LT3954
4
3954fa
For more information www.linear.com/3954
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, CTRL = 2V, PWM = 5V, unless otherwise noted.
PARAMETER CONDITIONS MIN TYP MAX UNITS
Linear Regulator
INTV
CC
Regulation Voltage 10V ≤ V
IN
≤ 40V
l
7.60 7.85 8.05 V
INTV
CC
Maximum Operating Voltage 8.1 V
INTV
CC
Minimum Operating Voltage 4.5 V
Dropout (V
IN
– INTV
CC
) I
INTVCC
= –10mA, V
IN
= 7V 390 mV
INTV
CC
Undervoltage Lockout
l
3.9 4.1 4.4 V
INTV
CC
Current Limit 8V ≤ V
IN
≤ 40V, INTV
CC
= 6V 30 36 42 mA
INTV
CC
Current in Shutdown EN/UVLO = 0V, INTV
CC
= 8V 8 13 µA
Logic Inputs/Outputs
EN/UVLO Threshold Voltage Falling
l
1.180 1.220 1.260 V
EN/UVLO Rising Hysteresis 40 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 2.7 µA
EN/UVLO Pin Bias Current High EN/UVLO = 1.33V 10 100 nA
VMODE Output Low I
VMODE
= 1mA 200 mV
VMODE Pin Leakage FB = 0V, VMODE = 12V 0.1 5 µA
PWM Pin Signal Generator
PWM Falling Threshold
l
0.78 0.83 0.88 V
PWM Threshold Hysteresis (V
PWMHYS
) I
DIM/SS
= 0µA 0.35 0.47 0.6 V
PWM Pull-Up Current (I
PWMUP
) PWM = 0.7V, I
DIM/SS
= 0µA 6 7.5 9 µA
PWM Pull-Down Current (I
PWMDN
) PWM = 1.5V, I
DIM/SS
= 0µA 68 88 110 µA
PWM Fault-Mode Pull-Down Current INTV
CC
= 3.6V 1.5 mA
PWMOUT Duty Ratio for PWM Signal Generator (Note 5) I
DIM/SS
= –6.5µA
I
DIM/SS
= 0µA
I
DIM/SS
= 21.5µA
I
DIM/SS
= 52µA
3.1
6.2
40
95
4.1
7.9
48
96.5
5.2
9.2
56
98
%
%
%
%
P
WMOUT Signal Generator Frequency PWM = 47nF to GND, I
DIM/SS
= 0µA 170 300 390 Hz
PWMOUT Driver
PWMOUT Driver Output Rise Time (t
r
) C
L
= 560pF 35 ns
PWMOUT Driver Output Fall Time (t
f
) C
L
= 560pF 35 ns
PWMOUT Output Low (V
OL
) PWM = 0V 0.05 V
PWMOUT Output High (V
OH
) INTV
CC
– 0.05 V
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: Do not apply a positive or negative voltage or current source to
PWMOUT pin, otherwise permanent damage may occur.
Note 3: The LT3954E is guaranteed to meet performance specifications
from the 0°C to 125°C junction temperature. Specifications over the –40°C
to 125°C operating junction temperature range are assured by design,
characterization and correlation with statistical process controls. The
LT3954I is guaranteed over the full –40°C to 125°C operating junction
temperature range.
Note 4: The LT3954 includes overtemperature protection that is intended
to protect the device during momentary overload conditions. Junction
temperature will exceed the maximum operating junction temperature
when overtemperature protection is active. Continuous operation above
the specified maximum junction temperature may impair device reliability.
Note 5: PWMOUT Duty Ratio is calculated:
Duty = I
PWMUP
/(I
PWMUP
+ I
PWMDN
)
