LT1161CS Ver la hoja de datos (PDF) - Linear Technology
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LT1161CS Datasheet PDF : 12 Pages
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LT1161
APPLICATIONS INFORMATION
V+
T1
1µF
V+
DS1
G1
8V TO 24V
1N4148
+ 10µF
51Ω
HV
HV
HV
LOAD LOAD
IRF630
LT1161
2N2222
51Ω
T2
DS2
1µF
G2
15V
1N4744
RS1
0.2Ω
IRF630
2N2222
51Ω
1/2
LT1013
15V
1N4744
RS2
0.02Ω
1161 F09b
Figure 9b. Low-Side Drivers with Two Approaches
for Source Current Sensing
Current sensing for protecting low-side drivers can be
done in several different ways. In the Figure 9a circuit, the
supply voltage for the load is assumed to be within the
supply operating range of the LT1161. This allows the load
to be returned to supply through current-sense resistor
RS, providing normal operation of the LT1161 protection
circuitry.
If the load cannot be returned to supply through RS, or the
load supply voltage is higher than the LT1161 supply, the
current sense must be moved to the source of the low-side
MOSFET. Figure 9b shows two approaches to source
sensing. On channel 1, current limit occurs when the
voltage across sense resistor RS1 thresholds the VBE of the
NPN transistor, causing the LT1161 drain sense pin to be
pulled down.
The channel 2 circuit of Figure 9b uses an operational
amplifier (must common mode to ground) to level shift the
voltage across RS2 up to the drain sense pin. This ap-
proach allows the use of a much smaller sense resistor
which could be made from PC trace material. In both
cases, the LT1161 restart timers function the same as in
high-side switch applications.
TYPICAL APPLICATIONS
Using an Extra Channel to Do Common Current Limit for Multiple/Paralleled Switches
100k
1µF
+
INPUTS
(MAY BE PARALLELED)
1
GND
V+ 20
2
T1
19
DS1
3
IN1
18
G1
4
T2
17
DS2
5
IN2
6
T3
16
G2
LT1161
15
DS3
7
IN3
14
G3
8
T4
13
DS4
9
IN4
12
G4
10
GND
V+ 11
24V
RS
15k
IRFZ44
IRFZ44
IRFZ44
10µF
50V
OUTPUTS
(MAY BE PARALLELED)
1161 TA05
9
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