ADM1027 datasheet(39/56 Pages) AD

39 / 56 page

REV. A

ADM1027

–39–

OPERATING FROM 3.3 V STANDBY

The ADM1027 has been specifically designed to operate from a

3.3 V STBY supply. In computers that support S3 and S5 states,

the core voltage of the processor will be lowered in these states.

Note that since other voltages can drop or be turned off during

a low power state, these voltage channels will set status bits or

generate

SMBALERTs. It is still necessary to mask out these

channels prior to entering a low power state by using the interrupt

mask registers. When exiting the low power state, the mask bits

can be cleared. This prevents the device from generating unwanted

SMBALERTs during the low power state.

XOR TREE TEST MODE

The ADM1027 includes an XOR tree test mode. This mode is

useful for in-circuit test equipment at board-level testing. By

applying stimulus to the pins included in the XOR tree, it is

possible to detect opens or shorts on the system board. Figure 43

shows the signals that are exercised in the XOR tree test mode.

The XOR tree test is invoked by setting Bit 0 (XEN) of the

XOR tree test enable register (Reg. 0x6F).

PWM1/XTO

PWM3

PWM2

TACH4

TACH3

TACH2

TACH1

VID4

VID3

VID2

VID1

VID0

Figure 43. XOR Tree Test

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