AK4955 Datasheet, PDF (100/117 Pages) Asahi Kasei Microsystems – 24bit Stereo CODEC with MIC/SPK/Cap-less VIDEO-AMP/ LDO & DSP

[AK4955]
1. Grounding and Power Supply Decoupling
The AK4955 requires careful attention to power supply and grounding arrangements. If AVDD, DVDD, TVDD, SVDD
and LVDD are supplied separately, the power-up sequence is not critical. VSS1, VSS2, and VSS3 of the AK4955 must be
connected to the analog ground plane. System analog ground and digital ground should be wired separately and
connected together as close as possible to where the supplies are brought onto the printed circuit board. Decoupling
capacitors must be as near to the AK4955 as possible, with the small value ceramic capacitor being the nearest.
2. Internal Regulated Voltage Power Supply
VCOM is a signal ground of this chip. A 2.2μF electrolytic capacitor in parallel with a 0.1μF ceramic capacitor attached
to the VSS1 pin eliminates the effects of high frequency noise. No load current may be drawn from the VCOM pin. All
signals, especially clocks, should be kept away from the VCOM pin in order to avoid unwanted coupling into the
AK4955.
3. Analog Inputs
The Mic and Line inputs supports single-ended. The input signal range scales with nominally at typ. 2.07Vpp (@ MGAIN
= 0dB), centered around the internal signal ground (typ. 1.15V). Usually the input signal is AC coupled with a capacitor.
The cut-off frequency is fc = 1/(2πRC). The AK4955 can accept input voltages from VSS1 to AVDD.
6. Analog Outputs
The input data format for the DAC is 2’s complement. The output voltage is a positive full scale for 7FFFFFH (@24bit)
and a negative full scale for 800000H (@24bit). The ideal output is VCOM voltage for 000000H (@24bit data). The
common voltage of stereo lineout is typ. 2.52Vpp centered on 1.5V (typ) (LVCM1-0 bits = “01”). The speaker outputs are
centered on SVDD/2 (typ).
MS1343-E-00
- 100 -
2011/12