LT1308 データシートの表示（PDF） - Linear Technology
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LT1308 Datasheet PDF : 8 Pages
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LT1308
ELECTRICAL CHARACTERISTICS
Industrial Grade – 40°C to 85°C. VIN = 1.2V, VSHDN = VIN, TA = 25°C, unless otherwise noted.
SYMBOL PARAMETER
Shutdown Pin Current
LBI Threshold Voltage
LBO Output Low
LBO Leakage Current
LBI Input Bias Current (Note 4)
Low-Battery Detector Gain
Switch Leakage Current
CONDITIONS
VSHDN = 1.2V
VSHDN = 6V
VSHDN = 0V
ISINK = 10µA
VLBI = 250mV, VLBO = 5V
VLBI = 150mV
1MΩ Load (–40°C)
1MΩ Load (85°C)
VSW = 5V
MIN
TYP
MAX UNITS
q
2.5
4.0
µA
q
13
26
µA
q
– 1.5
– 2.5
µA
q 180
200
220
mV
q
0.1
0.25
V
q
0.01
0.1
µA
q
5
30
nA
1000
3000
V/V
300
V/V
q
0.01
10
µA
The q denotes specifications which apply over the full operating
temperature range.
Note 1: C grade device specifications are guaranteed over the 0°C to 70°C
temperature range. In addition, C grade device specifications are assured
over the –40°C to 85°C temperature range by design or correlation, but
are not production tested.
Note 2: Bias current flows into FB pin.
Note 3: Switch current limit guaranteed by design and/or correlation to
static tests. Duty cycle affects current limit due to ramp generator (see
Block Diagram).
Note 4: Bias current flows out of LBI pin.
Note 5: The LT1308 will withstand continuous application of 1.6V applied
to GND pin while VIN and SW are grounded.
TYPICAL PERFORMANCE CHARACTERISTICS
Efficiency
90
VIN = 1.2V
85 VOUT = 3.3V
R1 = 169k
80
75
70
65
60
55
50
1
10
100
LOAD CURRENT (mA)
Transient Response
VOUT
200mV/DIV
AC COUPLED
100mA
ILOAD 5mA
VIN = 1.2V
VOUT = 5V
500µs/DIV
C2 = 22µF
RC, CC = 47k, 6.8nF
L = 4.7µH
1000
1308 G01
1308 G02
Switch Saturation Voltage vs
Current
500
400
85°C
300
25°C
200
–40°C
100
0
0
0.5
1.0
1.5
2.0
SWITCH CURRENT (A)
1308 G03
PIN FUNCTIONS
VC (Pin 1): Compensation Pin for Error Amplifier. Con-
nect a series RC from this pin to ground. Typical values
are 47kΩ and 22nF. Minimize trace area at VC.
FB (Pin 2): Feedback Pin. Reference voltage is 1.22V.
Connect resistive divider tap here. Minimize trace area at
FB. Set VOUT according to: VOUT = 1.22V(1 + R1/R2).
SHDN (Pin 3): Shutdown. Ground this pin to turn off
switcher. Must be tied to VIN (or higher voltage) to enable
switcher. Do not float the SHDN pin.
GND (Pin 4): Ground. Connect directly to local ground
plane. Ground plane should enclose all components
associated with the LT1308.
4
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