Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
Consult LTC Marketing for information on non-standard lead based finish parts.
For more information on lead free part marking, go to:
http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to:
http://www.linear.com/tapeandreel/
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
V
IN
V
OUT
I
VIN
PARAMETER
Operating Voltage
Operating Voltage
Input Quiescent Current
Shutdown Mode, V
RUN
= 0V
Burst Mode Operation
Forced Continuous Mode (Note 4), V
FB
< 0.6V
LTC3621/LTC3621-2
l
elecTrical characTerisTics
CONDITIONS
MIN
2.7
0.6
TYP
MAX
17
V
IN
UNITS
V
V
µA
µA
mA
V
V
nA
V
V
V
V
µA
%/V
%
µA
µA
Ω
Ω
%
ns
0.1
3.5
1.5
0.594
0.591
3.267
3.250
4.950
4.925
0.6
0.6
3.3
3.3
5.0
5.0
2
0.01
0.1
0.1
0.1
1.0
7
V
FB
I
FB
V
OUT
Regulated Feedback Voltage
FB Input Current
Regulated Fixed Output Voltage
0.606
0.609
10
3.333
3.350
5.050
5.075
10
0.015
1
1
LTC3621/LTC3621-2
LTC3621-3.3/LTC3621-23.3
l
LTC3621-5/LTC3621-25
l
I
FB(VOUT)
Feedback Input Leakage Current
Fixed Output Versions
V
IN
= 2.7V to 17V (Note 5)
(Note 5)
ΔV
LINE(REG)
Reference Voltage Line Regulation
ΔV
LOAD(REG)
Output Voltage Load Regulation
I
LSW
R
DS(ON)
D
MAX
t
ON(MIN)
V
RUN
I
RUN
NMOS Switch Leakage
PMOS Switch Leakage
NMOS On-Resistance (Bottom FET)
PMOS On-Resistance (Top FET)
Maximum Duty Cycle
Minimum On-Time
RUN Input High Threshold
RUN Input Low Threshold
RUN Input Current
V
IN
= 5V
V
FB
= 0.5V, V
MODE/SYNC
= 1.5V
l
0.15
0.37
100
60
0.3
1.0
0
20
V
V
nA
3621fc
V
RUN
= 12V
For more information
www.linear.com/LTC3621
3
LTC3621/LTC3621-2
elecTrical characTerisTics
SYMBOL
PARAMETER
V
MODE/SYNC
Pulse-Skipping Mode
Burst Mode Operation
Forced Continuous Mode
I
MODE/SYNC
t
SS
I
LIM
V
UVLO
V
UVLO(HYS)
V
OVLO
V
OVLO(HYS)
f
OSC
MODE/SYNC Input Current
Internal Soft-Start Time
Peak Current Limit
(E/I-Grade)
(H-Grade)
V
IN
Ramping Up
l
l
l
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.
CONDITIONS
MIN
V
INTVCC
– 0.4
1.0
0
0.8
1.44
1.30
1.2
2.4
18
0.92
0.82
0.78
2.05
1.8
1.7
60
V
IN
> 4V
PGOOD R
DS(ON)
at 500µA
PGOOD Low to High
PGOOD High to Low
3.6
±7.5
275
0
32
100
±12.5
350
1.60
1.76
1.80
1.80
2.7
20
1.08
1.16
1.16
2.45
2.6
2.6
140
TYP
MAX
0.3
V
INTVCC
– 1.2
20
UNITS
V
V
V
nA
ms
A
A
A
V
mV
V
mV
MHz
MHz
MHz
MHz
MHz
MHz
%
V
%
Ω
Cycles
Cycles
nA
V
INTVCC
Undervoltage Lockout
V
INTVCC
Undervoltage Lockout Hysteresis
V
IN
Overvoltage Lockout Rising
V
IN
Overvoltage Lockout Hysteresis
Oscillator Frequency
2.6
250
19
300
1.00
LTC3621/LTC3621-3.3/LTC3621-5
(E/I-Grade)
(H-Grade)
LTC3621-2/LTC3621-23.3/LTC3621-25
(E/I-Grade)
(H-Grade)
l
l
l
l
2.25
f
SYNC
V
INTVCC
ΔV
PGOOD
R
PGOOD
t
PGOOD
I
PGOOD
SYNC Capture Range
V
INTVCC
LDO Output Voltage
Power Good Range
Power Good Resistance
PGOOD Delay
PGOOD Leakage Current
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, and the LTC3621H is guaranteed over the –40°C to
150°C operating junction temperature range. High junction temperatures
degrade operating lifetimes; operating lifetime is derated for junction
temperatures greater than 125°C. 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 150°C when overtemperature protection is active.
Continuous operation above the specified maximum operating junction
1 Introduction
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