[AK4438]
1. Grounding and Power Supply Decoupling
The AK4438 requires careful attention to power supply and grounding arrangements. AVDD and TVDD
are usually supplied from the analog supply of the system. If AVDD and TVDD are supplied separately,
the power-up sequences between AVDD and TVDD is not critical. VSS1 and VSS2 must be connected
to the same 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 should be as near to the AK4438 as possible.
2. Voltage Reference
The differential voltage between VREFH pin and VREFL pin sets the analog output range. The VREFH
pin is normally connected to AVDD, and the VREFL pin is normally connected to VSS2. VREFHL and
VREFL should be connected with a 0.1µF ceramic capacitor and 10µF electrolytic capacitor as near as
possible to the pin to eliminate the effects of high frequency noise.
VCOM is a signal ground of this chip and output the voltage AVDDx1/2. A 2.2F ±50% ceramic capacitor
attached between the VCOM pin and VSS2 eliminates the effects of high frequency noise. This capacitor
should be as close to the pin as possible. No load current may be drawn from the VCOM pin. All signals,
especially clocks, should be kept away from the VREFH pin and the VCOM pin in order to avoid unwanted
coupling into the AK4438.
LDOO outputs 1.2V that is used for internal digital circuit. LDOO and VSS1 should be connected with a
2.2F ±50% ceramic capacitor as near as possible to the pin to stabilize internal LDO. No load current
may be drawn from the VCOM pin.
3. Analog Output
The output signal range is nominally 0.86 x VREFH Vpp centered around the VCOM voltage. The DAC
input data format is 2’s complement. The output voltage is a positive full scale for 7FFFFFFFH (@32bit)
and a negative full scale for 80000000H (@32bit). The ideal output is VCOM voltage for 00000000H
(@32bit). The internal analog filters remove most of the noise generated by the delta-sigma modulator of
DAC beyond the audio passband, in single-ended input mode.
Normally, DC component is cut by an external capacitor since the DAC outputs have DC offsets of a few
millivolts to the VCOM voltage.
016001925-E-00
2016/03
- 59 -
AKM [ ASAHI KASEI MICROSYSTEMS ]
