Diodes ZXCT1032 User Manual

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

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

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.

pin and R

SET

SENSE

Over-current detectior

When external capacitor CT has charged up above the V 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.

the ZXCT1032 switches from its

ISET

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 internally set discharge current (3µA typical). After C

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.

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⍀.

, V

ISET

and the

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

Ordering information

Order code Pack Part mark Reel size Tape width Quantity per reel

ZXCT1032N8TA SO8 1032 7” 12mm 500

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ZXCT1032

Load

ZXCT

1032

IN+

SET

GND

IN-

Drive

GND

Flag

µC

SENSE

GND-

ISET

Flag

IN+

N/C

IN-

Drive

Top view

SO8

Typical application circuit Pinout connections

Pin description

Pin Name Description

1 GND Ground reference for I

and Flag pins. Most negative terminal of the

SET

device. No other pin should go below this voltage.

An external capacitor is connected to this pin and is used to determine the period for constant-current mode and the timeout before restarting. To reduce excessive heating during the soft start mode capacitors less than 220nF are reocmmended.

3 ISET Determines the load current trip level or constant current level. This can

be driven via a DC voltage or via a µC PWM output.

An input <100mV will disable the high-side switch (i.e. set I

SENSE

= (V

-150mV)/10

ISET

OUT

= 0)

If left open-circuit, an accurate internal DC reference of 2.1V and source impedance of 50k⍀ is used to set the voltage on this pin. (External drivers must take this reference into account.)

4 Flag This is an active low open collector output that goes low whenever the

current limit set by the choice of R

SENSE

and I

is reached or in the

SET

event of a shorted load.

5 Drive This is the output drive pin to the external high side referred switch on

the ZXCT1032, capable of driving PMOS and PNP transistors.

6 IN- The load referred input to the current monitor control loop.

7 N/C Not connected

sense input to the current monitor control loop.

8 IN+ Acts as both the supply pin to the ZXCT1032 and the supply referred

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ZXCT1032

NOTES:

Absolute maximum ratings

max

(a)

...................................................................................................... 28 V

IN+

and V

IN-

) ................ 500 mV

SENSE

+0.5 V

IN+

Voltage on any pin relative to GND ............................................................. -0.6V and V

Maximum differential voltage between V

Junction temperature range ........................................................................ -40 to 150°C

Storage temperature range .......................................................................... -55 to 150°C

Operation above the absolute maximum rating may cause device failure. Operation at the absolute maximum ratings, for extended periods, may reduce device reliability.

NOTES:

(a) Up to a maximum of 24 hours

Recommended operating conditions

Symbol Parameter Min. Max. Units

IN+

FLAG

ISET

Supply range 9.5 21 V

Ambient temperature range -40 85 °C

Flag voltage range 0 V

IN+

Voltage on ISET pin 1 2.5 V

Electrical characteristics

Test conditions T

Symbol Parameter Conditions Min. Typ. Max. Units

Quiescent current

(*)

STRIP

ISET

DRIVEH

Flag trip threshold voltage

ISET open voltage I

ISET

ISET output current V

Drive high output voltage

DRIVEL

FLAGL

FLAGZ

Drive low output voltage

Drive low output resistance V

Flag Low output Voltage

Flag open circuit leakage current

STRIP-TC

IN- bias current V

IN-

Temperature coefficient of trip voltage

CT-CHG

Capacitor CT charging current

CT-DIS

Capacitor CT discharging current

= 25°C, V

amb

= 20V. Unless otherwise stated.

IN+

SENSE

ISET

DRIVE

ISET

DRIVE

ISET

FLAG

ISET

FLAG

ISET

See footnote

= 0V, V_

=1.1V 95 mV

=2.1V 185 195 205

= 0 2.0 2.1 2.2 V

=0V 30 45 60 ␮A

= 2.1V, V

SENSE

= 0,

= 2.1V, V

SENSE

= 0,

= 2.1V, V

SENSE

= 100µA

= 2.1V, V

= 5V

= 0V 100 200 nA

(†)

ISET

> 205mV,

< 185mV,

< 185mV

> 205mV

SENSE

= 2.1V

< 185mV,

IN-

– 0.4

IN-

- 7

1.6 2.5 mA

IN-

– 0.2

IN-

- 5.5

9k⍀

0.2 0.4 V

1200nA

FLAG = Open 130 200 270 ␮A

FLAG = Low 1.8 3.3 5.4 ␮A

- 4V

IN-

ppm/°C

(*) V (†) Temperature dependent measurements are extracted from characterization and simulation results.

SENSE

= V

IN+

- V

IN-

. V

is the sense voltage at which the device trips into over-current protection.

STRIP

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