
MAX4820/MAX4821
+3.3V/+5V, 8-Channel, Cascadable Relay Drivers
with Serial/Parallel Interface
Table 2. Parallel Interface Address Map
(MAX4821 Only)
CS
A2
Low
Low
A1
Low
Low
A0
Low
High
OUTPUT
OUT1
OUT2
t AS
t AH
Low
High
Low
OUT3
A_
LVL
t LS
t LH
Low
High
High
High
High
High
Low
Low
High
High
High
Low
High
Low
High
OUT4
OUT5
OUT6
OUT7
OUT8
SET / RESET Functions
t ON ,
t OFF
V OUT
Figure 2. Parallel Interface Timing Diagram (MAX4821 only)
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
V CC
0.1 μ F
V CC
0.1 μ F
V CC
0.1 μ F
V CC
V CC
V CC
DIN
DIN
DOUT
DIN
DOUT
DIN
DOUT
MAX4820 OUT1
MAX4820 OUT1
MAX4820 OUT1
SCLK
SCLK
OUT8
SCLK
SCLK
OUT8
SCLK
SCLK
OUT8
CS
GND
PGND
CS
GND
PGND
CS
GND
PGND
CS
Figure 3. Daisy-Chain Configuration
8
Maxim Integrated