High-Voltage, 350mA, Adjustable Linear High-Brightness LED (HB LED) Driver

Transcription

1 19-383; Rev 1; 4/9 High-Voltage, 35mA, Adjustable Linear General Description The current regulator operates from a 6.5V to 4V input voltage range and delivers up to a total of 35mA to one or more strings of high-brightness LEDs. The output current of the is adjusted by using an external current-sense resistor in series with the LEDs. An enable input allows wide-range pulsed dimming. Wave-shaping circuitry reduces EMI. The differential current-sense input increases noise immunity. The is well suited for applications requiring high-voltage input and is able to withstand automotive load-dump events up to 4V. An on-board pass element minimizes external components while providing ±3.5% output current accuracy. Additional features include a 5V regulated output and short-circuit and thermal protection. The is available in a thermally enhanced, 5mm x 5mm, 16-pin TQFN package and is specified over the automotive -4 C to +125 C temperature range. Applications Automotive Interior: Map, Courtesy, and Cluster Lighting Automotive Exterior: Tail Lights and CHMSL Warning Lights for Emergency Vehicles Navigation and Marine Indicators General Illumination Signage, Gasoline Canopies, Beacons Pin Configuration Features +6.5V to +4V Operating Range Adjustable Level (35mA to 35mA) ±3.5% Output Current Accuracy Integrated Pass Element with Low-Dropout Voltage (.5V typ) Output Short-Circuit Protection +5V Regulated Output with 4mA Source Capability Thermal Shutdown Differential LED Current Sense High-Voltage Enable Pin for Dimming Interface Low Shutdown Supply Current (12μA typ) Low 24mV Current-Sense Reference Reduces Power Losses Wave-Shaped Soft Edges Reduce Radiated EMI During PWM Dimming Available in Small, Thermally Enhanced, 5mm x 5mm, 16-Pin TQFN Package -4 C to +125 C Operating Temperature Range Ordering Information PART TEMP RANGE P-PACKAGE ATE+ -4 C to +125 C 16 TQFN-EP* ATE/V+ -4 C to +125 C 16 TQFN-EP* +Denotes a lead(pb)-free/rohs-compliant package. *EP = Exposed paddle. /V denotes an automotive qualified part. Simplified Diagram TOP VIEW EN V TO +4V.1μF PWM DIMMG EN +5V REG.1μF LEDs RSENSE TQFN Maxim Integrated Products 1 For pricing, delivery, and ordering information, please contact Maxim Direct at , or visit Maxim s website at

2 ABSOLUTE MAXIMUM RATGS,, and EN to...-.3v to +45V, to...-.3v to +6V to...-.3v to +.3V Short Circuited to Duration (at V = +16V)...6 minutes Maximum Current Into Any Pin (except V and )...±2mA Continuous Power Dissipation (T A = +7 C) 16-Pin TQFN 5mm x 5mm (derate 33.3mW/ C above +7 C) mW Operating Junction Temperature Range...-4 C to +125 C Junction Temperature C Storage Temperature Range C to +15 C Lead Temperature (soldering, 1s)...+3 C Stresses beyond those listed under Absolute Maximum Ratings may 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 in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ELECTRICAL CHARACTERISTICS (V = +12V, EN = V, C =.1µF to, I =, =, connect R SENSE =.58Ω between and. Connect to (Note 1). T J = -4 C to +125 C, unless otherwise noted. Typical values are at T A = +25 C.) (Note 2) PARAMETER SYMBOL CONDITIONS M TYP MAX UNITS Supply Voltage Range V (Note 1) V Ground Current I G I LOAD = 35mA ma Shutdown Supply Current I SHDN V EN.6V 12 4 μa Guaranteed Output Current I R SENSE = ma Output Current Accuracy 35mA < I < 35mA ±3.5 % Dropout Voltage (Note 3) Output Current Slew Rate VDO I = 35mA (current pulsed), 12V < V < 4V I = 35mA (current pulsed), 6.5V < V < 4V Current rising 5.4 Current falling V V Short-Circuit Current V = V, V = 12V ma LOGIC PUT EN Input Current I EN 1 na EN Input Voltage High V IH 2.8 V EN Input Voltage Low V IL.6 V Turn On Time t ON EN rising edge to 9% of μs CURRENT SENSE (Note 4) Regulated R SENSE Voltage V RSNS V SENSE = V - V mv Input Current () V = 22mV -14 μa Input Current () V = 22mV +84 μa ma/μs 2

3 ELECTRICAL CHARACTERISTICS (continued) (V = +12V, EN = V, C =.1µF to, I =, =, connect R SENSE =.58Ω between and. Connect to (Note 1). T J = -4 C to +125 C, unless otherwise noted. Typical values are at T A = +25 C.) (Note 2) PARAMETER SYMBOL CONDITIONS M TYP MAX UNITS THERMAL OVERLOAD Thermal-Shutdown Temperature +155 C Thermal-Shutdown Hysteresis 23 C +5V REGULATOR Output Voltage Regulation V Output Voltage Change < I LOAD < 4mA (Note 5) 15 6 Short-Circuit Current = V (Note 6) 3 ma Note 1: Resistors were added from to to aid with the power dissipation during testing. Note 2: All devices 1% production tested at T A = +25 C. Limits over the operating temperature range are guaranteed by design. Note 3: Dropout is measured as follows: Connect R O = 27Ω from to. Connect R SENSE =.58Ω from to. Set V = +12V (record V as V 1 ). Reduce V until V =.97 x V 1 (record as V 2 and V 2 ). ΔV DO = V 2 - V 2. Note 4: I = ma. Note 5: Current regulation varies with load (see the Typical Operating Characteristics). Note 6: Thermal shutdown does not function if the output of the 5V reference is shorted to ground. (V = V EN = +12V, T A = +25 C, unless otherwise noted.) Typical Operating Characteristics PUT CURRENT (ma) PUT CURRENT vs. TEMPERATURE ILOAD = 35mA ILOAD = 2mA ILOAD = 1mA ILOAD = 35mA TEMPERATURE ( C) toc1 (V - V) (V) (V - V) vs. PUT CURRENT V = 12V PUT CURRENT (ma) toc2 PUT CURRENT (ma) PUT CURRENT vs. PUT VOLTAGE PUT VOLTAGE (V) toc3 3

4 Typical Operating Characteristics (continued) (V = V EN = +12V, T A = +25 C, unless otherwise noted.) DROP VOLTAGE (V) DROP VOLTAGE vs. TEMPERATURE ILOAD = 35mA TEMPERATURE ( C) toc4 SHUTDOWN CURRENT (μa) SHUTDOWN CURRENT vs. TEMPERATURE V = 4V V = 2V V = 12V V = 6.5V TEMPERATURE ( C) toc5 5V REGULATOR PUT (V) V REGULATOR PUT vs. TEMPERATURE ILOAD = 1mA ILOAD = 5mA NO LOAD TEMPERATURE ( C) toc6 (V - V) (V) (V - V) vs. I ILOAD = 41mA I (ma) toc7 5V REGULATOR PUT (V) V REGULATOR PUT vs. V NO LOAD LOAD = 1mA LOAD = 5mA V (V) toc8 2Hz DIMMED OPERATION ILOAD = 35mA, V = VEN, V PULSED AT 2Hz (5% DUTY CYCLE) 1ms/div toc9 V 5V/div V ILOAD 2mA/div 2Hz DIMMED OPERATION EXPANDED toc1 2Hz DIMMED OPERATION EXPANDED toc11 2Hz DIMMED OPERATION toc12 V 5V/div V 5V/div EN 1V/div ILOAD = 35mA, V = VEN, V PULSED AT 2Hz (5% DUTY CYCLE) V ILOAD 1mA/div ILOAD = 35mA, V = VEN, V PULSED AT 2Hz (5% DUTY CYCLE) V ILED 1mA/div ILOAD = 35mA, V = 12V, EN PULSED AT 2Hz (5% DUTY CYCLE) V ILED 1mA/div 2μs/div 4μs/div 1ms/div 4

5 P NAME FUNCTION 1, 16 Current-Regulated Output. Connect pin 1 to pin 16. Pin Description 2, 3 Positive Input Supply. Bypass with a.1µf (min) capacitor to. Connect pin 2 to pin , 13, 14 Not Internally Connected 9 Positive Input of the Internal Differential Amplifier. Connect the current-sense resistor between and to program the output current level. EP Exposed Pad. Connect to the ground plane for effective power dissipation. Do not use as the only ground connection. Functional Diagram REGULATOR EN ENABLE REFERENCE GENERATOR I_ REQ DIFFERENTIAL SENSE AMPLIFIER 1 Negative Input of the Internal Differential Amplifier. Connect the current-sense resistor between and to program the output current level V Regulated Output. Connect a.1µf capacitor from to. 12 Ground 15 EN Enable Input. Drive EN high to enable the output. THERMAL SHUTDOWN Detailed Description The is a high-current regulator capable of providing up to a total of 35mA of current to one or more strings of high-brightness LEDs. A wide operating input voltage range of +6.5V to +4V makes the ideal for automotive applications. A +5V regulated output provides up to 4mA of current to power external circuitry. In addition, the features thermal and output short-circuit protection. The wide operating voltage range helps protect the against large transients such as those found in load-dump situations up to 4V. The uses a feedback loop to control the output current. The differential voltage across the sense resistor is compared to a fixed reference voltage, and the error is amplified to serve as the drive to the internal 5

6 power series pass device (see the Functional Diagram). The regulation point is factory set at (V - V ) = 24mV ±3.5%. The regulated current is user defined by the value of R SENSE. The is a current controller internally optimized for driving the impedance range expected from one or more HB LEDs. +5V Regulator The includes a fixed +5V output regulator that delivers up to 4mA of load current for low-power applications throughout the +6.5V to +4V input voltage range. Connect a.1µf compensation capacitor from to ground. Shorting to ground disables the thermal shutdown. Thermal Protection The enters a thermal-shutdown mode in the event of overheating. This typically occurs in overload or output short-circuit conditions. When the junction temperature exceeds T J = +155 C (typ), the internal thermal-protection circuitry turns off the series pass device. The recovers from thermal-shutdown mode once the junction temperature drops by 23 C (typ). The part will therefore protect itself by thermally cycling in the event of a short-circuit or overload condition. Applications Information Programming the LED Current The uses a sense resistor across and to set the LED current. The differential sense amplifier connected across R SENSE provides ground-loop immunity and low-frequency noise rejection. The LED current is given by the equation below: I LED = V SENSE / R SENSE Input Voltage Considerations For proper operation, the minimum input voltage must always be +1.2V (+1.5V for V <+12V) higher than the worst-case sum of all the forward drops of all seriesconnected LEDs to the output of the. The minimum operating voltage of the device is +6.5V. The device will operate below +6.5V; however, output current may not meet the full regulation specification (see the Typical Operating Characteristics). Low-Frequency PWM at the Output The provides pulsed or chopped current dimming. Generally, high-brightness LEDs are binned to match at their full-rated current; however, LEDs from the same bin exhibit poor matching at currents other than full-rated current. To achieve uniformity, HB LED manufacturers recommend PWM pulsing of the LED current at their full-rated value. There are two methods for producing a PWM output. One method is by pulsing the enable input (EN) while having a constant voltage at. The other method is to connect EN to and pulse both EN and. Both methods generate a regulated-amplitude PWM current (variable duty cycle) that can provide control over the LED brightness (see Figures 1 and 2). VEN V C EN C2 D1 ILED R SENSE V C EN C2 D1 ILED R SENSE Figure 1. Pulse Application with V at a Constant Voltage Figure 2. Pulse Application with EN Connected to V 6

7 V C Typical Operating Circuit EN C2 D1 R SENSE PROCESS: BiCMOS Chip Information Package Information For the latest package outline information and land patterns, go to PACKAGE TYPE PACKAGE CODE DOCUMENT NO. 16 TQFN-EP T

8 REVISION NUMBER REVISION DATE DESCRIPTION Revision History PAGES CHANGED 8/5 Initial release 1 4/9 Updated data sheet with automotive part. 1, 8 Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. 8 Maxim Integrated Products, 12 San Gabriel Drive, Sunnyvale, CA Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc.