NAU8812EVB Nuvoton Technology Corporation of America, NAU8812EVB Datasheet - Page 58

• Manufacturer Part Number: NAU8812EVB
• Description: BOARD EVAL FOR NAU8812
• Manufacturer: Nuvoton Technology Corporation of America
• Series: emPowerAudio™r

Specifications of NAU8812EVB

• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

This device has been designed to operate reliably using a wide range of power supply conditions and power-
on/power-off sequences. There are no special requirements for the sequence or rate at which the various power
supply pins change. Any supply can rise or fall at any time without harm to the device. However, pops and clicks
may result from some sequences. Optimum handling of hardware and software power-on and power-off sequencing
is described in more detail in the Power Up/Down Sequencing section of this document.
The NAU8812 does not have an external reset pin. The device reset function is automatically generated internally
when power supplies are too low for reliable operation. The internal reset is generated any time that either VDDA or
VDDC is lower than is required for reliable maintenance of internal logic conditions. The threshold voltage for VDDA
is approximately ~1.52Vdc and the threshold voltage for VDDC is approximately ~0.67Vdc. Note that these are much
lower voltages than are required for normal operation of the chip. These values are mentioned here as general
guidance as to overall system design.
If either VDDA or VDDC is below its respective threshold voltage, an internal reset condition may be asserted.
During this time, all registers and controls are set to the hardware determined initial conditions. Software access
during this time will be ignored, and any expected actions from software activity will be invalid.
When both VDDA and VDDC reach a value above their respective thresholds, an internal reset pulse is generated
which extends the reset condition for an additional time. The duration of this extended reset time is approximately 50
microseconds, but not longer than 100 microseconds. The reset condition remains asserted during this time. If either
VDDA or VDDC at any time becomes lower than its respective threshold voltage, a new reset condition will result.
The reset condition will continue until both VDDA and VDDC again higher than their respective thresholds. After
VDDA and VDDC are again both greater than their respective threshold voltage, a new reset pulse will be generated,
which again will extend the reset condition for not longer than an additional 100 microseconds.
There is no direct way for software to determine that the device is actively held in a reset condition. If there is a
possibility that software could be accessing the device sooner than 100 microseconds after the VDDA and VDDC
supplies are valid, the reset condition can be determined indirectly. This is accomplished by writing a value to any
register other than register 0x00, with that value being different than the power-on reset initial values. The optimum
choice of register for this purpose may be dependent on the system design, and it is recommended the system
engineer choose the register and register test bit for this purpose. After writing the value, software will then read back
the same register. When the register test bit reads back as the new value, instead of the power-on reset initial value,
software can reliably determine that the reset condition has ended.
emPowerAudio
Datasheet Revision 2.0
12.11. POWER SUPPLY
12.11.1. Power-On Reset
12.11.2. Power Related Software Considerations
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Page 58 of 109
NAU8812
January 2011