PC8374L datasheet(118/239 Pages) NSC

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118

Revision1.1

7.0

Glue Functions

This chapter describes the glue functions integrated in the PC8374L device.

7.1 OVERVIEW

This module contains the glue functions. Most of them operate independently of the other functions and of the other modules

in the PC8374L device.

The glue functions are divided into three groups:

• Power-related functions:

— Highest active Main supply reference (REF5V)

— Highest active Standby supply reference (REF5V_STBY)

— Resume reset (RSMRST)

— Main power good (PWRGD_3V)

— Power distribution control (BKFD_CUT, LATCHED_BF_CUT)

— Main power supply control (PS_ON)

• Miscellaneous functions:

— Hard-disk LED indicator control (HD_LED)

• SMBus support functions:

— SMBus voltage translation (CC_DDCSCL, CC_DDCSDA, 5V_DDCSCL, 5V_DDCSDA)

— SMBus isolation (SMB1_SCL, SMB1_SDA, SMB2_SCL, SMB2_SDA)

Each function is described in the following sections.

7.2 FUNCTIONAL DESCRIPTION

7.2.1

Highest Active Main Supply Reference

This function generates the REF5V analog output signal (see specification in Section 10.2.11 on page 216). When the Main

power supply is turned on or off, the REF5V signal tracks either the VDD3 or VDD5 power supplies, whichever has a higher

voltage.

The circuit that generates the REF5V output is composed of two parts:

● One part tracks the V

DD3 supply voltage and is implemented in the PC8374L device.

● One part tracks the V

DD5 supply voltage and is implemented by an external resistor connected to the VDD5 power

supply.

Figure 19 shows a simplified diagram of the circuit that generates the REF5V analog output signal

Figure 19. REF5 Generation (Simpliﬁed Diagram)

VDD5

1 K

Ω

VDD3

REF5V

Comp

0.1-1

µF

PC8374L

Winbond Electronics Corp. Advanced PC Product Center

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