ST AN2722 Application note

AN2722

Application note

Demonstration board user guidelines for the TS4601B high-performance stereo headphone driver

Introduction

This application note concerns the TS4601B’s demonstration board, designed to evaluate the TS4601B, a high-performance stereo headphone driver with capacitor-less outputs and I2C interface from STMicroelectronics.

This document provides:

■a brief description of the TS4601B device.

■a description of the demonstration board and all of its components.

■a description of the TS4601B control software provided.

■the layout of the demonstration board.

Figure 1. TS4601B demonstration board

About the TS4601B

The TS4601B is a stereo headphone driver dedicated to high audio performance and space-constrained applications. It is based on a low-power dissipation amplifier core technology. Special care was taken in the design of the amplification chain to achieve peerless PSRR (107 dB typ. at 217 Hz) and 101 dB of SNR.

The TS4601B can drive at minimum 0.9 Vrms output voltage into 16 Ω and 1.6 Vrms into 10 kΩ, regardless of the power supply voltage, in the range of 2.9 to 5.5 V.

An I²C interface is used to control the volume through 64 steps ranging from -60 dB to +4 dB and to configure the device in multiple modes. The traditionally-used output-coupling capacitors can be removed and a dedicated common-mode sense pin suppresses parasitic noise from the jack.

The TS4601B is designed to be used with an output serial resistor. It ensures unconditional stability over a wide range of capacitive loads. It is packaged in a tiny 16-bump flip chip package with a pitch of 500 µm and a 300-µm diameter ball size.

March 2009

Rev 2

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www.st.com

AN2722

The TS4601B has the following key features.

■Power supply range: 2.9 to 5.5 V

■107 dB of PSRR at 217 Hz

■Fully-differential inputs

■I²C interface for volume control

■Digital volume control range from -60 dB to +4 dB

■101 dB of SNR A-weighted

■Independent right and left channel shutdown control

■Low quiescent current: 4.8 mA typ. at 3.0 V

■Low standby current: 2 µA max

■Output coupling capacitors removed

■Flip-chip package: 2.1 mm x 2.1 mm, 500 µm pitch, 16 bumps

Refer to the datasheet for complete information on the TS4601B.

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AN2722	Description of the demonstration board

1 Description of the demonstration board

The TS4601B demonstration board is designed to help you evaluate the TS4601B audio differential input stereo headphone amplifier. The TS4601B device, in a flip chip package, is mounted on a four-layer PCB. An on-board RS-232 to I2C interface makes this board easy to control from a personal computer by using its serial port.

The provided software controls all of the TS4601B’s features (gain, mode, mute, standby and register status).

You can use the connectors on the demonstration board to directly control some of the features.

●The master standby of the TS4601B can be set directly by Cn8 or, if the jumper is removed, by an external digital control (see Table 1).

●By removing the jumpers on Cn6 and Cn7, you can disconnect the on-board I2C interface so that you can control the TS4601B by an external I2C bus interface.

●The -3 dB cut-off input high-pass filter is set at about 6 Hz (C4 to C7). If you want to change this frequency, you have to replace C4 to C7 at the same time. More information about these component calculations is available in the TS4601B datasheet.

●The actual current consumption of the TS4601B can be measured directly by removing the jumper on Cn3 and inserting a DC amperemeter in series. The overall current

consumption of the demonstration board is higher than the consumption of the TS4601B because the Cn1 power supply connector supplies the RS-232 to I2C adapter in addition to the TS4601B.

Table 1.	Demonstration board connectors
Connector		Description

Cn1		Power connector (VCC and GND). Power supply voltage from 2.9 V to 5.5 V.

		Fully-differential positive and negative input signal connectors (active input signal
Cn2, Cn9		and GND). By shorting one active input to GND, you can use the demonstration
Cn2, Cn9		board in single-ended input mode (refer to the TS4601B datasheet for more

		information).

Cn3		Connector that allows direct measurement of TS4601B’s current consumption.
Cn3		Remove the jumper and insert a DC amperemeter.
		Remove the jumper and insert a DC amperemeter.

Cn4		Left output connector (GND and active signal).

Cn5		Right output connector (GND and active signal).

		SCL and SDA connectors:
Cn6, Cn7		– pins shorted, TS4601B is controlled by the on-board RS 232 to I2C interface.
		– pins unshorted, TS4601B can be controlled by an external I2C bus.
		Standby control connector:
		– when pins 1 and 2 are shorted, the TS4601B is in operation mode.
		– when pins 2 and 3 are shorted, the TS4601B is in master standby mode.
Cn8		The connector pins are connected as follows:
		– pin 1 to VCC
		– pin 2 to SDZ of the TS4601B
		– pin 3 to GND

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Description of the demonstration board	AN2722

Table 1. Demonstration board connectors (continued)

Connector Description

J1	3.5 mm stereo headphone plug.

DB9 female connector enabling connection of the demonstration board to the

RS-232 serial port.

Caution: When you apply the power supply through Cn1, do not invert the polarity as this will damage the U1 amplifier.

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AN2722	Description of the demonstration board

Figure 2. Schematic diagram

Cn1

VccI2C

Vcc

1uF

Power

Cn3

TS4601

Gnd

GndP

Vcc

Gnd

Positive

Cn2

Reg

Gnd

Cn4

Left Output

2.2nF

2.2uF

InL-

VoutL

Cn8

Vcc

Gnd

B3 InL+

2.2uF

Left Input

D4 SDZ

Cn9

CMS

Stdby GndP

2.2uF

C3 InR+

VoutR

Gnd

InR-

Gnd

2.2uF

Cn5

Right Input

SDA

D3 SDA

C10

Right Output

2.2nF

I2C

Negative

SCL

Negative

Gnd

Supply

Reg

Gnd

PVcc

Gnd

PVss

Vcc

1uF

2.2uF

1uF

TS4601 main application

Gnd

GndP

Cn6

SCL

Cn7 SDA

Vcc

SCL

SDA

10K

VccI2C

180

U2A

100

BS170

KP1040

5GND

4DTR

GND2

GndP

3TXD

U2B

7RTS

6DSR

1N4148

KP1040

DB9

GND2

GndP

2k2

U2C

1N4148

KP1040

GND2

GndP

RS232 to I2C converter

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