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19-4029; Rev 1; 5/08
High-Voltage, 350mA, High-Brightness LED Driver with PWM Dimming and 5V Regulator
General Description
The MAX16836 current regulator operates from a 6.5V to 40V input-voltage range and delivers up to a total of 350mA to one or more strings of high-brightness LEDs (HB LEDs). The output current of the MAX16836 is adjusted by using an external current-sense resistor in series with the LEDs. A dimming input allows widerange "pulsed" PWM operation. Wave-shaping circuitry reduces EMI. The differential current-sense input increases noise immunity. The MAX16836 is well suited for applications requiring a high-voltage input and is able to withstand automotive load-dump events up to 40V. 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 MAX16836 is available in a thermally enhanced, 5mm x 5mm, 16-pin TQFN package and is specified over the automotive -40C to +125C temperature range. o o o o o o o o o o o o o o o
Features
+6.5V to +40V Operating Range Adjustable LED Current (35mA to 350mA) 3.5% LED Current Accuracy High-Voltage DIM Pin for Dimming Interface Integrated Pass Element with Low-Dropout Voltage (0.55V typ) +5V Regulated Output with 4mA Source Capability Parallel Operation for LED Current > 350mA Differential LED Current Sense Low Shutdown Supply Current (35A typ) Low 200mV Current-Sense Reference Reduces Power Losses Wave-Shaped Edges Reduce Radiated EMI During PWM Dimming Thermal Shutdown Output Short-Circuit Protection Available in Small, Thermally Enhanced, 5mm x 5mm, 16-Pin TQFN Package -40C to +125C Operating Temperature Range
MAX16836
Applications
Automotive Interior: Map, Courtesy, and Cluster Lighting Automotive Exterior: Tail Lights and CHMSL Emergency Vehicle Warning Lights Navigation and Marine Indicators General Lighting Signage, Gasoline Canopies, Beacons
Ordering Information
PART MAX16836ATE+ TEMP RANGE -40C to +125C PIN-PACKAGE 16 TQFN-EP*
+Denotes a lead-free package. *EP = Exposed pad.
Pin Configuration
GND CS+ CS-
Simplified Diagram
+6.5V TO +40V IN 0.1F +5V REG OUT
TOP VIEW
12
11
V5
10
9
DIM 13 N.C. 14 EN 15 OUT 16
8 7
N.C. N.C. N.C. N.C. PWM DIMMING DIM
V5 0.1F EN
LEDs
MAX16836
CS+ RSENSE CSGND
MAX16836 +
1 OUT 2 IN 3 IN 4 N.C.
6 5
TQFN ________________________________________________________________ Maxim Integrated Products 1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim's website at www.maxim-ic.com.
High-Voltage, 350mA, High-Brightness LED Driver with PWM Dimming and 5V Regulator MAX16836
ABSOLUTE MAXIMUM RATINGS
IN to GND ...............................................................-0.3V to +45V OUT, DIM, and EN to GND ..........................-0.3V to (VIN + 0.3V) CS+, CS-, V5 to GND ...............................................-0.3V to +6V OUT Short Circuited to GND Duration (at VIN = +16V) .........................................................60 minutes Maximum Current into Any Pin (except IN and OUT) .........20mA Continuous Power Dissipation (TA = +70C) 16-Pin TQFN 5mm x 5mm (derate 33.3mW/C above +70C) ............................2666.7mW Junction to Case Thermal Resistance (JC) (Note 1) ........2C/W Junction to Ambient Thermal Resistance (JA) (Note 1) .....30C/W Operating Junction Temperature Range ...........-40C to +125C Junction Temperature ......................................................+150C Storage Temperature Range .............................-65C to +150C Lead Temperature (soldering, 10s) .................................+300C
Note 1: Package thermal resistances obtained using the method described in JEDEC specification JESD51-7, using a four-layer board. For detailed information on package thermal considerations, see www.maxim-ic.com/thermal-tutorial.
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
(VIN = VEN = +12V, CV5 = 0.1F to GND, IV5 = 0, VCS- = 0V, VDIM = +4V, connect RSENSE = 0.58 between CS+ and CS-. TA = -40C to +125C, unless otherwise noted. Typical values are at TA = +25C.) (Note 2)
PARAMETER Supply Voltage Range Ground Current Shutdown Supply Current Guaranteed Output Current Output Current Accuracy SYMBOL VIN IG ISHDN IOUT (Note 3) ILOAD = 350mA VEN 0.6V RSENSE = 0.55 35mA < IOUT < 350mA IOUT = 350mA (current pulsed), 12V < VIN < 40V IOUT = 350mA (current pulsed), 6.5V < VIN < 12V Current rising, VDIM rising to 4V Current falling, VDIM falling to 0.6V VIN = 12V, VCS+ = 0V IEN VIH VIL tON VSENSE VEN rising edge to 90% of OUT VSENSE = VCS+ - VCSVCS+ = 220mV VCS+ = 220mV VIH VIL tON tOFF After VDIM rising to 4V (Note 5) After VDIM falling to 0.6V (Note 5) -50 -2.5 4 0.6 110 70 193 -0.3 2.7 17.2 -1.0 -0.2 110 200 400 -2.5 2.8 0.6 350 207 +4.1 7.0 350 3.5 0.55 0.55 7.8 7.8 500 -1.0 650 -0.2 1.2 V 1.5 mA/s mA A V V s mV V A A A V V s s CONDITIONS MIN 6.5 1.28 35 TYP MAX 40.0 3 70 UNITS V mA A mA %
Dropout Voltage (Note 4)
VDO
Output Current Slew Rate Short-Circuit Current LOGIC INPUT EN Input Current EN Input Voltage High EN Input Voltage Low Turn-On Time CURRENT SENSE Regulated RSENSE Voltage CS- Voltage Range Input Current (CS+) Input Current (CS-) DIM Input Current DIM Input Voltage High DIM Input Voltage Low Turn-On Time Turn-Off Time
2
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High-Voltage, 350mA, High-Brightness LED Driver with PWM Dimming and 5V Regulator
ELECTRICAL CHARACTERISTICS (continued)
(VIN = VEN = +12V, CV5 = 0.1F to GND, IV5 = 0, VCS- = 0V, VDIM = +4V, connect RSENSE = 0.58 between CS+ and CS-. TA = -40C to +125C, unless otherwise noted. Typical values are at TA = +25C.) (Note 2)
PARAMETER THERMAL OVERLOAD Thermal-Shutdown Temperature Thermal-Shutdown Hysteresis +5V REGULATOR Output Voltage Regulation V5 Short-Circuit Current VV5 (Note 6) VV5 = 0V (Note 7) 4.85 5.00 15 5.20 V mA +159 24 C C SYMBOL CONDITIONS MIN TYP MAX UNITS
MAX16836
Note 2: All devices are 100% production tested at TA = +25C. Limits over the operating temperature range are guaranteed by design. Note 3: Resistors were added from OUT to CS+ to aid with the power dissipation during testing. Note 4: Dropout is measured as follows: Connect RO = 27 from OUT to CS+. Connect RSENSE = 0.58 from CS+ to CS-. Set VIN = +12V (record VOUT as VOUT1). Reduce VIN until VOUT = 0.97 x VOUT1 (record as VIN2 and VOUT2). VDO = VIN2 - VOUT2. Note 5: tON time includes the delay and the rise time needed for IOUT to reach 90% of its final value. tOFF time is the time needed for IOUT to drop below 10%. See the Typical Operating Characteristics. tON and tOFF are tested with 13 from OUT to CS+. Note 6: Current regulation varies with V5 load (see the Typical Operating Characteristics). Note 7: Thermal shutdown does not function if the output of the 5V reference is shorted to ground.
Typical Operating Characteristics
(VIN = VEN = +12V, TA = +25C, unless otherwise noted.)
OUTPUT CURRENT vs. TEMPERATURE
MAX16836 toc01
(VCS+ - VCS-) vs. OUTPUT CURRENT
MAX16836 toc02
OUTPUT CURRENT vs. INPUT VOLTAGE
350 OUTPUT CURRENT (mA) 300 250 200 150 100 50
MAX16836 toc03
450 400 OUTPUT CURRENT (mA) 350 300 250 200 150 100 50 0 ILOAD = 35mA ILOAD = 100mA ILOAD = 200mA ILOAD = 350mA
0.208
400
0.206 (VCS+ - VCS-) (V)
0.204
0.202
0.200
0.198 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C) 20 50 80 110 140 170 200 230 260 290 320 350 OUTPUT CURRENT (mA)
0 0 5 10 15 20 25 30 35 40 INPUT VOLTAGE (V)
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3
High-Voltage, 350mA, High-Brightness LED Driver with PWM Dimming and 5V Regulator MAX16836
Typical Operating Characteristics (continued)
(VIN = VEN = +12V, TA = +25C, unless otherwise noted.)
DROPOUT VOLTAGE vs. TEMPERATURE
MAX16836 toc04
SHUTDOWN CURRENT vs. TEMPERATURE
90 SHUTDOWN CURRENT (A) 80 70 60 50 40 30 20 10 0 VIN = 12V VIN = 6.5V 4.8 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C) VIN = 20V VIN = 40V
MAX16836 toc05
+5V REGULATOR OUTPUT vs. TEMPERATURE
MAX16836 toc06
1.0 0.9 0.8 DROPOUT VOLTAGE (V) 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 ILOAD = 350mA
100
5.2
+5V REGULATOR OUTPUT (V)
5.1 IV5 = 1mA 5.0 NO LOAD
4.9 IV5 = 5mA
-40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
-40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
(VCS+ - VCS-) vs. IV5
MAX16836 toc07
+5V REGULATOR OUTPUT vs. VIN
MAX16836 toc08
0.206
5.2
+5V REGULATOR OUTPUT (V)
0.204 (VCS+ - VCS-) (V)
5.1 NO LOAD 5.0 IV5 = 5mA
0.202
0.200
ILOAD = 350mA
0.198
4.9 IV5 = 5mA
0.196 0 1 2 3 IV5 (mA) 4 5 6
4.8 5 10 15 20 25 30 35 40 VIN (V)
200Hz DIMMED OPERATION
MAX16836 toc09
200Hz DIMMED OPERATION (EXPANDED)
MAX16836 toc10
VDIM 2V/div 0V
ILOAD = 350mA VIN = VEN = 12V DIM PULSED AT 200Hz (5% DUTY CYCLE)
ILOAD = 350mA VIN = VEN = 12V DIM PULSED AT 200Hz (50% DUTY CYCLE)
VDIM 2V/div 0V ILOAD 200mA/div 0A
ILOAD 200mA/div 0A
100s/div
20s/div
4
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High-Voltage, 350mA, High-Brightness LED Driver with PWM Dimming and 5V Regulator
Typical Operating Characteristics (continued)
(VIN = VEN = +12V, TA = +25C, unless otherwise noted.)
MAX16836
200Hz DIMMED OPERATION (EXPANDED)
MAX16836 toc11
VSENSE vs. VCSILOAD = 350mA VDIM 2V/div VSENSE (mV) 0V ILOAD 200mA/div 0A 204
MAX16836 toc12
ILOAD = 350mA VIN = VEN = 12V DIM PULSED AT 200Hz (50% DUTY CYCLE)
206
202
200
198 20s/div 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 VCS- (V)
Pin Description
PIN 1, 16 2, 3 4-8, 14 9 10 11 12 13 15 -- NAME OUT IN N.C. CS+ CSV5 GND DIM EN EP FUNCTION Current-Regulated Output. Connect pin 1 to pin 16. Positive Input Supply. Bypass IN with a 0.1F (min) capacitor to GND. Connect pin 2 to pin 3. No Connection. Not internally connected. Positive Input of the Internal Differential Amplifier. Connect the current-sense resistor between CS+ and CS- to program the output current level. Negative Input of the Internal Differential Amplifier. Connect the current-sense resistor between CS- and CS+ to program the output current level. +5V Regulated Output. Connect a 0.1F capacitor from V5 to GND. Ground Pulsed Dimming Input. Drive DIM low to disable the output. Drive DIM high or leave unconnected to enable the output. Enable Input. Drive EN high to enable the output. Exposed Pad. Connect to the ground plane for effective power dissipation. Do not use as the only ground connection.
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5
High-Voltage, 350mA, High-Brightness LED Driver with PWM Dimming and 5V Regulator MAX16836
Functional Diagram
IN V5 DIM IN
REGULATOR
1A IN
EN
ENABLE
REFERENCE GENERATOR
I_REG
OUT DIFFERENTIAL SENSE AMPLIFIER THERMAL SHUTDOWN CS+ CS-
MAX16836
Detailed Description
The MAX16836 is a high-current regulator capable of providing up to a total of 350mA of current to one or more strings of HB LEDs. A wide operating input voltage range of +6.5V to +40V makes the MAX16836 ideal for automotive applications. A +5V regulated output provides up to 4mA of current to power external circuitry. In addition, the MAX16836 features thermal and output short-circuit protection. The wide operating voltage range helps protect the MAX16836 against large transients such as those found in load-dump situations up to 40V. The MAX16836 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 power series pass device (see the Functional Diagram). The regulation point is factory-set at (VCS+ VCS-) = 200mV 3.5%. The regulated current is user defined by the value of RSENSE. The MAX16836 is a current controller internally optimized for driving the impedance range expected from one or more HB LEDs.
+5V Regulator
The MAX16836 includes a fixed +5V output regulator that delivers up to 4mA of load current throughout the +6.5V to +40V input voltage range. Connect a 0.1F compensation capacitor from V5 to ground. Shorting V5 to ground disables the thermal shutdown. When EN is low, V5 is off. V5 stays on during PWM dimming, using the DIM input.
Thermal Protection
The MAX16836 enters a thermal-shutdown mode in the event of overheating. This typically occurs in overload or output short-circuit conditions. If the junction temperature exceeds TJ = +159C (typ), the internal thermal-protection circuitry turns off the series pass device. The MAX16836 recovers from thermal-shutdown mode once the junction temperature drops by 24C (typ). The part therefore protects itself by thermally cycling in the event of a short-circuit or overload condition. Shorting V5 to ground disables the thermal shutdown.
Applications Information
Programming the LED Current
The MAX16836 uses a sense resistor across CS+ and CS- to set the LED current. The differential sense amplifier connected across RSENSE provides ground-loop immunity and low-frequency noise rejection. The LED current is given by: ILED = VSENSE/RSENSE
6
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High-Voltage, 350mA, High-Brightness LED Driver with PWM Dimming and 5V Regulator
Input-Voltage Considerations
For proper operation, the minimum input voltage must always be: VIN(MIN) VSENSE(MAX) + VFT(MAX) + VDO(MAX) where VFT(MAX) is the total forward voltage of all series connected LEDs. The minimum operating voltage of the device is +6.5V. The device operates below +6.5V; however, output current may not meet the full regulation specification.
Paralleling Multiple MAX16836s to Drive One High-Power LED
For applications that require more than 350mA of LED current, two or more MAX16836s can be paralleled (see Figure 3). VCS- should not exceed 4.1V.
MAX16836
R1 IN OUT
Low-Frequency PWM Dimming at the Output
The MAX16836 provides pulsed or chopped current dimming input (DIM). The other method is to connect DIM to V5 and EN to IN and pulse EN. Both methods generate a regulated-amplitude PWM current (variable duty cycle) that can provide control over the LED brightness (see Figures 1 and 2).
VDIM
EN C1
V5 C2
MAX16836
V5 DIM CS+ CSGND
16 OUT 1 VIN C1 3 4 IN N.C. N.C. 5 2 OUT IN
15 EN
14 N.C.
13 DIM GND 12 D1 V5 11 ILED
MAX16836
C2 CS- 10 CS+ 9 RSENSE
VIN R2 IN OUT
N.C. 6
N.C. 7
N.C. 8
EN C3
V5 C4
Figure 1. Dimming with EN Connected to VIN at a Constant Voltage and DIM Pulsed
MAX16836
V5 DIM CS+ CSLEDs
16 OUT 1 VIN C1 3 4 IN N.C. N.C. 5 2 OUT IN
15 EN
14 N.C.
13 DIM GND 12 D1 V5 11 C2 CS- 10 CS+ 9 RSENSE ILED
GND
MAX16836
Figure 3. Paralleling MAX16836s
N.C. 6
N.C. 7
N.C. 8
Figure 2. Dimming with DIM Connected to V5, EN Connected to VIN
_______________________________________________________________________________________ 7
High-Voltage, 350mA, High-Brightness LED Driver with PWM Dimming and 5V Regulator MAX16836
Two Brightness Levels for TAIL/STOP Lights
Figure 4 shows PWM dimming operation for the MAX16836 with an ICM7555 timer. The ICM7555 provides adjustable duty cycle using two external resistors and a capacitor. In TAIL operation, the output of the ICM7555 feeds into DIM and lights up the LEDs. The LED's brightness depends on the duty cycle of the ICM7555. When VSTOP is present, DIM is pulled up to VSTOP. The PWM dimming operation is disabled and the LEDs light up to full brightness. See the ICM7555 data sheet for formulas to calculate the dimming frequency and the duty cycle.
D1 STOP D2 TAIL R1 R2 D3 IN DIS R3 TH TRG C3 *R4 300k OUT D4 DIM CS+ RSENSE R4* GND GND CSD5 C1 EN IN OUT
LED Current Thermal Foldback
With a minimum number of external components, the MAX16836 provides LED current thermal foldback using a negative temperature coefficient (NTC) thermistor. Figure 5 shows a thermistor connected to V5 and the CS+ of the MAX16836. As the temperature increases, the voltage drop across R2 increases causing the LED current to decrease. R + R2 ILED = [VSENSE - [R2 /(R2 + RT)] x V5] x T R1RT (assuming IRT < < ILED).
MAX16836
V5
+5V REG C2
LEDs
ICM7555
Figure 4. PWM Dimming Operation with ICM7555 Timer
VIN
IN EN
OUT V5 C2 LEDs
MAX16836
PWM DIMMING C1 DIM CS+
RT R2
R1 GND CS-
Figure 5. LED Current Thermal Foldback with an NTC Thermistor
8 _______________________________________________________________________________________
High-Voltage, 350mA, High-Brightness LED Driver with PWM Dimming and 5V Regulator
Other Applications
The application circuit in Figure 6 implements a twolevel brightness current for TAIL/STOP lights. In TAIL operation, Q1 is off and the R1 sets the output current. In STOP operation, Q1 turns on and the output current is set by a parallel combination of R1 and R2. Figure 7 shows an application circuit with the MAX16836 using a single BJT to provide high output current. For proper operation: VIN(MIN) > VCESAT(MAX) + VFT(MAX) + VSENSE where VCESAT(MAX) is the maximum saturation voltage of the external BJT.
MAX16836
STOP
TAIL
IN
OUT
EN V5 C1 DIM
V5
MAX16836
CS+
C2
LEDs
R2 R1 Q1 GND CS-
Figure 6. Two Brightness Level with Current Level Switch for Tail/Stop Lights
LEDs
VIN
IN EN
OUT V5 C2
Q1
MAX16836
PWM DIMMING C1 DIM CS+ RSENSE GND CS-
Figure 7. Increased LED Current (Ampere Range) with a Single BJT
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9
High-Voltage, 350mA, High-Brightness LED Driver with PWM Dimming and 5V Regulator MAX16836
Multichannel HB LED Driver
Figure 8 shows an array of MAX16836s with independent DIM control. The MAX5094C, a current-mode PWM
L1 VIN D1
controller, provides the input power to each LED driver preregulated voltage to multiple MAX16836 drivers.
CREF REF C2 R3 CCOMP COMP RCOMP C6 FB GND DIM CS+ R5 VCC C3 IN OUT IN OUT IN OUT
U2
EN
MAX5094C
OUT Q1 C4
LEDs V5 C7 C10 DIM EN
U4 MAX16836
V5 C11
LEDs EN C8 CS+ R7 DIM
U3 MAX16836
V5 C9
LEDs
MAX16836
CS+ R6
CT/RT CT
CS R2
R4
GND
CS-
GND
CS-
GND
CS-
Figure 8. Multichannel HB LED Driver for LCD Backlight
Typical Operating Circuit
PROCESS: BiCMOS
VDIM
Chip Information
16 OUT 1 VIN C1 3 4 IN N.C. N.C. 5 2 OUT IN
15 EN
14 N.C.
13 DIM GND 12 D1 V5 11 C2 CS- 10 CS+ 9 RSENSE
Package Information
For the latest package outline information and land patterns, go to www.maxim-ic.com/packages. PACKAGE TYPE 16 TQFN PACKAGE CODE T1655-3 DOCUMENT NO. 21-0140
MAX16836
N.C. 6
N.C. 7
N.C. 8
10
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High-Voltage, 350mA, High-Brightness LED Driver with PWM Dimming and 5V Regulator
Revision History
REVISION NUMBER 0 1 REVISION DATE 2/08 5/08 Initial release Updated Ordering Information, Electrical Characteristics, and Package Information. DESCRIPTION PAGES CHANGED -- 1, 2, 11, 12
MAX16836
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.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 11
(c) 2008 Maxim Integrated Products is a registered trademark of Maxim Integrated Products, Inc.
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