LT3957
4
3957f
ELECTRICAL CHARACTERISTICS
The l denotes the specifi cations which apply over the full operating temp-
erature range, otherwise specifi cations are at T
A
≈ T
J
= 25°C. V
IN
= 24V, EN/UVLO = 24V, SENSE2 = 0V, unless otherwise noted.
PARAMETER CONDITIONS MIN TYP MAX UNITS
INTV
CC
Current Limit V
IN
= 40V
V
IN
= 15V
32 40
95
55 mA
mA
INTV
CC
Load Regulation (ΔV
INTVCC
/V
INTVCC
)
0 < I
INTVCC
< 20mA, V
IN
= 8V –1 –0.5 %
INTV
CC
Line Regulation (ΔV
INTVCC
/[ΔV
IN
• V
INTVCC
])
6V < V
IN
< 40V 0.02 0.05 %/V
Dropout Voltage (V
IN
– V
INTVCC
)V
IN
= 5V, I
INTVCC
= 20mA, VC = 0V 450 mV
INTV
CC
Current in Shutdown EN/UVLO = 0V, INTV
CC
= 6V 17 µA
INTV
CC
Voltage to Bypass Internal LDO 5.5 V
Logic Inputs
EN/UVLO Threshold Voltage Falling V
IN
= INTV
CC
= 6V
l
1.17 1.22 1.27 V
EN/UVLO Voltage Hysteresis 20 mV
EN/UVLO Input Low Voltage I
VIN
Drops Below 1µA 0.4 V
EN/UVLO Pin Bias Current Low EN/UVLO = 1.15V 1.7 2 2.5 µA
EN/UVLO Pin Bias Current High EN/UVLO = 1.33V 20 100 nA
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 LT3957E is guaranteed to meet performance specifi cations
from the 0°C to 125°C operating 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 LT3957I is guaranteed over the full –40°C to 125°C operating junction
temperature range.
Note 3: The LT3957 is tested in a feedback loop which servos V
FBX
to the
reference voltages (1.6V and –0.8V) with the VC pin forced to 1.3V.
Note 4: FBX overvoltage lockout is measured at V
FBX(OVERVOLTAGE)
relative
to regulated V
FBX(REG)
.
Note 5: For 3V ≤ V
IN
< 6V, the EN/UVLO pin must not exceed V
IN
.
Note 6: EN/UVLO = 1.33V when V
IN
= 3V.
TYPICAL PERFORMANCE CHARACTERISTICS
Positive Feedback Voltage
vs Temperature, V
IN
Negative Feedback Voltage
vs Temperature, V
IN
Quiescent Current
vs Temperature, V
IN
T
A
≈ T
J
= 25°C, unless otherwise noted.
TEMPERATURE (°C)
–50
1580
REGULATED FEEDBACK VOLTAGE (mV)
1590
1600
1605
0
50
75
1585
–25
25
100
125
3957 G01
V
IN
= 40V
V
IN
= 24V
V
IN
= 8V
V
IN
= INTV
CC
= 3V,
SHDN/UVLO = 1.33V
TEMPERATURE (°C)
–50
–804
REGULATED FEEDBACK VOLTAGE (mV)
–802
–800
–796
–798
–794
–788
–790
0
50
75
–792
–25
25
100
125
3957 G02
V
IN
= 40V
V
IN
= 24V
V
IN
= 8V
V
IN
= INTV
CC
= 3V
SHDN/UVLO = 1.33V
TEMPERATURE (°C)
–50
1.4
QUIESCENT CURRENT (mA)
1.6
1.8
0
50
75
1.5
1.7
–25
25
100
125
3957 G03
V
IN
= 40V
V
IN
= 24V
V
IN
= INTV
CC
= 3V
