ST AN2474 APPLICATION NOTE

AN2474

Application note

TS4995 1.2W fully differential audio power amplifier with selectable

standby and 6db fixed gain - Evaluation board user guidelines

Introduction

This application note describes the DEMO TS4995, an evaluation board specifically designed for the TS4995 differential audio amplifier. In this document, you will find:

● a brief description of the TS4995 differential audio amplifier ,

● a description of the evaluation board,

● a detailed list of evaluation board components,

● the layout of the evaluation board.

About the TS4995

The TS4995 is fully differential structure po wer audio amplifier which is capab le of deliv ering

1.2W of continuous RMS output power into an 8Ω load at 5V. Due to its differential inputs, it exhibits outstanding noise immunity.

An external standby mode control reduces the supply curre nt to less than 10nA. A STBY MODE pin allows the standby to be acti ve High or Low. An internal thermal shutdown protection is also provided, making the device capable of su staining short-circuits.

The TS4995 features an internal fixed gain at 6dB which reduces the number of external components on the application board, and the flip-chip package with 9 bumps allows maximum space saving.

Its key features are:

● Differential inputs

● 90dB PSRR @ 217Hz with grounded inputs

● Operating range from V

● 1.2W rail to rail output power @ V

● 6dB integrated fixed gain

● Ultra-low consumption in standby mode (10nA)

● Selectable standby mode (active low or active high)

● Ultra-fast startup time: 10ms typ. at V

● Available in 9-bump flip-chip (300mm bump diameter)

● Ultra-low pop & click

Figure 1 on page 2 shows a typical application for the TS4995 amplifier.

For more detailed information about the TS4995, refer to the datasheet.

= 2.5V to 5.5V

=5V, THD+N=1%, F=1kHz, with 8Ω load

=3.3V

January 2007 Rev 1 1/7

www.st.com

Typical application AN2474

1 Typical application

Figure 1. Typical application for the TS4995 audio amplifier

VCC

Cs1 1uF

VinP1

P2 Vin+

Optional

Cin1

330nF Cin2

330nF

Cbypass1

1uF

VCC

TS4995

Vin-

Vin+

BYPASS

STDBY

Vcc

TS4995 FlipChip

Vo-

Vo+

8 Ohms

BIAS

STBY

STDBY MO DE

STD BY / Ope ration

GND

STDBY MODE

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AN2474 Description of the evaluation board

2 Description of the evaluation board

The DEMO TS4995 is an evaluation board designed to help you evaluate the TS4995 low power differential audio amplifier.

This section explains how to evaluate the amplifier in a ty pical application configuration. Using the board, you can:

● set the amplifier in standby/operat ion mode,

● select standby mode (active low or active high),

● modify the input configuration from capacitor coupled to common mode feedback.

The Cn4 connector is used to select between standby or operation mode; and the Cn5 connector is used for standby to select between active low or active high. For example, in

Figure 2, the jumper that connects pin 2 and pin 3 of the Cn4 connector puts the device in

standby mode, while the jumper t hat connects pin1 and pin 2 of the Cn5 connector determines that the standby is active high.

When the amplifier is used in common mode feedback input configuration, the input capacitors are shorted by placing jumpers on connectors Cn2 and Cn3.

Figure 2. Evaluation board schematic diagram

JP1

VCC

Cn1

Cs 1uF

STBY MODE

Cn5

1 2 3

Vcc

Vo-

Vo+

GND

JP2

1 2

Cn2

Cin1

4 3 2 1

1 2

330nF Cin2

1 2

330nF

Cn3

TS4995

Vin-

Vin+

BYPASS

Cb 1uF

Cn4

1 2 3

BIAS

STBY

VCC VCC

3/7

Description of the evaluation board AN2474

Table 1. Evaluation board bill of materials

Designation Quantity Description

U1 1

DIP14 socket with plugged flipchip to DIP adapter with the

TS4995 audio amplifier C1, C2 2 330nF/63V, ceramic capacitors Cb, Cs 2 1μF/50V, electrolytic capa citor

--- 2 Jumper, 2.54mm pitch (placed on Cn4 and Cn5 connectors)

Cn1, Cn2, Cn3 1 2 pins header, 2.54mm pitch

Cn4, Cn5 2 3 pins header, 2.54mm pitch

JP1 1 4 pins header, 2.54mm pitch JP2 1 2 pins header, 2.54mm pitch

Figure 3. TS4995 flip-chip adapter

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AN2474 Evaluation board connectors

3 Evaluation board connectors

Connector(s) Description

Cn1 Power connector (V

Cn2

Cn3

Connector used to short-circuit input capacitor C the amplifier is used with common mode feedback in put.

Cn4 Standby control connector (GND, Standby, V

Cn5

Standby mode control connector (V standby mode active high or low .

JP1 Input signal connector (V

, GND). Power supply voltage from 2.5V to 5.5V.

1 by placing jumper on it when

2 by placing jumper on it when

, Standby, GND). Allows you to select

, V

, 2 x GND).

in-

in+

JP2 Output signal connector (Vo-, Vo+).

Caution: When yo u apply the po wer supply th rough Cn1, DO N O T inv ert the polarity because it would

destroy the amplifier at U1.

5/7

Evaluation board layout AN2474

4 Evaluation board layout

The following schematics show the layers and the top view of the evaluation board.

Figure 4. PCB top layer Figure 5. PCB bottom layer

Figure 6. Top view of evaluation board

6/7

AN2474

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