General Description

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 2

Ω 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.

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.

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.

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.

Applications

Central Office

ATE

DSL, ADSL Line Cards

Industrial Equipment

E1/T1 Redundancy

Features

o 8 Independent Output Channels

o Built-In Inductive Kickback Protection

o Drive +3V and +5V Relays

o Guaranteed 70mA (min) Coil Drive Current

o SET Function to Turn On All Outputs

Simultaneously

o RESET Function to Turn Off All Outputs

Simultaneously

o SPI-/QSPI-/MICROWIRE-Compatible Serial

Interface (MAX4820)

o Serial Digital Output for Daisy Chaining

(MAX4820)

o Parallel Interface (MAX4821)

o Low 50µA (max) Quiescent Supply Current

o Space-Saving 20-Pin Thin QFN Package

+3.3V/+5V, 8-Channel, Cascadable Relay Drivers

with Serial/Parallel Interface

________________________________________________________________ Maxim Integrated Products

1

TOP VIEW

13

12

11

14

15

OUT5

COM

OUT4

OUT3

OUT6

4

3

2

1

SCLK

DIN

CS

RESET

5

DOUT

MAX4820

THIN QFN

Pin Configurations

Ordering Information

19-2751; Rev 0; 1/03

For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at

1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.

*For maximum heat dissipation, packages have an exposed pad

(EP) on the bottom. Solder exposed pad to GND.

Pin Configurations continued at end of data sheet.

Typical Application Circuits and Functional Diagrams

appear at end of data sheet.

SPI and QSPI are trademarks of Motorola, Inc.

MICROWIRE is a trademark of National Semiconductor Corp.

PART

TEMP RANGE

PIN-PACKAGE

MAX4820ETP*

-40°C to +85°C

20 Thin QFN-EP

MAX4820EUP*

-40°C to +85°C

20 TSSOP

MAX4821ETP*

-40°C to +85°C

20 Thin QFN-EP

MAX4821EUP*

-40°C to +85°C

20 TSSOP