Datasheet

LED Driver
4-Wire Interface
The MAX16809 also operates in a stand-alone mode (see
the Typical Operating Circuits). For use with a microcon-
troller, the MAX16809 features a 4-wire serial interface
using DIN, CLK, LE, OE inputs and DOUT as a data
output. This interface is used to write the LED channels?
data to the MAX16809. The serial-interface data word
length is 16 bits, D0?D15. See Figure 3.
The functions of the five interface pins are as follows:
DIN is the serial-data input, and must be stable when it
is sampled on the rising edge of CLK. Data is shifted in
MSB first. This means that data bit D15 is clocked in first,
followed by 15 more data bits, finishing with the LSB, D0.
CLK is the serial-clock input that shifts data at DIN into the
MAX16809's 16-bit shift register on its rising edge.
LE is the latch-enable input of the MAX16809 that trans-
fers data from the 16-bit shift register to its 16-bit output
latches (transparent latch). The data latches on the
falling edge of LE (Figure 4). The fourth input (OE) pro-
vides output-enable control of the output drivers. When
OE is driven high, the outputs (OUT0–OUT15) are forced
to high impedance without altering the contents of the
output latches. Driving OE low enables the outputs to fol-
low the state of the output latches. OE is independent of
the serial interface operation. Data can be shifted into
the serial-interface shift register and latched, regardless
of the state of OE. DOUT is the serial-data output that
shifts data out from the MAX16809's 16-bit shift regis-
ter on the rising edge of CLK. Data at DIN propagates
through the shift register and appears at DOUT 16 clock
cycles later. Table 1 shows the 4-wire serial-interface truth
table.
L = Low Logic Level
H = High Logic Level
X = Don't Care
P = Present State (Shift Register)
R = Previous State (Latched)
Table 1. 4-Wire Serial-Interface Truth Table
SERIAL
DATA
INPUT
DIN
CLOCK
INPUT
SHIFT REGISTER CONTENTS
LOAD
INPUT
LATCH CONTENTS
BLANKING
INPUT
OUTPUT CONTENTS
CURRENT AT OUT_ _
CLK D0 D1 D2 … Dn-1 Dn LE D0 D1 D2 … Dn-1 Dn OE D0 D1 D2 … Dn-1 Dn
H H R0 R1 … Rn-2 Rn-1
L L R0 R1 … Rn-2 Rn-1
X R0 R1 R2 … Rn-1 Rn
X X X … X X L R0 R1 R2 … Rn-1 Rn
P0 P1 P2 … Pn-1 Pn H P0 P1 P2 … Pn-1 Pn L P0 P1 P2 … Pn-1 Pn
X X X … X X H L L L … L L
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Maxim Integrated │ 15
MAX16809 Integrated 16-Channel LED Driver with
Switch-Mode Boost and SEPIC Controller