STAC9708 datasheet(52/56 Pages) ETC

52 / 56 page

SigmaTel, Inc.

Preliminary

STAC9708/11

10/02/98

Appendix B

+5.0V/+3.3V POWER SUPPLY OPERATION NOTES

The STAC9708 is capable of operating from a single 5V supply connected to both DVdd and AVdd. Even though

the STAC9708 has digital switching levels of 0.2Vdd to 0.5Vdd (See AC Link Electrical Characteristics in this

data book), we recommend that all digital interface signals to the AC-Link be 5V. If digital interface signals

below 5V are used, then appropriate level shifting circuitry must be provided to ensure adequate digital noise

immunity.

The STAC9708 can also operate from a 3.3V digital supply connected to DVdd while maintaining a 5V analog

supply on AVdd. On-chip level shifters ensure accurate logic transfers between the analog and digital portions of

the STAC9708. If digital interface signals above 3.3V are used (i.e. a +5V AC-Link interface), then appropriate

level shifting circuitry must be provided to ensure adequate digital noise immunity and to prevent on-chip ESD

protection diodes from turning on. (See Appendixes A concerning SPLIT INDEPENDENT POWER SUPPLY

OPERATION).

The STAC9711 must be run from a 3.3V supply connected to both DVdd and AVdd. If digital interface signals

above 3.3V are used (i.e. a +5V AC-Link interface), then appropriate level shifting circuitry must be provided to

ensure adequate digital noise immunity and to prevent on-ship ESD protection diodes from turning on.

*Always operate the STAC97xx digital supply from the same supply voltage as the digital controller

supply.

*All the analog inputs must be ac-coupled with a capacitor of 3.3 uF or greater. It is recommended that a

resistor of about 47K

Ω

Ω be connected from the signal side of the capacitor to analog GND as shown below.

*All the analog outputs must be ac-coupled. If an external amplifier is used, make sure that the input

impedance of the amplifier is at least 10K

Ω

Ω and use an ac-coupling capacitor of 3.3 uF.

47K

> 3.3 uF

SIGNAL

Analog Input

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