PC8374L datasheet(124/239 Pages) NSC

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7.0 Glue Functions (Continued)

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Figure 25. BKFD_CUT and LATCHED_BF_CUT Generation (Simpliﬁed Diagram)

For the AC characteristics, see “Power Distribution Control” on page 234.

7.2.6

Main Power Supply Control

This function generates the PS_ON signal, which turns the Main power supply on and off.

The Main power supply is turned on by an active low PS_ON signal, generated when all of the following are true:

● The processor is currently inserted in its socket (CPU_PRESENT = low).

● The system is not in one of the S3 to S5 sleep states (SLP_S3 = high).

● None of the conditions for ETC exists (see Section 8.2.10 on page 139).

● If an ETC event has occurred, the system has gone through one of the S3 to S5 sleep states (rising edge on SLP_S3).

Figure 26 shows a simplified diagram of the circuit that generates the PS_ON signal.

Figure 26. PS_ON Generation (Simpliﬁed Diagram)

For the AC characteristics, see “Main Power Supply Control” on page 235.

1 K

Ω

BKFD_CUT

VSB5

Reset

(BKFD_CUT)

SLP_S5

LATCHED_BF_CUT

SLP_S3

PWRGD_PS

R-S Flip-Flop

Set

Detector

22 K

Ω

PS_ON

VSB5

SLP_S3

CPU_PRESENT

Detector

Reset

R-S Flip-Flop

Set

ETC event

from HM

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PC8374L Datasheet(PDF) 124 Page - National Semiconductor (TI)

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