TDF8599 NXP Semiconductors, TDF8599 Datasheet - Page 15

• Manufacturer Part Number: TDF8599
• Description: I2C-bus controlled dual channel 43 W/2 W single channel 85 W/1 W class-D power amplifier
• Manufacturer: NXP Semiconductors

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NXP Semiconductors
TDF8599_1
Product data sheet
8.5.1 Thermal foldback
8.5.2 Overtemperature protection
8.5.3 Overcurrent protection
8.5 Protection
The TDF8599 includes a range of built-in protection functions. How the TDF8599 handles
the various possible fault conditions differs for each protection and is described in the
following sections:
Table 9.
Thermal Foldback Protection (TFP) is activated when the junction temperature exceeds
the threshold level (145 C). TFP decreases amplifier gain such that the combination of
dissipation and R
device will not completely switch off but remains operational at the lower output power
levels. If the junction temperature continues to increase, a second built-in temperature
protection threshold level shuts down the amplifier completely.
If the junction temperature T
and the power stage immediately shuts down.
OverCurrent Protection (OCP) is activated when the output current exceeds the maximum
output current of 8 A. OCP regulates the output voltage such that the maximum output
current is limited to 8 A. The amplifier outputs keep switching and the amplifier is NOT
shutdown completely. This is called current limiting.
OCP also detects when the loudspeaker terminals are short circuited or one of the
amplifier’s demodulated outputs is short circuited to one of the supply lines. In either case,
the shorted channel(s) are switched off.
The amplifier can distinguish between loudspeaker impedance drops and a low-ohmic
short across the load or one of the supply lines. This impedance threshold depends on the
supply voltage used. When a short is made across the load causing the impedance to
drop below the threshold level, the shorted channel(s) are switched off. They try to restart
every 50 ms. If the short circuit condition is still present after 50 ms, the cycle repeats. The
average dissipation will be low because of this forced reduced duty cycle.
When a channel is switched off due to a short circuit on one of the supply lines, Window
Protection (WP) is activated. WP ensures the amplifier does not start-up after 50 ms until
the supply line short circuit is removed.
Protection type
Thermal foldback
Overtemperature
Overcurrent
Window
DC Offset
Undervoltage
Overvoltage
Overview of protection types
th(j-a)
Rev. 01 — 13 November 2008
create a junction temperature around the threshold level. The
j
> 160 C, the OverTemperature Protection (OTP) is activated
Class-D power amplifier with load diagnostics
Reference
Section 8.5.1
Section 8.5.2
Section 8.5.3
Section 8.5.4
Section 8.5.5
Section 8.5.6
Section 8.5.6
TDF8599
© NXP B.V. 2008. All rights reserved.
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