UAC3552A 데이터 시트보기 (PDF) - Micronas

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UAC3552A

Universal serial bus DAC

Micronas 

UAC 3552A

PRELIMINARY DATA SHEET

2. Functional Description

2.1. Hardware

A detailed block diagram of the UAC 3552A is depicted

in Fig. 2–1. The functions of the blocks are explained

in the following sections.

2.1.1. USB Interface

2.1.1.1. Transceiver

The differential input receiver is used to accept the

USB data signal according to the full-speed (12 MB/s)

USB driver characteristics (USB SPEC 1.1 - 7.1.4).

2.1.1.2. Interface Engine

The interface engine comprises two major sections:

the transceiver logic and the receiver logic. The trans-

ceiver logic transmits data packets built in memory by

the microcontroller. These packets are converted from

a serial to a parallel data stream. This includes NRZI

encoding, bit stuffing, CRC-computation, and addition

of SYNC field and EOP. The receiver logic will receive

USB data and stores these packets in its memory for

processing by the microcontroller. Serial USB data is

converted to a byte-wide parallel data stream and

stored in system memory. In addition to USB basic

data decoding, the Rx logic performs a PID check and

protocol layer checks.

2.1.1.3. Microcontroller

The microcontroller manages buffers for all enabled

endpoints and interacts with the interface engine. The

buffers are built and decoded in memory. This way, the

microcontroller realizes the USB protocol handling, like

USB reset, enumeration, and all chapter 9 processing,

error handling, as well as class-specific endpoint han-

dling, like audio class and HID class. The audio-class

processing consists of interpreting the USB audio

commands and accordingly controlling the DSP-audio

function through a dedicated audio-control-interface to

the DSP. HID class processing means polling keys pro-

viding the corresponding key-codes to the host-com-

puter’s requests. These keys are connected to the

GPIO-pins. The RAM can be accessed by the micro-

controller and by the interface-engine’s DMA-control-

ler. All endpoint communication is realized with intelli-

gent buffer management built up in the RAM.

A part of the RAM is reserved for download software.

This allows adding extra functionality to the GPIO pins,

like I2C-handling or any other control of external com-

ponents via USB. Downloading is handled by an extra

driver which allows direct RAM/ROM access via USB.

The ROM contains the USB drivers for the microcon-

troller as well as the complete descriptor table includ-

ing the report descriptor for the HID-class. Some parts

of the descriptor which are subjected to be changed by

the customer, however, reside in the EEPROM.

The EEPROM is built to keep static customer-related

data that will customize the UAC 3552A-based USB

device during production.

The 128×8 bit EEPROM contains the customer spe-

cific information of the USB device descriptor, like ven-

dor ID, product ID, as well as strings for manufacturer,

product and serial number. Apart from this USB-

related information, the EEPROM holds customer-spe-

cific parameters for the PerfectSpeaker equalizer.

The UAC 3552A is shipped with a preprogrammed

EEPROM that allows normal USB functionality even if

no reprogramming is performed on the customer’s

side.

The EEPROM can be programmed via USB by means

of UAC 3552A application tools.

2.1.2. Audio Control Interface

The audio control interface links the microcontroller to

the DSP and is used to initialize the DSP and to trans-

mit audio-related USB control data, like volume setting,

tone control etc.

2.1.3. Audio Streaming Interface

The audio streaming interface directly connects the

serial interface engine to the DSP in order to transmit

the digital audio data. The interface collects and buff-

ers the burst audio data for further processing by the

audio processing unit.

2.1.4. Audio Processing Unit

The audio processing unit is a powerful DSP core

which allows high-quality sample conversion, base-

band audio processing, and interpolation filtering used

for oversampling DAC, as well as customized algo-

rithms. For more details on the software see Section

2.2.2. “Audio Processing Software” on page 11.

2.1.5. Analog Back-end

The analog back-end comprises the audio DAC, ana-

log filters, input mixer, op amps for optimal external

postfiltering, analog volume and mute, and the output

amplifier.

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