LT1308B Linear Technology, LT1308B Datasheet - Page 4

• Manufacturer Part Number: LT1308B
• Description: High Current/ Micropower Single Cell/ 600kHz DC/DC Converters
• Manufacturer: Linear Technology

Industrial Grade – 40 C to 85 C. V
PIN
LT1308
SYMBOL
TYPICAL PERFORMANCE CHARACTERISTICS
V
nect a series RC from this pin to ground. Typical values
are 47k and 22nF. Minimize trace area at V
FB (Pin 2): Feedback Pin. Reference voltage is 1.22V.
Connect resistive divider tap here. Minimize trace area at
FB. Set V
ELECTRICAL C
The
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.
4
C
90
85
80
75
70
65
60
55
50
U
(Pin 1): Compensation Pin for Error Amplifier. Con-
denotes specifications which apply over the full operating
1
Efficiency
FUNCTIONS
V
V
R1 = 169k
IN
OUT
OUT
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
= 1.2V
= 3.3V
U
LOAD CURRENT (mA)
according to: V
10
U
HARA TERISTICS
100
W
IN
OUT
= 1.2V, V
C
1308 G01
= 1.22V(1 + R1/R2).
U
1000
AC COUPLED
I
200mV/DIV
LOAD
SHDN
100mA
V
5mA
OUT
= V
C
Transient Response
IN
V
V
C2 = 22 F
R
L = 4.7 H
.
IN
OUT
C
, T
, C
= 1.2V
C
= 5V
A
CONDITIONS
V
V
V
I
V
V
1M Load (–40 C)
1M Load (85 C)
V
= 47k, 6.8nF
SINK
SHDN
SHDN
SHDN
LBI
LBI
SW
= 25 C, unless otherwise noted.
= 250mV, V
= 150mV
= 5V
= 10 A
= 1.2V
= 6V
= 0V
500 s/DIV
SHDN (Pin 3): Shutdown. Ground this pin to turn off
switcher. Must be tied to V
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.
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 V
LBO
= 5V
1308 G02
IN
and SW are grounded.
500
400
300
200
100
0
1000
MIN
180
300
Switch Saturation Voltage vs
Current
0
IN
(or higher voltage) to enable
0.5
SWITCH CURRENT (A)
3000
– 1.5
0.01
0.01
TYP
200
0.1
13
2.5
5
1.0
25 C
MAX
– 2.5
0.25
220
0.1
26
30
10
4.0
1.5
–40 C
85 C
UNITS
1308 G03
V/V
V/V
mV
nA
2.0
A
A
A
V
A
A