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AD1845 ADVANCED POWER-DOWN MODES

The AD1845 has eight Advanced Power-Down Modes available at any time. The user can control these power-down modes through hardware by asserting the PWRDWN and RESET pins or through software by writing to the Power-Down and the Total Power-Down Control Registers. Figure 24 summarizes the power-down delay, power-up delay, and power dissipation for each power down mode. A priority listing and description of the power-down modes follows. Note that the hardware controlled Power-Down and Reset modes take precedence over the software controlled power-down states. Hardware Controlled States

The hardware power-down states are accessed by bringing the PWRDWN or RESET pin LO. Either of these signals place the AD1845 into the maximum power conservation mode. Bringing the PWRDWN or RESET pin HI will power-up the codec in approximately 512 ms (see the Power-Up and Reset section of this data sheet). • Power-Down: PWRDWN immediately puts the AD1845 into its lowest power-down state. The AD1845’s parallel interface will not function and all bidirectional signal lines will be in a high-impedance state. • Reset: RESET powers down the AD1845 gradually to its lowest power-down state. The AD1845 performs a sequenced power-down that eliminates audible effects from the DAC’s output. The XTAL1 input must be clocked for the minimum duration of the RESET pulse width. The AD1845’s parallel interface will not function and all bidirectional signal lines will be in a high-impedance state. Software Controlled States

To enter the Total Power-Down mode requires entering the Mode Change Enable (MCE) state. After entering MCE, the Total Power-Down mode can be accessed by writing a “1” to the TOTPWD bit in the Total Power-Down Register. Exiting the Total Power-Down mode (writing a “0” to the TOTPWD bit in the Total Power-Down Register) will initialize the AD1845 in approximately 512 ms (see the Power-Up and Reset section of this data sheet). • Total Power-Down: In the Total Power-Down mode the ADC, DAC, Mixer, and voltage reference are turned off, but the digital interface remains active awaiting power-up. All ADC and DAC data is flushed including data in the capture and playback FIFOs.

To enter the software controlled power-down states in the Power-Down Control Register, write a “1” to the control bits. The AD1845 performs a sequenced power-down that eliminates audible effects from the DAC’s output, and saves the codec’s internal operating state. Clearing the bits (writing a “0” to the control bits) returns the AD1845 from the power-down state and begins the initialization sequence. The AD1845 exits the power-down mode within 1 sample period. However, an additional 128 sample periods are required to unmute the outputs and restore the internal settings to the pre-Power-Down operating state. • Standby: Entering the Standby mode powers down the ADC, DAC and the Mixer, and forces all outputs to be muted. Standby turns off all internal digital and analog circuitry with the exception of the digital interface and the voltage reference. All ADC and DAC data is flushed including data in the capture and playback FIFOs. • Mixer Power-Down: Entering the Mixer Power-Down mode, causes both the mixer and the DAC circuitry to be turned off. All DAC data is flushed including data in the playback FIFO. In this mode the mixer is off and the AD1845 is muted, but the ADC remains functional. • Mixer Only: The Mixer Only mode is initiated by powering down both the ADC and DAC, leaving the analog mixer and the digital interface active. MIC, LINE, AUX1, AUX2, and M_IN can be mixed in the analog domain on the AD1845 outputs. All ADC and DAC data is flushed including data in the capture and playback FIFOs. • ADC Power-Down: Entering the ADC Power-Down mode, causes the ADC digital and analog engines to be turned off. All ADC data is flushed including data in the capture FIFO and the AD1845 is rendered deaf. The input programmable gain amplifier (PGA) is also shut down. The DAC and mixer remain active allowing the AD1845 to continue to playback and mix samples. • DAC Power-Down: Entering the DAC Power-Down mode suspends the DAC digital and analog engines, and all DAC data is flushed including data in the playback FIFO. However, the mixer and ADC are functional allowing the AD1845 to continue to capture and mix samples.

Advanced Power-Down Mode

PWRDWN Pin

RESET Pin

TOTPWD ADCPWD DACPWD MIXPWD Power-Down Bit Bit Bit Bit Delay*

Power-Up Delay*

Power Dissipation

Operating 1. Power-Down 2. Reset 3. Total Power-Down 4. Standby 5. Mixer Power-Down 6. Mixer Only 7. ADC Power-Down 8. DAC Power-Down

HI LO HI HI HI HI HI HI HI

HI x LO HI HI HI HI HI HI

0 x x 1 0 0 0 0 0

x 512 ms 512 ms 512 ms 1/FS 1/FS 1/FS 1/FS 1/FS

600 mW 10 mW 10 mW 150 mW 180 mW 350 mW 260 mW 400 mW 425 mW

0 x x x 1 0 1 1 0

0 x x x x x 1 0 1

0 x x x 1 1 0 0 0

x 0s 3 ms 3 ms 1/FS 1/FS 1/FS 1/FS 1/FS

“x” = Don’t Care *Values shown are derived using a 24.576 MHz input clock source. All values are proportional to the input clock source.

Figure 24. Advanced Power-Down Mode Summary

–32–

REV. B


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