LT1910 Linear Technology, LT1910 Datasheet - Page 7

• Manufacturer Part Number: LT1910
• Description: Protected High Side MOSFET Driver
• Manufacturer: Linear Technology

OPERATIO
APPLICATIO S I FOR ATIO
Input/Supply Sequencing
There are no input/supply sequencing requirements for
the LT1910. The IN pin may be taken up to 15V with the
supply at 0V. When the supply is turned on with the IN pin
set HIGH, the MOSFET turn-on will be inhibited until the
timing capacitor charges up to 2.9V (i.e., for one restart
cycle).
Isolating the Inputs
Operation in harsh environments may require isolation to
prevent ground transients from damaging control logic.
The LT1910 easily interfaces to low cost optoisolators.
The network shown in Figure 2 ensures that the input will
be pulled above 2V, but not exceed the absolute maximum
rating for supply voltages of 12V to 48V over the entire
LOGIC
INPUT
LOGIC GROUND
2k
Figure 2. Isolating the Input
U
U
12V TO 48V
U
100k
TIMER
FAULT
51k
GATE
W
4
IN
POWER GROUND
IN
3.5V
2.9V
0V
0V
0V
5V
0V
V
LT1910
+
GND
1
12V
OFF
1910 F02
U
Figure 1. Timing Diagram
NORMAL
OVERCURRENT
temperature range. The optoisolator must have less than
20 A of dark current (leakage) at hot in order to maintain
the OFF State (see Figure 2).
Drain Sense Configuration
The LT1910 uses supply referenced current sensing. One
input of the current sense comparator is connected to a
drain sense pin, while the second input is offset 65mV below
the supply inside the device. For this reason, Pin 8 of the
LT1910 must be treated not only as a supply pin, but also
as the reference input for the current sense comparator.
Figure 3 shows the proper drain sense configuration for
the LT1910. Note that the SENSE pin goes to the drain end
of the sense resistor, while the V
FAULT OUTPUT
INPUT
24V
5V
0V
Figure 3. Drain Sense Configuration
3.4V
NORMAL
R1
5.1k
1910 F01
3
4
2
C
1 F
FAULT
IN
TIMER
T
LT1910
GND
SENSE
1
GATE
V
+
+
8
6
5
+
pin is connected to the
C1
100 F
50V
LT1910
1910 F03
R
0.02
(PTC)
Q1
IRFZ34
sn1910 1910fs
S
24V
2A
SOLENOID
7