TDF8591TH_1

© NXP B.V. 2008. All rights reserved.

Product data sheet

Rev. 01 — 5 March 2008

16 of 34

NXP Semiconductors

TDF8591TH

2

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

Peak output current, internally limited to 12 A:

SE:

A

BTL:

A

Variables:

load and the ripple current. The value of the ripple current is dependent on the coil

inductance and voltage drop over the coil.

12.3 External clock

If two or more class-D amplifiers are used it is recommended that all devices run at the

same switching frequency. This can be realized by connecting all OSC pins together and

feed them from an external oscillator.

above SGND. The internal oscillator is disabled and the PWM modulator will switch with

the external frequency. The duty cycle of the external clock should be between 47.5 %

and 52.5 %.

The noise contribution of the internal oscillator is supply voltage dependent. In low noise

applications running at high supply voltage an external low noise oscillator is

recommended.

12.4 Noise

Noise should be measured using a high-order low-pass filter with a cut-off frequency of

20 kHz. The standard audio band pass filters used in audio analyzers do not suppress the

residue of the carrier frequency sufficiently to ensure a reliable measurement of the

audible noise. Noise measurements should preferably be carried out using AES 17 (Brick

Wall) filters or the Audio Precision AUX 0025 filter, which was designed especially for

measuring switching (class-D) amplifiers.

I

OM

V

P

1t

w min

()

–

f

osc

2

----------

×





×

R

L

R

DSon hs

()

R

sL

()

++

-------------------------------------------------------------

=

I

OM

2V

P

1t

wmin

()

f

osc

2

---------

×

–





×

R

L

R

DSon hs

()

R

DSon ls

()

+

() 2R

sL

()

++

-------------------------------------------------------------------------------------------

=