UBA1707 NXP Semiconductors, UBA1707 Datasheet - Page 15

• Manufacturer Part Number: UBA1707
• Description: Cordless Telephone, Answering Machine Line Interface
• Manufacturer: NXP Semiconductors

Philips Semiconductors
D
The dynamic limiter of the UBA1707 prevents clipping of
the loudspeaker output stage and protects the operation of
the circuit when the supply voltage at V
2.7 V.
Hard clipping of the loudspeaker output stage is prevented
by rapidly reducing the gain when the output stage starts
to saturate. The time in which gain reduction is effected
(clipping attack time) is approximately a few milliseconds.
The circuit stays in the reduced gain mode until the peaks
of the loudspeaker signals no longer cause saturation.
The gain of the loudspeaker amplifier then returns to its
normal value within the clipping release time (typically
250 ms). Both attack and release times are proportional to
the value of the capacitor C
distortion of the loudspeaker output stage, in reduced gain
mode, stays below 5% up to 10 dB (minimum) of input
voltage overdrive [providing V
500 mV (RMS)].
1999 Feb 17
handbook, full pagewidth
YNAMIC LIMITER
Cordless telephone, answering machine
line interface
Bit names are given in italics.
LSAI2
LSAI1
(
PIN
2V d
2V d
DLC;
LSPD
LSPD
V
V
BIT
DLC
I
I
LSAI
DLCI)
. The total harmonic
is below
LSA1
LSA2
CC
falls below
0.5V CC
Fig.13 Loudspeaker channel.
I
LSPD
V
15
VOLUME CONTROL
DYNAMIC LIMITER
When the supply voltage drops below an internal threshold
voltage of 2.7 V, the gain of the loudspeaker amplifier is
rapidly reduced (approximately 1 ms). When the supply
voltage exceeds 2.7 V, the gain of the loudspeaker
amplifier is increased again.
The hard clipping of the dynamic limiter can be inhibited by
setting the DLCI bit at logic 1, via the serial interface.
The dynamic limiter is no longer supplied by setting the
LSPD bit at logic 1. In this case, the C
is maintained to allow the gain of the loudspeaker amplifier
to return to its nominal value as soon as the loudspeaker
channel is supplied again.
V
The loudspeaker amplifier voltage gain can be reduced in
steps of 3 dB via the serial interface (via bits VOL0, VOL1
and VOL2). These bits provide 7 steps of voltage gain
adjustment. The voltage gain is maximum when all bits are
at logic 1 and is reduced by 21 dB when all bits are at
logic 0.
OLUME CONTROL
V CC
UBA1707
(
BITS
3
VOL0
TO
VOL2
DLCI
LSPD
MGK713
VOL0, VOL1
LSAO
DLC
LSPGND
C DLC
Product specification
DLC
AND
UBA1707
capacitor charge
VOL2)
C LSAO
LSP