AK4637EN Datasheet, PDF (83/96 Pages) Asahi Kasei Microsystems – 24bit Mono CODEC with MIC/SPK-AMP

[AK4637]
1. Grounding and Power Supply Decoupling
The AK4637 requires careful attention to power supply and grounding arrangements. AVDD is usually
supplied from the system’s analog supply, and DVDD and TVDD are supplied from the system’s digital
power supply. If AVDD, DVDD and TVDD are supplied separately, the power-up sequence is not critical.
The PDN pin should be held “L” when power supplies are tuning on. The PDN pin is allowed to be “H”
after all power supplies are applied and settled.
To avoid pop noise on line output when power up/down, the AK4637 should be operated along the
following recommended power-up/down sequence.
1) Power-up
- The PDN pin should be held “L” when power supplies are turning on. The AK4637 can be reset by
keeping the PDN pin “L” for 200ns or longer after all power supplies are applied and settled.
2) Power-down
- Each of power supplies can be powered OFF after the PDN pin is set to “L”.
VSS1 and VSS2 of the AK4637 should 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 should be as close the power
supply pins as possible. Especially, the small value ceramic capacitor is to be closest.
2. Internal Regulated Voltage Power Supply
REGFIL is a power supply of the analog circuit (typ. 2.3V). A 2.2F ±10% capacitor attached to the VSS1
pin eliminates the effects of high frequency noise. This capacitor should be placed as near as possible to
the AK4637. No load current may be drawn from the REGFIL pin. All digital signals, especially clocks,
should be kept away from the REGFIL pin in order to avoid unwanted coupling into the AK4637.
3. Reference Voltage
VCOM is a signal ground of this chip. A 2.2F ±10%(AVDD ≤ 3.6V) or 4.7μF±10%(AVDD > 3.6V)
capacitor attached to the VSS1 pin eliminates the effects of high frequency noise. This capacitor should
be placed as near as possible to the AK4637. 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 AK4637. Attention must be paid to the printing pattern and the material of the capacitors to
prevent superimposed noises and voltage drops since the VCOM voltage is the reference of many
functions.
4. Analog Inputs
The microphone and line inputs support single-ended or full-differential format. When single-ended input,
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/(2RC).
5. 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 speaker amplifier (SPP and SPN pins) is BTL output, and they should be
connected directly to a speaker. There is no need for AC coupling capacitors. The monaural line output
(AOUT pin) is single-ended and centered on 1.5V (LVCM0 bit = “1”: default). This pin must be AC-coupled
using a capacitor.
015010680-E-00
- 83 -
2015/09