19-2751; Rev 2; 1/10
+3.3V/+5V, 8-Channel, Cascadable Relay Drivers
with Serial/Parallel Interface
0/MAX4821
General Description
Features
The MAX4820/MAX4821 8-channel relay drivers offer
built-in kickback protection and drive +3.3V/+5V non-
latching or dual-coil-latching relays. These devices are
especially useful when driving +3V relays. Each inde-
pendent open-drain output features a 2Ω on-resistance
and is guaranteed to sink 70mA (min) of load current.
Both devices consume less than 50µA (max) quiescent
current and have 1µA output off-leakage current.
♦ 8 Independent Output Channels
♦ Built-In Inductive Kickback Protection
♦ Drive +3V and +5V Relays
♦ Guaranteed 70mA (min) Coil Drive Current
♦ SET Function to Turn On All Outputs
Simultaneously
The MAX4820 features an SPI™-/QSPI™-/MICROWIRE™-
compatible serial interface. Input data is shifted into an 8-
bit shift register and latched to the outputs when CS
transitions from low to high. Each data bit in the shift reg-
ister corresponds to a specific output, allowing indepen-
dent control of all outputs.
♦ RESET Function to Turn Off All Outputs
Simultaneously
♦ SPI-/QSPI-/MICROWIRE-Compatible Serial
Interface (MAX4820)
♦ Serial Digital Output for Daisy Chaining
The MAX4821 features a 4-bit (A0, A1, A2, LVL) paral-
lel-input interface. The first three bits (A0, A1, A2) deter-
mine the output address, and the fourth bit (LVL)
determines whether the selected output is switched on
or off. Data is latched to the outputs when CS transi-
tions from low to high.
(MAX4820)
♦ Parallel Interface (MAX4821)
♦ Low 50µA (max) Quiescent Supply Current
♦ Space-Saving 20-Pin Thin QFN Package
Both devices feature separate set and reset functions
that allow the user to turn on or turn off all outputs simul-
taneously with a single control line. Built-in hysteresis
(Schmidt trigger) on all digital inputs allows this device
to be used with slow rising and falling signals, such as
those from optocouplers or RC power-up initialization
circuits. The MAX4820/MAX4821 are available in 20-pin
TSSOP and space-saving 20-pin Thin QFN packages.
Ordering Information
PART
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
20 Thin QFN-EP*
20 TSSOP-EP*
MAX4820ETP+
MAX4820EUP+
MAX4821ETP+
MAX4821EUP+
20 Thin QFN-EP*
20 TSSOP-EP*
+Denotes a lead(Pb)-free/RoHS-compliant package.
*EP = Exposed pad.
Applications
Central Office
Pin Configurations
ATE
TOP VIEW
DSL, ADSL Line Cards
Industrial Equipment
E1/T1 Redundancy
+
RESET
1
2
3
4
5
15 OUT3
14 OUT4
13 COM
12 OUT5
CS
DIN
MAX4820
Pin Configurations continued at end of data sheet.
SCLK
DOUT
Typical Application Circuits and Functional Diagrams
appear at end of data sheet.
*EP
11
OUT6
THIN QFN
SPI and QSPI are trademarks of Motorola, Inc.
*CONNECT EP TO GND.
MICROWIRE is a trademark of National Semiconductor Corp.
________________________________________________________________ Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.