MAX16831
High-Voltage, High-Power LED Driver with
Analog and PWM Dimming Control
9
Maxim Integrated
Detailed Description
The MAX16831 is a current-mode PWM LED driver
used for driving HBLEDs. By using two current regula-
tion loops, 5% output current accuracy is achieved.
One current regulation loop controls the external
switching MOSFET peak current through a sense resis-
tor, R
SENSE
, from SNS+ to SNS-, while the other current
regulation loop controls the average LED string current
through the sense resistor R
CS
in series with the LEDs.
The wide operating supply range of (6.0V/5.5V
ON/OFF) up to 76V makes the MAX16831 ideal in auto-
motive applications.
The MAX16831 features a programmable undervoltage
lockout (UVEN) that ensures predictable operation dur-
ing brownout conditions. The input UVEN circuit monitors
the supply voltage, V
CC
, and turns the driver off when
V
CC
drops below the UVLO threshold. Connect UVEN to
V
CC
to use the 5.7V (typ) default UVLO threshold. The
MAX16831 includes a cycle-by-cycle current limit that
turns off the gate drive to the external switching MOS-
FET (Q
S
) during an overcurrent condition. The
MAX16831 features a programmable oscillator that sim-
plifies and optimizes the design of external magnetics.
The MAX16831 includes three internal voltage regula-
tors, REG1, REG2, and CLMP, and a 3V buffered refer-
ence output, REF. Connect REG2 to the driver supply,
DRI, to power the switching MOSFET driver.
The MAX16831 is capable of synchronizing with an
external clock or operating in stand-alone mode. A sin-
gle resistor, R
T
, can be used to adjust the switching fre-
quency from 125kHz to 600kHz for stand-alone
operation. To synchronize the device with an external
clock, apply a clock signal directly to the RTSYNC
input. A buffered clock output, CLKOUT, is available to
configure the MAX16831 in multichannel applications.
Pin Description (continued)
PIN NAME FUNCTION
25 LO
Low-Voltage Input. LO is the return point for the LED current. When using the MAX16831 in a buck-
boost configuration, connect LO to V
CC
. When using the device in a boost configuration only,
connect LO to SGND. Connect LO to the junction of the inductor and LED current-sense resistor,
R
CS
, when using a buck configuration.
26 CS+
Noninverting Current-Sense Amplifier Input. Connect CS+ to the positive side of an external sense
resistor, R
CS
, connected in series with the load (LEDs).
27 CS-
Inverting Current-Sense Amplifier Input. Connect CS- to the negative side of an external sense
resistor, R
CS
, connected in series with the load (LEDs).
28 CLMP
Internal CLMP Regulator Output. CLMP supplies an 8V (typ) output when V
HI
≥ 9V. If V
HI
is lower than
9V, V
CLMP
is one diode drop below V
HI
. The CLMP regulator powers the current-sense amplifier and
provides the high reference for the dimming driver. V
CLMP
must be at least 2.5V higher than V
LO
to
enable the current-sense amplifier and dimming MOSFET driver. Bypass CLMP to LO with a 0.1µF
ceramic capacitor.
29 HI
High-Voltage Input. HI is referred to LO. HI supplies power to the current-sense amplifier and
dimming MOSFET gate driver through the CLMP regulator.
30 REG2
Internal Regulator Output. REG2 is an internal voltage regulator that generates a 7V output and
supplies power to internal circuitry. Connect REG2 to DRI to power the switching MOSFET driver
during normal operation. Bypass REG2 to AGND with a 10µF ceramic capacitor.
31 V
CC
Supply Voltage Input
32 I.C.
Internally Connected. This pin is internally pulled to REG1 through a 10kΩ resistor. Leave this pin
unconnected or connect it to QGND using a resistor of any value. If it is directly connected to QGND,
400µA to 600µA of current will flow out of this pin from V
CC
. Any resistor between this pin and QGND
will reduce the current accordingly.
—EP
Exposed Pad. Connect EP to AGND. EP also functions as a heatsink to maximize thermal dissipation.
Do not use as a ground connection.
