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

with Serial/Parallel Interface

_______________________________________________________________________________________

5

INPUT LOGIC THRESHOLD

vs. SUPPLY VOLTAGE

SUPPLY VOLTAGE (V)

5.1

4.7

2.7

3.1

3.5

3.9

4.3

0.75

1.00

1.25

1.50

1.75

2.00

2.25

2.50

0.50

2.3

5.5

PIN

MAX4820

MAX4821

THIN

QFN

TSSOP

THIN

QFN

TSSOP

NAME

FUNCTION

13

13

RESET

Reset Input. Drive RESET low to clear all latches and registers (all outputs

are turned off). RESET overrides all other inputs. If RESET and SET are pulled

low at the same time, then RESET takes precedence.

24

24

CS

Chip-Select Input.

MAX4820: Drive CS low to select the device. When CS is low, data at DIN is

clocked into the 8-bit shift register on SCLK’s rising edge. Drive CS from low

to high to latch the data to the registers and activate the appropriate relays.

MAX4821: Drive CS low to select the device and set level on LVL. Drive CS

from low to high to latch the address and level data to the output.

3

5

—

—

DIN

Serial-Data Input

4

6

—

—

SCLK

Serial-Clock Input

5

7

—

—

DOUT

Serial-Data Output. DOUT is the output of the 8-bit shift register. This output

can be used to daisy chain multiple MAX4820s. The data at DOUT appears

synchronous to SCLK’s falling edge.

6

8

—

—

N.C.

No Connection

7

9

7

9

GND

Ground

8

10

8

10

OUT8

Open-Drain Output 8. Connect OUT8 to the low side of a relay coil. This

output is pulled to PGND when activated, but otherwise is high impedance.

9

11

9

11

OUT7

Open-Drain Output 7. Connect OUT7 to the low side of a relay coil. This

output is pulled to PGND when activated, but otherwise is high impedance.

10, 16

12, 18

10, 16

12, 18

PGND

Power Ground. PGND is a return for the output sinks. Connect PGND pins

together and to GND.

11

13

11

13

OUT6

Open-Drain Output 6. Connect OUT6 to the low side of a relay coil. This

output is pulled to PGND when activated, but otherwise is high impedance.

Typical Operating Characteristics (continued)

BACK EMF CLAMPING

WITH STANDARD 3V RELAY

MAX4820 toc11

200

μs/div

5V/div

0

0

OUT_

1V/div

OUT_ TURNS OFF

Pin Description