Philips Semiconductors

TFA9843J

2-channel audio amplifier (2 x SE or 1 x BTL)

Preliminary data

Rev. 02 — 19 January 2004

6 of 21

9397 750 12587

© Koninklijke Philips Electronics N.V. 2004. All rights reserved.

Standby — In this mode the current consumption is very low and the outputs are

grounded.

Mute — In this mode the amplifier is DC-biased but not operational (no audio output).

This allows the input coupling capacitors to be charged to avoid pop-noise. The

On — In this mode the amplifier is operating normally. The operating mode is

8.4 Supply voltage ripple rejection

The supply voltage ripple rejection (SVRR) is measured with an electrolytic capacitor

of 150

µF on pin SVR using a bandwidth of 20 Hz to 22 kHz. Figure 17 illustrates the

SVRR as function of the frequency. A larger capacitor value on pin SVR improves the

ripple rejection behavior at the lower frequencies.

8.5 Built-in protection circuits

The TFA9843J contains two types of temperature sensors; one measures local

temperatures of the power stages and one measures the global chip temperature. At

stages for 2 ms. High impedance of the outputs is the result. After this time period the

power stages switch on automatically and the detection will take place again; still a

too high temperature switches off the power stages immediately. This protects the

TFA9843J against shorts to ground, to the supply voltage, across the load and too

high chip temperatures.

The protection will only be activated when necessary, so even during a short-circuit

condition, a certain amount of (pulsed) current will still be flowing through the short,

just as much as the power stage can handle without exceeding the critical

temperature level.

Fig 3.

Mode selection.

MCE502

standby

all mute

1/2 on

0.8

4.5

VCC−3.5

VCC

VMODE (V)

VCC−2.0