TDF8599B datasheet(16/54 Pages) NXP

16 / 54 page

TDF8599B_1

Product data sheet

Rev. 01 — 29 July 2009

16 of 54

NXP Semiconductors

TDF8599B

I2C-bus controlled dual channel class-D power ampliﬁer

• During the start-up sequence:

– When the TDF8599B is switched from standby to mute (td(stb-mute)). When a short

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

start-up procedure is interrupted and the TDF8599B 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 offset protection

DC offset 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. Figure 14 shows how 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.

In I2C-bus mode, DC offsets generate a voltage shift around the bias voltage. When the

voltage shift exceeds threshold values, the offset alarm bit DB1[D2] is set and if bit

IB1[D7] is not set, diagnostic information is also given. Any detected offset shuts down

both channels when bit IB2[D7] is not set. To restart the TDF8599B in I2C-bus mode, pin

EN must be toggled or DCP disabled by connecting pin DCP to pin AGND.

Fig 14. DC offset protection and diagnostic output

001aak078

OUT1P

OUT1N

V to I

OUT2P

OUT2N

DCP

DIAG

switch off channels

IB1[D6]

IB2[D6]

V to I

Vref

DB1[D2]

IB1[D7]

IB2[D7]

50 k

Ω

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