MAX16807_07 Datasheet, PDF (11/21 Pages) Maxim Integrated Products – Integrated 8-Channel LED Drivers with Switch-Mode Boost and SEPIC Controller

Integrated 8-Channel LED Drivers with
Switch-Mode Boost and SEPIC Controller
PIN
1, 13, 28
2
3
4
5
6–9
10
11
12
14
15, 16
17
18
19
20–23
24
25
26
27
—
Pin Description
NAME
N.C.
AGND
OUT
FUNCTION
No Connection. Not internally connected. Leave unconnected.
Analog Ground
MOSFET Driver Output OUT. Connects to the gate of the external n-channel MOSFET.
V_CC
Power-Supply Input. Bypass V_CC to AGND with a 0.1µF ceramic capacitor or a parallel combination
of a 0.1µF and a higher value ceramic capacitor.
REF
5V Reference Output. Bypass REF to AGND with a 0.1µF ceramic capacitor.
OUT4–OUT7 LED Driver Outputs. OUT4–OUT7 are open-drain, constant-current-sinking outputs rated for 36V.
OE
Active-Low Output Enable Input. Drive OE low to PGND to enable the OUT0–OUT7. Drive OE high to
disable OUT0–OUT7.
DOUT
Serial-Data Output. Data is clocked out of the 8-bit internal shift register to DOUT on CLK’s rising
edge.
SET
LED Current Setting. Connect R_SET from SET to PGND to set the LED current.
V+
LED Driver Positive Supply Voltage. Bypass V+ to PGND with a 0.1µF ceramic capacitor.
PGND Power Ground
DIN
Serial-Data Input
CLK
Serial-Clock Input
Latch-Enable Input. Data is loaded transparently from the internal shift register(s) to the output
LE
latch(es) while LE is high. Data is latched into the output latch(es) on LE’s falling edge, and retained
while LE is low.
OUT0–OUT3
COMP
FB
CS
LED Driver Outputs. OUT0–OUT3 are open-drain, constant-current-sinking outputs rated for 36V.
Error-Amplifier Output
Error-Amplifier Inverting Input
PWM Controller Current-Sense Input
RTCT
PWM Controller Timing Resistor/Capacitor Connection. A resistor R_T from RTCT to REF and a
capacitor C_T from RTCT to AGND set the oscillator frequency.
EP
Exposed Paddle. Connect to the ground plane for improved power dissipation. Do not use as the
only ground connection for the part.
Detailed Description
The MAX16807/MAX16808 LED drivers include an
internal switch-mode controller that can be used as
boost or buck-boost (SEPIC) converters to generate the
voltage necessary to drive the multiple strings of LEDs.
These devices incorporate an integrated low-side dri-
ver, a programmable oscillator (20kHz to 1MHz), an
error amplifier, a low-voltage (300mV) current sense for
higher efficiency, and a 5V reference to power up
external circuitry (see Figures 1a, 1b, and 1c).
The MAX16807/MAX16808 LED drivers include a 4-wire
serial interface and a current-mode PWM controller to
generate the necessary voltage for driving eight open-
drain, constant-current-sinking output ports. The drivers
use current-sensing feedback circuitry (not simple cur-
rent mirrors) to ensure very small current variations over
the full allowed range of output voltage (see the Typical
Operating Characteristics). The 4-wire serial interface
comprises an 8-bit shift register and an 8-bit transpar-
ent latch. The shift register is written through a clock
input, CLK, and a data input, DIN, and the data propa-
gates to a data output, DOUT. The data output allows
multiple drivers to be cascaded and operated together.
The contents of the 8-bit shift register are loaded into
the transparent latch through a latch-enable input, LE.
The latch is transparent to the shift register outputs
when high and latches the current state on the falling
edge of LE. Each driver output is an open-drain, con-
stant-current sink that should be connected to the cath-
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