LT1158CS LINER [Linear Technology], LT1158CS Datasheet - Page 12

• Manufacturer Part Number: LT1158CS
• Description: Half Bridge N-Channel Power MOSFET Driver
• Manufacturer: LINER [Linear Technology]

APPLICATIONS
LT1158
Low Current Shutdown
The LT1158 may be shutdown to a current level of 2mA by
pulling the enable pin 4 low. In this state both the top and
bottom MOSFETs are actively held off against any tran-
sients which might occur on the output during shutdown.
This is important in applications such as 3-phase DC
motor control when one of the phases is disabled while the
other two are switching.
If zero standby current is required and the load returns to
ground, then a switch can be inserted into the supply path
of the LT1158 as shown in Figure 5. Resistor R
that the top MOSFET gate discharges, while the voltage
across the bottom MOSFET goes to zero. The voltage drop
across the P-channel supply switch must be less than
300mV, and R
This technique is not recommended for applications which
require the LT1158 V
ON/OFF
Short-Circuit Protection in Bridge Applications
The LT1158 protects the top power MOSFET from output
shorts to ground, or in a full bridge application, shorts
across the load. Both standard 3-lead MOSFETs and
current-sensing 5-lead MOSFETs can be protected. The
bottom MOSFET is not protected from shorts to supply.
Current is sensed by measuring the voltage across a
current shunt in the source lead of a standard 3-lead
MOSFET (Figure 6). For the current-sensing MOSFET
12
CMOS
100k
2N2222
100k
TO OTHER
CONTROL
CIRCUITS
Figure 5. Adding Zero Current Shutdown
VP0300
GS
must be 330k or greater for DC operation.
+
U
DS
V
V
GND
+
+
sensing function.
INFORMATION
U
LT1158
B GATE DR
T GATE DR
T GATE FB
T SOURCE
B GATE FB
W
R
GS
GS
U
V
ensures
+
LOAD
+
1158 F05
shown in Figure 7, the sense resistor is inserted between
the sense and Kelvin leads.
The sense
at minimum spacing to prevent stray pickup, and a Kelvin
connection must be used at the current shunt for the 3-
lead MOSFET. Using a twisted pair is the safest approach
and is recommended for sense runs of several inches.
When the voltage across R
LT1158 fault pin begins to conduct, signaling a fault
condition. The current in a short circuit ramps very rapidly,
limited only by the series inductance and ultimately the
MOSFET and shunt resistance. Due to the response time
of the LT1158 current limit loop, an initial current spike of
Figure 7. Short-Circuit Protection with Current-Sensing MOSFET
Figure 6. Short-Circuit Protection with Standard MOSFET
10k
10k
5V
5V
+
and sense
FAULT
FAULT
LT1158
LT1158
–
PC traces must be routed together
T GATE DR
T GATE DR
T SOURCE
T GATE FB
T SOURCE
T GATE FB
SENSE
SENSE
SENSE
SENSE
SENSE
+
–
+
–
R
SENSE
exceeds 110mV, the
SENSE
V
V
+
+
R
SENSE
+
OUTPUT
+
KELVIN
1158 F07
1158 F06