Download MAX16804 High-Voltage, 350mA LED Driver with Analog and PWM Dimming Control General Description

19-0589; Rev 1; 5/08
High-Voltage, 350mA LED Driver with
Analog and PWM Dimming Control
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 -40°C to +125°C temperature range.
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
Features
o Flexible Dimming Control, Analog or PWM
Control Signal for PWM and Theater Dimming
o 200Hz On-Board Ramp Generator
o Syncs to External PWM Signal (Up to 2kHz)
o 5.5V to 40V Operating Range
o 35mA to 350mA Adjustable LED Current
o 3% LED Current Accuracy
o High-Voltage (Up to 40V) DIM Pin
o Integrated Pass Element with Low-Dropout
Voltage (0.5V typ)
o Additional +5V On-Board Regulator with 2mA
Capability
o Differential LED Current Sense
o Low 200mV Current-Sense Reference Reduces
Power Losses
o Wave-Shaped Edges Minimize EMI During PWM
Dimming
o Output Short-Circuit and Thermal-Shutdown
Protection
o Available in Small, Thermally Enhanced,
5mm x 5mm, 20-Pin TQFN Package
o -40°C to +125°C Operating Temperature Range
Ordering Information
PART
TEMP RANGE
MAX16804ATP+
-40°C to +125°C
PIN-PACKAGE
20 TQFN-EP*
+Denotes a lead-free/RoHS-compliant package.
*EP = Exposed pad.
Pin Configuration appears at end of data sheet.
Simplified Diagrams
ILED
+5.5V TO +40V
IN
+5.5V TO +40V
OUT
0.1μF
+5V REG
0.1μF
EN
MAX16804
OUT
0.1μF
V5
V5
ILED
IN
+5V REG
V5
LEDs
0.1μF
EN
CS+
MAX16804
CS+
RSENSE
RSENSE
PWM DIMMING
DIM
GND
CS-
ANALOG CONTROL PWM DIMMING
LEDs
DIM
GND
CS-
PWM CONTROL DIMMING
________________________________________________________________ Maxim Integrated Products
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.
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1
MAX16804
General Description
MAX16804
High-Voltage, 350mA LED Driver with
Analog and PWM Dimming Control
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/µs
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 = +70°C)
20-Pin TQFN (derate 34.5mW/°C above +70°C) ......2758.6mW
Operating Temperature Range .........................-40°C to +125°C
Junction Temperature ......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°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
(VIN = VEN = 12V, CV5 = 0.1µF, IV5 = 0, CS- = GND, RSENSE = 0.56Ω (see the Typical Operating Circuit), VDIM = 4V, TA = TJ = -40°C
to +125°C, unless otherwise noted. Typical values are at TA = TJ = +25°C.) (Note 1)
PARAMETER
Supply Voltage Range
Ground Current
Shutdown Supply Current
Guaranteed Output Current
SYMBOL
(Note 2)
IG
ILOAD = 350mA
VEN ≤ 0.3V
ISHDN
IOUT
RSENSE = 0.55Ω
MIN
TYP
MAX
UNITS
40.0
V
2.5
4.5
mA
12
40
5.5
350
ΔVDO
µA
mA
35mA < IOUT < 350mA, not including
RSENSE tolerance
Output Current Accuracy
Dropout Voltage (Note 3)
CONDITIONS
VIN
3
IOUT = 350mA, 12V < VIN < 40V
0.4
1.2
IOUT = 350mA, 6.5V < VIN < 12V
0.5
1.5
Output Current Slew Rate
(External PWM Signal at DIM)
Current rising, DIM rising to 4V
17
Current falling, DIM falling to 0.6V
17
Short-Circuit Current
VOUT = 0V
600
%
V
mA/µs
mA
ENABLE INPUT
EN Input Current
IEN
EN Input-Voltage High
VIH
EN Input-Voltage Low
VIL
Enable Turn–On Time
tON
100
2.8
V
0.6
EN rising edge to 90% of OUT
nA
250
V
µs
CURRENT SENSE (Note 4)
Regulated RSENSE Voltage
VRSENSE
VSENSE = VCS+ - VCS-
Input Current (CS+)
VCS+ = 220mV
Input Current (CS-)
VCS+ = 220mV
192
198
204
+14
-75
mV
µA
µA
INTERNAL RAMP GENERATOR
Internal Ramp Frequency
External Sync Frequency Range
fRAMP
180
fDIM
80
200
220
Hz
2000
Hz
0.4
V
External Sync Voltage Low
External Sync Voltage High
2.8
V
EXTERNAL PWM DIMMING INPUT
DIM Input Current
1
µA
Turn-On Time
tON
After DIM rising to 4V (Note 5)
28
52
µs
Turn-Off Time
tOFF
After DIM falling to 0.6V (Note 5)
19
38
µs
2
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High-Voltage, 350mA LED Driver with
Analog and PWM Dimming Control
(VIN = VEN = 12V, CV5 = 0.1µF, IV5 = 0, CS- = GND, RSENSE = 0.56Ω (see the Typical Operating Circuit), VDIM = 4V, TA = TJ = -40°C
to +125°C, unless otherwise noted. Typical values are at TA = TJ = +25°C.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
THERMAL PROTECTION
Thermal-Shutdown Temperature
TJ(SHDN)
Thermal-Shutdown Hysteresis
+155
°C
23
°C
+5V REGULATOR
Output Voltage Regulation
V5
V5 Short-Circuit Current
0 ≤ IV5 ≤ 2mA
4.8
5.1
V5 = 0V (Note 6)
5.4
V
12
mA
Note 1: All devices are 100% production tested at TA = +25°C. 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 = 0.56Ω 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). ΔVDO = 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 13Ω 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 = 0.1µF, IV5 = 0, CS- = GND, RSENSE = 0.56Ω, connect OUT to CS+, VDIM = 4V, TA = +25°C, unless
otherwise noted.)
300
250
200
150
ILOAD = 200mA
ILOAD = 100mA
100
50
MAX16804 toc02
0.201
400
350
IOUT = 350mA
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)
ILOAD = 350mA
350
VIN = 12V
0.202
(VCS+ - VCS-) (V)
400
0.203
MAX16804 toc01
450
OUTPUT CURRENT
vs. INPUT VOLTAGE
(VCS+ - VCS-) vs. OUTPUT CURRENT
0.200
0.199
0.198
0.197
0.196
300
250
200
150
100
0.195
ILOAD = 35mA
0
MAX16804 toc03
OUTPUT CURRENT
vs. TEMPERATURE
IOUT = 100mA
50
0.194
0
0.193
-40 -25 -10 5 20 35 50 65 80 95 110 125
20 50 80 110 140 170 200 230 260 290 320 350
TEMPERATURE (°C)
OUTPUT CURRENT (mA)
0
2
4
6
8
10
12
14
16
INPUT VOLTAGE (V)
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3
MAX16804
ELECTRICAL CHARACTERISTICS (continued)
Typical Operating Characteristics (continued)
(VIN = 12V, VEN = VIN, CV5 = 0.1µF, IV5 = 0, CS- = GND, RSENSE = 0.56Ω, connect OUT to CS+, VDIM = 4V, TA = +25°C, unless
otherwise noted.)
0.6
0.5
0.4
0.3
0.2
25
VIN = 20V
20
15
VIN = 12V
10
0.1
5
0
0
VIN = 6.5V
NO LOAD
ILOAD = 1mA
5.15
5.10
ILOAD = 2mA
5.05
VIN = 12V
5.00
-40 -25 -10 5 20 35 50 65 80 95 110 125
-40 -25 -10 5 20 35 50 65 80 95 110 125
-40 -25 -10 5 20 35 50 65 80 95 110 125
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
(VCS+ - VCS-) vs. IV5
200Hz DIMMED OPERATION
+5V REGULATOR OUTPUT vs. VIN
NO LOAD
0.1988
(VCS+ - VCS-) (V)
ILOAD = 2mA
ILOAD = 350mA
VIN = 12V
0.1989
5.15
5.10
MAX16804 toc09
0.1990
MAX16804 toc07
5.20
ILOAD = 1mA
VDIM
2V/div
0.1987
0V
0.1986
ILOAD = 350mA
VIN = 12V
DIM PULSED AT
200Hz (1% DUTY
CYCLE)
0.1985
0.1984
0.1983
5.05
ILOAD
200mA/div
0A
0.1982
0.1981
5.00
0.1980
5
10
15
20
25
30
35
40
0
1
2
VIN (V)
3
4
5
6
7
8
9
10
20μs/div
IV5 (mA)
LED CURRENT RISE TIME (EXPANDED)
LED CURRENT FALL TIME (EXPANDED)
MAX16804 toc11
MAX16804 toc10
DIM PULSED AT
200Hz
20μs/div
4
MAX16804 toc06
MAX16804 toc05
VIN = 40V
30
+5V REGULATOR OUTPUT (V)
0.7
35
5.20
MAX16804 toc08
DROPOUT VOLTAGE (V)
0.8
40
SHUTDOWN CURRENT (μA)
VIN = 12V
ILOAD = 350mA
MAX16804 toc04
1.0
0.9
+5V REGULATOR OUTPUT
vs. TEMPERATURE
SHUTDOWN CURRENT
vs. TEMPERATURE
DROPOUT VOLTAGE
vs. TEMPERATURE
+5V REGULATOR OUTPUT (V)
MAX16804
High-Voltage, 350mA LED Driver with
Analog and PWM Dimming Control
VDIM
2V/div
DIM PULSED AT
200Hz
VDIM
2V/div
0V
0V
ILED
200mA/div
ILED
200mA/div
0A
0A
20μs/div
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High-Voltage, 350mA LED Driver with
Analog and PWM Dimming Control
OUTPUT CURRENT DUTY CYCLE
vs. ANALOG DIM VOLTAGE
IDIM vs. VDIM
VIN = 12V
100
MAX16804 toc13
300
MAX16804 toc12
VIN = 16V
250
200
80
IDIM (μA)
OUTPUT CURRENT DUTY CYCLE (%)
120
60
150
40
100
20
50
0
0
0
1
2
3
0
4
2
4
6
8
10
12
14
16
VDIM (V)
ANALOG DIM VOLTAGE (V)
Pin Description
PIN
NAME
1, 20
OUT
2, 3
IN
FUNCTION
Current-Regulated Output. Connect pin 1 to pin 20.
Input Supply. Bypass IN with a 0.1µF (min) capacitor to GND. Connect pin 2 to pin 3.
4, 9, 11, 18
N.C.
No Connection. Leave unconnected (internal connection).
5–8, 10, 16
GND
Ground
12, 15
V5
13
CS+
Positive Input of the Internal Differential Amplifier. Connect the current-sense resistor between CS+
and CS- to program the output current level.
14
CS-
Negative Input of the Internal Differential Amplifier. Connect the current-sense resistor between
CS- and CS+ to program the output current level.
17
DIM
Dimming Input. See the Dimming Input (DIM) section.
19
EN
Enable Input. Drive EN high to enable the output and the 5V LDO.
—
EP
Exposed Pad. Connect to the ground plane for effective power dissipation. Do not use as the only
ground connection.
+5V Regulated Output. Connect a 0.1µF capacitor from V5 to GND.
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5
MAX16804
Typical Operating Characteristics (continued)
(VIN = 12V, VEN = VIN, CV5 = 0.1µF, IV5 = 0, CS- = GND, RSENSE = 0.56Ω, connect OUT to CS+, VDIM = 4V, TA = +25°C, unless
otherwise noted.)
High-Voltage, 350mA LED Driver with
Analog and PWM Dimming Control
MAX16804
Functional Diagram
V5
IN
IN
REGULATOR
EN
TRIMMED
BANDGAP
1.25V
I_REG
OUT
GND
DIFFERENTIAL
SENSE
AMPLIFIER
MAX16804
CS+
CS-
THERMAL
SHUTDOWN
210mV
200Hz RAMP
GENERATOR
MUX
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.
6
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
+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 0.1µF 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.
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 = +155°C (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 23°C (typ). The
part therefore protects itself by thermally cycling in the
event of a short-circuit or overload condition.
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)
Input-Voltage Considerations
For proper operation, the minimum input voltage must
always be:
VIN(MIN) ≥ VRSENSE(MAX) + VFT(MAX) + ΔVDO(MAX) (3)
where VFT(MAX) is the maximum forward voltage of all
series connected LEDs and ΔVDO(MAX) is the maximum
drop output voltage. The minimum operating voltage of
the device is +5.5V.
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.
D1
STOP
VIN
IN
OUT
EN
V5
TAIL
+5V REG
D2
LEDs
IN
OUT
EN
V5
0.1μF
THEATER
DIMMING
SIGNAL
MAX16804
CS+
MAX16804
R1
D4
RSENSE
DIM
CS+
DIM
CSGND
R2
RSENSE
GND
Figure 1. Theater Dimming
LEDs
D3
CS-
Figure 2. Two-Level Brightness Operation
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7
MAX16804
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.
MAX16804
High-Voltage, 350mA LED Driver with
Analog and PWM Dimming Control
LED Current Thermal Foldback
Other Applications
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
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
IN
OUT
EN
V5
C1
LEDs
C2
MAX16804
RT
PWM DIMMING
R2
DIM
CS+
R1
CS-
GND
Figure 3. LED Current Thermal Foldback Operation with an NTC Thermistor
LEDs
VIN
IN
OUT
EN
V5
Q1
C1
C2
MAX16804
PWM DIMMING
DIM
CS+
RSENSE
GND
CS-
Figure 4. Increased Output Current (Ampere Range) with a Single BJT
8
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High-Voltage, 350mA LED Driver with
Analog and PWM Dimming Control
ANALOG OR PWM
CONTROL SIGNAL
20
1
VIN
OUT
OUT
19
18
17
16
EN
N.C.
DIM
GND
V5 15
LEDs
CS- 14
2 IN
C1
3
IN
V5 12
4 N.C.
5 GND
GND
6
RSENSE
CS+ 13
MAX16804
GND
GND
N.C.
7
8
9
C2
N.C. 11
GND
10
Pin Configuration
Chip Information
PROCESS: BiCMOS
V5
CS-
CS+
V5
N.C.
TOP VIEW
15
14
13
12
11
Package Information
GND 16
10
GND
DIM 17
9
N.C.
8
GND
7
GND
6
GND
N.C. 18
MAX16804
EN 19
1
2
3
4
5
IN
IN
N.C.
GND
+
OUT
OUT 20
For the latest package outline information and land patterns, go
to www.maxim-ic.com/packages.
PACKAGE TYPE
PACKAGE CODE
DOCUMENT NO.
20 TQFN
T2055MN-5
21-0140
THIN QFN
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9
MAX16804
Typical Operating Circuit
MAX16804
High-Voltage, 350mA LED Driver with
Analog and PWM Dimming Control
Revision History
REVISION
NUMBER
REVISION
DATE
0
7/06
Initial release
—
1
5/08
Corrected Figure 2.
7
DESCRIPTION
PAGES
CHANGED
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.
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