Datasheet

MAX4822–MAX4825
where N is the total number of MAX4822 devices in a
single chain, and R
ON
is the on-resistance of the
n-channel MOSFET in Ωs.
For example, if N = 10:
R
ON
< 142Ω
An n-channel MOSFET with R
ON
less than 142Ω is
required for a daisy chain of 10 MAX4822 devices.
Inductive Kickback Protection with
Fast Recovery Time
The MAX4822–MAX4825 feature built-in inductive kick-
back protection to reduce the voltage spike on OUT_
generated by a relay’s coil inductance when the output
is suddenly switched off. An internal Zener clamp
allows the inductor current to flow back to ground. The
Zener configuration significantly reduces the recovery
time (time it takes to turn off the relay) when compared
to protection configurations with just one diode across
the coil.
+3.3V/+5V, 8-Channel Relay Drivers with Fast
Recovery Time and Power-Save Mode
14 ______________________________________________________________________________________
MAX4822
DINDIN
SCLK
SCLK
CS
DOUT
OUT8
PGNDCS
V
CC
V
CC
0.1µF
GND
OUT1
MAX4822
DIN
SCLK
DOUT
OUT8
PGND
CS
V
CC
V
CC
0.1µF
GND
OUT1
MAX4822
DIN
SCLK
PSAVE
DOUT
OUT8
PGNDCS
V
CC
V
CC
0.1µF
0.47µF
GND
OUT1
PSAVE
0.47µF
PSAVE
0.47µF
Figure 9. Daisy-Chained MAX4822s with a Capacitor Connected to PSAVE
MAX4823
DINDIN
SCLKSCLK
CS
SCLK
DOUT
OUT8
PGNDCS
V
CC
V
CC
0.1µF
GND
OUT1
MAX4823
DIN
SCLK
DOUT
OUT8
PGND
CS
V
CC
V
CC
0.1µF
GND
OUT1
MAX4823
DIN
SCLK
DOUT
OUT8
PGNDCS
V
CC
V
CC
0.1µF
GND
OUT1
SCLK
Figure 8. Daisy-Chain Configuration