275 mV Output Current Slew Time tr Current rising from 10% to 90% 50 80 120 μs tf Current falling from 90% to 10% 60 100 150 μs Logic Input Input Low Voltage V IL – – 0.8 V Input High Voltage V IH 2––V Input Hysteresis V Ihys 150 350 – mV Protection Switch Overcurrent Trip Level I LAOC –600 –500 –400 mA Overcurrent Detection Time2 tOCD From detection to ISCU > –1.2 mA – 3 – μs Switch Current Limit I LALIM – 1.5× ILAOC –m A LC Short Circuit Release Voltage V SCCR Measured at VLC, when rising 1.0 1.2 1.4 V Short Circuit Source Current2 ISCU When short is detected –1.5 –1.1 –0.7 mA Thermal Monitor Activation Temperature T JM TJ at ILC = 90%, THTH open 90 105 120 ºC Thermal Monitor Low Current Temperature T JL TJ at ILC = 25%, THTH open 110 130 150 ºC Overtemperature Shutdown Threshold T JF Temperature increasing – 165 – ºC Overtemperature Hysteresis T Jhys Recovery = TJF – TJhys –1 5–º C 1Functions correctly, but parameters are not guaranteed, below the general limit (7 V). 2For input and output current specifications, negative current is defined as coming out of (sourcing) the specified device pin. ELECTRICAL CHARACTERISTICS valid at TJ = –40°C to 150°C, VIN = 7 to 40 V, unless noted otherwise

High Brightness LED Current RegulatorA6260 5Allegro MicroSystems, Inc. Worcester, Massachusetts 01615-0036 U.S.A. The A6260 is a linear current regulator that is designed to provide drive current and protection for series-connected, high bright- ness LEDs in automotive applications. It provides programmable current output at load voltages up to 3 V below the main supply voltage. For automotive applications optimum performance is achieved when driving 1 to 3 LEDs at currents up to 350 mA. The LED current is set by a single low-power sense resistor and the LED brightness can be further controlled by a PWM input to the EN pin. The EN input can also be used as an on/off switched input and the A6260 will enter a low current (<10 μA) sleep mode if EN is held low. For incandescent replacement configurations, the EN input can be connected directly to the VIN pin with the supply to VIN con- trolled by a simple on/off switch. The LEDs and the regulator are protected from excessive currents caused by short circuits to ground or supply or by reversal of the power supply connections. Integrated thermal management circuits can be used to reduce the regulated current level at high temperatures to limit power dissipation. Pin Functions VIN Pin Supply to the control circuit. A small-value ceramic bypass capacitor (typically 100 nF) should be connected from close to this pin to the GND pin. GND Pin Ground reference connection. Should be connected directly to the negative supply as close as possible to the bottom (ground connection) of the sense resistor. EN Pin Logic input to enable operation. Can be used as a direct PWM input. Chip enters a low-power sleep mode when this pin is held low. THTH Pin Sets the thermal monitor threshold, TJM, where the output current starts to be reduced with increasing temperature. When this pin is left open, the threshold temperature will typi- cally be the specified default value. A resistor connected between THTH and GND can be used to increase the threshold tempera- ture. A resistor connected between THTH and VIN can be used to decrease the threshold temperature. Connecting THTH directly to GND disables the thermal monitor function. LA Pin Switched and protected current source connected to the anode of the LEDs. LC Pin Controlled current sink connected to the cathode of the LEDs. LSS Pin Low-side current sink connection from the current regu- lator to power ground via a sense resistor. A current sense resistor (240 mΩ to 3 Ω) is connected between LSS and power ground. SENSE Pin LED current sense input. The high impedance SENSE input should have an independent connection to the top (LSS connection side) of the sense resistor. LED Current Level The LED current is controlled by the internal current regulator between the LC and LSS pins. This current, defined as the current into the LC pin, I LC, is set by the value, RS , of the sense resis- tor. The voltage across the sense resistor, measured between the SENSE pin and the GND pin, is compared to a reference voltage, nominally 102 mV , allowing the use of a low-value sense resistor with low power dissipation. The LED current is thus defined as: I LC = VSENREF / RS (1) conversely: R S = VSENREF / ILC The nominal output current settings, ILC, versus the current setting resistor values, RS, are given in the following table. The current level defined here is the 100% current level before any current reduction effects due to the temperature monitor, described later in this document. Sense Resistor Selection ILC (mA) RS (mΩ) PD(RS) (mW) ILC (mA) RS (mΩ) PD(RS) (mW) 350 286 35 125 800 13 300 333 30 100 1000 10 250 400 25 70 1429 7 200 500 20 50 2000 5 150 667 15 35 2857 4 Parallel operation The A6260 is a constant current controller, that is, it controls the output current irrespective of output voltage (within the compli- ance range). This allows the outputs of two or more A6260s to be connected in parallel (see figure 4e, in the Applications Infor- mation section). In this configuration, each A6260 must have a Functional Description

Worcester, Massachusetts 01615-0036 U.S.A. control input with little effect on the LED color. linear regulator and the high-side switch. the Electrical Characteristics table. high-side switch is bypassed. (See figure 4(d)). to the power supply under all conditions. than the overcurrent detection time, tOCD. current limit due to the regulation. extreme overtemperature conditions. voltages (see figure 4d in the Applications Information section). longer than the overcurrent detection time, tOCD (3 μs typical). Figure 1. Short circuit conditions detected

Worcester, Massachusetts 01615-0036 U.S.A. shutdown level, at which point the regulator will be disabled. longer than the overcurrent detection time, tOCD (3 μs typical). above VSCCR, and the switch and regulator are re-enabled. shutdown level, at which point the regulator will be disabled. also be used to reduce LED current as LED temperature increases. where RTH, in kΩ, is the resistor between THTH and GND. Figure 2. Temperature monitor current reduction

Worcester, Massachusetts 01615-0036 U.S.A. threshold provided by the specified hysteresis, TJhys. Figure 3. TJM versus RTH (pull-up or –down), and VTHTH

Worcester, Massachusetts 01615-0036 U.S.A. Figure 4. Typical applications circuits

High Brightness LED Current RegulatorA6260 10Allegro MicroSystems, Inc. Worcester, Massachusetts 01615-0036 U.S.A. Copyright ©2007, Allegro MicroSystems, Inc. Allegro MicroSystems, Inc. reserves the right to make, from time to time, such de par tures from the detail spec i fi ca tions as may be required to per- mit improvements in the per for mance, 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 life support devices or systems, if a failure of an Allegro product can reasonably be expected to cause the failure of that life support device or system, or to affect the safety or effectiveness of that device or system. The in for ma tion in clud ed herein is believed to be ac cu rate and reliable. How ev er, Allegro MicroSystems, Inc. assumes no re spon si bil i ty for its use; nor for any in fringe ment of patents or other rights of third parties which may result from its use. For the latest version of this document, visit our website: www.allegromicro.com Package LJ 8-Pin SOICN with Exposed Thermal Pad

1.75 MAX

0.18 4º 4.90 3.90 6.00 0.84 0.21 0.41 0.25 SEATING PLANE 1.27 C0.10 8X C B Exposed thermal pad (mounting side) GAUGE PLANE SEATING PLANE A A Terminal #1 mark area All dimensions nominal, not for tooling use (reference JEDEC MS-012 AA) Dimensions in millimeters 3.30 2.41 B