synchronous monolithic step-down regulator. The switch-
ing frequency is fixed to 1MHz or 2.25MHz. The regulator
features ultralow quiescent current and high efficiencies
over a wide V
OUT
range.
The step-down regulator operates from an input voltage
range of 2.7V to 17V and provides an adjustable output
range from 0.6V to V
IN
while delivering up to 1A of output
current. A user-selectable mode input is provided to allow
the user to trade off ripple noise for light load efficiency;
Burst Mode operation provides the highest efficiency at
light loads, while pulse-skipping mode provides the low-
est voltage ripple.
List of LTC3621 Options
PART NAME
LTC3621
LTC3621-2
FREQUENCY
1.00MHz
2.25MHz
V
OUT
Adjustable
Adjustable
n
n
n
n
Wide V
IN
Range: 2.7V to 17V
Wide V
OUT
Range: 0.6V to V
IN
95% Max Efficiency
Low I
Q
< 3.5µA, Zero-Current Shutdown
Constant Frequency (1MHz/2.25MHz)
Full Dropout Operation with Low I
Q
1A Rated Output Current
±1% Output Voltage Accuracy
Current Mode Operation for Excellent Line and Load
Transient Response
Pulse-Skipping, Forced Continuous, Burst Mode
®
Operation
Internal Compensation and Soft-Start
Overtemperature Protection
Compact 6-Lead DFN (2mm
×
3mm) Package or
8-Lead MSOPE Package with Power Good Output
and Independent SGND Pin
applicaTions
n
n
n
Portable-Handheld Scanners
Automotive Applications
Emergency Radio
L,
LT, LTC, LTM, Burst Mode, Linear Technology and the Linear logo are registered trademarks
and Hot Swap is a trademark of Linear Technology Corporation. All other trademarks are the
property of their respective owners. Protected by U.S. Patents, including 5481178, 6580258,
6498466, 6611131, 6177787, 5705919, 5847554.
Typical applicaTion
2.5V V
OUT
with 400mA Burst Clamp, f
SW
= 1MHz
V
IN
2.7V TO 17V
4.7µH
V
IN
10µF
SW
604k
191k
1µF
22pF
LTC3621
RUN
FB
MODE
INTV
CC
GND
V
OUT
2.5V
1A
22µF
3621 TA01a
Efficiency and Power Loss vs Load
100
90
80
EFFICIENCY (%)
70
60
50
40
30
20
10
0
0.0001
POWER LOSS
0.001
0.01
EFFICIENCY
0.1
POWER LOSS (W)
1.0
V
IN
= 12V
0.01
0.001
0.1
LOAD CURRENT (A)
1
3621 TA01b
0.0001
3621f
For more information
www.linear.com/LTC3621
1
LTC3621/LTC3621-2
absoluTe MaxiMuM raTings
(Note 1)
V
IN
Voltage (Note 2) ................................... 17V to –0.3V
SW Voltage DC................................. V
IN
+ 0.3V to –0.3V
Transient (Note 2) ...................................19V to –2.0V
RUN Voltage................................................ V
IN
to –0.3V
MODE, FB Voltages ...................................... 6V to –0.3V
INTV
CC
, PGOOD Voltages ............................ 6V to –0.3V
Operating Junction Temperature Range
(Note 3) .................................................. –40°C to 125°C
Storage Temperature Range .................. –65°C to 125°C
pin conFiguraTion
TOP VIEW
TOP VIEW
SW 1
V
IN
2
RUN 3
7
GND
6 MODE
5 INTV
CC
4 FB
SW
V
IN
RUN
PGOOD
1
2
3
4
9
GND
8
7
6
5
SGND
MODE
INTV
CC
FB
DCB PACKAGE
6-LEAD (2mm
×
3mm) PLASTIC DFN
T
JMAX
= 125°C,
θ
JA
= 64°C/W,
θ
JC
= 9.6°C/W
EXPOSED PAD (PIN 7) IS GND, MUST BE SOLDERED TO PCB
MS8E PACKAGE
8-LEAD PLASTIC MSOP
T
JMAX
= 125°C,
θ
JA
= 40°C/W,
θ
JC
= 10°C/W
EXPOSED PAD (PIN 9) IS GND, MUST BE SOLDERED TO PCB
orDer inForMaTion
LEAD FREE FINISH
LTC3621EDCB#PBF
LTC3621IDCB#PBF
LTC3621EMS8E#PBF
LTC3621IMS8E#PBF
LTC3621EDCB-2#PBF
LTC3621IDCB-2#PBF
LTC3621EMS8E-2#PBF
LTC3621IMS8E-2#PBF
TAPE AND REEL
LTC3621EDCB#TRPBF
LTC3621IDCB#TRPBF
LTC3621EMS8E#TRPBF
LTC3621IMS8E#TRPBF
LTC3621EDCB-2#TRPBF
LTC3621IDCB-2#TRPBF
PART MARKING*
LGDG
LGDG
LTGDH
LTGDH
LGHY
LGHY
PACKAGE DESCRIPTION
6-Lead (2mm
×
3mm) Plastic DFN
6-Lead (2mm
×
3mm) Plastic DFN
8-Lead Plastic MSOP
8-Lead Plastic MSOP
6-Lead (2mm
×
3mm) Plastic DFN
6-Lead (2mm
×
3mm) Plastic DFN
8-Lead Plastic MSOP
8-Lead Plastic MSOP
TEMPERATURE RANGE
–40°C to 125°C
–40°C to 125°C
–40°C to 125°C
–40°C to 125°C
–40°C to 125°C
–40°C to 125°C
–40°C to 125°C
–40°C to 125°C
LTC3621EMS8E-2#TRPBF LTGHZ
LTC3621IMS8E-2#TRPBF LTGHZ
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/
elecTrical characTerisTics
SYMBOL
V
IN
V
OUT
I
VIN
PARAMETER
Operating Voltage
Operating Voltage
Input Quiescent Current
The
l
denotes the specifications which apply over the full operating
junction temperature range, otherwise specifications are at T
J
= 25°C. V
IN
= 12V, unless otherwise noted. (Notes 3, 6)
CONDITIONS
MIN
2.7
0.6
Shutdown Mode, V
RUN
= 0V
Burst Mode Operation
Forced Continuous Mode
(Note 4), V
FB
< 0.6V
0
3.5
1.5
TYP
MAX
17
V
IN
0.1
4.5
UNITS
V
V
µA
µA
mA
3621f
2
For more information
www.linear.com/LTC3621
LTC3621/LTC3621-2
elecTrical characTerisTics
SYMBOL
V
FB
I
FB
ΔV
LINE(REG)
ΔV
LOAD(REG)
I
LSW
R
DS(ON)
D
MAX
t
ON(MIN)
V
RUN
I
RUN
V
MODE
I
MODE
t
SS
I
LIM
V
UVLO
V
UVLO(HYS)
V
OVLO
V
OVLO(HYS)
f
OSC
PARAMETER
Regulated Feedback Voltage
l
The
l
denotes the specifications which apply over the full operating
junction temperature range, otherwise specifications are at T
J
= 25°C. V
IN
= 12V, unless otherwise noted. (Notes 3, 6)
CONDITIONS
MIN
0.594
0.591
TYP
0.6
0.6
0.01
0.1
0.1
0.1
V
IN
= 5V
V
FB
= 0.5V, V
MODE
= 1.5V
V
FB
= 0.7V, V
MODE
= 1.5V
0.3
V
RUN
= 12V
V
INTVCC
– 0.4
1.0
V
MODE
= 3.6V
1.44
1.30
2.4
l
l
MAX
0.606
0.609
10
0.015
1
1
UNITS
V
V
nA
%/V
%
µA
µA
Ω
Ω
%
ns
FB Input Current
Reference Voltage Line Regulation
Output Voltage Load Regulation
NMOS Switch Leakage
PMOS Switch Leakage
NMOS On-Resistance
PMOS On-Resistance
Maximum Duty Cycle
Minimum On-Time
RUN Input High Threshold
RUN Input Low Threshold
RUN Input Current
Pulse-Skipping Mode
Burst Mode Operation
Forced Continuous Mode
MODE Input Current
Internal Soft-Start Time
Peak Current Limit
l
V
IN
= 2.7V to 17V (Note 5)
(Note 5)
0.15
0.37
100
60
1.0
0
20
0.3
V
INTVCC
– 1.0
0
0.5
1.60
2.6
250
18
2.05
0.92
1.8
0.82
3.3
19
300
20
2.45
1.08
2.6
1.16
3.9
±11
350
1.76
1.80
2.7
10
V
V
nA
V
V
V
nA
ms
A
A
V
mV
V
mV
MHz
MHz
MHz
MHz
V
%
Ω
Cycles
Cycles
V
INTVCC
Undervoltage Lockout
V
INTVCC
Undervoltage Lockout Hysteresis
V
IN
Overvoltage Lockout Rising
V
IN
Overvoltage Lockout Hysteresis
Oscillator Frequency
V
IN
Ramping Up
2.25MHz Parts
1MHz Parts
2.25MHz Parts
1MHz Parts
V
IN
> 4V
PGOOD R
DS(ON)
at 500µA
PGOOD Low to High
PGOOD High to Low
l
l
2.25
1.00
3.6
±7.5
275
0
32
V
INTVCC
ΔV
PGOOD
R
PGOOD
t
PGOOD
I
PGOOD
V
INTVCC
LDO Output Voltage
Power Good Range
Power Good Resistance
PGOOD Delay
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
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