Diodes ZXCT1032 - Manual

Issue 4 - June 2007 1 www.zetex.com
© Zetex Semiconductors plc 2007
ZXCT1032
High-side inrush controller and electronic fuse
Description
Ordering information
The ZXCT1032 is a high-side current monitor
that drives a PMOS or PNP transistor to
provide in-rush current limit and over-current
protection. The ZXCT1032 includes a high
accuracy high-side current monitor, a start-up
timer and a re-try inhibit timer.
The ZXCT1032 takes the voltage developed
across a current shunt resistor and compares
this with an externally set trip point. It works
in three modes:
• Linear soft-start
• Over-current detector
• Over-current disconnect/fuse
Linear soft-start
Upon power up the ZXCT1032 enters a linear
soft-start mode. During which the output
current ramps up from zero to a maximum
user defined trip point. The trip point is set by
the voltage on I
SET
pin and R
SENSE
.
The ramp rate is determined by capacitor C
T
.
The soft start ensures that capacitive loads are
smoothly charged without causing excessive
power supply startup transients.
Over-current detectior
When external capacitor CT has charged up
above the V
ISET
the ZXCT1032 switches from its
soft-start mode to its over-current detection
mode. During this mode the external MOSFET
will be fully enhanced reducing the its voltage
drop and power dissipation.
While in this mode the internal current monitor
continually checks the output current and
compares it to the trip-current level determined
by V
ISET
.
Over-current disconnect/fuse
If the trip current limit is exceeded at any time the
ZXCT1032 enters its Over-current disconnect
mode. The drive pin is driven high, turning the
pass MOSFET off; the flag output goes low
indicating a fault.
The drive and flag outputs are latched in these
states for a period determined by C
T
, V
ISET
and the
internally set discharge current (3µA typical). After
C
T
has discharged to 80mV the ZXCT1032 will
restart into its linear soft-start mode.
The C
T
charge and discharge times have been
ratioed to so that the power dissipation in the
pass MOSFET should allow indefinite operation
in the event of a continuous load failure.
Pin 3 description:
Determines the load current trip level or
constant current level. ISET can be left open
circuit (internal 2.1V reference) or driven via a
DC voltage or µC PWM output. Its source
impedance is 50k
⍀.
Features
• Accurate high-side current sensing
• User defined and dynamically adjustable
trip current
• Load switch control
• Fault flag logic output
• User defined ramp and inhibit timers
• SO8 package
• Temperature range -40 to 85°C
Applications
• Electronic fuse
• Short circuit protected supply feed
• Hot swap
• Power over twisted pair
Order code Pack Part mark Reel size Tape width Quantity per reel
ZXCT1032N8TA SO8 1032 7” 12mm 500