19-4047; Rev 2; 12 /09
Programmable, Four-String HB LED Driver with
Output-Voltage Optimization and Fault Detection
General Description
The MAX16826 high-brightness LED (HB LED) driver is
designed for backlighting automotive LCD displays and
other display applications such as industrial or desktop
monitors and LCD televisions. The MAX16826 integrates
a switching regulator controller, a 4-channel linear cur-
rent sink driver, an analog-to-digital converter (ADC),
and an I
2
C interface. The IC is designed to withstand
automotive load dump transients up to 40V and can
operate under cold crank conditions.
The MAX16826 contains a current-mode PWM switching
regulator controller that regulates the output voltage to
the LED array. The switching regulator section is config-
urable as a boost or SEPIC converter and its switching
frequency is programmable from 100kHz to 1MHz.
The MAX16826 includes 4 channels of programmable,
fault-protected, constant-current sink driver controllers
that are able to drive all white, RGB, or RGB plus amber
LED configurations. LED dimming control for each chan-
nel is implemented by direct PWM signals for each of the
four linear current sinks. An internal ADC measures the
drain voltage of the external driver transistors and the
output of the switching regulator. These measurements
are then made available through the I
2
C interface to an
external microcontroller (µC) to enable output voltage
optimization and fault monitoring of the LEDs.
The amplitude of the LED current in each linear current-
sink channel and the switch-mode regulator output volt-
age is programmed using the I
2
C interface. Additional
features include: cycle-by-cycle current limit, shorted
LED string protection, and overtemperature protection.
The MAX16826 is available in a thermally enhanced,
5mm x 5mm, 32-pin thin QFN package and is specified
over the automotive -40°C to +125°C temperature range.
Features
o
External MOSFETs Allow Wide-Range LED
Current with Multiple LEDs per String
o
Individual PWM Dimming Inputs per String
o
Very Wide Dimming Range
o
LED String Short and Open Protection
o
Adjustable LED Current Rise/Fall Times Improve
EMI Control
o
Microcontroller Interface Using I
2
C Allows
LED Voltage Monitoring and Optimization
Using a 7-Bit Internal ADC
LED Short and Open Detection
Dynamic Adjustment of LED String Currents
and Output Voltage
Standby Mode
o
Integrated Boost/SEPIC Controller
o
External Switching Frequency Synchronization
o
4.75V to 24V Operating Voltage Range and
Withstands 40V Load Dump
o
Overvoltage and Overtemperature Protection
MAX16826
Ordering Information
PART
MAX16826ATJ+
MAX16826ATJ/V+
TEMP RANGE
-40°C to +125°C
-40°C to +125°C
PIN-PACKAGE
32 TQFN-EP*
32 TQFN-EP*
+Denotes
a lead(Pb)-free/RoHS-compliant package.
*EP
= Exposed pad.
/V
denotes an automotive qualified part.
Simplified Diagram
V
IN
Applications
LCD Backlighting:
Automotive Infotainment Displays
Automotive Cluster Displays
Industrial and Desktop Monitors
LCD TVs
Automotive Lighting:
Adaptive Front Lighting
Low- and High-Beam Assemblies
IN
DIM1
DIM2
DIM3
DIM4
DL
CS
FB
DR4
DIMMING
INPUTS
DR1
DL1
CS1
MAX16826
SDA I
2
C
SCL INTERFACE
Typical Application Circuit and Pin Configuration appear at
end of data sheet.
BOOST LED DRIVER
GND
DL4
CS4
________________________________________________________________
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.
Programmable, Four-String HB LED Driver with
Output-Voltage Optimization and Fault Detection
MAX16826
ABSOLUTE MAXIMUM RATINGS
IN to GND (Continuous) .........................................-0.3V to +30V
IN Peak Current (≤ 400ms) ...............................................300mA
IN Continuous Current ........................................................50mA
PGND to GND .......................................................-0.3V to +0.3V
All Other Pins to GND...............................................-0.3V to +6V
DL Peak Current (< 100ns)....................................................±3A
DL Continuous Current .....................................................±50mA
DL1, DL2, DL3, DL4 Peak Current ..................................±50mA
DL1, DL2, DL3, DL4 Continuous Current ........................±20mA
V
CC
Continuous Current .....................................................50mA
All Other Pins Current .......................................................±20mA
Continuous Power Dissipation (T
A
= +70°C)
32-Pin Thin QFN (derate 34.5mW/°C above +70°C)
Multilayer Board ..........................................................2759mW
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
(V
IN
= 12V, R19 = 2kΩ, C33 = 2200pF, R17 = 1.27kΩ, C
DL_
= 0.01µF, T
J
= -40°C to +125°C, unless otherwise noted. Typical values
are at T
A
= +25°C.) (Note 1)
PARAMETER
Power-Supply Voltage
Quiescent Current
Shutdown Current
Standby Current
I
2
C-COMPATIBLE I/O (SCL, SDA)
Input High Voltage
Input Low Voltage
Input Hysteresis
Input High Leakage Current
Input Low Leakage Current
Input Capacitance
Output Low Voltage
Output High Current
I
2
C-COMPATIBLE TIMING
Serial Clock (SCL) Frequency
BUS Free Time Between STOP
and START Conditions
START Condition Hold Time
STOP Condition Setup Time
Clock Low Period
Clock High Period
Data Setup Time
Data In Hold Time
Data Out Hold Time
f
SCL
t
BUF
t
HD:STA
t
SU:STO
t
LOW
t
HIGH
t
SU:DAT
t
HD:DATIN
t
HD:DATOUT
1.3
0.6
0.6
1.3
0.6
0.3
0.03
0.3
0.9
400
kHz
µs
µs
µs
µs
µs
µs
µs
µs
V
IH
V
IL
V
HYS
I
IH
I
IL
C
IN
V
OL
I
OH
I
OL
= 3mA
V
OH
= 5V
V
LOGIC
= 5V
V
LOGIC
= 0
-1
-1
10
0.4
1
25
+1
+1
1.5
0.5
V
V
mV
µA
µA
pF
V
µA
SYMBOL
V
IN
I
IN
I
IN,SD
I
IN,SB
V
SYNC
= 3V
DL_ = unconnected; R19, C33 = open
V
SYNC
= 0
I
2
C standby activated
CONDITIONS
MIN
4.75
5
20
3
TYP
MAX
24
10
75
UNITS
V
mA
µA
mA
2
_______________________________________________________________________________________
Programmable, Four-String HB LED Driver with
Output-Voltage Optimization and Fault Detection
ELECTRICAL CHARACTERISTICS (continued)
(V
IN
= 12V, R19 = 2kΩ, C33 = 2200pF, R17 = 1.27kΩ, C
DL_
= 0.01µF, T
J
= -40°C to +125°C, unless otherwise noted. Typical values
are at T
A
= +25°C.) (Note 1)
PARAMETER
Maximum Receive SCL/SDA Rise
Time
Minimum Receive SCL/SDA Rise
Time
Maximum Receive SCL/SDA Fall
Time
Minimum Receive SCL/SDA Fall
Time
Transmit SDA Fall Time
Pulse Width of Suppressed Spike
INTERNAL REGULATORS (IN, V
CC
)
V
CC
Output Voltage
V
CC
Undervoltage Lockout
V
CC
Undervoltage Lockout
Hysteresis
IN Shunt Regulation Voltage
PWM GATE DRIVER (DL)
Peak Source Current
Peak Sink Current
DL High-Side Driver Resistance
DL Low-Side Driver Resistance
Minimum DL Pulse Width
PWM CONTROLLER, SOFT-START (FB, COMP, OVP)
FB Voltage Maximum
FB Voltage Minimum
FB Voltage LSB
FB Input Bias Current
Feedback-Voltage Line
Regulation
Soft-Start Current
OVP Input Bias Current
Slope Compensation
I
SS
I
OVP
I
SLOPE
I
FB
V
FB,MAX
V
FB,MIN
FB shorted to COMP
FB shorted to COMP
FB shorted to COMP
0 < V
FB
< 5.5V
Level to produce V
COMP
= 1.25V,
4.5V < V
VCC
< 5.5V
V
CSS
= 0.5V
VCC
0 < V
OVP
< 5.5V
3.2
-100
19
6.0
0
26
-100
1.230
862
1.250
876
2.94
0
+100
±0.25
10.4
+100
32
1.260
885
V
mV
mV
nA
%/V
µA
nA
µA/µs
I
DL
= -100mA
I
DL
= +100mA
2
2
2.25
1.30
40
A
A
Ω
Ω
ns
V
VCC
V
VCC_UVLO
V
VCC_HYS
I
IN
= 250mA
0 < I
VCC
< 30mA (Note 2),
4.75V < V
IN
< 24V, DL, DL1 to DL4
unconnected
V
CC
rising
135
24.05
175
26.0
4.5
5.25
5.65
4.5
205
27.5
V
V
mV
V
SYMBOL
t
R
t
R
t
F
t
F
t
F
t
SP
C
B
= 400pF
C
B
= 400pF
C
B
= 400pF
C
B
= 400pF
C
B
= 400pF, I
O
= 3mA
60
50
CONDITIONS
MIN
TYP
300
60
300
60
250
MAX
UNITS
ns
ns
ns
ns
ns
ns
MAX16826
_______________________________________________________________________________________
3
Programmable, Four-String HB LED Driver with
Output-Voltage Optimization and Fault Detection
MAX16826
ELECTRICAL CHARACTERISTICS (continued)
(V
IN
= 12V, R19 = 2kΩ, C33 = 2200pF, R17 = 1.27kΩ, C
DL_
= 0.01µF, T
J
= -40°C to +125°C, unless otherwise noted. Typical values
are at T
A
= +25°C.) (Note 1)
PARAMETER
ERROR AMPLIFIER (FB, COMP)
Open-Loop Gain
Unity-Gain Bandwidth
Phase Margin
Error-Amplifier Output Current
COMP Clamp Voltage
COMP Short-Circuit Current
PWM CURRENT LIMIT (CS)
Cycle-by-Cycle Current-Limit
Threshold
Cycle-by-Cycle Current-Limit
Propagation Time To DL
Gross Current-Limit Threshold
Gross Current-Limit Propagation
Time To DL
Input Bias Current
PWM OSCILLATOR (RTCT)
RTCT Voltage Ramp (Peak to
Peak)
RTCT Voltage Ramp Valley
Discharge Current
Frequency Range
SYNCHRONIZATION (SYNC/ENABLE)
Input Rise/Fall Time
Input Frequency Range
Input High Voltage
Input Low Voltage
Input Minimum Pulse Width
Input Bias Current
Delay to Shutdown
LED DIMMING (DIM1–DIM4)
Input High Voltage
Input Low Voltage
Minimum Dimming Frequency
Input Bias Current
V
DIM,MAX
V
DIM,MIN
f
DIM
I
DIM
t
ON
= 2µs (Note 3)
0 < V
DIM_
< 5.5V
45
-100
0
+100
1.5
0.5
V
V
Hz
nA
0 < V
SYNC
< 5.5V
V
SYNC
= 0V
200
-100
13
0
32
+100
65
100
1.5
0.5
200
1000
ns
kHz
V
V
ns
nA
µs
V
RAMP
V
RAMP_VALLEY
I
DIS
f
OSC
5.5V < V
IN
< 24V
5.5V < V
IN
< 24V
V
RTCT
= 2V
5.5V < V
IN
< 24V
1.60
1.11
7.8
100
1.65
1.20
8.4
1.80
1.27
9.1
1000
V
V
mA
kHz
V
CL
t
PROP, CL
V
GCL
t
PROP,GCL
V
DL
= 0
10mV overdrive
V
CSS
= 0
10mV overdrive
0 < V
CS
< 5.5V
-100
250
187
200
80
270
80
0
+100
280
217
mV
ns
mV
ns
nA
A
OL
BW
PM
I
COMP
V
COMP
I
COMP_SC
Sourcing, V
COMP
= 3V
Sinking, V
COMP
= 2V
V
FB
= 0
3.25
12
80
2
65
1.9
0.9
4.5
dB
MHz
Degrees
mA
V
mA
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
4
_______________________________________________________________________________________
Programmable, Four-String HB LED Driver with
Output-Voltage Optimization and Fault Detection
MAX16826
ELECTRICAL CHARACTERISTICS (continued)
(V
IN
= 12V, R19 = 2kΩ, C33 = 2200pF, R17 = 1.27kΩ, C
DL_
= 0.01µF, T
J
= -40°C to +125°C, unless otherwise noted. Typical values
are at T
A
= +25°C.) (Note 1)
PARAMETER
ADC (DR1–DR4, OVP)
Maximum Error
ADC Single Bit Acquisition
Latency
DR Channel Sample Time
OVP Channel Sample Time
Full-Scale Input Voltage
Least Significant Bit
DR Input Bias Current
Drain Fault Comparator
Threshold
Drain Fault Comparator Delay
Transconductance
Maximum Output Current
CS1–CS4 Input Bias Current
CS1–CS4 Regulation Voltage
Maximum
CS1–CS4 Regulation Voltage
Minimum
CS1–CS4 Regulation Voltage LSB
t
DR,SMPL
t
OVP,SMPL
V
FS
V
LSB
I
DR
0 < V
DR_
< 5.5V
-100
1.215
E
MAX
(Note 4)
2
190
20
1.24
9.76
0
+100
1.2550
±50
mV
µs
ms
µs
V
mV
nA
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
DRAIN FAULT COMPARATORS (DR1–DR4) (Shorted LED String Comparator)
V
DFTH
t
DFD
Gm
I
DL
I
CS
V
CS,MAX
V
CS,MIN
V
CS,LSB
Voltage to drive DL1–DL4 low
10mV overdrive
∆I
= -500µA
Sourcing or sinking
0 < V
CS
< 5.5V
CS_ = DL_, FB DAC full scale
CS_ = DL_, FB DAC minus full scale
CS_ = DL_, FB DAC 1-bit transition
-100
306
90
1.4
1.52
1
75
15
0
316
97
1.72
+100
324
105
1.63
V
µs
mS
mA
nA
mV
mV
mV
LINEAR REGULATORS (DL1–DL4, CS1–CS4)
All devices are 100% production tested at T
J
= +25°C and T
J
= +125°C. Limits to -40°C are guaranteed by design.
I
CC
includes the internal bias currents and the current used by the gate drivers to drive DL, DL1, DL2, DL3, and DL4.
Minimum frequency to allow the internal ADC to complete at least one measurement. t
ON
is the on-time with the LED current
in regulation.
Note 4:
Minimum LED current pulse duration, which is required to correctly acquire 1 bit.
Note 1:
Note 2:
Note 3:
_______________________________________________________________________________________
5
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