Datasheet

LT1308A/LT1308B
4
1308abfb
ELECTRICAL CHARACTERISTICS
LT1308B
3.3V Output Effi ciency
LT1308A
3.3V Output Effi ciency
LT1308A
5V Output Effi ciency
The l denotes the specifi cations which apply over the full operating temperature
range, otherwise specifi cations are at T
A
= 25°C. Industrial Grade –40°C to 85°C. V
IN
= 1.2V, V
SHDN
= V
IN
, unless otherwise noted.
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
f
OSC
Switching Frequency
l
500 600 750 kHz
Maximum Duty Cycle
l
82 90 %
Switch Current Limit Duty Cycle = 30% (Note 4) 2 3 4.5 A
Switch V
CESAT
I
SW
= 2A (25°C, –40°C), V
IN
= 1.5V
I
SW
= 2A (85°C), V
IN
= 1.5V
290
330
350
400
mV
mV
Burst Mode Operation Switch Current Limit
(LT1308A)
V
IN
= 2.5V, Circuit of Figure 1 400 mA
Shutdown Pin Current V
SHDN
= 1.1V
V
SHDN
= 6V
V
SHDN
= 0V
l
l
2
20
0.01
5
35
0.1
µA
µA
µA
LBI Threshold Voltage
l
196
193
200
200
204
207
mV
mV
LBO Output Low I
SINK
= 50µA
l
0.1 0.25 V
LBO Leakage Current V
LBI
= 250mV, V
LBO
= 5V
l
0.01 0.1 µA
LBI Input Bias Current (Note 5) V
LBI
= 150mV 33 100 nA
Low-Battery Detector Gain 3000 V/V
Switch Leakage Current V
SW
= 5V
l
0.01 10 µA
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2: The LT1308ACS8, LT1308ACF, LT1308BCS8 and LT1308BCF are
designed, characterized and expected to meet the industrial temperature
limits, but are not tested at –40°C and 85°C. I grade devices are
guaranteed over the –40°C to 85°C operating temperature range.
Note 3: Bias current fl ows into FB pin.
Note 4: 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 5: Bias current fl ows out of LBI pin.
Note 6: Connect the four GND pins (Pins 4–7) together at the device.
Similarly, connect the three SW pins (Pins 8–10) together and the two V
IN
pins (Pins 11, 12) together at the device.
TYPICAL PERFORMANCE CHARACTERISTICS
LOAD CURRENT (mA)
95
90
85
80
75
70
65
60
55
50
1 100 1000
1308A/B G01
10
EFFICIENCY (%)
V
IN
= 1.8V
V
IN
= 2.5V
V
IN
= 1.2V
LOAD CURRENT (mA)
95
90
85
80
75
70
65
60
55
50
1 100 1000
1308A/B G02
10
EFFICIENCY (%)
V
IN
= 1.8V
V
IN
= 2.5V
V
IN
= 1.2V
LOAD CURRENT (mA)
1
EFFICIENCY (%)
95
90
85
80
75
70
65
60
55
50
10 100 1000
1308A/B G03
V
IN
= 4.2V
V
IN
= 2.5V
V
IN
= 3.6V
V
IN
= 1.5V