LM1937
ABSOLUTE MAXIMUM RATINGS
(Note 1)
Input Voltage (V
IN
)
10V
Operating Temperature Range
SW Voltage
36V
Maximum Junction Temperature
FB Voltage
10V
Storage Temperature Range
SHDN Voltage
Lead Temperature (Soldering, 10 sec)
10V
Note 1:
Absolute Maximum Ratings are those values beyond which the life of the device may be impaired.
0°C to 70°C
125°C
–65°C to 150°C
300°C
ELECTRICAL CHARACTERISTICS
T
A
= 25°C, V
IN
= 3V, V
SHDN
= 3V, unless otherwise noted.
PARAMETER
Minimum Operating Voltage
Maximum Operating Voltage
Feedback Voltage
FB Pin Bias Current
Supply Current
Switching Frequency
Maximum Duty Cycle
Switch Current Limit
Switch V
CESAT
Switch Leakage Current
SHDN Voltage High
SHDN Voltage Low
SHDN Pin Bias Current
I
SW
= 250mA
V
SW
= 5V
1.5
0.4
65
SHDN = 0V
0.8
85
I
SW
= 100mA, Duty Cycle = 66%
86
10
95
45
1.9
0.1
1.2
90
320
350
0.01
5
CONDITIONS
MIN.
2.5
10
104
100
2.5
1.0
1.6
TYP.
MAX.
UNIT
V
V
mV
nA
mA
μA
MHz
%
mA
mV
μA
V
V
μA
Figure 2.
BLOCK DIAGRAM LM1937
V
IN
5
FB
3
1 SW
COMPARATOR
A1
–
V
REF
1.25V
95mV
+
R
C
C
C
Switch Pin.
Σ
–
RAMP
GENERATOR
SHDN
4
SHUTDOWN
1.2MHz
OSCILLATOR
+
–
A2
R
S
Q
DRIVER
Q1
+
0.2Ω
2 GND
1937 BD1
2
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