Datasheet
LT3757/LT3757A
3
3757afe
For more information www.linear.com/LT3757
elecTrical characTerisTics
The l denotes the specifications which apply over the full operating temp-
erature range, otherwise specifications are at T
A
= 25°C. V
IN
= 24V, SHDN/UVLO = 24V, SENSE = 0V, unless otherwise noted.
PARAMETER CONDITIONS MIN TYP MAX UNITS
V
IN
Operating Range 2.9 40 V
V
IN
Shutdown I
Q
SHDN/UVLO = 0V
SHDN/UVLO = 1.15V
0.1 1
6
µA
µA
V
IN
Operating I
Q
V
C
= 0.3V, R
T
= 41.2k 1.6 2.2 mA
V
IN
Operating I
Q
with Internal LDO Disabled V
C
= 0.3V, R
T
= 41.2k, INTV
CC
= 7.5V 280 400 µA
SENSE Current Limit Threshold
l
100 110 120 mV
SENSE Input Bias Current Current Out of Pin –65 µA
Error Amplifier
FBX Regulation Voltage (V
FBX(REG)
) V
FBX
> 0V (Note 3)
V
FBX
< 0V (Note 3)
l
l
1.569
–0.816
1.6
–0.80
1.631
–0.784
V
V
FBX Overvoltage Lockout V
FBX
> 0V (Note 4)
V
FBX
< 0V (Note 4)
6
7
8
11
10
14
%
%
FBX Pin Input Current V
FBX
= 1.6V (Note 3)
V
FBX
= –0.8V (Note 3)
–10
70 100
10
nA
nA
Transconductance g
m
(∆I
VC
/∆V
FBX
) (Note 3) 230 µS
V
C
Output Impedance (Note 3) 5 MΩ
V
FBX
Line Regulation [∆V
FBX
/(∆V
IN
• V
FBX(REG)
)] V
FBX
> 0V, 2.9V < V
IN
< 40V (Notes 3, 7)
V
FBX
< 0V, 2.9V < V
IN
< 40V (Notes 3, 7)
0.002
0.0025
0.056
0.05
%/V
%/V
V
C
Current Mode Gain (∆V
VC
/∆V
SENSE
) 5.5 V/V
V
C
Source Current V
FBX
= 0V, V
C
= 1.5V –15 µA
V
C
Sink Current V
FBX
= 1.7V
V
FBX
= –0.85V
12
11
µA
µA
Oscillator
Switching Frequency R
T
= 41.2k to GND, V
FBX
= 1.6V
R
T
= 140k to GND, V
FBX
= 1.6V
R
T
= 10.5k to GND, V
FBX
= 1.6V
270 300
100
1000
330 kHz
kHz
kHz
RT Voltage V
FBX
= 1.6V 1.2 V
Minimum Off-Time 220 ns
Minimum On-Time 220 ns
SYNC Input Low 0.4 V
SYNC Input High 1.5 V
SS Pull-Up Current SS = 0V, Current Out of Pin –10 µA
Low Dropout Regulator
INTV
CC
Regulation Voltage
l
7 7.2 7.4 V
INTV
CC
Undervoltage Lockout Threshold Falling INTV
CC
UVLO Hysteresis
2.6 2.7
0.1
2.8 V
V
INTV
CC
Overvoltage Lockout Threshold 16 17.5 V
INTV
CC
Current Limit V
IN
= 40V
V
IN
= 15V
30 40
95
55 mA
mA
INTV
CC
Load Regulation (∆V
INTVCC
/V
INTVCC
) 0 < I
INTVCC
< 20mA, V
IN
= 8V –0.9 –0.5 %
INTV
CC
Line Regulation ∆V
INTVCC
/(V
INTVCC
• ∆V
IN
) 8V < V
IN
< 40V 0.008 0.03 %/V
Dropout Voltage (V
IN
– V
INTVCC
) V
IN
= 6V, I
INTVCC
= 20mA 400 mV
INTV
CC
Current in Shutdown SHDN/UVLO = 0V, INTV
CC
= 8V 16 µA
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