AK7841 Datasheet, PDF (9/21 Pages) Asahi Kasei Microsystems – Monaural Audio Class-D Amp with Power Booster for PiezoSpeaker

ASAHI KASEI
AKM CONFIDENTIAL
[AK7840]
Power-Down Control
VBAT and DVDDI must be turned off as (4) or (5) below.
(4) VBAT=DVDDI=”OFF” at the same time.
(5) DVDDI=”OFF” first, then VBAT=”OFF”.
Set PDN pin to “Low” when shutting down. Then, 1µs wait is necessary before pulling down VBAT
and DVDDI. Do not do them simultaneously.
※ When PDN pin is “High” and VBAT/DVDDI supply is suddenly cut off due to unexpected event, pop noise may be
detected while sound signal is being output. Even under such cases LSI will not be harmed.
VBAT “OFF”
0V
DVDDI “OFF”
0V
PDN pin
> 1us _0V
Figure. 5 Power-Down Sequence (4)
///_{VBAT “OFF”}
>0
0V
DVDDI “OFF”
0V
PDN pin
> 1us
0V
Figure. 6 Power –Down Sequence (5)
Attention: The performance of the device will not be guaranteed after the below sequence.
(6) VBAT=”OFF” first, then DVDDI=”OFF”
„ Analog inputs
The AK7841 correspond to both single and differential-ended input. Use ac coupling capacitors as described below.
Avoid the change from 0.1uF of the recommended value as much as possible because these change of capacitance
may influence not only HPF (High Pass Filter) at input but also the operation of the pop noise prevention circuit.
When single-ended input
Connect SDSEL pin to ground. Input t analog signal to INN pin through a 0.1uF capacitor. Then, INP pin should
be open. ( Figure. 16)
When differential-ended input
Connect SDSEL pin to DVDDI. Input t analog signal to between INN and INP pins through ac-coupling 0.1uF
capacitors ( Figure. 17). If two conditions are fulfilled as below, ac-coupling capacitors are not needed
( Figure. 18).
1. The voltage of INP and INN are VSS while shutting down.
2. The common level of INP and INN pin is between 0.8V and 1.6V, and input signals are within
common level±0.5V for each pin (2Vpp).
Rev.08
2008/3
-9-