Texas Instruments PCM270xEVM-U User's Guide

Document ID: SLEU114

Introduction

This user's guide provides information on the setup, operation, and construction of the PCM270xEVM-U, an evaluation module (EVM) for the PCM2704 and PCM2705 digital-to-analog converters (DACs).

1. Description

The PCM270xEVM-U is an evaluation board designed for the USB interface DACs PCM2704 (DEM-PCM2704) and PCM2705 (DEM-PCM2705). It features a USB connector for evaluating DAC performance via a USB interface.

The EVM can be powered either from the USB bus or an external 5-V power supply, selectable via jumper settings on the board.

Outputs include a stereo audio signal for headphones via a stereo minijack connector (CN2) and an S/PDIF digital interface output via an optical Toslink™ connector (U4).

The PCM270xEVM-U is compliant with the USB 1.1 specification, including the full-speed transceiver format.

1.1 Related Documentation

Refer to the datasheet for PCM2704, PCM2705, PCM2706, PCM2707 Stereo Audio DAC With USB Interface, Single-Ended Headphone Output and S/PDIF Output (document number SLES081) for detailed technical specifications.

Note: Toslink is a trademark of Kabushiki Kaisha Toshiba DBA Toshiba Corporation. All other trademarks are the property of their respective owners.

1.2 Block Diagram

The block diagram illustrates the PCM270xEVM-U's architecture. Key components include:

USB Bus Interface: Connected via connector CN4.
Core DACs: PCM2704 and PCM2705, operating with a 12-MHz crystal oscillator (XTAL).
Outputs: Stereo headphone output via minijack CN2 and S/PDIF digital output via optical connector U4 (TOTX141P).
Control Interfaces: SPI interface (CN1) for PCM2705.
Power Control: Bus/Self power control managed by jumpers JP1-JP11.
Power Supply: Includes a 3.3-V regulator, with external power input via CN3, TM1, or TM2 (+5V).

1.3 Basic Operating Connections

1.3.1 Universal Serial Bus (USB)

The USB interface connects to the evaluation module via connector CN4.

1.3.2 Stereo Headphone Output

A stereo headphone plug connects to the stereo minijack audio output connector CN2.

1.3.3 Bus-Power/Self-Power Selection

Operation mode (bus-powered or self-powered) is user-selectable using jumper settings on the board. The default setting is self-powered operation.

Bus-Powered Mode:

JP1: Shorting plug must be connected. (JP7 can be removed if the application draws less than 100 mA.)
JP2–JP6, JP8: Shorting plugs must be removed.
JP9, JP10, JP11: Shorting plugs must be connected on the BUS side.
External Power: External 5-V power supply must NOT be connected to CN3 or TM1, TM2.

Self-Powered Mode (Default):

JP1: Shorting plug must be removed.
JP2–JP8: Shorting plugs must be connected.
JP9, JP10, JP11: Shorting plugs must be connected on the SELF side.
External Power: An external 5-V power supply must be connected to either CN3 or to TM1 and TM2. (Input voltage range: 4.5 V to 10 V; current: 30 mA typical, 70 mA maximum.) A 3.3-V regulator provides power for the DACs and logic circuitry from the external supply.
Device Enable: The device is enabled when the USB interface is connected and the HOST is set to High.

1.3.4 SPI Interface (PCM2705)

An SPI interface (MS, MC, MD) for controlling the PCM2705 can be connected at CN1.

1.3.5 Suspend

Suspend status is indicated at the SSPND pin of CN1.

1.3.6 S/PDIF Output

USB audio data is output by the PCM2704/2705 in S/PDIF format. This signal is sent to U4, which converts it into light for optical transmission.

2. Schematic, BOM, and Printed-Circuit Board

This chapter details the PCM270xEVM-U printed-circuit board and schematic.

2.1 PCM270xEVM-U Schematic

The circuit diagram (Figure 2) provides a detailed view of the evaluation module's electronic components and connections.

2.2 PCM270xEVM-U Parts List (BOM)

The Bill of Materials (Table 1) lists the components used in the PCM270xEVM-U assembly, including their manufacturer, part number, reference designator, description, and function.

Item	QTY	REF DES	MFG	MFG Part#	Description	Value or Function
1	REF			PCM2704/2705 EVMA	ASSEMBLY
2	REF			PCM2704/2705 EVMA	SCHEMATIC
3	REF			PCM2704/2705 EVMA	FABRICATION
4	1	SO1, SO2, SO3, SO4	One Source Group	2031	STANDOFF,4-40,1.0INx3/16IN,ALUM RND F-F
5	3	JP9, JP10, JP11		26630301RP2	HEADER 3 PIN, PCB 2.0MM ROHS
6	1	CN1		26630601RP2	HEADER 6 PIN, PCB 2.0MM ROHS
7	1	CN3		RAPC722X	JACK MINI-PWR THRU-RA 2,1ID/5.5OD 5A ROHS
8	1	CN2		STX-3000	JACK, MINI-STEREO, ROHS
9	1	U4		TOTX141P	TOSLINK TRANSMITTER 3.3V 15MB SHUTTER ROHS
10	6	C3, C4, C5, C6, C7, C12	PANASONIC	GRM185R61A105KE36D	CAP SMD0603 CERM 1.0UFD 10V 10% X5R ROHS
11	1	C8	PANASONIC	GRM21BR71A106KE51LVSA	CAP SMD0805 CERM 10UFD 10V10% X7R ROHS
12	1	TM2		3750-0	BINDING POST, BLACK 60V/15A GOLD ROHS
13	1	C18	PANASONIC	ECQ-B1H104JF	CAP, THU, POLYES-FILM, 0.1μF,50V,5%, 85C
14	2	C9, C10	MURATA	GRM39X7R223K16V	CAPACITOR, SMT, 0603, CERAMIC, 16V, 10%, .022μF
15	2	C1, C2	MURATA	GRM40COG150J50V	CAP, SMT, 0805 50V,±5%,15pF
16	2	C11, C13	MURATA	GRM40X7R103K50V	CAP, SMT, 0805 50V, 10%, .010µF
17	2	C14, C15	PANASONIC	EEVFC0J101P	CAPACITOR, SMT, ELEC, 100uF,6.3V,20%, -40~105°C
18	1	CN4	ASSMANN ELEC	A-USBS-B-R	CONNECTOR, THU, 4P, USB RECEPTACLE, TYPE B, PCB MOUNT
19	1	X1	ECS	ECS-120-18-5P	CRYSTAL, SMT, 12.000MHz, 18pF, Fund, 50ppm, -10~70°C
20	3	SW1, SW2, SW3		G12AP-RO	SWITCH THRU SPDT STRAIGHT ULTRA MINIATURE ROHS
21	8	JP1, JP2, JP3, JP4, JP5, JP6, JP7, JP8	SAMTEC	TSW-101-07-G-D	HEADER, THU, 2P, 2X1, MALE, DUAL ROW, 100LS, 100TL
22	1	U3	ATMEL	AT24C64N-10SI-2.7TR	IC, SMT, 8P 2 WIRE SERIAL EEPROM
23	1	L1	PANASONIC	ELJFA100KJ/F	INDUCTOR, SMT	10.0μH
24	2	C16, C17	ECA1CM100	CAP ALUM ELEC M RADIAL 10UFD 16V 20% ROHS
25	2	R19, R20	VISHAY	CRCW08051002F	RES, SMT, 0805	RESISTOR, SMT, 0805, THICK FILM, 1%, 1/8W, 10.0K
26	3	R1, R15, R16	VISHAY	CRCW08051004F	RES, SMT, 0805	RESISTER, SMT, 0805, THICK FILM, 1%, 1/8W, 1.00M
27	1	R17	VISHAY	CRCW080510R0F	RES, SMT, 0805	RESISTER, SMT, 0805, THICK FILM, 1%, 1/8W, 10.0 Ω
28	9	R2, R5, R6, R7, R10, R11, R12, R13, R14	VISHAY	CRCW08051501F	RES, SMT, 0805	RESISTER, SMT, 0805, THICK FILM, 1%, 1/8W, 1.50K
29	1	R18	PANASONIC	ERJ-6GEYJ106V	RES, SMT, 0805	RESISTOR, SMT, 0805, THICK FILM, 10M,5%, 1/8W
30	2	R8, R9	PANASONIC	ERJ-6GEYJ160V	RES, SMT, 0805	RESISTOR, SMT, 0805, THICK FILM, 5%, 1/8W,16
31	2	R3, R4	PANASONIC	ERJ-6GEYJ270V	RES, SMT, 0805	RESISTOR, SMT, 0805, THICK FILM, 5%, 1/8W,27
32	1	R21	PANASONIC	ERA-6YEB223V	RES, SMT, 2P	RESISTOR, SMT, 0805,22K, 0.1%, 1/10W, 25ppm
33	1	TM1		3750-2	BINDING POST, RED 60V/15A GOLD ROHS
34	1	U2		REG1117-3.3	VOLT REG 3.3V 800mA SOT223-DCY ROHS
35	1	U1		PCM2705DB	STEREO AUDIO DAC W/USB SE HEADPHONE/SPDIF OUT SSOP28-DB ROHS

2.3 Printed-Circuit Board Layout

The document includes visual representations of the printed-circuit board:

Figure 3: PCM270xEVM-U Silkscreen: Shows component placement and labels on the PCB.
Figure 4: PCM270xEVM-U - Top View: Displays the top layer of the PCB layout.
Figure 5: PCM270xEVM-U - Bottom View: Displays the bottom layer of the PCB layout.

Important Notices and Warnings

Evaluation Board/Kit Important Notice

This evaluation board/kit is intended solely for ENGINEERING DEVELOPMENT, DEMONSTRATION, OR EVALUATION PURPOSES. It is not a finished end-product for general consumer use and requires electronics training and good engineering practices for handling.

It may not meet all technical requirements of European Union directives (e.g., EMC, RoHS, WEEE, FCC, CE, UL) and is not covered by them.

A refund is available within 30 days of delivery if the board/kit does not meet specifications. Texas Instruments (TI) disclaims all other warranties.

Users assume all responsibility for safe handling and must take precautions against electrostatic discharge due to the open construction.

TI is not liable for applications assistance, customer product design, software performance, or patent infringement.

Users should consult the User's Guide for safety information regarding temperatures and voltages.

No license is granted for TI products used in machines, processes, or combinations without specific agreements.

FCC Warning

This evaluation board/kit is for engineering development only. It generates, uses, and may radiate radio frequency energy. It has not been tested for compliance with FCC Part 15 limits for computing devices. Operation may cause interference with radio communications, requiring the user to take corrective measures at their own expense.

EVM Warnings and Restrictions

Voltage Range: Operate within the input voltage range of 5 V and output voltage range of 5 V. Exceeding these limits may cause unexpected operation or irreversible damage.

Loading: Applying loads outside specified output ranges may cause unintended operation or permanent damage. Consult the EVM User's Guide for load specifications.

Component Temperatures: Some components may exceed 55°C during normal operation. This is expected for components like linear regulators, transistors, and current sense resistors. Users should be aware of warm components when placing measurement probes.

Mailing Address: Texas Instruments, Post Office Box 655303, Dallas, Texas 75265.

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