AK7841 Datasheet, PDF (18/21 Pages) Asahi Kasei Microsystems – Monaural Audio Class-D Amp with Power Booster for PiezoSpeaker

ASAHI KASEI
AKM CONFIDENTIAL
[AK7840]
1. Grounding and Power Supply Decoupling
The AK7841 requires careful attention to power supply and grounding arrangements. Supply VBAT with Battery
Power. VDD1 must be supplied with boosted flat voltage. Connect VSS1, VSS2 and VSS3 to analog ground plane.
System analog and digital ground should be isolated from each other and be connected nearby the power supply pin
on the printed circuit board. Decoupling capacitors should be as close to the power supply pins as possible, with the
small value ceramic capacitor nearby power supply.
2. Voltage Reference
VC pin is the analog common voltage (ground for signals). Insert a 0.01µF ceramic capacitor between VC and VSS3
to eliminate the effects of high frequency noise. This capacitor should be as close to the VC pin as possible. Do not
take out load current from the VC pin. All signals, especially clocks, should be kept away from the VC pin in order to
avoid unwanted coupling.
3. Class-D Outputs
The Class-D outputs are in BTL signal format. Locate the outputs close to the speaker to minimize interconnect
resistance and capacitance to suppress noise. Match the length and pattern of the plus and minus output interconnect.
Keep AK7841 or Class-D outputs away as far away as possible from the devices such as antennas that are sensitive to
high frequency noise.
4. Effect on RF bands
Power Booster or Class-D Outputs may affect high frequency signal while applying to some applications.
Apply previous section (3. Class-D Outputs) in PCB layout.
5. Drivable Piezo Speakers
AK7841 is designed to drive typical piezo speakers but in some cases electric characteristics of the speakers differ by
manufacturers. Feel free to ask us whether your speakers can be driven or not before using them.
Rev.08
- 18 -
2008/3