Datasheet

SET / RESET Functions
The MAX4820/MAX4821 feature set and reset inputs that
allow the user to simultaneously turn all outputs on or off
using a single control line. Drive SET low to set all latch-
es and registers to 1 and turn all outputs on. SET over-
rides all serial/parallel control inputs. Drive RESET low to
clear all latches and registers and turn all outputs off.
RESET overrides all other inputs, including SET.
Applications Information
Daisy Chaining
The MAX4820 features a digital output, DOUT, that pro-
vides a simple way to daisy chain multiple devices. This
feature allows the user to drive large banks of relays
using only a single serial interface. To daisy chain multi-
ple devices, connect all CS pins together, and connect
the DOUT of one device to the DIN of another device
(see Figure 3). During operation, a stream of serial data
+3.3V/+5V, 8-Channel, Cascadable Relay Drivers
with Serial/Parallel Interface
CS
A_
LVL
V
OUT
t
AS
t
AH
t
LS
t
LH
t
ON
,
t
OFF
Figure 2. Parallel Interface Timing Diagram (MAX4821 only)
MAX4820
DINDIN
SCLKSCLK
CS
SCLK
DOUT
OUT8
PGNDCS
V
CC
V
CC
0.1μF
GND
OUT1
MAX4820
DIN
SCLK
DOUT
OUT8
PGND
CS
V
CC
V
CC
0.1μF
GND
OUT1
MAX4820
DIN
SCLK
DOUT
OUT8
PGNDCS
V
CC
V
CC
0.1μF
GND
OUT1
SCLK
Figure 3. Daisy-Chain Configuration
Table 2. Parallel Interface Address Map
(MAX4821 Only)
A2 A1 A0 OUTPUT
Low Low Low OUT1
Low Low High OUT2
Low High Low OUT3
Low High High OUT4
High Low Low OUT5
High Low High OUT6
High High Low OUT7
High High High OUT8
MAX4820/MAX4821
8
Maxim Integrated