19-0809; Rev 1; 4/09
IT
TION K
VALUA
E
BLE
AVAILA
High-Voltage, High-Power LED Driver with
Analog and PWM Dimming Control
General Description
The MAX16831 is a current-mode, high-brightness LED
(HBLED) driver designed to control two external
n-channel MOSFETs for the single-string LED current
regulation. The MAX16831 integrates all the building
blocks necessary to implement fixed-frequency HBLED
drivers with wide-range dimming control. The
MAX16831 is configurable to operate as a step-down
(buck), step-up (boost), or step-up/-down (buck-boost)
current regulator.
Current-mode control with leading-edge blanking simpli-
fies control-loop design. Internal slope compensation
stabilizes the current loop when operating at duty cycles
above 50%. The MAX16831 operates over a wide input
voltage range and is capable of withstanding automo-
tive load-dump events. Multiple MAX16831s can be
synchronized to each other or to an external clock. The
MAX16831 includes a floating dimming driver for
brightness control with an external n-channel MOSFET
in series with the LED string.
HBLED drivers using the MAX16831 achieve efficien-
cies of over 90% in automotive applications. The
MAX16831 also includes a 1.4A source and 2.5A sink
gate driver for driving switching MOSFETs in high-power
LED driver applications, such as front light assemblies.
The dimming control allows for wide PWM dimming at
frequencies up to 2kHz. Higher dimming ratios of up to
1000:1 are achievable at lower dimming frequencies.
The MAX16831 is available in a 32-pin thin QFN package
with exposed pad and operates over the -40°C to
+125°C automotive temperature range.
Features
o
Wide Input Range: 6V to 76V With Cold-Start
Operation to 5.5V
o
Integrated Differential LED Current-Sense
Amplifier
o
Floating Dimming Driver Capable of Driving an
n-Channel MOSFET
o
5% LED Current Accuracy
o
200Hz On-Board Ramp Syncs to External PWM
Dimming Signal
o
Programmable Switching Frequency (125kHz to
600kHz) and Synchronization
o
Output Overvoltage Load Dump, LED Short,
Overtemperature Protection
o
Low 107mV LED Current Sense for High
Efficiency
o
Enable/Shutdown Input with Shutdown Current
Below 45µA
MAX16831
Ordering Information
PART
MAX16831ATJ+
TEMP RANGE
-40°C to +125°C
PIN-PACKAGE
32 TQFN-EP*
+Denotes
a lead(Pb)-free/RoHS-compliant package.
*EP
= Exposed pad.
Typical Operating Circuits
BUCK-BOOST CONFIGURATION
V
IN
R
CS
Applications
Automotive Exterior Lighting:
High-Beam/Low-Beam/Signal Lights
Rear Combination Lights (RCL)
Daytime Running Lights (DRL)
Fog Light and Adaptive Front Light Assemblies
Industrial and Architectural Lighting
Emergency Lighting
Projectors with RGB LED Light Sources
Navigation and Marine Indicators
COMP
R1
CS
FB
C
REG1
R
T
RTSYNC
R
UV2
C
CLMP
R
UV1
UVEN
C
UVEN
V
CC
LO
CLMP
CS-
CS+
DGT
R
D
DRV
SNS+
Q
S
LEDs
DIM
R
SENSE
DIM
REG1
SNS-
MAX16831
QGND
HI
C
F
R
OV1
OV
AGND
SGND
REG2
DRI
R
OV2
C
REG2
C2
R2
C1
Pin Configuration appears at end of data sheet.
Typical Operating Circuits continued at end of data sheet.
________________________________________________________________
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, High-Power LED Driver with
Analog and PWM Dimming Control
MAX16831
ABSOLUTE MAXIMUM RATINGS
V
CC
, HI, LO, CLMP to QGND .................................-0.3V to +80V
CS+, CS-, DGT, UVEN to QGND............................-0.3V to +80V
UVEN to QGND ..........................................-0.3V to (V
CC
+ 0.3V)
DRV to SGND .........................................................-0.3V to +18V
DRI, REG2, DIM to AGND ......................................-0.3V to +18V
QGND, SGND to AGND ........................................-0.3V to +0.3V
SNS+ to SNS- ...........................................................-0.3V to +6V
CS, FB, COMP, SNS+, SNS-, OV, REF,
RTSYNC to AGND .................................................-0.3V to +6V
REG1, CLKOUT to AGND ........................................-0.3V to +6V
CS+ to CS- .............................................................-0.3V to +12V
HI to LO ..................................................................-0.3V to +36V
CS+, CS-, DGT, CLMP to LO .................................-0.3V to +12V
CS+, CS-, DGT, CLMP to LO ........................-0.3V to (HI + 0.3V)
HI to CLMP .............................................................-0.3V to +28V
Continuous Power Dissipation* (T
A
= +70°C)
32-Pin TQFN (derate 34.5mW/°C above +70°C) ........2758mW
Thermal Resistance*
θ
JA
.................................................................................29°C/W
θ
JC
................................................................................1.7°C/W
Operating Temperature Range .........................-40°C to +125°C
Maximum Junction Temperature .....................................+150°C
Storage Temperature Range .............................-60°C to +150°C
Reflow Temperature.........................................................+240°C
Lead Temperature (soldering, 10s) .................................+300°C
*As per JEDEC 51 standard, multilayer board (PCB).
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
CC
= V
UVEN
= 14V, C
REG1
= 1µF, C
REG2
= 1µF, C
CLMP
= 0.1µF, R
T
= 25kΩ, T
A
= T
J
= -40°C to +125°C, unless otherwise noted.
Typical specifications are at T
A
= +25°C.)
PARAMETER
Input Voltage Range
Supply Current
Shutdown Current
UVEN
V
CC
UVLO Threshold
V
CC
Threshold Hysteresis
UVEN Threshold
UVEN Input Current
REGULATORS
REG1 Regulator Output
REG1 Dropout Voltage
REG1 Load Regulation
REG2 Regulator Output
REG2 Dropout Voltage
REG2 Load Regulation
CLMP UVLO Threshold
CLMP UVLO Threshold
Hysteresis
ΔV/ΔI
V
CLMPTH
V
CLMPHYS
ΔV/ΔI
V
REG2
V
REG1
0
≤
I
REG1
≤
2mA, 7.5V
≤
V
CC
≤
76V
I
REG1
= 2mA, V
CC
= 5.7V
I
REG1
= 2mA (Note 1)
V
CC
= 7.5V, 0
≤
I
REG1
≤
2mA
7.5V
≤
V
CC
≤
76V, I
REG2
= 1mA
V
CC
= 5.7V, 0
≤
I
REG2
≤
20mA
I
REG2
= 20mA (Note 1)
V
CC
= 7.5V, 0
≤
I
REG2
≤
20mA
V
CLMP
rising
2.0
2.5
0.22
6.65
4.5
7.00
5.0
0.5
25
3.0
4.75
4.00
5.00
4.50
0.5
5.25
5.25
1.0
25
7.35
V
V
Ω
V
V
Ω
V
V
V
CC_R
V
CC_F
V
CC_HYS
V
UVR
V
UVF
I
UVEN
V
UVEN
rising
V
UVEN
falling
V
UVEN
= 0V and V
UVEN
= 76V, V
CC
= 77V
1.100
1.000
-0.2
V
CC
rising
V
CC
falling
5.5
5.0
0.4
1.244
1.145
1.360
1.260
+0.2
6.0
5.5
V
V
V
µA
SYMBOL
V
CC
I
Q
I
SHDN
I
REG2
= 0A
V
UVEN
≤
0.8V
CONDITIONS
MIN
5.5
2.7
25
TYP
MAX
76.0
4.5
45
UNITS
V
mA
µA
HIGH-SIDE REGULATOR (CLMP) (All Voltages Referred to LO) (Note 2)
2
_______________________________________________________________________________________
High-Voltage, High-Power LED Driver with
Analog and PWM Dimming Control
MAX16831
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= V
UVEN
= 14V, C
REG1
= 1µF, C
REG2
= 1µF, C
CLMP
= 0.1µF, R
T
= 25kΩ, T
A
= T
J
= -40°C to +125°C, unless otherwise noted.
Typical specifications are at T
A
= +25°C.)
PARAMETER
CLMP Regulator Output Voltage
SYMBOL
V
CLMP
CONDITIONS
8.7V
≤
(V
HI
- V
LO
)
≤
36V, I
CLMP
= 1mA
5.0V
≤
(V
HI
- V
LO
)
≤
8.7V, I
CLMP
= 250µA
MIN
5.5
TYP
8.0
(V
HI
- V
LO
)
- 0.7
MAX
10.0
V
UNITS
CURRENT-SENSE AMPLIFIER (CSA)
Differential Input Voltage Range
Common-Mode Range
CS+ Input Bias Current
CS- Input Bias Current
Unity-Gain Bandwidth
REF OUTPUT BUFFER
REF Output Voltage
DIM DRIVER
Source Current
Sink Current
GATE DRIVER
DRI UVLO Threshold
DRI UVLO Threshold Hysteresis
Driver Output Impedance
Peak Sink Current
Peak Source Current
PWM Comparator Offset Voltage
Peak Current-Limit Comparator
Trip Threshold
Peak Current-Limit Comparator
Propagation Delay (Excluding
Blanking Time)
HICCUP Comparator Trip
Threshold
SNS+ Input Bias Current
SNS- Input Bias Current
Blanking Time
t
BLNK
V
SNS+
= 0V, V
SNS-
= 0V
V
SNS+
= 0V, V
SNS-
= 0V
50mV overdrive
V
UVLO_TH
V
UVLO_HYST
Z
OUT_L
Z
OUT_H
I
SK
I
SR
V
DRI
= 7.0V, DRV sinking 250mA
V
DRI
= 7.0V, DRV sourcing 250mA
V
DRI
= 7.0V
V
DRI
= 7.0V
V
COMP
- (V
SNS+
- V
SNS-)
160
DRI rising
4.0
4.2
0.3
2.8
5.0
2.5
1.4
0.7
200
240
4
8
4.4
V
V
Ω
A
A
V
mV
V
CLMP
- V
LO
= 4V
V
CLMP
- V
LO
= 8V
V
CLMP
- V
LO
= 4V
V
CLMP
- V
LO
= 8V
5
30
10
40
20
67
22
76
mA
mA
V
REF
-100µA
≤
I
REF
≤
+100µA
2.85
3.00
3.15
V
I
CS+
I
CS-
V
CS+
- V
CS-
= 0.3V
V
CS+
- V
CS-
= 0.3V
From (CS+ - CS-) to CS
1.0
V
CS+
-
V
CS-
0
0
-250
0.3
V
CC
+250
400
V
V
µA
µA
MHz
PWM, ILIM, AND HICCUP COMPARATOR
40
ns
235
-100
-100
300
-65
-65
40
385
mV
µA
µA
ns
_______________________________________________________________________________________
3
High-Voltage, High-Power LED Driver with
Analog and PWM Dimming Control
MAX16831
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= V
UVEN
= 14V, C
REG1
= 1µF, C
REG2
= 1µF, C
CLMP
= 0.1µF, R
T
= 25kΩ, T
A
= T
J
= -40°C to +125°C, unless otherwise noted.
Typical specifications are at T
A
= +25°C.)
PARAMETER
ERROR AMPLIFIER
FB Input Bias Current
EAMP Output Sink Current
EAMP Output Source Current
EAMP Input Common-Mode
Voltage
EAMP Output Clamp Voltage
Voltage Gain
Unity-Gain Bandwidth
A
V
GBW
R
COMP
= 100kΩ to AGND
R
COMP
= 100kΩ to AGND, C
COMP
= 100pF
to AGND
V
FB
= 1.735V, V
COMP
= 1V
V
FB
= 0.735V, V
COMP
= 1V
-100
3
2
0
1.1
1.7
80
0.5
7
7
3.0
2.4
+100
nA
mA
mA
V
V
dB
MHz
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
OSCILLATOR, OSC SYNC, CLK, AND CLKOUT
RTSYNC Frequency Range
RTSYNC Oscillator Frequency
RTSYNC High-Level Voltage
RTSYNC Low-Level Voltage
CLKOUT High Level
CLKOUT Low Level
CLKOUT Maximum Load
Capacitance
Internal Ramp Frequency
External Sync Frequency Range
External Sync Low-Level Voltage
External Sync High-Level Voltage
DIM Comparator Offset
DIGITAL SOFT-START
Soft-Start Duration
OVP Overvoltage Comparator
Threshold
OVP Overvoltage Comparator
Hysteresis
SLOPE COMPENSATION
Slope Compensation Peak
Voltage Per Cycle
Slope Compensation
Clock generated by R
T
External clock applied to RTSYNC
120
15
mV
mV/µs
t
SS
4.0
ms
OVERVOLTAGE COMPARATOR, LOAD OVERCURRENT COMPARATOR
V
OV
V
OV_HYST
V
OV
rising
1.20
1.235
63.5
1.27
V
mV
C
CLK_CAP
V
SIHL
V
SILL
I
SINK
= 0.8mA
I
SOURCE
= 1.6mA
f
SW
= 500kHz
2.8
0.4
500
f
SWMIN
f
SWMAX
R
T
= 25kΩ
R
T
= 100kΩ
500
475
106
2.8
0.4
500
125
525
143
125
kHz
kHz
V
V
V
V
pF
DIM SYNC, DIM RAMP, AND DIM PWM GEN
f
RAMP
f
DIM
V
LTH
V
HTH
V
DIMOS
170
200
160
80
0.4
3.2
300
200
240
2000
Hz
Hz
V
V
mV
4
_______________________________________________________________________________________
High-Voltage, High-Power LED Driver with
Analog and PWM Dimming Control
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= V
UVEN
= 14V, C
REG1
= 1µF, C
REG2
= 1µF, C
CLMP
= 0.1µF, R
T
= 25kΩ, T
A
= T
J
= -40°C to +125°C, unless otherwise noted.
Typical specifications are at T
A
= +25°C.)
PARAMETER
THERMAL SHUTDOWN
Thermal Shutdown Temperature
Hysteresis
T
SHDN
ΔT
SHDN
Temperature rising
+165
20
°C
°C
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
MAX16831
Note 1:
Dropout voltage is defined as the input to output differential voltage at which the regulator output voltage drops 100mV below
the nominal output voltage.
Note 2:
V
CLMPTH
determines the voltage required to operate the current-sense amplifier. The DIM driver requires 2.5V for (V
CLMP
- V
LO
)
to drive the external MOSFET. V
HI
is typically one diode drop above V
CLMP
. A large capacitor connected to V
CLMP
slows the
response of the LED current-sense circuitry, resulting in current overshoot. To ensure proper operation, connect a 0.1µF
capacitor from CLMP to LO.
Typical Operating Characteristics
(V
CC
= V
UVEN
= 14V, C
REG1
= 1µF, C
REG2
= 10µF, C
CLMP
= 0.1µF, R
T
= 25kΩ, R
CS
= 0.1Ω, T
A
= +25°C, unless otherwise noted.)
SHUTDOWN CURRENT
vs. TEMPERATURE
MAX16831 toc01
OPERATING CURRENT
vs. TEMPERATURE
MAX16831 toc02
VOLTAGE ACROSS LED CURRENT-SENSE
RESISTOR vs. SUPPLY VOLTAGE
110
VOLTAGE ACROSS R
CS
(mV)
100
90
80
70
60
50
40
30
20
10
0
0
10
20
SUPPLY VOLTAGE (V)
30
40
MAX16831 toc03
28
27
SHUTDOWN CURRENT (μA)
26
25
24
23
22
21
20
19
18
-60 -40 -20 0
3.0
2.9
OPERATING CURRENT (mA)
2.8
2.7
2.6
2.5
2.4
2.3
2.2
2.1
2.0
DGT AND DRV NOT
SWITCHING
-60 -40 -20 0
120
20 40 60 80 100 120 140
20 40 60 80 100 120 140
TEMPERATURE (°C)
TEMPERATURE (°C)
_______________________________________________________________________________________
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