UAC3552A datasheet(9/28 Pages) MICRONAS

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PRELIMINARY DATA SHEET

UAC 3552A

Micronas

2.1.5.5. Analog Volume Control

The analog volume control covers a range from 0 dB to

−75 dB plus an additional mute position.

The analog step size is split into a 3-dB and a 1.5-dB

range:

−75 dB...−54 dB: 3 dB step size

−54 dB...0 dB:

1.5 dB step size

The overall volume system, however, consists not only

of the analog volume. An additional digital volume con-

trol allows a step size of 0.5 dB over the complete

range. See Section 2.2.2.7. “Volume and Balance Con-

trol” on page 13.

Please note that analog input signals (AUXL, AUXR)

do not have the additional digital volume control.

2.1.5.6. Line-out/Headphone Amplifier

The line-out/headphone amplifier output is provided at

the OUTL and OUTR pins connected either to stereo

headphones or to the power amplifier within an USB

speaker. The stereo headphones require external

47-

Ω serial resistors in both channels. See Section 4.

“Applications” on page 26.

2.1.6. General Purpose I/O

The GPIO pins are used to connect keys which are

related to the USB HID class or for vendor-specific

control functions and LEDs in order to indicate on/off

states for example. The standard configuration defines

the GPIOs as four input pins (GPIO0...GPIO3) and

four output pins (GPIO4...GPIO7). The function of the

input pins is shown in Table 2–2.

The keys are polled by the microcontroller and the cor-

responding key codes are transmitted to the host on

request. The relation between key code and usage ID

(see Universal Bus HID Usage Tables, Version 1.0,

Chapter 14 – Consumer Page) is defined in the HID

report descriptor (see Section 2.2.1.4. “HID Report

Descriptor” on page 11) which is transmitted to the

host along with the configuration descriptor during the

bus enumeration.

When the device is not connected to USB, the func-

tionality of the volume-control and mute pins are pre-

served. In this case, however, the parameters are

directly transferred to the DSP-core. This allows using

the device in stand-alone mode providing volume and

mute control for analog sources.

The output pins are not predefined and therefore not

related to any USB functions. They can be set or reset

by vendor-specific software.

The standard configuration can be changed also by

vendor-specific USB software, but in this case, Table

2–2 is no longer valid.

Table 2–2: Standard Key Configuration

Function

Key

Code

Usage

GPIO0

Volume Up

GPIO1

Volume Down

GPIO2

MuteToggle

GPIO3

BassBoost Toggle

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