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19-0589; Rev 0; 7/06
High-Voltage, 350mA LED Driver with Analog and PWM Dimming Control
General Description
The MAX16804 current regulator operates from a 5.5V to 40V input voltage range and delivers 35mA to 350mA to one or more strings of high-brightness LEDs (HB LEDs). The output current of the MAX16804 is set by using an external current-sense resistor in series with the LEDs. A dual-mode DIM pin and on-board 200Hz ramp generator allow PWM dimming with an analog or PWM input signal. The analog control signal at dimming input DIM allows for a theater-dimming effect to be implemented. Fast turn-on and turn-off times ensure a wide-range PWM operation, while wave-shaping circuitry minimizes EMI. The differential current-sense input increases LED current accuracy and noise immunity. The MAX16804 is well suited for applications requiring high-voltage input and is able to withstand automotive load-dump events up to 45V. An on-board pass element minimizes external components while providing 3% output-current accuracy. Additional features include a 5V regulated output and short-circuit and thermal protection. The MAX16804 is available in a thermally enhanced, 5mm x 5mm, 20-pin TQFN package and is specified over the automotive -40C to +125C temperature range.
Features
Flexible Dimming Control, Analog or PWM Control Signal for PWM and Theater Dimming 200Hz On-Board Ramp Generator Sinks to External PWM Signal (Up to 2kHz) 5.5V to 40V Operating Range 35mA to 350mA Adjustable LED Current 3% LED Current Accuracy High-Voltage (Up to 40V) DIM Pin Integrated Pass Element with Low-Dropout Voltage (0.5V typ) Additional +5V On-Board Regulator with 2mA Capability Differential LED Current Sense Low 200mV Current-Sense Reference Reduces Power Losses Wave-Shaped Edges Minimize EMI During PWM Dimming Output Short-Circuit and Thermal-Shutdown Protection Available in Small, Thermally Enhanced, 5mm x 5mm, 20-Pin TQFN Package -40C to +125C Operating Temperature Range
MAX16804
Applications
Automotive Interior: Map, Dome, and Courtesy Lighting Automotive Exterior: Rear Combination Light (RCL) Daytime Running Light (DRL) Adaptive Front Light Warning Lights for Emergency Vehicles Navigation and Marine Indicators Signage, Canopies, and Beacons
Ordering Information
PART TEMP RANGE PINPACKAGE PKG CODE
MAX16804ATP+ -40C to +125C
20 TQFN-EP* T2055M-5
+Denotes lead-free package. *EP = Exposed pad. Pin Configuration appears at end of data sheet.
Simplified Diagrams
+5.5V TO +40V IN 0.1F V5 0.1F V5 EN LEDs EN RSENSE DIM GND CSOUT +5V REG ILED +5.5V TO +40V IN 0.1F V5 0.1F LEDs OUT +5V REG ILED
MAX16804
CS+ PWM DIMMING
MAX16804
CS+ RSENSE
DIM
GND
CS-
ANALOG CONTROL PWM DIMMING
PWM CONTROL DIMMING
________________________________________________________________ Maxim Integrated Products
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High-Voltage, 350mA LED Driver with Analog and PWM Dimming Control MAX16804
ABSOLUTE MAXIMUM RATINGS
IN to GND ...............................................................-0.3V to +45V DIM, OUT, EN to GND .................................-0.3V to (VIN + 0.3V) IN Slew Rate (20V < VIN < 45V) ...................................250mV/s CS+, V5 to GND .......................................................-0.3V to +6V CS- to GND............................................................-0.3V to +0.3V OUT Short Circuited to GND Duration (at VIN < +16V).................................................................1hour Maximum Current Into Any Pin (except IN and OUT).........20mA Continuous Power Dissipation (TA = +70C) 20-Pin TQFN (derate 34.5mW/C above +70C) ......2758.6mW Operating Temperature Range .........................-40C to +125C Junction Temperature ......................................................+150C Storage Temperature Range .............................-65C to +150C Lead Temperature (soldering, 10s) .................................+300C
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, IV5 = 0, CS- = GND, RSENSE = 0.56 (see the Typical Operating Circuit), VDIM = 4V, TA = TJ = -40C to +125C, unless otherwise noted. Typical values are at TA = TJ = +25C.) (Note 1)
PARAMETER Supply Voltage Range Ground Current Shutdown Supply Current Guaranteed Output Current Output Current Accuracy Dropout Voltage (Note 3) Output Current Slew Rate (External PWM Signal at DIM) Short-Circuit Current ENABLE INPUT EN Input Current EN Input-Voltage High EN Input-Voltage Low Enable Turn-On Time CURRENT SENSE (Note 4) Regulated RSENSE Voltage Input Current (CS+) Input Current (CS-) INTERNAL RAMP GENERATOR Internal Ramp Frequency External Sync Frequency Range External Sync Voltage Low External Sync Voltage High EXTERNAL PWM DIMMING INPUT DIM Input Current Turn-On Time Turn-Off Time tON tOFF After DIM rising to 4V (Note 5) After DIM falling to 0.6V (Note 5) 28 19 1 52 38 A s s 2.8 fRAMP fDIM 180 80 200 220 2000 0.4 Hz Hz V V VRSENSE VSENSE = VCS+ - VCSVCS+ = 220mV VCS+ = 220mV -75 192 198 204 +14 mV A A IEN VIH VIL tON EN rising edge to 90% of OUT 250 2.8 0.6 100 nA V V s VDO SYMBOL VIN IG ISHDN IOUT (Note 2) ILOAD = 350mA VEN 0.3V RSENSE = 0.55 35mA < IOUT < 350mA, not including RSENSE tolerance IOUT = 350mA, 12V < VIN < 40V IOUT = 350mA, 6.5V < VIN < 12V Current rising, DIM rising to 4V Current falling, DIM falling to 0.6V VOUT = 0V 0.4 0.5 17 17 600 350 3 1.2 1.5 CONDITIONS MIN 5.5 2.5 12 TYP MAX 40.0 4.5 40 UNITS V mA A mA % V mA/s mA
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High-Voltage, 350mA LED Driver with Analog and PWM Dimming Control
ELECTRICAL CHARACTERISTICS (continued)
(VIN = VEN = 12V, CV5 = 0.1F, IV5 = 0, CS- = GND, RSENSE = 0.56 (see the Typical Operating Circuit), VDIM = 4V, TA = TJ = -40C to +125C, unless otherwise noted. Typical values are at TA = TJ = +25C.) (Note 1)
PARAMETER THERMAL PROTECTION Thermal-Shutdown Temperature Thermal-Shutdown Hysteresis +5V REGULATOR Output Voltage Regulation V5 Short-Circuit Current V5 0 IV5 2mA V5 = 0V (Note 6) 4.8 5.1 12 5.4 V mA TJ(SHDN) +155 23 C C SYMBOL CONDITIONS MIN TYP MAX UNITS
MAX16804
Note 1: All devices are 100% production tested at TA = +25C. Limits over the operating temperature range are guaranteed by design. Note 2: Resistors were added from OUT to CS+ to aid with the power dissipation during testing. Note 3: Dropout is measured as follows: Connect a resistor from OUT to CS+. Connect RSENSE = 0.56 from CS+ to CS-. Set VIN = VOUT +3V (record VOUT as VOUT1). Reduce VIN until VOUT = 0.97 x VOUT1 (record as VIN2 and VOUT2). VDO = VIN2 - VOUT2. Note 4: IV5 = 0mA. 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: Thermal shutdown does not function if the output of the 5V reference is shorted to ground. Shorting V5 to GND disables the output.
Typical Operating Characteristics
(VIN = 12V, VEN = VIN, CV5 = 0.1F, IV5 = 0, CS- = GND, RSENSE = 0.56, connect OUT to CS+, VDIM = 4V, TA = +25C, unless otherwise noted.)
OUTPUT CURRENT vs. TEMPERATURE
MAX16804 toc01
(VCS+ - VCS-) vs. OUTPUT CURRENT
MAX16804 toc02
OUTPUT CURRENT vs. INPUT VOLTAGE
350 IOUT = 350mA OUTPUT CURRENT (mA) 300 250 200 150 100 IOUT = 100mA 50 0
MAX16804 toc03
450 400 ILOAD = 350mA OUTPUT CURRENT (mA) 350 300 250 ILOAD = 200mA 200 150 100 50 0 ILOAD = 35mA ILOAD = 100mA
0.203 0.202 0.201 (VCS+ - VCS-) (V) 0.200 0.199 0.198 0.197 0.196 0.195 0.194 0.193 VIN = 12V
400
-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
2
4
6
8
10
12
14
16
INPUT VOLTAGE (V)
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High-Voltage, 350mA LED Driver with Analog and PWM Dimming Control MAX16804
Typical Operating Characteristics (continued)
(VIN = 12V, VEN = VIN, CV5 = 0.1F, IV5 = 0, CS- = GND, RSENSE = 0.56, connect OUT to CS+, VDIM = 4V, TA = +25C, unless otherwise noted.)
DROPOUT VOLTAGE vs. TEMPERATURE
MAX16804 toc04
SHUTDOWN CURRENT vs. TEMPERATURE
35 SHUTDOWN CURRENT (A) 30 25 20 15 10 5 VIN = 12V VIN = 6.5V VIN = 20V
MAX16804 toc05
+5V REGULATOR OUTPUT vs. TEMPERATURE
MAX16804 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 VIN = 12V ILOAD = 350mA
40 VIN = 40V
5.20 NO LOAD 5.15 ILOAD = 1mA
+5V REGULATOR OUTPUT (V)
5.10
5.05
ILOAD = 2mA
VIN = 12V 5.00 -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)
-40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
0
+5V REGULATOR OUTPUT vs. VIN
MAX16804 toc07
(VCS+ - VCS-) vs. IV5
0.1989 0.1988 (VCS+ - VCS-) (V) 0.1987 0.1986 0.1985 0.1984 0.1983 ILOAD = 350mA VIN = 12V
MAX16804 toc08
200Hz DIMMED OPERATION
MAX16804 toc09
5.20 NO LOAD 5.15
0.1990
+5V REGULATOR OUTPUT (V)
VDIM 2V/div 0V ILOAD = 350mA VIN = 12V DIM PULSED AT 200Hz (1% DUTY CYCLE)
5.10 ILOAD = 2mA 5.05 ILOAD = 1mA
ILOAD 200mA/div 0A
0.1982 0.1981
5.00 5 10 15 20 25 30 35 40 VIN (V)
0.1980 0 1 2 3 4 5 IV5 (mA) 6 7 8 9 10 20s/div
LED CURRENT FALL TIME (EXPANDED)
MAX16804 toc10
LED CURRENT RISE TIME (EXPANDED)
MAX16804 toc11
DIM PULSED AT 200Hz
VDIM 2V/div 0V
DIM PULSED AT 200Hz
VDIM 2V/div 0V
ILED 200mA/div 0A
ILED 200mA/div 0A
20s/div
20s/div
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High-Voltage, 350mA LED Driver with Analog and PWM Dimming Control MAX16804
Typical Operating Characteristics (continued)
(VIN = 12V, VEN = VIN, CV5 = 0.1F, IV5 = 0, CS- = GND, RSENSE = 0.56, connect OUT to CS+, VDIM = 4V, TA = +25C, unless otherwise noted.)
OUTPUT CURRENT DUTY CYCLE vs. ANALOG DIM VOLTAGE
OUTPUT CURRENT DUTY CYCLE (%) VIN = 12V 100 80 IDIM (A) 60 40 20 0 0 1 2 3 4 ANALOG DIM VOLTAGE (V)
MAX16804 toc12
IDIM vs. VDIM
VIN = 16V 250 200 150 100 50 0 0 2 4 6 8 VDIM (V) 10 12 14 16
MAX16804 toc13
120
300
Pin Description
PIN 1, 20 2, 3 4, 9, 11, 18 5-8, 10, 16 12, 15 13 14 17 19 -- NAME OUT IN N.C. GND V5 CS+ CSDIM EN EP FUNCTION Current-Regulated Output. Connect pin 1 to pin 20. Input Supply. Bypass IN with a 0.1F (min) capacitor to GND. Connect pin 2 to pin 3. No Connection. Leave unconnected (internal connection). Ground +5V Regulated Output. Connect a 0.1F capacitor from V5 to GND. 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. Dimming Input. See the Dimming Input (DIM) section. Enable Input. Drive EN high to enable the output and the 5V LDO. Exposed Pad. Connect to the ground plane for effective power dissipation. Do not use as the only ground connection.
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High-Voltage, 350mA LED Driver with Analog and PWM Dimming Control MAX16804
Functional Diagram
IN V5
IN REGULATOR TRIMMED BANDGAP 1.25V I_REG OUT CS+ CS-
EN
GND
MAX16804
THERMAL SHUTDOWN 210mV 200Hz RAMP GENERATOR MUX
DIFFERENTIAL SENSE AMPLIFIER
DIM POR PULSE DETECTOR
Detailed Description
The MAX16804 is a high-current regulator capable of providing up to 350mA of current to one or more strings of HB LEDs. A wide operating input voltage range of 5.5V to 40V makes the MAX16804 ideal for automotive applications. A +5V regulated output provides up to 2mA of current to power external circuitry. In addition, the MAX16804 features thermal and output short-circuit protection. The wide operating voltage range helps protect the MAX16804 against large transients such as those found in load-dump situations up to 45V. The MAX16804 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 pass device (see the Functional Diagram). The regulation point is factory-set at (VCS+ - VCS-) = 198 6mV. The regulated current is user-defined by the value of RSENSE.
The MAX16804 is a current controller internally optimized for driving the impedance range expected from one to ten or more HB LEDs.
Dimming Input (DIM)
The MAX16804's dimming input functions with either an analog or PWM control signal. If the pulse detector detects three edges of a PWM signal with a frequency range between 80Hz to 2kHz, the MAX16804 synchronizes to external PWM input signal and pulse-widthmodulates the LED current. If an analog control signal is applied to DIM, the MAX16804 compares the DC input to an internally generated 200Hz ramp to pulsewidth-modulate the LED current. The output current duty cycle is adjustable from 0% to 100% (0.21V < VDIM < 3.1V). Use the following formula to calculate the output current duty cycle: Duty cycle = (VDIM - 0.21V) / (2.895V) (1)
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High-Voltage, 350mA LED Driver with Analog and PWM Dimming Control
The dimming feature can be used for LED brightness adjustment (see the Simplified Diagrams) and theater dimming. If an external PWM signal is used, the theaterdimming effect can be achieved by varying the PWM duty cycle. Figure 1 shows a simple circuit that implements theater dimming with a DC input signal.
Applications Information
Programming the LED Current
The MAX16804 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 (2)
MAX16804
+5V Regulator
The MAX16804 includes a fixed +5V output regulator that delivers up to 2mA 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.
Input-Voltage Considerations
For proper operation, the minimum input voltage must always be: VIN(MIN) VRSENSE(MAX) + VFT(MAX) + VDO(MAX) (3) where VFT(MAX) is the maximum forward voltage of all series connected LEDs and VDO(MAX) is the maximum drop output voltage. The minimum operating voltage of the device is +5.5V.
Thermal Protection
The MAX16804 enters a thermal-shutdown mode in the event of overheating. This typically occurs in overload or short-circuit conditions on the output. If the junction temperature exceeds TJ = +155C (typ), the internal thermal-protection circuitry turns off the series pass device. The MAX16804 recovers from thermal-shutdown mode once the junction temperature drops by 23C (typ). The part therefore protects itself by thermally cycling in the event of a short-circuit or overload condition.
Two Brightness Levels for TAIL/STOP Lights
Figure 2 shows two-level brightness adjustment using the MAX16804 with minimum external components. Set the dimming level with a resistive divider connected to DIM. See Equation 1 for details.
STOP VIN IN OUT TAIL EN +5V REG V5 0.1F THEATER DIMMING SIGNAL LEDs
D1
D2 IN OUT
EN
V5
MAX16804
CS+ RSENSE DIM CSGND GND CSR2 R1 DIM
LEDs
MAX16804
CS+ RSENSE
Figure 1. Theater Dimming
Figure 2. Two-Level Brightness Operation
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High-Voltage, 350mA LED Driver with Analog and PWM Dimming Control MAX16804
LED Current Thermal Foldback
With a minimum number of external components, the MAX16804 provides LED current thermal foldback using a negative temperature coefficient (NTC) thermistor. Figure 3 shows a thermistor connected to V5 and the CS+ of the MAX16804. As the temperature increases, the voltage drop across R2 increases causing the LED current to decrease. (4) ILED = [VSENSE - [R2 / (R2 + RT)] x V5] / R1
Other Applications
Figure 4 shows an application circuit with the MAX16804 using a single BJT to provide high output current. For proper operation: VIN(MIN) > VCESAT(MAX) + VFT(MAX) + VRSENSE (5) where VCESAT(MAX) is the maximum saturation voltage of the external BJT.
VIN C1
IN EN
OUT V5 C2 LEDs
MAX16804
PWM DIMMING DIM CS+
RT R2
R1 GND CS-
Figure 3. LED Current Thermal Foldback Operation with an NTC Thermistor
LEDs
VIN C1
IN EN
OUT V5 C2
Q1
MAX16804
PWM DIMMING DIM CS+ RSENSE GND CS-
Figure 4. Increased Output Current (Amper Range) with a Single BJT
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High-Voltage, 350mA LED Driver with Analog and PWM Dimming Control
Typical Operating Circuit
ANALOG OR PWM CONTROL SIGNAL
MAX16804
20 1 VIN C1 3 IN OUT OUT
19 EN
18 N.C.
17 DIM
16 GND V5 15 CS- 14 LEDs
2 IN
MAX16804
CS+ 13 V5 12 N.C. 11 GND 10 C2
RSENSE
4 N.C. 5 GND GND 6
GND 7
GND 8
N.C. 9
Pin Configuration
PROCESS: BiCMOS
TOP VIEW
CS+ 15 14 13 12 N.C. CSV5 V5 11
Chip Information
GND 16 DIM 17 N.C. 18 EN 19 OUT 20
10 9
GND N.C. GND GND GND
MAX16804
8 7
+
1 OUT 2 IN 3 IN 4 N.C. 5 GND
6
THIN QFN
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High-Voltage, 350mA LED Driver with Analog and PWM Dimming Control MAX16804
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information go to www.maxim-ic.com/packages.)
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QFN THIN.EPS
High-Voltage, 350mA LED Driver with Analog and PWM Dimming Control
Package Information (continued)
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information go to www.maxim-ic.com/packages.)
MAX16804
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) 2006 Maxim Integrated Products is a registered trademark of Maxim Integrated Products, Inc.
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