19-4972; Rev 2; 4/11
TION KIT
EVALUA BLE
AVAILA
Integrated, 2-Channel, High-Brightness LED Driver
with High-Voltage Boost and SEPIC Controller
General Description
The MAX16838
is a dual-channel LED driver that inte-
grates both the DC-DC switching boost regulator and
two 150mA current sinks. A current-mode switching
DC-DC controller provides the necessary voltage to
both strings of HB LEDs. The MAX16838 accepts a wide
4.75V to 40V input voltage range and directly withstands
automotive load-dump events. For a 5V
Q10%
input volt-
age, connect V
IN
to V
CC
. The wide input range allows
powering HB LEDs for small-to-medium-sized LCD dis-
plays in automotive and display backlight applications.
An internal current-mode switching DC-DC controller
supports the boost or SEPIC topologies and operates
in an adjustable frequency range between 200kHz and
2MHz. The current-mode control provides fast response
and simplifies loop compensation. The MAX16838 also
features an adaptive output-voltage adjustment scheme
that minimizes the power dissipation in the LED current
sink paths. The MAX16838 can be combined with the
MAX15054 to achieve a buck-boost LED driver with two
integrated current sinks.
The channel current is adjustable from 20mA to 150mA
using an external resistor. The external resistor sets both
channel currents to the same value. The device allows
connecting both strings in parallel to achieve a maximum
current of 300mA in a single channel. The MAX16838
also features pulsed dimming control with minimum
pulse widths as low as 1Fs, on both channels through a
logic input (DIM).
The MAX16838 includes an output overvoltage protec-
tion, open LED, shorted LED detection and overtempera-
ture protection. The device operates over the -40NC to
+125NC automotive temperature range. The MAX16838
is available in the 20-pin TSSOP and 4mm x 4mm, 20-pin
TQFN packages.
Features
S
Integrated, 2-Channel, 20mA to 150mA Linear LED
Current Sinks
S
Boost or SEPIC Power Topologies for Maximum
Flexibility
S
Adaptive Voltage Optimization to Minimize Power
Dissipation in Linear Current Sinks
S
4.75V to 40V or 5V ±10% Input Operating Voltage
Range
S
5000:1 PWM Dimming at 200Hz
S
Open-Drain Fault Indicator Output
S
LED Open/Short Detection and Protection
S
Output Overvoltage and Overtemperature
Protection
S
Programmable LED Current Foldback at Lower
Input Voltages
S
200kHz to 2MHz Resistor Programmable
Switching Frequency with External
Synchronization
S
Current-Mode Control Switching Stage with
Internal Slope Compensation
S
Enable Input
S
Thermally Enhanced, 20-Pin TQFN (4mm x 4mm)
and 20-Pin TSSOP Packages
MAX16838
Ordering Information
PART
MAX16838ATP+
MAX16838ATP/V+
MAX16838AUP+
MAX16838AUP/V+
TEMP RANGE
-40NC to +125NC
-40NC to +125NC
-40NC to +125NC
-40NC to +125NC
PIN-PACKAGE
20 TQFN-EP*
20 TQFN-EP*
20 TSSOP-EP*
20 TSSOP-EP*
+Denotes
a lead(Pb)-free/RoHS-compliant package.
*EP
= Exposed pad.
/V denotes an automotive qualified part.
Simplified Schematic
4.75V TO 40V
C
IN
L
D
C
OUT
Applications
Automotive Display Backlights
LCD Display Backlights
Automotive Lighting Applications
R2
OV
IN
EN
CFB
V
CC
DRV
DRAIN
OV
NDRV
GATE
OUT1
R1
OV
LED
STRINGS
MAX16838
OUT2
ISET
FLT
R
ISET
DIM
COMP
C
COMP
R
COMP
SGND
PGND
CS
RT
LEDGND
R
RT
R
CS
Typical Operating Circuit and Pin Configurations appear 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.
Integrated, 2-Channel, High-Brightness LED Driver
with High-Voltage Boost and SEPIC Controller
MAX16838
ABSOLUTE MAXIMUM RATINGS
IN, OUT_, DRAIN to SGND ...................................-0.3V to +45V
EN to SGND ...............................................-0.3V to (V
IN
+ 0.3V)
PGND to SGND ....................................................-0.3V to +0.3V
LEDGND to SGND ...............................................-0.3V to +0.3V
DRV to PGND .......... -0.3V to the lower of (V
IN
+ 0.3V) and +6V
GATE to PGND ........................................................-0.3V to +6V
NDRV to PGND .......................................-0.3V to (V
DRV
+ 0.3V)
V
CC
,
FLT,
DIM, CS, OV, CFB, to SGND .................-0.3V to +6V
RT, COMP, ISET to SGND.........................-0.3V to (V
CC
+ 0.3V)
DRAIN and CS Continuous Current ..................................
Q2.5A
OUT_ Continuous Current ................................................175mA
V
DRV
Short-Circuit Duration .....................................Continuous
Continuous Power Dissipation (T
A
= +70NC)
20-Pin TQFN (derate 25.6mW/NC above +70NC) ............2051mW
20-Pin TSSOP (derate 26.5mW/NC above +70NC) ......2122mW
Operating Temperature Range ........................ -40NC to +125NC
Junction Temperature .....................................................+150NC
Storage Temperature Range............................ -65NC to +150NC
Soldering Temperature (reflow) ......................................+260NC
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.
PACKAGE THERMAL CHARACTERISTICS (Note 1)
20 TQFN
Juction-to-Ambient Thermal Resistance (B
JA
) .......... +39NC/W
Junction-to-Case Thermal Resistance (B
JC
)............... +6NC/W
20 TSSOP
Junction-to-Ambient Thermal Resistance (B
JA
) ..... +37.7NC/W
Junction-to-Case Thermal Resistance (B
JC
) ............... +2NC/W
Note 1:
Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-
layer board. For detailed information on package thermal considerations, refer to
www.maxim-ic.com/thermal-tutorial.
ELECTRICAL CHARACTERISTICS
(V
IN
= V
EN
= 12V, R
RT
= 12.2kI, R
ISET
= 15kI, C
VCC
= 1FF, V
CC
= V
DRV
= V
CFB
, DRAIN, COMP, OUT_,
FLT
= unconnected, V
OV
= V
CS
= V
LEDGND
= V
DIM
= V
PGND
= V
SGND
= 0V, V
GATE
= V
NDRV
, T
A
= T
J
= -40NC to +125NC, unless otherwise noted. Typical
values are at T
A
= 25NC.) (Note 2)
PARAMETER
Input Voltage Range
Input Voltage Range
Quiescent Supply Current
Standby Supply Current
Undervoltage Lockout
Undervoltage Lockout Hysteresis
DRV REGULATOR
Output Voltage
Dropout Voltage
Short-Circuit Current Limit
V
CC
Undervoltage Lockout
Threshold
V
CC
(UVLO) Hysteresis
UVLO
VCC
V
DRV
5.75V < V
IN
< 10V, 0.1mA < I
LOAD
< 30mA
6.5V < V
IN
< 40V, 0.1mA < I
LOAD
< 3mA
4.75
5
0.11
97
3.4
4.0
123
4.4
5.25
0.5
V
V
mA
V
mV
SYMBOL
V
IN
V
IN
I
Q
I
SH
UVLO
IN
V
IN
= V
CC
V
DIM
= 5V
V
EN
= SGND (Note 3)
V
IN
rising, V
DIM
= 5V
4
CONDITIONS
Internal LDO on
MIN
4.75
4.55
3.1
15.5
4.3
177
TYP
MAX
40
5.5
5
40
4.55
UNITS
V
V
mA
FA
V
mV
V
DO
V
IN
= 4.75V, I
OUT
= 30mA
(V
IN
- V
DRV
)
DRV shorted to GND
V
CC
rising
2
______________________________________________________________________________________
Integrated, 2-Channel, High-Brightness LED Driver
with High-Voltage Boost and SEPIC Controller
ELECTRICAL CHARACTERISTICS (continued)
(V
IN
= V
EN
= 12V, R
RT
= 12.2kI, R
ISET
= 15kI, C
VCC
= 1FF, V
CC
= V
DRV
= V
CFB
, DRAIN, COMP, OUT_,
FLT
= unconnected, V
OV
= V
CS
= V
LEDGND
= V
DIM
= V
PGND
= V
SGND
= 0V, V
GATE
= V
NDRV
, T
A
= T
J
= -40NC to +125NC, unless otherwise noted. Typical
values are at T
A
= 25NC.) (Note 2)
PARAMETER
RT OSCILLATOR
Switching Frequency Range
Duty Cycle
Oscillator Frequency Accuracy
Synchronization Logic-High
Synchronization Logic-Low
Logic-Level Before SYNC
Capacitor
Synchronization Pulse Width
SYNC Frequency Range
PWM COMPARATOR
Leading-Edge Blanking
Propagation Delay to NDRV
SLOPE COMPENSATION
Slope Compensation Peak
Voltage per Cycle
CS LIMIT COMPARATOR
CS Threshold Voltage
CS Limit Comparator Propagation
Delay to NDRV
CS Input Current
ERROR AMPLIFIER
OUT_ Regulation Voltage
Transconductance
No-Load Gain
COMP Sink Current
COMP Source Current
MOSFET DRIVER
NDRV On-Resistance
Peak Sink Current
Peak Source Current
POWER MOSFET
Power Switch On-Resistance
Switch Leakage Current
Switch Gate Charge
I
SWITCH
= 0.5A, V
GS
= 5V
V
DRAIN
= 40V, V
GATE
= 0V
V
DRAIN
= 40V, V
GS
= 4.5V
0.15
0.003
3.1
0.35
1.2
I
FA
nC
I
SINK
= 100mA, V
IN
> 5.5V
I
SOURCE
= 100mA, V
IN
> 5.5V
V
NDRV
= 5V
V
NDRV
= 0V
1.5
1.5
0.8
0.8
4
4
I
I
A
A
Gm
A
I
SINK
I
SOURCE
(Note 4)
V
DIM
= V
OUT_
= 5V, V
COMP
= 3V
V
DIM
= 5V, V
OUT_
= V
COMP
= 0V
V
DIM
= 5V
0.9
340
1
600
50
400
400
800
800
1.1
880
V
FS
dB
FA
FA
I
CS
V
CS_MAX
V
COMP
= 3V
10mV overdrive (including leading-edge
blanking time)
0
P
V
CS
P
0.35V
-1.3
285
300
100
+0.5
315
mV
ns
FA
Voltage ramp added to CS
0.12
V
Including leading-edge blanking time
66
100
ns
ns
f
SYNC
f
SW
D
MAX
f
SW
= 200kHz
f
SW
= 2000kHz
f
SW
= 200kHz to 2MHz
V
RT
rising
V
RT
falling
3.1
50
1.1 x
f
SW
1.5 x
f
SW
200
87
83
-7.5
1.8
2.5
3.8
90
85
2000
95
91
+7.5
3.6
kHz
%
%
%
V
V
V
ns
Hz
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
MAX16838
_______________________________________________________________________________________
3
Integrated, 2-Channel, High-Brightness LED Driver
with High-Voltage Boost and SEPIC Controller
MAX16838
ELECTRICAL CHARACTERISTICS (continued)
(V
IN
= V
EN
= 12V, R
RT
= 12.2kI, R
ISET
= 15kI, C
VCC
= 1FF, V
CC
= V
DRV
= V
CFB
, DRAIN, COMP, OUT_,
FLT
= unconnected, V
OV
= V
CS
= V
LEDGND
= V
DIM
= V
PGND
= V
SGND
= 0V, V
GATE
= V
NDRV
, T
A
= T
J
= -40NC to +125NC, unless otherwise noted. Typical
values are at T
A
= 25NC.) (Note 2)
PARAMETER
LED CURRENT SINKS
OUT_ Current Range
LED Strings Current Matching
Maximum Peak-to-Peak Boost
Ripple
I
OUT_
V
DIM
= 5V, V
OUT_
= 1.0V
I
OUT_
= 100mA, R
ISET
= 15kI
1% I
OUT
variation, I
OUT
= 100mA,
R
ISET
= 15kI
I
OUT_
= 100mA,
R
ISET
= 15kI
T
A
= +25NC
T
A
= -40NC to +125NC
97
95
18.7
0.3
100
100
20
1
1.23
0
P
V
CFB
P
1.3V
V
ENHI
V
EN_HYS
V
EN
= 40V
V
IH
V
IL
V
DIM_HYS
I
DIM
V
DIM
= 5V or 0
V
DIM
rising edge to 90% of set current
V
DIM
falling edge to 10% of set current
t
R
t
F
Rise time measured from 10% to 90%
Fall time measured from 90% to 10%
3.1
3.55
6
6.8
-600
50
10
290
121
120
50
110
+100
1000
700
600
500
5.5
4.85
9.5
8.6
-500
2.1
0.8
V
EN
rising
-0.3
1.1
1.24
71
+50
+700
+0.3
1.34
20
150
Q2
0.5
103
105
21.3
300
mA
%
V
mA
mA
mA
nA
V
FA
V
mV
nA
V
V
mV
nA
ns
ns
ns
ns
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Output Current Accuracy
OUT_ Leakage Current
Current Foldback Threshold
Voltage
CFB Input Bias Current
ENABLE COMPARATOR (EN)
Enable Threshold
Enable Threshold Hysteresis
Enable Input Current
DIM LOGIC
DIM Input Logic-High
DIM Input Logic-Low
Hysteresis
DIM Input Current
DIM to LED Turn-On Time
DIM to LED Turn-Off Time
I
OUT_
Rise Time
I
OUT_
Fall Time
LED FAULT DETECTION
LED Shorted Fault Indicator
Threshold
LED String Shorted Shutoff
Threshold
Shorted LED Detection FLAG
Delay
I
OUT_
= 20mA, R
ISET
T
A
= -40NC to +125NC
= 75kI
V
DIM
= 0V, V
OUT_
= 40V
T
A
= +125NC
T
A
= +125NC
4.2
7.7
6
V
V
Fs
4
______________________________________________________________________________________
Integrated, 2-Channel, High-Brightness LED Driver
with High-Voltage Boost and SEPIC Controller
ELECTRICAL CHARACTERISTICS (continued)
(V
IN
= V
EN
= 12V, R
RT
= 12.2kI, R
ISET
= 15kI, C
VCC
= 1FF, V
CC
= V
DRV
= V
CFB
, DRAIN, COMP, OUT_,
FLT
= unconnected, V
OV
= V
CS
= V
LEDGND
= V
DIM
= V
PGND
= V
SGND
= 0V, V
GATE
= V
NDRV
, T
A
= T
J
= -40NC to +125NC, unless otherwise noted. Typical
values are at T
A
= 25NC.) (Note 2)
PARAMETER
FLT
LOGIC
Output-Voltage Low
Output Leakage Current
OVERVOLTAGE PROTECTION
OV Trip Threshold
OV Hysteresis
OV Input Bias Current
THERMAL SHUTDOWN
Thermal Shutdown
Thermal Shutdown Hysteresis
165
15
o
C
o
C
MAX16838
SYMBOL
V
OL
CONDITIONS
V
IN
= 4.75V and I
SINK
= 5mA
V
FILT
= 5.5V
V
OV
rising
0
P
V
OV
P
1.3V
MIN
TYP
MAX
0.4
UNITS
V
nA
V
mV
nA
-300
1.19
-100
1.23
70
+300
1.265
+100
Note 2:
All devices are 100% tested at T
A
= +125NC. Limits over temperature are guaranteed by design, not production tested.
Note 3:
The shutdown current does not include currents in the OV and CFB resistive dividers.
Note 4:
Gain =
DV
COMP
/DV
CS
, 0.05V < V
CS
< 0.15V.
Typical Operating Characteristics
(V
IN
= V
EN
= 12V, R
RT
= 12.2kI, R
ISET
= 15kI, C
VCC
= 1FF, V
CC
= V
DRV
= V
CFB,
V
DRAIN
= V
COMP
= V
OUT_
,
FLT
= unconnected,
V
OV
= V
CS
= V
LEDGND
= V
DIM
= V
PGND
= V
SGND
= 0V, V
GATE
= V
NDRV
, T
A
= +25NC, unless otherwise noted.)
SWITCHING WAVEFORM AT 200Hz
(50% DUTY CYCLE)
I
IN
vs. SUPPLY VOLTAGE
MAX16838 toc02
MAX16838 toc01
5.0
4.5
V
LX
10V/div
I
IIN
(mA)
0V
4.0
3.5
3.0
T
A
= -40°C
2.5
2.0
1ms/div
4
8
12
16
20
24
28
SUPPLY VOLTAGE (V)
V
IN
= 12V
32
36
T
A
= +125°C
T
A
= +25°C
I
LED
100mA/div
0A
V
OUT
20V/div
0V
40
_______________________________________________________________________________________
5
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