Dual, Audio, Log Taper Digital Potentiometers

6

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Detailed Description

Digital Serial Interface

An SPI-compatible serial interface controls the

MAX5408–MAX5411. The input word to the device is

eight bits long, composed of three address bits (A0,

A1, and A2), followed by five data bits, with MSB first

(see Tables 1 and 2). The first three address bits set

the value of internal registers. The five data bits control

the wiper position. For certain commands, some of the

five data bits are “don’t cares”, but must be sent to the

device.

The serial data is listed in Tables 1 and 2.

The control code determines:

• Potentiometer to update or register to set.

• Data for mute register (Tables 3 and 4).

• Data for zero-crossing detection register (Tables 5

and 6).

The data bits control the position of the wiper (Table 7).

A logic low on the chip-select input (CS) enables the

device’s serial interface. A logic high on CS disables

the interface control circuitry. See Figure 1 for serial-

interface timing description.

8-BIT SERIAL WORD

A0

A1

A2

D4–D0

FUNCTION

0

0

0

5-bit DAC data

Set position of wiper W0A

0

0

1

5-bit DAC data

No change

0

1

0

5-bit DAC data

Set position of wiper W1A

0

1

1

5-bit DAC data

No change

1

0

0

4-bit mute data, D0 = “don’t care”

Data for mute register (see Table 3)

10

1

4-bit zero-crossing detection data,

D0 = “don’t care”

Data for zero-crossing detection register

(see Table 5)

1

1

0

00000

Readback contents of wiper register for W0A

at DOUT

1

1

0

00001

No change

1

1

0

00010

Readback contents of wiper register for W1A

at DOUT

1

1

0

00011

No change

1

1

0

00100

Readback contents of mute register at DOUT

1

1

0

00101

Readback contents of zero-crossing detection

register at DOUT

1

1

1

D4 = 0, D3–D0 = “don’t care

Immediate update then analog power-down

when zero crossing is enabled. No effect

when zero crossing is disabled.

Table 1. Serial Interface Programming Commands for MAX5408/MAX5410

WIPER

DOUT

DIN

SCLK

CS

DOUT

DIN

SCLK

CS

Figure 1. Serial Timing Diagram