Philips TDA8946J - Manual (Page 4)

Philips Semiconductors
TDA8946J
2 x 15 W stereo BTL audio amplifier
Product specification Rev. 02 — 14 March 2000 4 of 23
9397 750 06863 © Philips Electronics N.V. 2000. All rights reserved.
8. Functional description
The TDA8946J is a stereo BTL audio power amplifier capable of delivering 2
×
15 W
output power to an 8
Ω
load at THD = 10%, using a 18 V power supply and an
external heatsink. The voltage gain is fixed at 32 dB.
With the three-level MODE input the device can be switched from ‘standby’ to ‘mute’
and to ‘operating’ mode.
The TDA8946J outputs are protected by an internal thermal shutdown protection
mechanism and a short-circuit protection.
8.1 Input configuration
The TDA8946J inputs can be driven symmetrical (floating) as well as asymmetrical.
In the asymmetrical mode one input pin is connected via a capacitor to the signal
ground which should be as close as possible to the SVR (electrolytic) capacitor
ground. Note that the DC level of the input pins is half of the supply voltage V
CC
, so
coupling capacitors for both pins are necessary.
The input cut-off frequency is:
(1)
For R
i
= 45 k
Ω
and C
i
= 220 nF:
(2)
As shown in Equation 1 and 2 , large capacitor values for the inputs are not
necessary; so the switch-on delay during charging of the input capacitors, can be
minimized. This results in a good low frequency response and good switch-on
behaviour.
Remark: To prevent HF oscillations do not leave the inputs open, connect a capacitor
of at least 1.5 nF across the input pins close to the device.
n.c. 13 not connected
OUT2
−
14 negative loudspeaker terminal 2
GND2 15 ground channel 2
V
CC2
16 supply voltage channel 2
OUT2+ 17 positive loudspeaker terminal 2
Table 3: Pin description …continued
Symbol Pin Description
f
i cut off –
( )
1
2
π
R
i
C
i
× ( )
----------------------------- =
f
i cut off –
( )
1
2
π
45 10
3 Ч
220
Ч
10
9 – Ч ( )
----------------------------------------------------------------- 16 Hz = =