Datasheet

LT3640
4
3640f
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 LT3640E 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
LT3640I is guaranteed and tested over the full –40°C to 125°C operating
junction temperature range.
PARAMETER CONDITIONS MIN TYP MAX UNITS
SS1, SS2 Charge Current SS1 = 0.5V, SS2 = 0.5V 1.4 1.9 2.5 µA
SS1 to FB1 Offset Voltage SS1 = 0.6V 5 30 mV
SS2 to FB2 Offset Voltage SS2 = 0.3V 5 30 mV
RST1 Threshold as Percentage of V
FB
l
90 92 94 %
RST2 Threshold as Percentage of V
FB
l
89 92 94 %
Undervoltage to RST Assert Time 20 µs
RST1, RST2, WDO Pull-Up Current RST1, RST2, WDO = 0V 5 15 30 µA
RST1, RST2, WDO Output Voltage I
RST1
, I
RST2
, I
WDO
= 2mA 150 250 mV
RST1, RST2 Timeout Period (t
RST
) CPOR = 220pF
l
8 9.5 11 ms
Watchdog Start Delay Time (t
DLY
) CWDT = 820pF 14 16 18 ms
Watchdog Upper Boundary (t
WDU
) CWDT = 820pF
l
27 32 35 ms
Watchdog Lower Boundary (t
WDL
) CWDT = 820pF
l
1.68 2 2.2 ms
WDI Pull-Up Current WDI = 1.2V 2 µA
WDI Voltage Threshold 0.55 0.85 1.15 V
WDI Low Minimum Pulse Width 300 ns
WDI High Minimum Pulse Width 300 ns
WDE Pull-Down Current WDE = 2V 1 µA
WDE Threshold
l
0.5 0.7 0.9 V
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 12V, V
IN2
= 3.3V, EN/UVLO = 12V, EN2 = 3.3V, unless otherwise noted.
Note 3: SW1, SW2 current limit is guaranteed by design and/or correlation
to static test. Slope compensation reduces current limit at higher duty
cycle.
Note 4: The oscillator cycle is extended when DA current exceeds its limit.
DA current limit is flat over duty cycle.
Note 5: If the SW2 NMOS current exceeds its limit at the start of an
oscillator cycle, the PMOS will not be turned on in the cycle.
Note 6: The QFN switch R
DS(ON)
is guaranteed by correlation to wafer level
measurement.
Note 7: Absolute maximum voltage at V
IN
and RUN/SS pin is 55V for
nonrepetitive one second transients, and 36V for continuous operation.
elecTrical characTerisTics