Detailed Description

Serial Interface (MAX4822/MAX4823)

Depending on the MAX4822/MAX4823 device, the serial

interface can be controlled by either 8- or 16-bit words

as depicted in Figures 1 and 2. The MAX4823 does not

support power-save mode, so the serial interface con-

sists of an 8-bit-only shift register for faster control.

The MAX4822 consists of a 16-bit shift register and par-

allel latch controlled by SCLK and CS. The input to the

shift register is a 16-bit word. In the MAX4822, the first

8 bits determine the register address and are followed

by 8 bits of data as depicted in Figure 1. Bit A7 corre-

sponds to the MSB of the 8-bit register address in

Figure 1, while bit D7 corresponds to the MSB of the 8

bits of data in the same Figure 1.

The MAX4823 consists of an 8-bit shift register and par-

allel latch controlled by SCLK and CS. The input to the

shift register is an 8-bit word. Each data bit controls

one of the eight outputs, with the most significant bit

(D7) corresponding to OUT8, and the least significant

bit (D0) corresponding to OUT1 (see Figure 2).

+3.3V/+5V, 8-Channel Relay Drivers with Fast

Recovery Time and Power-Save Mode

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9

PIN

MAX4824

MAX4825

NAME

FUNCTION

13

—

PSAVE

Power-Save Control. Connect a timing capacitor from PSAVE to ground. The capacitor

value determines power-save timing as explained under the Applications Information

section. PSAVE can also be driven externally to control power-save mode

asynchronously. When PSAVE is asserted high, the current through the coils is reduced

to 60% of the initial nominal current value. To disable power-save mode in all channels,

drive PSAVE low for at least 3ms after last output setting.

14

14

OUT4

Open-Drain Output 4. Connect OUT4 to the low side of a relay coil. This output is pulled

to PGND when activated, but otherwise is high impedance.

15

15

OUT3

Open-Drain Output 3. Connect OUT3 to the low side of a relay coil. This output is pulled

to PGND when activated, but otherwise is high impedance.

17

17

OUT2

Open-Drain Output 2. Connect OUT2 to the low side of a relay coil. This output is pulled

to PGND when activated, but otherwise is high impedance.

18

18

OUT1

Open-Drain Output 1. Connect OUT1 to the low side of a relay coil. This output is pulled

to PGND when activated, but otherwise is high impedance.

19

19

20

20

SET

Set Input. Drive SET low to set all latches and registers high (all outputs are low

impedance). SET overrides all parallel and serial control inputs. RESET overrides SET

under all conditions.

—13

N.C.

No Connection. Not internally connected.

EP

EP

EP

Exposed Pad. Connect exposed paddle to ground.

MAX4824/MAX4825 Pin Description (continued)