ST AN2862 APPLICATION NOTE
AN2862
Application note
Demonstration board user guidelines for the TS2007FC 3 W filter-free class D audio amplifier with 6-12 dB fixed gain select
Introduction
This application note concerns the TS2007FC demonstration board, designed to evaluate the class D audio differential amplifier TS2007FC.
This document provides:
■a brief description of the TS2007FC device.
■a description of the demonstration board and all of its components.
■the layout of the demonstration board.
About the TS2007FC
The TS2007FC is an audio power class D amplifier that can drive up to 1.4 W into an 8 Ω load at 5 V. It achieves better efficiency compared to a typical class AB audio power amplifier.
This device allows switching between two different gains: 6 or 12 dB via a logic signal on the GS pin. Pop and click reduction circuitry provides low on/off switch noise while allowing the device to start within 1 ms. A standby function (active low) reduces the current consumption to 1 μA typical. The TS2007FC also integrates an output short-circuit protection mechanism and thermal shutdown protection to avoid damage to the amplifier.
Key features of the TS2007FC
■Operating range from VCC = 2.4 to 5.5 V.
■Standby mode active low.
■Output power: 1.4 W at 5 V or 0.5 W at 3.0 V into 8 Ω with 1% THD+N maximum.
■Output power: 2.3 W at 5 V or 0.75 W at 3.0 V into 4 Ω with 1% THD+N maximum.
■Two fixed gain selects: 6 or 12 dB.
■Low current consumption.
■Efficiency: 88% typical.
■Signal-to-noise ratio: 90 dB typical.
■PSRR: 68 dB typical at 217 Hz with 6 dB gain.
■PWM base frequency: 280 kHz
■Low pop and click noise.
■Thermal shutdown protection.
■Output short-circuit protection.
■Flip-chip lead-free 9-bump package.
Refer to the datasheet for complete information on the TS2007FC.
February 2009 |
Rev 1 |
1/7 |
www.st.com
Description of the evaluation board |
AN2862 |
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1 Description of the evaluation board
The TS2007FC demonstration board is designed for the TS2007FC class D audio differential amplifier. The TS2007FC device, in a flip-chip package, is mounted on a twolayer PCB. Easily-accessible connectors on the board allow changing or driving the gain select and standby control pins, as well as changing the input configuration of the TS2007FC.
The TS2007FC’s gain can be set to either 6 or 12 dB via the P1 connector (see Table 1).
The input configuration is either capacitor-coupled or common-mode feedback. On the evaluation board, the JP3 and JP4 connectors allow you to change the input configuration.
In the capacitor-coupled configuration, the -3 dB cut-off frequency in Hz is:
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2----π-----------Z---in------------C----1- |
2----π-----------Z----in----- |
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with Zin in Ω (Zin = 75 kΩ typically), C in Farads and C1 = C2.
More information about component calculations is available in the TS2007FC datasheet.
Table 1. Evaluation board connectors
Connector(s) Description
JP1 |
Input signal connector (GND, In+, In-, GND). |
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JP1 |
Output signal connector (GND, Out-, Out+, GND). |
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Input configuration: |
JP3, JP4 |
– capacitor-coupled when JP3 and JP4 are open. |
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– common-mode feedback when JP3 and JP4 are shorted by jumpers. |
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Gain select control connector: |
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pins 1 and 2 are shorted or pin 2 is floating, the gain is 6 dB. |
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pins 2 and 3 are shorted, the gain is 12 dB. |
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P1 |
The connector pins are connected as follows: |
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–1 to VCC
–2 to GS of the TS2007FC
–3 to GND
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Standby control connector: |
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pins 1 and 2 are shorted, the TS2007FC is in operation mode. |
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pins 2 and 3 are shorted, the TS2007FC is in standby mode. |
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P2 |
The connector pins are connected as follows: |
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–1 to VCC
–2 to STANDBY of the TS2007FC
–3 to GND
JP5 |
Power connector (VCC and GND). Power supply voltage from 2.4 to 5.5 V. |
Caution: When you apply the power supply through JP5, do not invert the polarity since this will irreversibly damage the U1 amplifier.
2/7
AN2862 |
Description of the evaluation board |
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Figure 1. Schematic diagram
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VCC |
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VCC |
JP5 |
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P1 |
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JP3 |
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C3 |
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1uF |
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1 2 |
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A2 |
B1 |
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B2 |
TS2007 |
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C1 |
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U1 |
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GS |
Vcc |
Vcc |
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JP1 |
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JP2 |
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GND |
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220nF |
C1 |
IN- |
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OUT+ |
C3 |
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GND |
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IN- |
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Gain |
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OUT+ |
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PWM |
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IN+ |
3 |
C2 |
A1 |
Select |
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Bridge |
A3 |
3 |
OUT- |
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GND |
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IN+ |
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OUT- |
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GND |
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220nF |
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Standby |
Oscillator |
Protection |
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Control |
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Circuit |
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Standby |
Gnd |
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C2 |
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B3 |
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JP4 |
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VCC |
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P2 |
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Table 2. |
Component list for the demonstration board |
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Designation |
Quantity |
Description |
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C1, C2 |
2 |
220 nF/16 V, SMD ceramic capacitors, 0603 |
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C3 |
1 |
1 µF/16 V, SMD ceramic capacitor, 0603 |
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JP1, JP2 |
2 |
4-pin header 2.54 mm pitch |
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JP3, JP4, JP5 |
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2-pin header 2.54 mm pitch |
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P1, P2 |
2 |
3-pin header 2.54 mm pitch |
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U1 |
1 |
TS2007EIJT |
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3/7
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