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 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.
= 2.5 to 5.5 V
CC
August 2009 Doc ID 14535 Rev 1 1/8
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)
00 62
01 124
10 188
1 1 24 16
`
123
`
123
`
123
`
123
`
123
`
123
`
123
`
123
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 F
1
-------------------------------------=
F
with Z
c
in Ω (Zin= 30 kΩ typically), Cin in Farads, C13 = C14 and C23 = C24.
in
⋅⋅
2π Z
inCin
Note: On the TS2012 demonstration board C
that F
= 24.1 Hz for both channels.
C
= C13 = C14 = C23 = C24 = 220 nF, which means
in
in Hz is:
C
More information on component calculations is available in the TS2012 datasheet.
2/8 Doc ID 14535 Rev 1
AN2725 Description of the demonstration board
Table 2. Demonstration board connectors
Connector(s) Description
P1 Power connector (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 V
CC
– 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
– logical "0": pins 2 and 3 are shorted
Standby control connector - P4 for the right channel, P5 for the left channel.
The connector pins are connected as follows:
– 1 to V
CC
– 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.
123
`
– when pins 2 and 3 are shorted or pin 2 is floating, the channel is in
123
standby mode.
P11
Left channel positive input signal connectors (active input signal L
GND)
and GND). Power supply voltage from 2.5 to 5.5 V.
CC
`
123
`
123
+ and
in
P12
P21
P22
Left channel negative input signal connectors (active input signal L
GND)
Right channel positive input signal connectors (active input signal R
GND)
Right channel negative input signal connectors (active input signal R
GND)
in
in
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.
- and
+ and
- and
in
Doc ID 14535 Rev 1 3/8
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