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 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.
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.
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-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.
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
ZXCT1032N8TA
Issue 4 - June 2007
© Zetex Semiconductors plc 2007
Pack
SO8
Part mark
1032
Reel size
7”
1
Tape width
12mm
Quantity per reel
500
www.zetex.com
ZXCT1032
Typical application circuit
V
IN
R
SENSE
8
IN+
ISET
GND
1
6
IN-
Drive 5
Load
Flag
4
C
T
GND
µC
GND-
C
T
ISET
Flag
1
Pinout connections
SO8
8
IN+
N/C
IN-
Drive
2
7
3
6
3
ZXCT
1032
C
T
2
4
5
Top view
Pin description
Pin
1
2
Name
GND
C
T
Description
Ground reference for I
SET
and Flag pins. Most negative terminal of the
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.
Determines the load current trip level or constant current level. This can
be driven via a DC voltage or via a µC PWM output.
V
SENSE
= (V
ISET
-150mV)/10
An input <100mV will disable the high-side switch (i.e. set I
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
SET
is reached or in the
event of a shorted load.
This is the output drive pin to the external high side referred switch on
the ZXCT1032, capable of driving PMOS and PNP transistors.
The load referred input to the current monitor control loop.
Not connected
Acts as both the supply pin to the ZXCT1032 and the supply referred
sense input to the current monitor control loop.
3
ISET
5
6
7
8
Drive
IN-
N/C
IN+
Issue 4 - June 2007
© Zetex Semiconductors plc 2007
2
www.zetex.com
ZXCT1032
Absolute maximum ratings
V
IN+
max
(a)
...................................................................................................... 28 V
Voltage on any pin relative to GND ............................................................. -0.6V and V
IN
+0.5 V
Maximum differential voltage between V
IN+
and V
IN-
(V
SENSE
) ................ 500 mV
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
V
IN+
T
A
V
FLAG
V
ISET
Parameter
Supply range
Ambient temperature range
Flag voltage range
Voltage on ISET pin
Min.
9.5
-40
0
1
Max.
21
85
V
IN+
2.5
Units
V
°C
V
V
Electrical characteristics
Test conditions T
amb
= 25°C, V
IN+
= 20V. Unless otherwise stated.
Symbol Parameter
I
Q
Quiescent current
V
STRIP (*)
Flag trip threshold
voltage
V
ISET
I
ISET
ISET open voltage
ISET output current
Conditions
V
SENSE1
= 0V, V_
ISET
= 2.1V
V
ISET
=1.1V
V
ISET
=2.1V
I
ISET
= 0
V
ISET
=0V
V
ISET
= 2.1V, V
SENSE
> 205mV,
I
DRIVE
= 0,
185
2.0
30
V
IN-
– 0.4
V
IN-
-7
Min.
Typ.
1.6
95
195
2.1
45
V
IN-
– 0.2
V
IN-
- 5.5
9
0.2
1
100
95
130
1.8
200
3.3
270
5.4
0.4
200
200
V
IN-
-
4
205
2.2
60
V
A
V
V
k
V
nA
nA
ppm/°C
A
A
Max. Units
2.5
mA
mV
V
DRIVEH
Drive high output
voltage
V
DRIVEL
Drive low output voltage V
ISET
= 2.1V, V
SENSE
< 185mV,
I
DRIVE
= 0,
R
DRIVEL
Drive low output resistance V
ISET
= 2.1V, V
SENSE
< 185mV
V
FLAGL
Flag Low output Voltage V
ISET
= 2.1V, V
SENSE
> 205mV
I
FLAG
= 100µA
I
FLAGZ
Flag open circuit leakage V
ISET
= 2.1V, V
SENSE
< 185mV,
current
V
FLAG
= 5V
I
IN-
IN- bias current
V
ISET
= 0V
V
STRIP-TC
Temperature coefficient See footnote
(†)
of trip voltage
I
CT-CHG
Capacitor C
T
charging
FLAG = Open
current
I
CT-DIS
Capacitor C
T
discharging FLAG = Low
current
NOTES:
(*) V
SENSE
= V
IN+
- V
IN-
. V
STRIP
is the sense voltage at which the device trips into over-current protection.
(†) Temperature dependent measurements are extracted from characterization and simulation results.
Issue 4 - June 2007
© Zetex Semiconductors plc 2007
3
www.zetex.com
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