buck regulator using a phase-lockable controlled on-time,
current mode architecture capable of supplying up to 2.5A
of output current. The operating supply voltage range is
3.6V to 20V, making it suitable for a wide range of power
supply applications.
The operating frequency is programmable from 500kHz to
3MHz with an external resistor allowing the use of small
surface mount inductors. For applications sensitive to
switching noise, the LTC3626 can be externally synchro-
nized over the same frequency range. An internal phase-
locked loop aligns the on-time of the top power MOSFET to
the internal or external clock. This unique controlled on-time
architecture is ideal for high step-down ratio applications
that demand high switching frequencies and fast transient
response. An internal phase lock loop servos the on-time
of the internal one-shot timer to match the frequency of
the internal clock or an applied external clock.
The LTC3626 offers two operational modes: Burst
Mode and forced continuous mode to allow the user
to optimize output voltage ripple, noise and light load
efficiency for a given application.
L,
LT, LTC, LTM, Burst Mode, Linear Technology and the Linear logo are registered 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, 5847554, 6580258,
6304066, 6476589, 6774611, 5994885.
n
n
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n
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n
3.6V to 20V Input Voltage Range
Wide Output Voltage Range of 0.6V to 97% V
IN
Opti-
mized for 0.6V to 6V
Low R
DS(ON)
Integrated Switches Provide Up to 95%
Efficiency
Up to 2.5A of Output Current
Average Input and Output Current Monitoring
Programmable Average Input/Output Current Limit
Die Temperature Monitor and Programmable Limit
Adjustable Switching Frequency: 500kHz to 3MHz
External Frequency Synchronization
Current Mode Operation for Excellent Line and Load
Transient Response
0.6V Reference with 1% Accuracy Over Temperature
User Selectable Burst Mode
®
Operation or Forced
Continuous Operation
Short-Circuit Protected
Output Voltage Tracking Capability
Power Good Status Output
Available in Small, Thermally Enhanced, 20-Lead
(3mm
×
4mm) QFN Package
applicaTions
n
n
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Distributed Power Systems
Battery-Powered Instruments
Point-of-Load Power Supply
Typical applicaTion
V
IN
3.6V TO 20V
BOOST
LTC3626
PGOOD
INTV
CC
TRACK/SS
SW
2.2µF
ITH
MODE/SYNC
V
ON
TSET
IMON
IN
FB
TMON
RT
IMON
OUT
SGND
PGND
1µF
5.1k
47µF
PV
IN
SV
IN
RUN
EFFICIENCY (%)
0.1µF
2.2µH
115k
22pF
25.5k
324k
3626 TA01
Efficiency vs Load Current
100
90
80
70
60
50
40
30
20
10
0
1
0.1
1
V
OUT
= 3.3V
10
POWER LOSS (W)
V
OUT
3.3V
47µF 2.5A
Burst Mode
0.01
OPERATION
V
IN
= 12V
V
IN
= 5V
0.001
10
100
1000
10000
3626 TA01b
LOAD CURRENT (mA)
3626fa
For more information
www.linear.com/LTC3626
1
LTC3626
absoluTe MaxiMuM raTings
(Note 1)
pin conFiguraTion
TOP VIEW
MODE/SYNC
16 PV
IN
15 PV
IN
21
PGND
14 SV
IN
13 RUN
12 RT
11 ITH
7
IMON
IN
8
IMON
OUT
9 10
TRACK/SS
FB
PGOOD
PV
IN
........................................................... –0.3V to 22V
SV
IN
........................................................... –0.3V to 22V
BOOST .................................................... –0.3V to 25.6V
BOOST-SW................................................ –0.3V to 3.6V
INTV
CC
...................................................... –0.3V to 3.6V
ITH, RT, FB .................................–0.3V to INTV
CC
+ 0.3V
MODE/SYNC ..............................–0.3V to INTV
CC
+ 0.3V
TRACK/SS, IMON
IN
, IMON
OUT
...–0.3V to INTV
CC
+ 0.3V
TSET, TMON ..............................–0.3V to INTV
CC
+ 0.3V
SW, RUN .......................................... –0.3V to V
IN
+ 0.3V
PGOOD....................................................... –0.3V to 22V
V
ON
............................................................ –0.3V to 18V
SW Source Current (DC, Note 2)..............................2.5A
Operating Junction Temperature Range
(Notes 3, 4) ........................................... –40°C to 125°C
Storage Temperature Range .................. –65°C to 150°C
SW
BOOST 1
INTV
CC
2
V
ON
3
TSET 4
TMON 5
SGND 6
20 19 18 17
UDC PACKAGE
20-LEAD (3mm
×
4mm) PLASTIC QFN
T
JMAX
= 125°C,
θ
JA
= 47°C/W
EXPOSED PAD (PIN 21) IS PGND, MUST BE SOLDERED TO PCB
orDer inForMaTion
LEAD FREE FINISH
LTC3626EUDC#PBF
LTC3626IUDC#PBF
TAPE AND REEL
LTC3626EUDC#TRPBF
LTC3626IUDC#TRPBF
PART MARKING*
LGCC
LGCC
PACKAGE DESCRIPTION
20-Lead (3mm
×
4mm) Plastic QFN
20-Lead (3mm
×
4mm) Plastic QFN
TEMPERATURE RANGE
–40°C to 125°C
–40°C to 125°C
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/
SW
2
3626fa
For more information
www.linear.com/LTC3626
LTC3626
elecTrical characTerisTics
SYMBOL
PV
IN
SV
IN
V
VOUT
I
Q
PARAMETER
Input Supply Range
Input Supply Range
Output Voltage Range (Note 5)
Input DC Supply Current
Forced Continuous Operation
PV
IN
SV
IN
Sleep Current
PV
IN
SV
IN
Shutdown
PV
IN
SV
IN
V
FB
∆V
LINE(REG)
Feedback Reference Voltage
V
FB
Line Regulation
PV
IN
= SV
VIN
= 3.6V to 20V
ITH = 0.6V to 1.5V
V
FB
= 0.6V
ITH = 1.2V
V
VON
=1V, PV
IN
= SV
VIN
= 3.6V
PV
IN
= SV
IN
= 6V
2.4
V
RT
= INTV
CC
R
RT
= 158k
R
RT
= 105k
1.4
1.7
2.5
1.5
20
40
2.9
–1
2
2
3
115
70
I
SW
= 2.5A
I
SW
= 1.5A
I
SW
= 0.5A
l
The
l
denotes the specifications which apply over the specified operating
junction temperature range, otherwise specifications are at T
A
= 25°C (Note 3). PV
IN
= SV
IN
= 12V unless otherwise specified.
CONDITIONS
l
l
MIN
3.0
3.6
0.6
TYP
MAX
20
20
6
UNITS
V
V
V
V
ON
= V
OUT
MODE = 0, R
RT
= 158k, IMON
IN
, IMON
OUT
,
TMON, TSET = INTV
CC
V
FB
> 0.6V, IMON
IN
, IMON
OUT
, TMON, TSET,
MODE = INTV
CC
I
LOAD
= 0A, V
RUN
= 0V
30
900
30
270
0.01
13
l
39
1200
39
350
2
17
0.606
µA
µA
µA
µA
µA
µA
V
%/V
%
0.594
0.600
0.01
0.1
∆V
LOAD(REG)
V
FB
Load Regulation
Feedback Pin Input Current
Error Amplifier Transconductance
t
ON(MIN)
t
OFF(MIN)
Minimum On-Time
Minimum Off-Time
Valley Switch Current Limit
Negative Valley Switch Current Limit
f
OSC
Oscillator Frequency
±30
nA
mS
ns
60
3.6
2.6
2.3
3.5
ns
A
A
MHz
MHz
MHz
mΩ
mΩ
R
DS(ON)
Top Switch On-Resistance
Bottom Switch On-Resistance
IMON
OUT
Current (Note 6)
148.5
89.1
29.7
1.15
29.7
17.8
5.9
l
156.25
93.75
31.25
1.22
31.25
18.75
6.25
1.22
1.5
200
50
164.0
98.4
33.5
1.28
32.8
19.7
6.7
1.28
µA
µA
µA
V
µA
µA
µA
V
V
°C/V
mV
V
V
I
OUT
Limit Regulation Voltage
IMON
IN
Current (Note 6)
I
SW
= 2.5A, 20% Duty Cycle
I
SW
= 1.5A, 20% Duty Cycle
I
SW
= 0.5A, 20% Duty Cycle
T
A
= 25°C
I
IN
Limit Regulation Voltage
Internal Temperature Monitor
Internal Temperature Monitor Slope (Note 7)
Temperature Limit Hysteresis
PV
IN
Overvoltage Lockout Threshold
V
INTVCC
V
RUN
INTV
CC
Voltage
INTV
CC
Load Regulation (Note 8)
RUN Threshold
RUN Leakage Current
PV
IN
Rising
PV
IN
Falling
3.6V < PV
IN
= SV
VIN
< 20V
I
INTVCC
= 0mA to 20mA
RUN Rising
RUN Falling
PV
VIN
= SV
VIN
= 20V
1.15
20
3.1
l
l
21.5
20.5
3.3
0.6
1.23
1.0
0
3.5
1.27
1.03
±1
V
%
V
V
μA
3626fa
1.19
0.97
For more information
www.linear.com/LTC3626
3
LTC3626
elecTrical characTerisTics
SYMBOL
PARAMETER
PGOOD Good-to-Bad Threshold
PGOOD Bad-to-Good Threshold
Power Good Filter Time
R
PGOOD
t
SS
I
TRACK/SS
PGOOD Pull-Down Resistance
Switch Leakage Current
Internal Soft-Start Time
TRACK/SS Pull-Up Current
MODE Threshold Voltage
SYNC Threshold Voltage
MODE Input Current
MODE V
IH
MODE V
IL
SYNC V
IH
MODE = 0V
MODE = INTV
CC
l
l
l
The
l
denotes the specifications which apply over the specified operating
junction temperature range, otherwise specifications are at T
A
= 25°C (Note 3). PV
IN
= SV
IN
= 12V unless otherwise specified.
CONDITIONS
FB Rising
FB Falling
FB Rising
FB Falling
10mA Load
V
RUN
= 0V
V
FB
from 10% to 90% Full Scale
1.0
1.4
–1.5
1.5
–3
3
20
MIN
TYP
8
–8
–5
5
40
20
0.01
400
1.4
0.4
1
700
MAX
10
–10
UNITS
%
%
%
%
μs
Ω
μA
μs
μA
V
V
V
μA
µA
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:
Guaranteed by long term current density limitations.
Note 3:
The LTC3626 is tested under pulsed load conditions such that
T
J
≈ T
A
. The LTC3626E is guaranteed to meet performance specifications
from 0°C to 85°C. Specifications over the –40°C to 125°C operating
junction temperature range are assured by design, characterization, and
correlation with statistical process controls. The LTC3626I 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:
This IC includes overtemperature protection that is intended to
protect the device during momentary overload conditions. The maximum
rated junction temperature will be exceeded when this protection is active.
Continuous operation above the specified absolute maximum operating
junction temperature may impair device reliability or permanently damage
the device.
Note 5:
Output voltages above 6V are not optimized for controlled
on-time operation. Refer to the Applications Information section for
further discussions related to the output voltage range. Verified at test by
comparison of measured on-time to V
ON
voltage.
Note 6:
Tested in a proprietary test mode, where I
SW
flows through the
synchronous switch only.
Note 7:
Guaranteed by design.
Note 8:
Maximum allowed current draw when used as a regulated output
is 5mA. This supply is only intended to supply additional DC load currents
as needed and not intended to regulate large transient or AC behavior as
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