LTC7803 datasheet(17/42 Pages) AD

17 / 42 page

LTC7811

Rev. 0

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Buck Foldback Current

When the buck output voltage falls to less than 50% of its

nominal level, foldback current limiting is activated, pro-

gressively lowering the peak current limit in proportion to

the severity of the overcurrent or short-circuit condition.

Foldback current limiting is disabled during the soft-start

interval (as long as the VFB voltage is keeping up with

the TRACK/SS1,2 voltage). There is no foldback current

limiting for the boost channel.

Channel 1 Power Good (PGOOD1)

Channel 1 has a PGOOD1 pin that is connected to an

open drain of an internal N-channel MOSFET. The MOSFET

turns on and pulls the PGOOD1 pin low when the VFB1

pin voltage is not within ±10% of the 0.8V reference. The

PGOOD1 pin is also pulled low when the RUN1 pin is

low (shut down). When the VFB1 pin voltage is within the

±10% requirement, the MOSFET is turned off and the

pin is allowed to be pulled up by an external resistor to a

source no greater than 6V, such as INTVCC.

Low Battery Indicator

The BATTGOOD pin is connected to an open drain of

an internal N-channel MOSFET that is pulled low when

the voltage on the BATTSNS pin is low. When BATTSNS

is below 9.5V, the MOSFET turns on and pulls the

BATTGOOD pin low. When BATTSNS is greater than

9.75V, the MOSFET is turned off and the BATTGOOD pin is

allowed to be pulled up by an external resistor to a source

no greater than 6V, such as INTVCC. The BATTGOOD pin

is also low when RUN3 is low (when the boost channel

is shutdown).

OPERATION

LTC7803 Datasheet(PDF) 17 Page - Analog Devices