Datasheet

LT3958
3
3958fa
For more information www.linear.com/LT3958
elecTrical characTerisTics
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 24V, EN/UVLO = 24V, SENSE2 = 0V, unless otherwise noted.
PARAMETER CONDITIONS MIN TYP MAX UNITS
V
IN
Operating Range 5 80 V
V
IN
Shutdown I
Q
EN/UVLO = 0V
EN/UVLO = 1.15V
0.1 1
6
µA
µA
V
IN
Operating I
Q
VC = 0.3V, R
T
= 41.2k 1.6 2.2 mA
V
IN
Operating I
Q
with Internal LDO Disabled VC = 0.3V, R
T
= 41.2k, INTV
CC
= 7.5V 350 400 µA
SW Pin Current Limit SENSE2 = SENSE1
l
3.3 4.0 4.6 A
SW Pin On Voltage I
SW
= 2A 180 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
(∆I
VC
/∆FBX)
(Note 3) 230 µS
VC Output Impedance (Note 3) 5 MΩ
V
FBX
Line Regulation (∆V
FBX
/[∆V
IN
• V
FBX(REG)
])
FBX > 0V, 5V < V
IN
< 80V (Notes 3, 6)
FBX < 0V, 5V < V
IN
< 80V (Notes 3, 6)
0.006
0.005
0.03
0.038
%/V
%/V
VC Current Mode Gain (∆V
VC
/∆V
SENSE
)
10 V/V
VC Source Current VC = 1.5V, FBX = 0V, Current Out of Pin –15 µA
VC Sink Current FBX = 1.7V
FBX = –0.85V
12
11
µA
µA
Oscillator
Switching Frequency R
T
= 140k to SGND, FBX = 1.6V, VC = 1.5V
R
T
= 41.2k to SGND, FBX = 1.6V, VC = 1.5V
R
T
= 10.5k to SGND, FBX = 1.6V, VC = 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 200 275 ns
SW Minimum On-Time 250 300 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
7 7.2 7.4 V
INTV
CC
Undervoltage Lockout Threshold Falling INTV
CC
UVLO Hysteresis
3.55 3.75
0.15
4.00 V
V
INTV
CC
Overvoltage Lockout Threshold 11.5 12.8 V
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