Datasheet

2
LT1949
V
IN
, LBO Voltage..................................................... 12V
SW Voltage ............................................... –0.4V to 30V
FB Voltage .................................................... V
IN
+ 0.3V
V
C
Voltage ................................................................ 2V
LBI Voltage ............................................ 0V ≤ V
LBI
≤ 1V
SHDN Voltage ........................................................... 6V
(Note 1)
LT1949EMS8
LTJC
Consult factory for Military grade parts.
1
2
3
4
V
C
FB
SHDN
GND
8
7
6
5
LBO
LBI
V
IN
SW
TOP VIEW
MS8 PACKAGE
8-LEAD PLASTIC MSOP
T
JMAX
= 125°C, θ
JA
= 120°C/W
Junction Temperature.......................................... 125°C
Operating Temperature Range (Note 2)
LT1949EMS8.......................................–40°C to 85°C
LT1949ES8/LT1949IS8 .......................–40°C to 85°C
Storage Temperature ........................... –65°C to 150°C
Lead Temperature (Soldering, 10sec).................. 300°C
ORDER PART
NUMBER
LT1949ES8
LT1949IS8
S8 PART MARKING
1949E
1949I
1
2
3
4
8
7
6
5
TOP VIEW
LBO
LBI
V
IN
SW
V
C
FB
SHDN
GND
S8 PACKAGE
8-LEAD PLASTIC SO
T
JMAX
= 125°C, θ
JA
= 120°C/W
ORDER PART
NUMBER
MS8 PART MARKING
The ● denotes specifications which apply over the full operating
temperature range, otherwise specifications are T
A
= 25°C. V
IN
= 2V, V
SHDN
= 2V unless otherwise noted.
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
I
Q
Quiescent Current ● 4.5 7.5 mA
V
SHDN
= 0V ● 25 40 µA
V
FB
Feedback Voltage 1.22 1.24 1.26 V
● 1.20 1.24 1.26 V
I
B
FB Pin Bias Current (Note 3) ● 12 80 nA
Input Voltage Range ● 1.7 12 V
g
m
Error Amp Transconductance ∆I = 5µA ● 70 140 240 µmhos
A
V
Error Amp Voltage Gain 700 V/V
Maximum Duty Cycle ● 80 85 %
Switch Current Limit (Note 4) V
IN
= 2.5V, Duty Cycle = 30% 1 1.13 1.5 A
V
IN
= 2.5V, Duty Cycle = 30% ● 0.95 1.5 A
f
OSC
Switching Frequency ● 500 600 750 kHz
Shutdown Pin Current V
SHDN
= V
IN
● 0.015 0.1 µA
V
SHDN
= 0V ● –2.3 –7 µA
LBI Threshold Voltage 190 200 210 mV
● 180 200 220 mV
LBO Output Low I
SINK
= 10µA ● 0.15 0.25 V
LBO Leakage Current V
LBI
= 250mV, V
LBO
= 5V ● 0.02 0.1 µA
LBI Input Bias Current (Note 5) V
LBI
= 150mV ● 560nA
Low-Battery Detector Gain 1MΩ Pull-Up 2000 V/V
Switch Leakage Current V
SW
= 5V ● 0.01 3 µA
PACKAGE/ORDER I FOR ATIO
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W
ABSOLUTE AXI U RATI GS
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ELECTRICAL CHARACTERISTICS