ST AN2933 APPLICATION NOTE
March 2009 Rev 1 1/10
AN2933
Application note
Demo board user guidelines for the TS4999 filter-free stereo
2 x 2.8 W class D audio power amplifier with selectable 3D effect
Introduction
This application note concerns the TS4999 demonstration board, designed to evaluate the
stereo class D audio differential amplifier TS4999.
This document provides:
■ a brief description of the TS4999 device.
■ a description of the demonstration board and all of its components.
■ the layout of the demonstration board.
About the TS4999
The TS4999 is a fully-differential class D stereo power amplifier. It can drive up to 1.35 W
into an 8 Ω load at 5 V per channel. The device has four different gain settings utilizing two
discrete pins, G0 and G1.
Pop and click reduction circuitry provides low on/off switch noise while allowing the device to
start within 8 ms. 3D enhancement effects are selected through one digital input pin that
allows more amazing stereo audio sound.
Two standby pins (active low) allow each channel to be switched off separately.
The TS4999 is available in an 18-bump flip-chip package.
Key features of the TS4999
■ Operating range from V
CC
= 2.4 V to 5.5 V.
■ Dedicated standby mode active low for each channel.
■ Output power per channel: 2.8 W at 5 V into 4 Ω with 10% THD+N or 0.7 W at 3.6 V into
8 Ω with 1% THD+N max.
■ Selectable 3D sound effect.
■ Four gain setting steps: 3.5, 6, 9.5 and 12 dB.
■ Low current consumption.
■ PSRR: 63 dB typical at 217 Hz.
■ Fast start-up phase: 7.8 ms.
■ Output short-circuit and thermal shutdown protection.
■ Flip-chip 18-bump lead-free package.
Refer to the datasheet for complete information on the TS4999.
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Description of the demonstration board AN2933
2/10
1 Description of the demonstration board
The TS4999 demonstration board is designed to evaluate the TS4999, a fully-differential
class D stereo power amplifier. The TS4999 device, in a flip-chip package, is mounted on a
four-layer PCB. Easily-accessible connectors on the board allow changing or driving the
gain select pins (G0 and G1), the standby control pins for the left and right channels (STBL
and STBR) and the 3D sound effect pin (3D).
The differential gain of the TS4999 can be set to 3.5, 6, 9.5, or 12 dB, depending on the
logic level of the G0 pin (connected to pin 2 of S1) and G1 pin (connected to pin 2 of S2).
Note: An internal 300 k
Ω
(+/-20%) resistor is placed between pins G0, G1 and GND. When the
pins are floating (S1 and S2 included), the gain is 3.5 dB. In full standby (left and right
channels OFF), these resistors are disconnected (HiZ input).
Table 1. Gain settings with G0 and G1 pins
G1 G0 S1 S2 Gain (dB) Gain (V/V)
00 3.51.5
01 62
10 9.53
11 124
`
123
`
123
`
123
`
123
`
123
`
123
`
123
`
123
Table 2. Truth table for 3D effect pin and STANDBY pins
3D STBYL STBYR 3D Effect Left channel Right channel
0 0 0 X STDBY STDBY
001OFFSTDBYON
010OFFONSTDBY
011OFFONON
1 0 0 X STDBY STDBY
1 0 1 N/A N/A N/A
1 1 0 N/A N/A N/A
1 1 1 ON ON ON
AN2933 Description of the demonstration board
3/10
Note: 1 An internal 300 k
Ω
(+/-20%) resistor is placed between pins STBYL, STBYR, 3D and GND.
When the 3D pin is floating (S5 included), the 3D effect is switched off. When pins STBYL,
STBYR are floating (S3 and S4 included), the amplifier is in full standby mode. In full
standby (left and right channels OFF), the internal resistors of the gain and 3D effect pins
(G0, G1 and 3D) are disconnected (HiZ input).
2 When the 3D effect is switched on, both channels must be in operation or in shutdown mode
at the same time.
The amplifier’s inputs are capacitor-coupled, meaning that the -3 dB cut-off frequency F
c
in
Hz is:
with Z
in
in Ω, C
in
in Farads, C1 = C2 and C3 = C4.
3 On the TS4999 demonstration board, C
in
= C1 = C2 = C3 = C4 = 220 nF. The input
impedance Zin changes with the set gain, as does F
C
.
More information on component calculations is available in the TS4999 datasheet.
F
c
1
2π Z
in
C
in
⋅⋅
-------------------------------------=
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