TFA9842AJ_1

© Koninklijke Philips Electronics N.V. 2006. All rights reserved.

Preliminary specification

Rev. 01 — 28 April 2006

11 of 18

Philips Semiconductors

TFA9842AJ

7.5 W stereo power amplifier with volume control

13.1.2 Volume control drive options

13.2 Printed-circuit board

13.2.1 Layout and grounding

To obtain a high-level system performance, certain grounding techniques are essential.

The input reference grounds have to be tied with their respective source grounds and

must have separate tracks from the power ground tracks; this will prevent the large output

signal currents from interfering with the small AC input signals. The small-signal ground

tracks should be physically located as far as possible from the power ground tracks.

Supply and output tracks should be as wide as possible for delivering maximum output

power.

Fig 12. Volume control drive circuit with 3.3 V PWM

Fig 13. Volume control drive circuit with 5 V

PWM

Fig 14. Volume control drive circuit with

potentiometer

001aae337

1 k

Ω

R5

1 k

Ω

R4

R2

1 k

Ω

R1

10 k

Ω

D1

5.6 V

R3

1 k

Ω

T3

T1

T2

C1

10

µF

PWM

3.3 V

VC

GND

5 V

001aae338

1 k

Ω

R4

C1

10

µF

PWM

5 V

VC

001aae339

16 k

Ω

R5

R6

16 k

Ω

R1

10 k

Ω

D1

10 V

T1

C1

10

µF

VC