5
LTC1153
Auto-Reset Time*Shutdown Threshold Voltage MOSFET Gate Drive Current
CCHARA TERISTICS
UW
AT
Y
P
I
CALPER
F
O
RC
E
TEMPERATURE (°C)
–50
0.4
SHUTDOWN THRESHOLD VOLTAGE (V)
0.6
1.O
1.2
1.4
2.4
1.8
050 75
LTC1153 • TPC13
0.8
2.0
2.2
1.6
–25 25 100 125
V
S
= 18V
V
S
= 5V
TEMPERATURE (°C)
–25
0.1
1
10
25
LTC1153 • TPC14
AUTO-RESET TIME (s/µF)
–50 1250 50 75 100
*SECONDS OF DELAY
PER µF C
T
V
S
= 5V
V
S
= 12V
V
S
= 18V
PI FU CTIO S
U
UU
Input and Shutdown Pins
The LTC1153 input pin is active high and activates all of the
protection and charge pump circuitry when switched ON.
The shutdown pin is designed to break the circuit if a
secondary fault condition (over temperature, etc.) is de-
tected. The LTC1153 logic and shutdown inputs are high
impedance CMOS gates with ESD protection diodes to
ground and supply and therefore should not be forced
beyond the power supply rails. The shutdown pin should
be connected to ground when not in use.
Timing Capacitor Pin (Auto-Reset Timer)
The small capacitor charging current (4.2µA) produces
large delays with relatively small valued capacitors, but
care must be taken to ensure that this current is not
shunted to ground through a leaky capacitor or printed
circuit board trace. The timing capacitor voltage is sensed
by a high impedance CMOS comparator input with ESD
clamp diodes to ground and supply and therefore should
not be forced beyond the power supply rails. This pin can
be grounded if the auto-reset function is not used.
MOSFET Gate Drive Pin
The MOSFET gate drive pin is either driven to ground when
the switch is turned OFF or driven above the supply rail
when the switch is turned ON. This pin is a relatively high
impedance when driven above the rail (the equivalent of a
few hundred kΩ). Care should be taken to minimize any
loading of this pin by parasitic resistance to ground or
supply.
Supply Pin
The supply pin of the LTC1153 serves two vital purposes.
The first is obvious: it powers the input, gate drive, regu-
lation and protection circuitry. The second purpose is less
obvious: it provides a Kelvin connection to the top of the
drain sense resistor for the internal 100mV reference.
The LTC1153 is designed to be
continuously powered
so
that the gate of the MOSFET is actively driven at all times.
If it is necessary to remove power from the supply pin and
then re-apply it, the input pin (or enable pin) should be
cycled a few milliseconds
after
the power is re-applied to
reset the input latch and protection circuitry. Also, the
input and enable pins should be isolated with 10k resistors
to limit the current flowing through the ESD protection
diodes to the supply pin.
The supply pin of the LTC1153 should never be forced
below ground as this may result in permanent damage to
the device.
A 300Ω resistor should be inserted in series
with the ground pin if negative supply voltage transients
are anticipated.
GATE VOLTAGE ABOVE SUPPLY (V)
1
GATE DRIVE CURRENT (µA)
10
100
1000
0 8 12 16
0.1 420
LTC1153 • TPC15
V
S
= 18V
T
A
= 25°C
V
S
= 12V
V
S
= 5V