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TDA8547

2 × 1 W BTL audio amplifier with output channel switching

Philips Electronics 

Philips Semiconductors

2 × 1 W BTL audio amplifier with output

channel switching

Preliminary specification

TDA8547

TEST AND APPLICATION INFORMATION

Test conditions

Because the application can be either Bridge-Tied Load

(BTL) or Single-Ended (SE), the curves of each

application are shown separately.

The thermal resistance = 55 K/W for the DIP16; the

maximum sine wave power dissipation for Tamb = 25 °C

is: -1---5---0--5---5–-----2---5-- = 2.3 W

For Tamb = 60 °C the maximum total power dissipation is:

-1---5---0--5---5–-----6---0-- = 1.7 W

BTL application

Tamb = 25 °C if not specially mentioned, VCC = 5 V,

f = 1 kHz, RL = 8 Ω, Gv = 20 dB, audio band-pass

22 Hz to 22 kHz.

The BTL application circuit is illustrated in Fig.4.

The quiescent current has been measured without any

load impedance and both channels driven. When one

channel is active the quiescent current will be halved.

The total harmonic distortion as a function of frequency

was measured using a low-pass filter of 80 kHz.

The value of capacitor C3 influences the behaviour of the

SVRR at low frequencies: increasing the value of C3

increases the performance of the SVRR.

The figure of the MODE voltage (VMODE) as a function of

the supply voltage shows three areas; operating, mute

and standby. It shows, that the DC-switching levels of the

mute and standby respectively depend on the supply

voltage level. The figure of the SELECT voltage (VSELECT)

as a function of the supply voltage shows the voltage

levels for switching the channels in the active, mute or

standby mode.

SE application

Tamb = 25 °C if not specially mentioned, VCC = 7.5 V,

f = 1 kHz, RL = 4 Ω, Gv = 20 dB, audio band-pass

22 Hz to 22 kHz.

The SE application circuit is illustrated in Fig.16.

Increasing the value of electrolytic capacitor C3 will result

in a better channel separation. Because the positive

output is not designed for high output current (2 × Io) at

low load impedance (≤16 Ω), the SE application with

output capacitors connected to ground is advised.

The capacitor value of C6/C7 in combination with the load

impedance determines the low frequency behaviour.

The THD as a function of frequency was measured using

a low-pass filter of 80 kHz. The value of capacitor C3

influences the behaviour of the SVRR at low frequencies:

increasing the value of C3 increases the performance of

the SVRR.

General remark

The frequency characteristic can be adapted by

connecting a small capacitor across the feedback

resistor. To improve the immunity to HF radiation in radio

circuit applications, a small capacitor can be connected in

parallel with the feedback resistor (56 kΩ); this creates a

low-pass filter.

1997 Oct 07

9

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