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STANDBY (POWER-DOWN MODE)

GENERAL PURPOSE DAC

VSP1221

SLES012A – SEPTEMBER 2001 – REVISED JULY 2004

PRINCIPLES OF OPERATION (continued)

To save power, the VSP1221 can be put into standby mode (power-down mode) both through hardware and

software. Pulling the STBY signal low puts the device into standby mode (hardware power-down). In this mode,

the reference is pulled down, all the functional blocks are disabled, the output is all zero, and the power

dissipation is zero. The power-up time is of the order of 10 ms. Software power down can be exercised by

resetting the STBYZ bit in the control register through the serial port (see the control register section). This is

similar to hardware power down, except that the reference is not pulled down. Hence, the power dissipation is

around 4 mW and the power-up time is of the order of 10 µs. The user can still program all the internal registers

during both hardware and software power down.

The VSP1221 has two 8-bit general-purpose digital-to-analog converters (DACs) that can be used for external

analog settings. The output voltage of each DAC can be independently set and has a range of 0 V to the supply

voltage with eight-bit resolution. The digital input to the DACs can be set by programming the User DAC1 and

User DAC2 registers through the serial port (see the User DAC1 register and User DAC2 register sections).

When not used in the system, the DACs can be put in standby mode by programming the above-mentioned

registers. The DACs are, by default, in standby mode. The average power consumed by each DAC is

approximately 1 mW.

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