Rainbow Electronics MAX6971 - Manual (Page 8)

MAX6971
16-Port, 36V Constant-Current LED Driver
8 _______________________________________________________________________________________
CLK is the serial-clock input, which shifts data at DIN
into the MAX6971 16-bit shift register on its rising edge.
LE is the latch load input of the MAX6971 that transfers
data from the MAX6971 16-bit shift register to its 16-bit
latch when LE is high (transparent latch), and latches
the data on the falling edge of LE (Figure 2).
The fourth input provides output-enable control of the
output drivers. OE is high to force outputs
OUT0–OUT15 high impedance, without altering the
contents of the output latches, and low to enable out-
puts OUT0–OUT15 to follow the state of the output
latches.
OE is independent of the operation of the serial inter-
face. Data can be shifted into the serial-interface shift
register and latched, regardless of the state of OE.
DOUT is the serial-data output, which shifts data out
from the MAX6971’s 16-bit shift register on the rising
edge of CLK. Data at DIN is propagated through the
shift register and appears at DOUT 16 clock cycles later.
LE
OUT_
LE
OUT_
CLK
OUT_
CLK
OUT_
t CRR
t
CRF
t
LRR
t
LRF
Figure 3. LE and CLK to OUT_ Timing
Table 1. 4-Wire Serial-Interface Truth Table
SHIFT-REGISTER
CONTENTS
LATCH CONTENTS OUTPUT CONTENTS
SERIAL
DATA
INPUT
DIN
CLOCK
INPUT
CLK
D 0 D 1 D 2 … D n-1 D n
LOAD
INPUT
LE
D 0 D 1 D 2 … D n-1 D n
BLANKING
INPUT
OE
D 0 D 1 D 2 … D n-1 D n
H H R 1 R 2 … R n-2 R n-1 — — — — — — — — — — — — — —
L L R
1
R
2
… R
n-2
R
n-1
— — — — — — — — — — — — — —
X R 0 R 1 R 2 … R n-1 R n — — — — — — — — — — — — — —
— — X X X … X X H R 0 R 1 R 2 — R n-1 R n — — — — — — —
— — P 1 P 2 P 3 … P n-1 P n L P 0 P 1 P 2 … P n-1 P n L P 0 P 1 P 2 … P n-1 P n
— — — — — — — — — X X X … X X H Hi-Z Hi-Z Hi-Z … Hi-Z Hi-Z
L = Low-logic level.
H = High-logic level.
X = Don’t care.
P = Present state.
R = Previous state.
Hi-Z = High impedance.