LT1952
4
1952f
ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. COMP = open, FB = 1.4V, R
OSC
= 178k, SYNC = 0V, SS_MAXDC = V
REF
,
V
REF
= 0.1µF, SD_V
SEC
= 2V, BLANK = 40k, DELAY = 40k, I
SENSE
= 0V, OC = 0V, OUT = 1nF, V
IN
= 15V, SOUT = open, unless otherwise
specified.
PARAMETER CONDITIONS MIN TYP MAX UNITS
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: The LT1952EGN is guaranteed to meet performance specifications
from 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
LT1952IGN is guaranteed over the full –40°C to 125°C operating junction
temperature range.
Note 3: Rise and Fall times are measured at 10% and 90% levels.
Note 4: Guaranteed by correlation to static test.
Note 5: This IC includes over-temperature protection that is intended to
protect the device during momentary overload conditions. Junction
temperature will exceed 125°C when over-temperature protection is active.
Continuous operation above the specified maximum operating junction
temperature may impair device reliability.
Note 6: Guaranteed but not tested.
Note 7: Maximum recommended SYNC frequency = 500kHz.
Note 8: In applications where the V
IN
pin is supplied via an external RC
network from a SYSTEM V
IN
> 25V, an external zener with clamp voltage
V
IN ON(MAX)
< V
Z
< 25V should be connected from the V
IN
pin to ground.
Note 9: V
IN
start-up current is measured at V
IN
= V
IN ON
– 0.25V and
scaled by x 1.18 (to correlate to worst case V
IN
start-up current at V
IN ON
).
Note 10: Timing for R = 40k derived from measurement with R = 240k.
OUT Max Duty Cycle COMP = 2.5V, FB = 1V, R
DELAY
= 10k
(f
OSC
= 200kHz)
SD_V
SEC
= 1.4V, SS_MAXDC = V
REF
83 90 %
OUT Max Duty Cycle Clamp COMP = 2.5V, FB = 1V, R
DELAY
= 10k
(f
OSC
= 200kHz)
SD_V
SEC
= 1.32V, SS_MAXDC = 1.84V 63.5 72 80.5 %
SD_V
SEC
= 2.64V, SS_MAXDC = 1.84V 25 33 41 %
SOFT-START
SS_MAXDC Low Level: V
OL
I
(SS_MAXDC)
= 150µA, OC = 1V 0.2 V
SS_MAXDC Soft-Start Reset Threshold Measured on SS_MAXDC 0.45 V
SS_MAXDC Active Threshold FB = 1V, DC > 0% 0.8 V
SS_MAXDC Input Current (Soft-Start Pulldown: Idis) SS_MAXDC = 1V, SD_V
SEC
= 1.4V, OC = 1V 800 µA