LTC1154 Linear Technology, LTC1154 Datasheet - Page 5

• Manufacturer Part Number: LTC1154
• Description: High-Side Micropower MOSFET Driver
• Manufacturer: Linear Technology

PI FU CTIO S
TYPICAL PERFOR
Input and Shutdown Pins
The LTC1154 input pin is active high and activates all of the
protection and charge pump circuitry when switched ON.
The shutdown pin is designed to immediately disable the
switch if a secondary fault condition (over temperature,
etc.) is detected. The LTC1154 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.
ENABLE Input Pin
The ENABLE input can be used to enable a number of
LTC1154 high-side switches in banks or to provide a
secondary means of control. It can also act as an inverting
input. The ENABLE input is a high impedance CMOS gate
with ESD clamp diodes to ground and supply and there-
fore should not be forced beyond the power supply rails.
This pin should be grounded when not in use.
Gate Drive Pin
The 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
1.O
2.4
2.2
2.0
1.8
1.6
1.4
1.2
0.8
0.4
0.6
U
–50
Shutdown Threshold Voltage
–25
U
0
TEMPERATURE (°C)
25
V
V
U
50
S
S
= 5V
= 18V
75
W
LTC1154 • TPC13
100
A
U
125
CE
C
HARA TERISTICS
3.0
5.0
4.5
4.0
3.5
2.5
2.0
1.5
1.0
0.5
0
–50
ENABLE Threshold Voltage
V
S
–25
= 12V
C
0
TEMPERATURE (°C)
25
DISABLE
ENABLE
few hundred k ). 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 LTC1154 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 LTC1154 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 LTC1154 should never be forced
below ground as this may result in permanent damage to
the device. A 300 resistor should be inserted in series
with the ground pin if negative supply voltage transients
are anticipated.
50
75
LTC1154 • TPC14
100
125
1000
100
0.1
10
1
0
Gate Drive Current
T
A
= 25°C
GATE VOLTAGE ABOVE SUPPLY (V)
V
S
4
= 5V
V
8
S
= 12V
LTC1154
12
V
S
= 18V
LTC1154 • TPC15
16
5
20