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TFA9843AJ_1 © Koninklijke Philips Electronics N.V. 2006. All rights reserved.
Preliminary data sheet Rev. 01 — 28 April 2006 6 of 19
Philips Semiconductors
TFA9843AJ
20 W stereo power amplifier with volume control
8.5 Built-in protection circuits
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 V
CC
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
10. Thermal characteristics
Table 6. Limiting values
In accordance with the Absolute Maximum Rating System (IEC 60134).
Symbol Parameter Conditions Min Max Unit
V
CC
supply voltage operating −0.3 +28 V
V
I
input voltage −0.3 V
CC
+ 0.3 V
I
ORM
repetitive peak output current - 4 A
T
stg
storage temperature non-operating −55 +150 °C
T
amb
ambient temperature operating −40 +85 °C
P
tot
total power dissipation - 35 W
V
CC(scp)
short-circuit protection supply
voltage
-26 V
Table 7. Thermal characteristics
Symbol Parameter Conditions Value Unit
R
th(j-a)
thermal resistance from
junction to ambient
in free air 40 K/W
R
th(j-c)
thermal resistance from
junction to case
both channels
driven
2.0 K/W