PM8801 datasheet(10/37 Pages) STMICROELECTRONICS

10 / 37 page

Pin descriptions and connection diagram

PM8801

10/37

DocID018560 Rev 2

Pin descriptions and connection diagram

Figure 5. Pin connections (top view)

Table 2. Pin descriptions

Pin#

Name

Function

1ENSL

Sleep mode input: active-low signal.

An optocoupler may be used to force the PM8801 to enter into sleep mode, shutting

down its internal DC/DC controller.

ENDC

MPS duty cycle / LED enable: active-low signal.

Drive this pin low to disable the LED driver during normal operations.

Entering sleep mode the host of the PoE-PD may drive this pin through an

optocoupler to set the MPS current profile. The signal value is sampled on the

ENSL pin during transition to sleep mode. If low the MPS current is pulsed, if high

the MPS current is constant.

3CTL

Input of the pulse width modulator.

CTL pull-up to VB is provided by an external resistor which may be used to bias an

opto-coupler transistor.

4VB

5 V, up to 10 mA bias regulator.

This reference voltage can be used to bias an opto-coupler transistor.

In sleep mode VB regulator is switched off.

5CS

Current sense input for current mode control and overcurrent protection.

Current sensing is accomplished using a dedicated current sense comparator. If the

CS pin voltage exceeds 0.5 V, the GAT1 pin switches low for cycle-by-cycle current

limiting. CS is internally held low for 60 ns after GAT1 switches high to blank leading

edge current spikes.

6RTN1

Power ground for the GAT1 driver.

This pin must be connected to RTN2 and ARTN.

DIM

FRS

T2P

RTN1

CTL

DET

CLS

ARTN

GAT2

GAT1

VSS

RTN2

VDD

ENSL

ENDC

LED

WKUP

AM045037v1

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