Datasheet

LT3988
3
3988f
elecTrical characTerisTics
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: The LT3988E 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
LT3988I is guaranteed over the full –40°C to 125°C operating junction
temperature range. The LT3988H is guaranteed over the full –40°C to
150°C operating junction temperature range. High junction temperatures
degrade operating lifetimes. Operating lifetime is derated at junction
temperatures greater than 125°C.
Note 3: Undervoltage lockout occurs when V
IN
is lower than the
undervoltage threshold. Overvoltage lockout occurs when V
IN
exceeds the
threshold voltage. See Applications Information.
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN1
/V
IN2
= 12V, unless otherwise noted. (Notes 2, 5, 6)
PARAMETER CONDITIONS MIN TYP MAX UNITS
V
IN1
Quiescent Current V
FB1
= 0.9V, V
BD
= 0V 2.7 4.5 mA
V
IN1
Quiescent Current V
FB1
= 0.9V, V
BD
= 5V 1.6 3 mA
V
IN2
Quiescent Current V
FB2
= 0.9V, V
BD
= 5V 250 1000 µA
BD Pin Current V
BD
= 0V –8 –30 µA
BD Pin Quiescent Current V
BD
= 5V 1.1 2.2 mA
Shutdown Current (I
VIN1
+I
VIN2
) V
EN/UVLO
≤ 0.3V 0.1 1 µA
FB Voltage
l
0.74
0.735
0.75
0.75
0.76
0.765
V
V
FB Pin Bias Current V
FB
= 0.75V
l
–5 –100 nA
FB Line Voltage Regulation 5V < V
IN
< 60V 0.01 %/V
Switching Frequency R
T
= 40.2k
l
0.9 1 1.1 MHz
Switching Frequency R
T
= 200k 250 kHz
Switching Frequency R
T
= 14.7k 2.15 MHz
Switching Phase, SW1 to SW2 R
T
= 40.2k 150 180 210 Deg
DA Comparator Current Threshold
l
1.1 1.32 1.58 A
Switch V
SAT
I
SW
= 1A 850 mV
Switch Current Limit (Note 4) Duty Cycle = 35% 1.4 1.87 2.25 A
Switch Leakage Current 0.01 1 µA
Minimum Boost Voltage 2 2.5 V
Boost Pin Current I
SW
= 1A 20 50 mA
Boost Diode Forward Voltage I
BD
= 50mA 0.7 0.9 V
Boost Diode Leakage Current V
R
= 5V 0.1 5 µA
TRACK/SS Pin Current V
TRACK/SS
= 1V –0.8 –1.3 –2.2 µA
SYNC Input High Voltage V
IH
l
1.5 V
SYNC Input Low Voltage V
IL
l
0.4 V
SYNC Input Frequency 0.25 2.5 MHz
SYNC Pin Input Current V
SYNC
= 1.5V 0.3 µA
Note 4: Current limit is guaranteed by design and/or correlation to static
test. Slope compensation reduces current at higher duty cycles.
Note 5: Polarity specification for all currents into pins is positive. All
voltages are referenced to GND unless otherwise specified.
Note 6: This IC 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 operating junction temperature may impair device
reliability.
Note 7: Absolute Maximum Voltage at V
IN
and EN/UVLO is 80V for
nonrepetitive 1 second transients, and 60V for continuous operation.
Note 8: If V
IN2
is driven above 60V, V
IN2
must be connected to V
IN1
.