AN10436 PHILIPS [NXP Semiconductors], AN10436 Datasheet - Page 11

• Manufacturer Part Number: AN10436
• Description: TDA8932B/33(B) Class-D audio amplifier
• Manufacturer: PHILIPS [NXP Semiconductors]

NXP Semiconductors
AN10436_1
Application note
2.3.1 Supply turn-on
2.3.2 Supply turn-off
2.2 Half Supply Voltage (HVP) chargers
2.3 Pop free power supply on/off cycling
2.4 Oscillator frequency
The internal HVPREF, HVP1 and HVP2 buffers will quickly charge the reference capacitor
(C
charge current of the HVP1 (pin 30) and the HVP2 (pin 19) buffers is 80 mA (dependent
on the junction temperature). The charge time of the SE capacitor can be estimated as
follows:
Where:
Example:
Charging an SE capacitor of 1000 μF at a supply voltage of 22 V takes about 138 ms.
Remark: The half supply voltage buffers are short circuit protected.
Internal logic will delay the operation (regardless of the control voltages) until the
HVPREF, HVP1 and HVP2 buffers are settled at ½(V
an optimum pop performance, a capacitor of 470 nF should be attached to the
ENGAGE (pin 5). This will make sure the gain and therefore the offset will be increased
gradually to avoid pop sound (see
Either the UnBalance Protection (UBP) or the UnderVoltage Protection (UVP) will avoid
pop noise when the power supply is turned off. The power stage is disabled when either
V
(9.5 V typical) is reached.
Remark: During power supply on/off cycling, an unwanted input signal from the audio
source can still cause a pop noise. To prevent this the ENGAGE pin should be pulled
down to CGND to mute any unwanted signal.
An external resistor connected between the OSCREF (pin 10) and V
frequency of the PWM output. The oscillator frequency can be estimated with this
equation:
t
f
osc
DDA
=
C
V
V
I = typical charge current (A)
HVPREF
DDA
SSA
SE
C
------------------------------------------------------------- -
=
drops more than 20 % (see
SE
= single ended capacitor (F)
12.45 10
------------------------- -
= negative analog supply voltage (V)
= analog supply voltage (V)
⋅
) and the SE capacitors (C
0.5
R
osc
⋅
⋅
(
V
I
9
DDA
–
Rev. 01 — 12 December 2007
V
SSA
)
Section 2.6.6
Figure
SE
) before the power stage is enabled. The typical
21).
TDA8932B/33(B) Class-D audio amplifier
for more detail) or the UVP threshold level
DDA
− V
SSA
) to avoid pop noise. For
SSA
AN10436
© NXP B.V. 2007. All rights reserved.
sets the oscillator
11 of 55
(1)
(2)