Datasheet

LT3957A
3
3957afa
ELECTRICAL CHARACTERISTICS
The l denotes the specifications which apply over the full operating temp-
erature range, otherwise specifications 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
V
IN
Operating Range 340V
V
IN
Shutdown I
Q
EN/UVLO = 0V
EN/UVLO = 1.15V
0.1 1
6
µA
µA
V
IN
Operating I
Q
V
C
= 0.3V, R
T
= 41.2k 1.7 2.3 mA
V
IN
Operating I
Q
with Internal LDO Disabled V
C
= 0.3V, R
T
= 41.2k, INTV
CC
= 5.5V 350 400 µA
SW Pin Current Limit
l
5 5.9 6.8 A
SW Pin On Voltage I
SW
= 3A 100 mV
SENSE2 Input Bias Current Current Out of Pin –65 µA
Error Amplifier
FBX Regulation Voltage (V
FBX(REG)
) FBX > 0V (Note 3)
FBX < 0V (Note 3)
l
l
1.569
–0.816
1.6
–0.800
1.631
–0.784
V
V
FBX Overvoltage Lockout FBX > 0V (Note 4)
FBX < 0V (Note 4)
6
7
8
11
10
14
%
%
FBX Pin Input Current FBX = 1.6V (Note 3)
FBX = –0.8V (Note 3) –10
70 100
10
nA
nA
Transconductance g
m
(ΔI
VC
/ΔFBX)
(Note 3) 230 µS
V
C
Output Impedance (Note 3) 5 M
V
FBX
Line Regulation (ΔV
FBX
/[ΔV
IN
• V
FBX(REG)
])
FBX > 0V, 3V < V
IN
< 40V (Notes 3, 6)
FBX < 0V, 3V < V
IN
< 40V (Notes 3, 6)
0.04
0.03
0.06
0.06
%/V
%/V
V
C
Current Mode Gain (ΔV
VC
/ΔV
SENSE
)
10 V/V
V
C
Source Current V
C
= 1.5V, FBX = 0V, Current Out of Pin –15 µA
V
C
Sink Current FBX = 1.7V
FBX = –0.85V
12
11
µA
µA
V
C
Low Side Clamp Voltage FBX = 1.65V 0.8 V
Oscillator
Switching Frequency R
T
= 140k to SGND, FBX = 1.6V, V
C
= 1.5V
R
T
= 41.2k to SGND, FBX = 1.6V, V
C
= 1.5V
R
T
= 10.5k to SGND, FBX = 1.6V, V
C
= 1.5V
80
270
850
100
300
1000
120
330
1200
kHz
kHz
kHz
RT Voltage FBX = 1.6V 1.2 V
SW Minimum Off-Time 220 275 ns
SW Minimum On-Time 240 320 ns
SYNC Input Low 0.4
SYNC Input High 1.5
SS Pull-Up Current SS = 0V, Current Out of Pin –10 µA
Low Dropout Regulator
INTV
CC
Regulation Voltage
l
5 5.2 5.45 V
INTV
CC
Undervoltage Lockout Threshold Falling INTV
CC
UVLO Hysteresis
2.6 2.7
0.15
2.85 V
V