Philips TDA8542 - Manual (Page 8)

1998 Apr 01 8
Philips Semiconductors Product specification
2
×
1 W BTL audio amplifier TDA8542
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 T
amb
= 25
°
C is:
For T
amb
= 60
°
C the maximum total power dissipation is:
BTL application
T
amb
= 25
°
C if not specially mentioned, V
CC
= 5 V,
f = 1 kHz, R
L
= 8
Ω
, G
v
= 20 dB, audio band-pass
22 Hz to 22 kHz.
The BTL application diagram is illustrated in Fig.3.
The quiescent current has been measured without any
load impedance. The total harmonic distortion as a
function of frequency was measured with 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 select voltage (V
ms
) 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 depends on the supply
voltage level.
150 25 –
55
---------------------- 2.3 W =
150 60 –
55
---------------------- 1.7 W =
SE application
T
amb
= 25
°
C if not specially mentioned, V
CC
= 7.5 V,
f = 1 kHz, R
L
= 4
Ω
, G
v
= 20 dB, audio band-pass
22 Hz to 22 kHz.
The SE application diagram is illustrated in Fig.14.
If the BTL/SE pin (pin 5) is connected to ground, the
positive outputs (pins 2 and 7) will be in mute condition
with a DC level of
1 ⁄
2
V
CC
. When a headphone is used
(R
L
≥
25
Ω)
the SE headphone application can be used
without output coupling capacitors; load between negative
output and one of the positive outputs (e.g. pin 2) as
common pin.
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
×
I
o
) at low load
impedance (
≤
16
Ω
), the SE application with output
capacitors connected to ground is advised. The capacitor
value of C4/C5 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 of HF radiation in radio circuit
applications, a small capacitor can be connected in
parallel with the feedback resistor (56 k
Ω
); this creates a
low-pass filter.