FeaTures
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LT3470
Micropower Buck Regulator
with Integrated Boost and
Catch Diodes
DescripTion
The LT
®
3470 is a micropower step-down DC/DC con-
verter that integrates a 300mA power switch, catch diode
and boost diode into low profile 3mm
×
2mm DD and
ThinSOT™ packages. The LT3470 combines Burst Mode
and continuous operation to allow the use of tiny induc-
tor and capacitors while providing a low ripple output to
loads of up to 200mA.
With its wide input range of 4V to 40V, the LT3470 can
regulate a wide variety of power sources, from 2-cell Li-Ion
batteries to unregulated wall transformers and lead-acid
batteries. Quiescent current in regulation is just 26µA in
a typical application while a zero current shutdown mode
disconnects the load from the input source, simplifying
power management in battery-powered systems. Fast
current limiting and hysteretic control protects the LT3470
and external components against shorted outputs, even
at 40V input.
L,
LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks
and ThinSOT is a trademark of Linear Technology Corporation. All other trademarks are the
property of their respective owners.
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Low Quiescent Current: 26µA at 12V
IN
to 3.3V
OUT
Integrated Boost and Catch Diodes
Input Range: 4V to 40V
Low Output Ripple: <10mV
< 1µA in Shutdown Mode
Output Voltage: 1.25V to 16V
200mA Output Current
Hysteretic Mode Control
– Low Ripple Burst Mode
®
Operation at Light Loads
– Continuous Operation at Higher Loads
Solution Size as Small as 50mm
2
Low Profile (0.75mm) 3mm
×
2mm Thermally
Enhanced 8-Lead DD and 1mm ThinSOT Packages
applicaTions
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Automotive Battery Regulation
Power for Portable Products
Distributed Supply Regulation
Industrial Supplies
Wall Transformer Regulation
Typical applicaTion
Efficiency and Power Loss vs Load Current
V
IN
7V TO 40V
V
IN
OFF ON
SHDN
BOOST
LT3470
SW
BIAS
22pF
2.2µF
GND
FB
604k
1%
200k
1%
3470 TA01a
90
0.22µF
33µH
V
OUT
5V
200mA
22µF
80
70
EFFICIENCY (%)
60
50
40
30
20
V
IN
= 12V
1000
100
POWER LOSS (mW)
10
1
10
0.1
1
10
LOAD CURRENT (mA)
100
3470 TA02
0.1
3470fd
1
LT3470
absoluTe MaxiMuM raTings
(Note 1)
V
IN
,
SHDN
Voltage ................................................... 40V
BOOST Pin Voltage .................................................. 47V
BOOST Pin Above SW Pin ........................................ 25V
FB Voltage .................................................................. 5V
BIAS Voltage .............................................................25V
SW Voltage ................................................................V
IN
Maximum Junction Temperature
LT3470E, LT3470I ............................................. 125°C
LT3470H ........................................................... 150°C
Operating Temperature Range (Note 2)
LT3470E...............................................– 40°C to 85°C
LT3470I ............................................. –40°C to 125°C
LT3470H ............................................ –40°C to 150°C
Storage Temperature Range .................. –65°C to 150°C
Lead Temperature (Soldering, 10 sec) .................. 300°C
pin conFiguraTion
TOP VIEW
FB 1
BIAS 2
BOOST 3
SW 4
9
8
7
6
5
SHDN
NC
V
IN
GND
TOP VIEW
SHDN
1
NC 2
V
IN
3
GND 4
8 FB
7 BIAS
6 BOOST
5 SW
DDB8 PACKAGE
8-LEAD (3mm
×
2mm) PLASTIC DFN
θ
JA
= 180°C/W
EXPOSED PAD (PIN 9) IS GROUND (MUST BE SOLDERED TO PCB)
TS8 PACKAGE
8-LEAD PLASTIC TSOT-23
θ
JA
= 140°C/W
orDer inForMaTion
LEAD FREE FINISH
LT3470EDDB#PBF
LT3470IDDB#PBF
LT3470HDDB#PBF
LT3470ETS8#PBF
LT3470ITS8#PBF
LT3470HTS8#PBF
LEAD BASED FINISH
LT3470EDDB
LT3470IDDB
LT3470HDDB
LT3470ETS8
LT3470ITS8
LT3470HTS8
TAPE AND REEL
LT3470EDDB#TRPBF
LT3470IDDB#TRPBF
LT3470HDDB#TRPBF
LT3470ETS8#TRPBF
LT3470ITS8#TRPBF
LT3470HTS8#TRPBF
TAPE AND REEL
LT3470EDDB#TR
LT3470IDDB#TR
LT3470HDDB#TR
LT3470ETS8#TR
LT3470ITS8#TR
LT3470HTS8#TR
PART MARKING
LBPN
LBPP
LCNR
LTBDM
LTBPW
LTCNQ
PART MARKING
LBPN
LBPP
LCNR
LTBDM
LTBPW
LTCNQ
PACKAGE DESCRIPTION
8-Lead (3mm
×
2mm) Plastic DFN
8-Lead (3mm
×
2mm) Plastic DFN
8-Lead (3mm
×
2mm) Plastic DFN
8-Lead Plastic TSOT-23
8-Lead Plastic TSOT-23
8-Lead Plastic TSOT-23
PACKAGE DESCRIPTION
8-Lead (3mm
×
2mm) Plastic DFN
8-Lead (3mm
×
2mm) Plastic DFN
8-Lead (3mm
×
2mm) Plastic DFN
8-Lead Plastic TSOT-23
8-Lead Plastic TSOT-23
8-Lead Plastic TSOT-23
TEMPERATURE RANGE
–40°C to 85°C
–40°C to 125°C
–40°C to 150°C
–40°C to 85°C
–40°C to 125°C
–40°C to 150°C
TEMPERATURE RANGE
–40°C to 85°C
–40°C to 125°C
–40°C to 150°C
–40°C to 85°C
–40°C to 125°C
–40°C to 150°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
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/
3470fd
2
LT3470
elecTrical characTerisTics
PARAMETER
Minimum Input Voltage
Quiescent Current from V
IN
Quiescent Current from Bias
V
SHDN
= 0.2V
V
BIAS
= 3V, Not Switching
V
BIAS
= 0V, Not Switching
V
SHDN
= 0.2V
V
BIAS
= 3V, Not Switching
V
BIAS
= 0V, Not Switching
V
FB
Falling
V
FB
= 1V, E- and I-Grade
H-Grade
FB Voltage Line Regulation
Minimum Switch Off-Time (Note 5)
Switch Leakage Current
Switch V
CESAT
Switch Top Current Limit
Switch Bottom Current Limit
Catch Schottky Drop
Catch Schottky Reverse Leakage
Boost Schottky Drop
Boost Schottky Reverse Leakage
Minimum Boost Voltage (Note 4)
BOOST Pin Current
SHDN
Pin Current
SHDN
Input Voltage High
SHDN
Input Voltage Low
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 LT3470E is guaranteed to meet performance specifications
from 0°C to 85°C. Specifications over the –40°C to 85°C operating
temperature range are assured by design, characterization and
correlation with statistical process controls. The LT3470I specifications
I
SW
= 100mA
V
SHDN
= 2.5V
2.5
0.2
I
SW
= 100mA (TS8 Package)
I
SW
= 100mA (DD8 Package)
V
FB
= 0V
V
FB
= 0V
I
SH
= 100mA (TS8 Package)
I
SH
= 100mA (DD8 Package)
V
SW
= 10V
I
SH
= 30mA
V
SW
= 10V, V
BIAS
= 0V
●
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 10V, V
SHDN
= 10V, V
BOOST
= 15V, V
BIAS
= 3V unless otherwise specified.
CONDITIONS
●
●
MIN
TYP
0.1
10
35
0.1
25
0.1
MAX
4
0.5
18
50
0.5
60
1.5
1.265
80
150
225
0.01
1.5
300
435
775
2
775
2
2.2
12
5
UNITS
V
µA
µA
µA
µA
µA
µA
V
nA
nA
nA
%/V
ns
µA
mV
mV
mA
mA
mV
mV
µA
mV
µA
V
mA
µA
V
V
●
●
●
●
FB Comparator Trip Voltage
FB Pin Bias Current (Note 3)
1.228
1.250
35
35
35
0.0006
500
0.7
215
215
4V < V
IN
< 40V
250
325
225
630
630
0.2
650
0.2
1.7
7
1
are guaranteed over the –40°C to 125°C temperature range. LT3470H
specifications are guaranteed over –40°C to 150°C temperature range.
Note 3:
Bias current flows out of the FB pin.
Note 4:
This is the minimum voltage across the boost capacitor needed to
guarantee full saturation of the switch.
Note 5:
This parameter is assured by design and correlation with statistical
process controls.
3470fd
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LT3470
Typical perForMance characTerisTics
90
80
EFFICIENCY (%)
70
60
50
40
30
0.1
V
IN
= 24V
V
IN
= 36V
Efficiency, V
OUT
= 3.3V
L = TOKO D52LC 47µH
T
A
= 25°C
V
IN
= 12V
V
IN
= 7V
90
80
EFFICIENCY (%)
70
Efficiency, V
OUT
= 5V
L = TOKO D52LC 47µH
T
A
= 25°C
V
IN
= 12V
V
IN
= 36V
V
FB
(V)
1.250
1.260
V
FB
vs Temperature
1.255
V
IN
= 24V
60
50
1.245
40
30
0.1
1.240
–50
1
10
LOAD CURRENT (mA)
100
3470 G01
1
10
LOAD CURRENT (mA)
100
3470 G02
–25
75
0
25
50
TEMPERATURE (°C)
100
125
3470 G03
400
350
CURRENT LIMIT (mA)
Top and Bottom Switch Current
Limits (V
FB
= 0V) vs Temperature
V
IN
Quiescent Current
vs Temperature
50
30
25
BIAS CURRENT (µA)
BIAS < 3V
30
20
15
10
5
BIAS Quiescent Current
(Bias > 3V) vs Temperature
300
250
200
150
100
50
0
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
3470 G04
40
V
IN
CURRENT (µA)
20
BIAS > 3V
10
0
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
3470 G05
0
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
3470 G06
SHDN
Bias Current
vs Temperature
9
8
7
SHDN
CURRENT (µA)
FB CURRENT (nA)
V
SHDN
= 2.5V
6
5
4
3
2
1
0
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
3470 G07
FB Bias Current (V
FB
= 1V)
vs Temperature
60
50
40
30
20
10
0
–50 –25
V
SHDN
= 36V
0
25 50 75 100 125 150
TEMPERATURE (°C)
3470 G08
3470fd
4
LT3470
Typical perForMance characTerisTics
FB Bias Current (V
FB
= 0V)
vs Temperature
120
100
FB CURRENT (µA)
80
60
40
20
0
–50 –25
SWITCH V
CESAT
(mV)
300
250
SCHOTTKY V
F
(V)
200
150
100
50
0
–50 –25
Switch V
CESAT
(I
SW
= 100mA)
vs Temperature
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
25 50 75 100 125 150
TEMPERATURE (°C)
3470 G10
Boost Diode V
F
(I
F
= 50mA)
vs Temperature
0
25 50 75 100 125 150
TEMPERATURE (°C)
3470 G09
0
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
3470 G11
Catch Diode V
F
(I
F
= 100mA)
vs Temperature
0.7
SCHOTTKY DIODE LEAKAGE (µA)
0.6
0.5
0.4
0.3
0.2
0.1
0
–50 –25
60
55
50
45
40
35
30
25
20
15
10
5
0
25 50 75 100 125 150
TEMPERATURE (°C)
3470 G12
Diode Leakage (V
R
= 36V)
vs Temperature
CATCH
BOOST
SWITCH V
CESAT
(mV)
700
600
500
400
300
200
100
0
25 50 75 100 125 150
TEMPERATURE (°C)
3470 G13
Switch V
CESAT
SCHOTTKY V
F
(V)
0
–50 –25
0
0
100
300
SWITCH CURRENT (mA)
200
400
3470 G14
BOOST Pin Current
14
12
BOOST PIN CURRENT (mA)
10
8
6
4
2
0
0
100
300
SWITCH CURRENT (mA)
200
400
3470 G15
Catch Diode Forward Voltage
1.0
0.8
SCHOTTKY V
F
(V)
0.6
0.4
0.2
0
0
200
100
300
CATCH DIODE CURRENT (mA)
400
3470 G16
3470fd
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