AK7744VT Datasheet, PDF (25/50 Pages) Asahi Kasei Microsystems – 24bit 3ch ADC + 24bit 4ch DAC with Audio DSP

[ASAHI KASEI]
[AK7744]
(3) Power supply startup sequence
Turn on the power and reset the AK7744 by setting the INIT_RESET = "L" and S_RESET = "L". The VREF
(Analog reference level) of the AK7744 is set and its control registers are initialized by setting the INIT_RESET =
"H". The time for the VREF to become stable depends on the external capacitance on the VCOM pin. For example,
connecting a 10uF and a 0.1uF capacitor takes about 300ms before VREF is stable. Additional capacitance will
increase this time, and this rise time is the MINIMUM amount of time for a stable VREF. You can guarantee a stable
VREF by waiting longer than this minimum time after INIT_RESET ="H" to S_RESET ="H” (ADC and DAC
start to work.).
Normally, INIT_RESET sequence is executed when power is applied to the device.
Note 1): Set INIT_RESET = "H" after setting the oscillation when a crystal oscillator is used.
This setting time may differ depending on the crystal oscillator and its external circuit.
NOTE: Do not stop the system clock (slave mode: XTI, LRCLK, BITCLK, master mode: XTI) except when
S_RESET = "L". If these clock signals are not supplied, excess current will flow due to dynamic logic that is
used internally, and an operation failure may result.
Don’t set S_RESET ="H" during INIT_RESET ="L", or else the the crystal oscillator will stop or become
unstable.
AVDD
DVDD
INIT_RESET
S_RESET
Power OFF
When a crystal oscillator is
used, ensure stable oscillation
in this period.
After VREF is stable, then rise
up S_RESET. It will take
300ms(reference)
Fig. Power supply startup sequence
<MS0167-E-00>
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2002/10