High-side inrush controller and electronic fuse - Zetex Semiconductors
Description
ZXCT1032 High-side inrush controller and electronic fuse
Description
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 While in this mode the internal current monitor continually checks the output current and compares it to the trip-current level determined by VISET.
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 CT, VISET and the internally set discharge current (3µA typical).
After CT has discharged to 80mV the ZXCT1032 will restart into its linear soft-start mode.
The CT 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.
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 ISET pin and RSENSE.
The ramp rate is determined by capacitor CT.
The soft start ensures that capacitive loads are smoothly charged without causing excessive power supply startup transients.
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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⍀.
Over-cu...
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