UAC3552A 데이터 시트보기 (PDF) - Micronas

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UAC3552A

Universal serial bus DAC

Micronas 

UAC 3552A

PRELIMINARY DATA SHEET

2.1.7. Special I/O

2.1.7.1. SOF (Start of Frame)

The SOF-pin provides a 1-ms signal which is synchro-

nous to the USB 1-ms frame rate. It can be used for

test purpose or as an USB-synchronous reference for

vendor-specific external circuitry.

2.1.7.2. AUXEN

This is a digital input that has to be used if an analog

signal is connected to the AUX R/L pins. It triggers the

microcontroller to switch the input mixer to the analog

input (the DAC signal always remains active!) and it

keeps the device from entering the low-power mode

which can be requested by the host PC or by discon-

necting the device from the USB.

2.1.7.3. SUSPEND

The SUSPEND pin indicates the low-power mode. It

can be used to power down external circuitry, like

power amplifiers in an USB speaker.

Table 2–3: SUSPEND pin

SUSPEND

low

high

normal power

low power

2.1.8. Clock System

The UAC 3552A requires a 12-MHz clock source,

which is realized as an on-chip oscillator with external

crystal. Also an external oscillator can be used. In this

case, the clock has to be connected to XTI. The

12 MHz is the input clock for a PLL circuit which gener-

ates all clocks needed within the IC.

2.2. Software

The functionality of the UAC 3552A is mainly defined

by software. The internal µ-controller handles the USB

requests whereas the Audio Processing Unit pro-

cesses the sound features.

2.2.1. USB Microcontroller Software

2.2.1.1. Chapter 9 Functions

The chapter 9 of the USB Spec 1.1 defines the USB

device framework which is the middle layer of the USB

protocol hierarchy (see USB Spec 1.1 page 175). It

handles routing data between the bus interface and

various endpoints. The endpoint is a source or sink for

data within the device.

2.2.1.2. Device Descriptor

Unlike the configuration descriptor, which is located in

ROM, the device descriptor is more flexible. The man-

ufacturer-related data are stored in the on-chip

EEPROM, and can be adapted individually. In detail

these data are

– vendor ID

– product ID

– device release number

– manufacturer string

– product string

– serial number string

A comfortable programming tool allows this data to be

defined and writes it into the corresponding EEPROM

location.

The UAC 3552A is shipped with the Micronas device

descriptor and allows USB functionality without any

EEPROM reprogramming.

2.2.1.3. String Descriptor

The string descriptor is located in the EEPROM. The

UAC 3552A holds three strings. The programming tool

handles the programming of strings and will take care

of string length control also.

The UAC 3552A is shipped with the Micronas string

descriptor and allows USB functionality without any

EEPROM reprogramming.

10

Micronas

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