Datasheet

LTC3621/LTC3621-2
4
3621fb
For more information www.linear.com/LTC3621
elecTrical characTerisTics
The l denotes the specifications which apply over the specified operating
junction temperature range, otherwise specifications are at T
J
= 25°C. (Note 3) V
IN
= 12V, unless otherwise noted.
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
V
MODE/SYNC
Pulse-Skipping Mode
Burst Mode Operation
Forced Continuous Mode
V
INTVCC
– 0.4
1.0
0.3
V
INTVCC
– 1.2
V
V
V
I
MODE/SYNC
MODE/SYNC Input Current 0 20 nA
t
SS
Internal Soft-Start Time 0.8 ms
I
LIM
Peak Current Limit
l
1.44
1.30
1.60 1.76
1.80
A
A
V
UVLO
V
INTVCC
Undervoltage Lockout V
IN
Ramping Up 2.4 2.6 2.7 V
V
UVLO(HYS)
V
INTVCC
Undervoltage Lockout Hysteresis 250 mV
V
OVLO
V
IN
Overvoltage Lockout Rising
l
18 19 20 V
V
OVLO(HYS)
V
IN
Overvoltage Lockout Hysteresis 300 mV
f
OSC
Oscillator Frequency LTC3621/LTC3621-3.3/LTC3621-5
l
0.92
0.82
1.00 1.08
1.16
MHz
MHz
LTC3621-2/LTC3621-23.3/LTC3621-25
l
2.05
1.8
2.25 2.45
2.6
MHz
MHz
f
SYNC
SYNC Capture Range 60 140 %
V
INTVCC
V
INTVCC
LDO Output Voltage V
IN
> 4V 3.3 3.6 3.9 V
ΔV
PGOOD
Power Good Range ±7.5 ±12.5 %
R
PGOOD
Power Good Resistance PGOOD R
DS(ON)
at 500µA 275 350 Ω
t
PGOOD
PGOOD Delay PGOOD Low to High
PGOOD High to Low
0
32
Cycles
Cycles
I
PGOOD
PGOOD Leakage Current 100 nA
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: Transient absolute maximum voltages should not be applied for
more than 4% of the switching duty cycle.
Note 3: The LTC3621 is tested under pulsed load conditions such that
T
J
≈ T
A
. The LTC3621E is guaranteed to meet specifications from
0°C to 85°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
LTC3621I is guaranteed over the –40°C to 125°C operating junction
temperature range. Note that the maximum ambient temperature
consistent with these specifications is determined by specific operating
conditions in conjunction with board layout, the rated package thermal
impedance and other environmental factors.
Note 4: The quiescent current in forced continuous mode does not include
switching loss of the power FETs.
Note 5: The LTC3621 is tested in a proprietary test mode that connects V
FB
to the output of error amplifier.
Note 6: T
J
is calculated from the ambient, T
A
, and power dissipation, P
D
,
according to the following formula:
T
J
= T
A
+ (P
D
• θ
JA
)
Note 7: This IC includes overtemperature protection that is intended
to protect the device during momentary overload conditions. Junction
temperature will exceed 125°C when overtemperature protection is active.
Continuous operation above the specified maximum operating junction
temperature may impair device reliability.