AK4648 Datasheet, PDF (102/119 Pages) Asahi Kasei Microsystems – Stereo CODEC with MIC/HP/SPK-AMP

[AK4648]
1. Grounding and Power Supply Decoupling
The AK4648 requires careful attention to power supply and grounding arrangements. AVDD, DVDD, TVDD and HVDD
are usually supplied from the system’s analog supply. If AVDD, DVDD, TVDD and HVDD are supplied separately, the
power-up sequence is not critical.
PDN pin should be held to “L” upon power-up. PDN pin should be set to “H” after all power supplies are powered-up.
In case that the pop noise should be avoided at speaker output, line output, and headphone output, the AK4648 should be
operated by the following recommended power-up/down sequence.
1) Power-up
- PDN pin should be held to “L” upon power-up. The AK4648 should be reset by bringing PDN pin “L” for 150ns or
more.
- In case that the power supplies are separated in two or more groups, the power supply including TVDD should be
powered ON at first. Regarding the relationship between DVDD and HVDD, the power supply including DVDD
should be powered ON prior to the power supply including HVDD.
2) Power-down
- Each power supplies should be powered OFF after PDN pin is set to “L”.
- In case that the power supplies are separated in two or more groups, the power supply including TVDD should be
powered OFF at last. Regarding the relationship between DVDD and HVDD, the power supply including HVDD
should be powered OFF prior to the power supply including DVDD.
VSS1, VSS2, and VSS3 of the AK4648 should be connected to the analog ground plane. System analog ground and
digital ground should be connected together near to where the supplies are brought onto the printed circuit board.
Decoupling capacitors should be as near to the AK4648 as possible, with the small value ceramic capacitor being the
nearest.
2. Voltage Reference
VCOM is a signal ground of this chip. A 2.2μF electrolytic capacitor in parallel with a 0.1μF ceramic capacitor attached
to the VCOM 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
AK4648.
3. Analog Inputs
The Mic, Line and MIN inputs are single-ended. The input signal range scales with nominally at 0.06 x AVDD Vpp(typ.)
@MGAIN1-0 bits = “01”, 0.03 x AVDD Vpp(typ.) @MGAIN1-0 bits = “10”, 0.015 x AVDD Vpp(typ.) @MGAIN1-0
bits = “11” or 0.6 x AVDD Vpp(typ.) @MGAIN1-0 bits = “00” for the Mic/Line input and 0.6 x AVDD Vpp (typ.) for the
MIN input, centered around the internal common voltage (0.45 x AVDD). Usually the input signal is AC coupled using a
capacitor. The cut-off frequency is fc =1/ (2πRC). The AK4648 can accept input voltages from VSS1 to AVDD.
4. Analog Outputs
The input data format for the DAC is 2’s complement. The output voltage is a positive full scale for 7FFFH(@16bit) and
a negative full scale for 8000H(@16bit). The ideal output is VCOM voltage for 0000H(@16bit). Stereo Line Output is
centered at 0.45 x AVDD. Headphone-Amp and Speaker-Amp outputs are centered at HVDD/2.
MS0625-E-01
- 102 -
2007/06