LTC4229
7
4229f
For more information www.linear.com/LTC4229
pin FuncTions
CPO: Charge Pump Output. Connect a capacitor from
CPO to the DSRC pin. The value of this capacitor is ap-
proximately 10× the
gate capacitance (C
ISS
) of the external
MOSFET for ideal diode control. The charge stored on this
capacitor is used to pull up the ideal diode MOSFET gate
during a fast turn-on. Leave this pin open if fast ideal diode
turn-on is not needed.
DCFG: Logic Input. Configures status indication of DFLT
output depending on diode sense (DSNS) connection.
Connect this pin to GND when the diode sense is only
across the ideal diode MOSFET. Connect to INTV
CC
when
the diode sense is across the ideal diode MOSFET, sense
resistor and Hot Swap MOSFET.
DFLT: Diode MOSFET Fault Status Output. This pin is pulled
low by an internal switch when the voltage between IN and
DSNS exceeds 250mV. The external ideal diode MOSFET
is not turned off during the fault. An internal 10µA current
source pulls this pin up to a diode below INTV
CC
. It may
be pulled above INTV
CC
using an external pull-up. Leave
open if unused.
DGATE: Ideal Diode MOSFET Gate Drive Output. Connect
this pin to the
gate of an external N-channel MOSFET
for ideal diode control. An internal clamp limits the gate
voltage to 12V above and a diode voltage below DSRC.
During fast turn-on, a 1.5A pull-up charges DGATE from
CPO. During fast turn-off, a 1.5A pull-down discharges
DGATE to DSRC.
DOFF: Control Input. A rising edge above 1.235V turns off
the external ideal diode MOSFET and a falling edge below
1.215V allows the MOSFET to be turned on.
DSNS: Ideal Diode Output Voltage Sense Input. Connect
this pin to the output of either the ideal diode MOSFET or
the Hot Swap MOSFET for diode output sense. The voltage
sensed at this pin is used to control DGATE for forward
voltage regulation and reverse turn-off.
DSRC: Ideal Diode’s MOSFET Gate Drive Return. Connect
this pin to the source of the external N-channel MOSFET
switch. The gate fast pull-down current returns through
this pin when DGATE is discharged.
DSTAT: Diode MOSFET Status Output. Open drain output
that pulls low when the MOSFET gate drive voltage between
DGATE and DSRC exceeds 0.7V. Otherwise it goes high
impedance and requires an external pull-up resistor to
a
positive supply as there is no internal 10µA current source
at this pin. Leave open if unused.
DTMR: Debounce Timer Capacitor Terminal. Connect
this pin to either INTV
CC
for fixed 100ms delay or an
external capacitor to ground for adjustable start-up delay
(123ms/µF) when EN toggles low.
EN: Enable Input. Ground this pin to enable Hot Swap con
-
trol. If this pin is pulled high, the MOSFET is not allowed
to
turn on. A 10µA current source pulls this pin up to a
diode below INTV
CC
. Upon EN going low when UV is high
and OV is low, there is a start-up delay for debounce as
configured at the DTMR pin, after which the fault is cleared.
Exposed Pad (UFD Package): The exposed pad may be
left open or connected to device ground.
FAULT: Overcurrent Fault Status Output. Output that pulls
low when the fault filter times out during an overcurrent
fault. Otherwise it is pulled high by a 10µA current source
to a diode below INTV
CC
. It may be pulled above INTV
CC
using an external pull-up. Leave open if unused.
FB: Foldback and Power Good Comparator Input. Connect
this
pin to an external resistive divider from OUT. If the
voltage falls below 1.215V, the PWRGD pin pulls high to
indicate the power is bad. If the voltage falls below 0.9V,
the output power is considered bad and the current limit
is reduced. Tie to INTV
CC
to disable foldback.
FTMR: Fault Timer Capacitor Terminal. Connect a capacitor
between this pin and ground to set a 12ms/µF duration
for current limit before the external Hot Swap MOSFET is
turned off. The duration of the off time is 11s/µF, resulting
in a 0.1% duty cycle.
GND: Device Ground.
