SMH4803BEN データシートの表示（PDF） - Summit Microelectronics

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SMH4803BEN

Distributed Power Hot-Swap Controller

Summit Microelectronics 

SMH4803

ENPGA (16)

The ENPGA input controls the PG2# and PG3# outputs.

When ENPGA is pulled low, the PG2# output is immedi-

ately placed in a high impedance state. If ENPGA is driven

high, then the PG2# output will immediately be driven low,

provided PG1# has been active for at least tPGD.

PG3# (17)

PG3# is an open drain active low output with no internal

pull-up. PG3# is the last power good signal to be enabled

after Vgate, PG1# and PG2# have been turned on. PG3#

is delayed PGD after PG2# is active and 2xPGD after

PG1# is active. PG3# can be used to switch a third load

or a DC/DC converter.

PG1# (18)

PG1# is an open drain active low output with no internal

pull-up. PG1# is enabled after Vgate is enabled and

voltage across the load is within spec. PG1# can be used

to switch a load or enable a DC/DC converter.

PG2# (19)

PG2# is an open drain active low output with no internal

pull-up. PG2# is enabled after Vgate and PG1# have been

turned on. PG2# is delayed PGD after PG1# is active.

PG2# can be used to switch a second load or a DC/DC

converter.

test all combinations (all 128 possibilities) are readily

available as off the shelf stock items.

Power Good Delay

The PG delay timer that controls the delay from PG1# to

PG2# and PG2# to PG3# being asserted can be set to

typical values of 5ms, 20ms, 80ms or 160ms.

Quick-Trip Circuit Breaker Threshold

The Quick-Trip circuit breaker threshold can be set to

200mV, 100mV, 60mv or OFF. This is the threshold

voltage drop across RS that is placed between VSS and

CBSense.

Circuit Breaker Delay

The circuit breaker delay defines the period of time the

voltage drop across RS is greater than 50mV but less than

VQCB before the Vgate output will be shut down. This is

effectively a filter to prevent spurious shutdowns of Vgate.

The delays that can be programmed are 5µs, 50µs, 150µs

and 400µs.

Pin Detect

The Pin Detect function can be enabled or disabled.

VDD (20)

VDD is the positive supply connection. An internal shunt

regulator connected between VDD and VSS develops

approximately 12 volts that supplies the SMH4803. A

resistor must be placed in series with the VDD pin to limit

the regulator current (RD in the application illustrations).

PROGRAMMABLE FEATURES

Because the SMH4803 is electrically programmable it

can be fine-tuned for a wide variety of applications prior to

shipment to the customer. Because of this a manufacturer

can use a common part type across a wide range of

boards that are used on a common host but have different

electrical loads, power-on timing requirements, host volt-

age monitoring needs etc.

This ability to use a common solution across many plat-

forms shifts the focus of design away from designing a

new power interface for each board to concentrating on

the value added back-end logic.

Because the programming of the features is done at final

SUMMIT MICROELECTRONICS

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2041 8.4 6/15/00

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