Philips TFA9843AJ 9. Limiting values, 10. Thermal characteristics

Preliminary data sheet Rev. 01 — 28 April 2006 6 of 19

Philips Semiconductors TFA9843AJ

20 W stereo power ampliﬁer with volume control

The TFA9843AJ contains two types of temperature sensors; one measures the local

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

local temperature of the power stage of approximately 185 °C or a global temperature of

approximately 150 °C this detection circuit switches off the power stages for 2 ms. When

the outputs are switched off the voltage is measured on the outputs. In the event of a

short-circuit to ground or to VCC the device will remain in Protection mode. In all other

cases the power stages switch-on automatically and the detection will take place again;

however a too high temperature will switch-off the power stages immediately. This can

result in repetitive switching during too high junction temperature. This protects the

TFA9843AJ against short-circuits 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 ﬂow through the short-circuit (as

much as the power stage can handle without exceeding the critical temperature level).

9. Limiting values

Table 6. Limiting values

In accordance with the Absolute Maximum Rating System (IEC 60134).

Symbol Parameter Conditions Min Max Unit

VCC supply voltage operating −0.3 +28 V

VIinput voltage −0.3 VCC + 0.3 V

IORM repetitive peak output current - 4 A

Tstg storage temperature non-operating −55 +150 °C

Tamb ambient temperature operating −40 +85 °C

Ptot total power dissipation - 35 W

VCC(scp) short-circuit protection supply

voltage -26 V

Table 7. Thermal characteristics

Symbol Parameter Conditions Value Unit

Rth(j-a) thermal resistance from

junction to ambient in free air 40 K/W

Rth(j-c) thermal resistance from

junction to case both channels

driven 2.0 K/W