TDF8591TH datasheet(5/34 Pages) NXP

5 / 34 page

TDF8591TH_1

Product data sheet

Rev. 01 — 5 March 2008

5 of 34

NXP Semiconductors

TDF8591TH

× 100 W SE (4 Ω) or 1 × 310 W BTL (4 Ω) class-D ampliﬁer

The value of the RC time constant should be dimensioned for 500 ms. If the 100

µF

capacitor is left out of the application the voltage on pin MODE will be applied with a much

smaller time constant, which might result in audible pop noises during start-up (depending

on DC output offset voltage and used loudspeaker).

In order to fully charge the coupling capacitors at the inputs, the ampliﬁer will remain

automatically in Mute mode for approximately 150 ms before switching to Operating

mode. A complete overview of the start-up timing is given in Figure 4.

6.3 Pulse width modulation frequency

The output signal of the ampliﬁer is a PWM signal with a switching frequency that is set by

an external resistor Rext(OSC) connected between pins OSC and VSSA. An optimum setting

for the carrier frequency is between 300 kHz and 350 kHz. An external resistor Rext(OSC) of

30 k

Ω sets the frequency to 310 kHz.

Fig 4.

Timing on mode selection input

audio

operating

mute

standby

5 V

2.5 V

0 V (SGND)

time

VMODE

100 ms

>50 ms

switching

audio

operating

standby

5 V

0 V (SGND)

time

001aad837

VMODE

100 ms

50 ms

switching

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