AD1988BJSTZ datasheet(19/20 Pages) AD

19 / 20 page

AD1988A/AD1988B

Rev. 0 | Page 19 of 20

HARDWARE VOLUME CONTROL

VDD

10kΩ

3.3kΩ

SW1

5.1kΩ

SW2

DOWN

3.3kΩ

SW3

MUTE

GPIO_0/VOLUME

OPTIONAL

Figure 4 . Volume Control Circuitry

The AD1988A/AD1988B support external volume control on

Pin 2 (GPIO_0/VOLUME). The circuit diagram in Figure 4

allows up/down/mute control using only three switches and

four resistors external to the codec. The up/down switches can

also be replaced by a center-position-off SPDT toggle switch.

The mute switch is optional, but desirable, for a satisfactory user

interface.

To use the GPIO_0/VOLUME pin (Pin 2) as a GPIO pin, it is

recommended to pull it down using a 10 kΩ resistor (Pin 2 to

DVSS). In the GPIO configuration, the volume control widget

has no effect.

When the GPIO_0/VOLUME pin (Pin 2) is used as a volume con-

trol, pull-up Pin 2 to AVDD. The volume control widget operates

the codec volumes only under software control. If one of the

buttons is pressed, the control volume setting is incremented

(up), decremented (down), or set Bit 7 (mute). The volume

control supports 40 steps (other than mute) and uses a range of

0 (0x00, minimum volume) to 63 (0x3F, maximum volume).

Pressing the mute switch (or both up and down simultaneously)

toggles Bit 7 which indicates mute on/off.

AD1988BJSTZ Datasheet(PDF) 19 Page - Analog Devices