Datasheet

LTC3125
3
3125fa
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 LTC3125 is tested under pulsed load conditions such that
T
J
≈ T
A
. The LTC3125E (E Grade) is guaranteed to meet specifi cations
from 0°C to 85°C junction temperature. Specifi cations over the –40°C
to 125°C operating junction temperature range are assured by design,
characterization and correlation with statistical process controls. The
junction temperature (T
J
) is calculated from the ambient temperature
(T
A
) and power dissipation (P
D
) according to the formula: T
J
= T
A
+ (P
D
)
(θ
JA
°C/W), where θ
JA
is the package thermal impedance. The maximum
ambient temperature consistent with these specifi cations is determined by
PARAMETER CONDITIONS MIN TYP MAX UNITS
PROG Current Gain (Note 3) 22.1 k-A/A
Maximum Duty Cycle V
FB
= 1.15V
l
85 92 %
Minimum Duty Cycle V
FB
= 1.3V
l
0%
Frequency
l
1.3 1.6 1.9 MHz
SHDN Input High 1V
SHDN Input Low 0.35 V
SHDN Input Current V
SHDN
= 1.2V 0.3 1 µA
ELECTRICAL CHARACTERISTICS
The l denotes the specifi cations which apply over the full operating
junction temperature range, otherwise specifi cations are at T
A
= 25°C. V
IN
= 3.3V, V
OUT
= 4.5V unless otherwise noted (Note 2).
specifi c operating conditions in conjunction with board layout, the rated
package thermal resistance and other environmental factors.
Note 3: Specifi cation is guaranteed by design and not 100% tested in
production.
Note 4: Current measurements are made when the output is not switching.
Note 5: This IC includes overtemperature protection that is intended
to protect the device during momentary overload conditions. Junction
temperature will exceed 125°C when overtemperature protection is active.
Continuous operation above the specifi ed maximum operating junction
temperature may result in device degradation or failure.
Note 6: Failure to solder the exposed backside of the package to the PC
board ground plane will result in a thermal resistance much higher than
60°C/W.
TYPICAL PERFORMANCE CHARACTERISTICS
Effi ciency vs Load Current,
V
OUT
= 2.5V
Effi ciency vs Load Current,
V
OUT
= 3.3V
(T
A
= 25°C unless otherwise noted)
LOAD CURRENT (A)
0.001
40
EFFICIENCY (%)
POWER LOSS (W)
50
60
70
80
0.01 0.1 1
3125 G01
30
20
10
0
90
100
0.1
0.01
0.0001
0.001
1
V
IN
= 2.1V
V
IN
= 1.8V
LOAD CURRENT (A)
0.001
40
EFFICIENCY (%)
POWER LOSS (W)
50
60
70
80
0.01 0.1 1
3125 G02
30
20
10
0
90
100
0.1
0.01
0.001
1
V
IN
= 2.8V
V
IN
= 2.4V
V
IN
= 2V