TDF8599TH datasheet(16/52 Pages) NXP

16 / 52 page

TDF8599_1

Product data sheet

Rev. 01 — 13 November 2008

16 of 52

NXP Semiconductors

TDF8599

Class-D power ampliﬁer with load diagnostics

8.5.4 Window protection

Window Protection (WP) checks the PWM output voltage before switching from Standby

mode to Mute mode (outputs switching) and is activated as follows:

• During the start-up sequence:

– When the TDF8599 is switched from standby to mute (td(stb-mute)). When a short

circuit on one of the output terminals (i.e. between VP and GND) is detected, the

start-up procedure is interrupted and the TDF8599 waits for open circuit outputs.

No large currents ﬂow in the event of a short circuit to the supply lines because the

check is performed before the power stages are enabled.

• During operation:

–

A short to one of the supply lines activates OCP causing the ampliﬁer channel to

shutdown. After 50 ms the ampliﬁer channel restarts and WP is activated.

However, the corresponding ampliﬁer channel will not start-up until the supply line

short circuit has been removed.

8.5.5 DC Protection

DC Protection (DCP) is activated when the DC content in the demodulated output voltage

exceeds a set threshold (typically 2 V). DCP is active in both Mute mode and Operating

mode. False triggering of the DCP by low frequencies in the audio signal is prevented

using the external capacitor (CF) to generate a cut-off frequency as shown in Figure 15.

Fig 15. DC offset protection and diagnostic output

001aai785

OUT1P

OUT1N

V to I

OUT2P

OUT2N

DCP

DIAG

switch off channels

IB1[D6]

IB2[D6]

V to I

Vref

DB1[D7]

IB1[D7]

IB2[D7]

50 k

Ω

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