Datasheet

LT8641
3
Rev B
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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 LT8641E 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
LT8641I is guaranteed over the full –40°C to 125°C operating junction
temperature range. The LT8641H 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.
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C.
PARAMETER CONDITIONS MIN TYP MAX UNITS
Feedback Pin Input Current V
FB
= 1V –20 20 nA
BIAS Pin Current Consumption V
BIAS
= 3.3V, 2MHz 9 mA
Minimum On-Time I
LOAD
= 1.5A, SYNC = 0V
I
LOAD
= 1.5A, SYNC = 2V
l
l
35
35
50
50
ns
ns
Minimum Off-Time 80 110 ns
Oscillator Frequency R
T
= 221k
R
T
= 60.4k
R
T
= 18.2k
l
l
l
180
665
1.85
210
700
2.00
240
735
2.15
kHz
kHz
MHz
Top Power NMOS On-Resistance I
SW
= 1A 105 mΩ
Top Power NMOS Current Limit
l
6.2 8.2 9.9 A
Bottom Power NMOS On-Resistance V
INTVCC
= 3.4V, I
SW
= 1A 55 mΩ
Bottom Power NMOS Current Limit V
INTVCC
= 3.4V 4.8 5.8 7.25 A
SW Leakage Current V
IN
= 42V, V
SW
= 0V, 42V –15 15 µA
EN/UV Pin Threshold EN/UV Rising
l
0.95 1.01 1.07 V
EN/UV Pin Hysteresis 45 mV
EN/UV Pin Current V
EN/UV
= 2V –20 20 nA
PG Upper Threshold Offset from V
FB
V
FB
Falling
l
5 7.5 10.25 %
PG Lower Threshold Offset from V
FB
V
FB
Rising
l
–5.25 –8 –10.75 %
PG Hysteresis 0.4 %
PG Leakage V
PG
= 3.3V –40 40 nA
PG Pull-Down Resistance V
PG
= 0.1V
l
750 2000 Ω
SYNC/MODE Threshold SYNC/MODE DC and Clock Low Level Voltage
SYNC/MODE Clock High Level Voltage
SYNC/MODE DC High Level Voltage
0.7
2.3
0.9
1.2
2.6
1.4
2.9
V
V
V
Spread Spectrum Modulation
FrequencyRange
R
T
= 60.4k, V
SYNC
= 3.3V 22 %
Spread Spectrum Modulation Frequency V
SYNC
= 3.3V 2.5 kHz
TR/SS Source Current
l
1.2 1.9 2.6 µA
TR/SS Pull-Down Resistance Fault Condition, TR/SS = 0.1V 220 Ω
The junction temperature (T
J
, in °C) is calculated from the ambient
temperature (T
A
in °C) and power dissipation (PD, in Watts) according to
the formula:
T
J
= T
A
+ (PD • θ
JA
)
where θ
JA
(in °C/W) is the package thermal impedance.
Note 3: θ values determined per JEDEC 51-7, 51-12. See Applications
Information section for information on improving the thermal resistance
and for actual temperature measurements of a demo board in typical
operating conditions.
Note 4: This IC includes overtemperature protection that is intended to
protect the device during overload conditions. Junction temperature will
exceed 150°C when overtemperature protection is active. Continuous
operation above the specified maximum operating junction temperature
will reduce lifetime.
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