ST AN2725 Application note

AN2725

Application note

Demonstration board user guidelines for the TS2012 filter-free stereo 2 x 2.8 W class D audio power amplifier

Introduction

This application note applies to the STEVAL-CCA007V1 demonstration board, designed to evaluate the stereo class D audio differential amplifier TS2012.

The document provides:

■a brief description of the TS2012 device,

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

■the layout of the demonstration board.

About the TS2012

The TS2012 is a fully-differential class D stereo power amplifier that can drive up to 1.35 W into an 8 Ω load at 5 V per channel. It achieves outstanding efficiency compared to typical class AB audio amplifiers.

The device has four different gain settings that use two digital pins: G0 and G1. Pop and click reduction circuitry provides low on/off switch noise while allowing the device to start within 1 ms. Two standby pins (active low) allow each channel to be switched off independently.

The TS2012 is available in a 4 x 4 mm QFN20 package.

Key features of the TS2012

■Operating range from VCC = 2.5 to 5.5 V

■Standby mode active low

■Output power per channel: 1.35 W at 5 V or 0.68 W at 3.6 V into 8 Ω with 1% THD+N max

■Output power per channel: 2.2 W at 5 V into 4 Ω with 1% THD+N max

■Four gain select settings: 6, 12, 18, 24 dB

■Low current consumption

■PSRR: 70 dB typ at 217 Hz with 6 dB gain

■Fast start-up phase: 1 ms

■Thermal shutdown protection

■QFN20 4 x 4 mm lead-free package

Refer to the datasheet for complete information on the TS2012.

August 2009

Doc ID 14535 Rev 1

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www.st.com

Description of the demonstration board	AN2725

1 Description of the demonstration board

The STEVAL-CCA007V1 is designed to evaluate the TS2012, a fully-differential class D stereo power amplifier. The TS2012 device, available in a QFN package, is mounted on a two-layer PCB with a copper area acting as a heatsink. Easily-accessible on-board connectors are used to change or drive the gain select pins (G0 and G1) and the standby control pins. The input configuration of the TS2012 can also be changed.

The differential gain of the TS2012 can be set to 6, 12 18, or 24 dB, depending on the logic level of the G0 pin (connected to pin 2 of the P3) and G1 pin (connected to pin 2 of the P2).

	Table 1.	Gain settings with G0 and G1 pins
	G1		G0					P2									P3						Gain (dB)		Gain (V/V)
	0		0																				6		2
								`									`
						1		2			3				1		2			3
	0		1																				12		4
								`										`
						1		2			3				1		2			3
	1		0																				18		8
									`								`
						1		2			3				1		2			3
	1		1																				24		16
									`									`
						1		2			3				1		2			3
Note:	There is an internal 300 kΩ (+/-20%) resistor between pins G0, G1 and GND. When the
	pins are floating (P2 and P3 included), the gain is 6 dB. In full standby mode (left and right
	channels OFF), these resistors are disconnected (HiZ input).
	The input configuration is either capacitor-coupled or common-mode feedback. On the
	board, the connectors for the left channel (P13 and P14) and those for the right channel
	(P23 and P24) allow you to change the input configuration.
	In the capacitor-coupled configuration, the -3 dB cut-off frequency FC in Hz is:
			Fc =	1
				2----π---------Zin C--------------------in----
	with Zin in Ω (Zin= 30 kΩ typically), Cin in Farads, C13 = C14 and C23 = C24.
Note:	On the TS2012 demonstration board Cin = C13 = C14 = C23 = C24 = 220 nF, which means
	that FC = 24.1 Hz for both channels.

More information on component calculations is available in the TS2012 datasheet.

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AN2725

Description of the demonstration board

Table 2.

Demonstration board connectors

Connector(s)

Description

P1

Power connector (VCC and GND). Power supply voltage from 2.5 to 5.5 V.

Gain setting connectors - P2 for the G1 pin, P3 for the G0 pin of the TS2012.

The connector pins are connected as follows:

– 1 to VCC

– 2 of P2 to the G1 pin

P2, P3

– 2 of P3 to the G0 pin

– 3 to GND

Jumper positions:

– logical "1": pins 1 and 2 are shorted

`

1

2

3

– logical "0": pins 2 and 3 are shorted

`

1

2

3

Standby control connector - P4 for the right channel, P5 for the left channel.

The connector pins are connected as follows:

– 1 to VCC

– 2 of P4 to the STBYR pin of the TS2012

P4, P5

– 2 of P5 to the STBYL pin of the TS2012

– 3 to GND

Jumper positions:

–

when pins 1 and 2 are shorted, the channel is operating.

`

1

2

3

–

`

when pins 2 and 3 are shorted or pin 2 is floating, the channel is in

1

2

3

standby mode.

P11

Left channel positive input signal connectors (active input signal Lin+ and

GND)

P12

Left channel negative input signal connectors (active input signal Lin- and

GND)

P21

Right channel positive input signal connectors (active input signal Rin+ and

GND)

P22

Right channel negative input signal connectors (active input signal Rin- and

GND)

Input configuration:

P13, P14, P23, P24 – capacitor coupled when P13 and P14 (P23 and P24) are disconnected.

–common-mode feedback when P13 and P14 (P23 and P24) are shorted by jumpers.

P15	Left channel output signal connector (positive and negative output)
P25	Right channel output signal connector (positive and negative output)

Caution: When you apply the power supply through P1, do not invert the polarity as this will irreversibly damage the U1 amplifier.

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