AK7846 Datasheet, PDF (14/16 Pages) Asahi Kasei Microsystems – Stereo Audio Class-D Amp with Power Booster for Piezo Speakers

AKEMDAKEMD CONFIDENTIAL
[AK7846]
1. Grounding and Power Supply Decoupling
The AK7846 requires careful attention to power supply and grounding arrangements. VBAT is usually supplied from
Li-Ion battery in the system. VDD1 and VDD2 are supplied from smoothed boosted voltage. VSS1, VSS2, VSS3 and
VSS4 must be connected to analog ground plane. Analog and digital ground in the system should be connected
together near where the supplies are brought onto the printed circuit board. Decoupling capacitors with the small
value ceramic should be as close to the AK7846 as possible.
2. Voltage Reference
VC is a signal ground of this device. A 0.01µF ceramic capacitor (C3) between VC and VSS4 pin eliminates 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 analog Inputs
AC-coupling capacitors are necessary in series to INL and INR respectively.
4. 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 AK7846 or Class-D outputs away as far away as possible from the devices such as antennas that are sensitive to
high frequency noise.
5. Effect on RF bands
Power Booster or Class-D Outputs may affect high frequency signal outside the AK7846.
Apply previous section (4. Class-D Outputs) in PCB layout.
6. Drivable Piezo Speakers
The AK7846 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.
7. Boost DCDC Converter
Ceramic capacitor (C1, C9), Inductance (L1) and Schottky Diode (D1) should be located as close to the
AK7846 as possible.
Rev.04.9
– 14 –
2008/03