LT3470
Micropower Buck Regulator
with Integrated Boost and
Catch Diodes
FEATURES
■
■
■
■
■
■
■
■
DESCRIPTIO
■
■
Low Quiescent Current: 26
µ
A 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 x 2mm Thermally
Enhanced 8-Lead DD and 1mm ThinSOT Packages
The LT
®
3470 is a micropower step-down DC/DC converter
that integrates a 300mA power switch, catch diode
and boost diode into low profile 3mm x 2mm DD and
ThinSOT
TM
packages. The LT3470 combines Burst Mode
and continuous operation to allow the use of tiny inductor
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, simpli-
fying power management in battery-powered systems.
Fast current limiting and hysteretic control protects the
LT3470 and external components against shorted out-
puts, even at 40V input.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
Burst Mode is a registered trademark of Linear Technology Corporation. ThinSOT is a
trademark of Linear Technology Corporation. All other trademarks are the property of their
respective owners.
APPLICATIO S
■
■
■
■
■
Automotive Battery Regulation
Power for Portable Products
Distributed Supply Regulation
Industrial Supplies
Wall Transformer Regulation
TYPICAL APPLICATIO
V
IN
7V TO 40V
V
IN
OFF ON
SHDN
BOOST
Efficiency and Power Loss vs Load Current
90
V
IN
= 12V
1000
0.22µF
LT3470
SW
BIAS
22pF
2.2µF
FB
GND
200k
1%
604k
1%
22µF
33µH
V
OUT
5V
200mA
80
70
100
EFFICIENCY (%)
60
50
40
30
20
10
0.1
0.1
1
10
LOAD CURRENT (mA)
100
3470 TA02
U
POWER LOSS (mW)
10
1
3470fc
U
U
1
LT3470
ABSOLUTE
AXI U
RATI GS
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
PI CO FIGURATIO
TOP VIEW
FB 1
BIAS 2
BOOST 3
SW 4
9
8
7
6
5
SHDN
NC
V
IN
GND
DDB8 PACKAGE
8-LEAD (3mm
×
2mm) PLASTIC DFN
θ
JA
= 80°C/ W
EXPOSED PAD (PIN 9) IS GROUND (MUST BE SOLDERED TO PCB)
ORDER I FOR ATIO
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
LT3470EDDB#TR
LT3470EDDB#TR
LT3470ETS8#TR
LT3470ITS8#TR
LT3470HTS8#TR
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/
3470fc
2
U
U
W W
U
W
W
(Note 1)
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
U
U
U
TOP VIEW
SHDN 1
NC 2
V
IN
3
GND 4
8 FB
7 BIAS
6 BOOST
5 SW
TS8 PACKAGE
8-LEAD PLASTIC TSOT-23
θ
JA
= 140°C/ W
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
LT3470
ELECTRICAL CHARACTERISTICS
The
●
denotes specifications which apply over the full operating temperature range, otherwise specifications are T
A
= 25°C.
V
IN
= 10V, V
SHDN
= 10V, V
BOOST
= 15V, V
BIAS
= 3V unless otherwise specified.
PARAMETER
Minimum Input Voltage
Quiescent Current from V
IN
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
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
●
●
●
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
Quiescent Current from Bias
●
●
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
with statistical process controls. The LT3470I specifications 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.
3470fc
3
LT3470
TYPICAL PERFOR A CE CHARACTERISTICS
Efficiency, V
OUT
= 3.3V
90
80
L = TOKO D52LC 47µH
T
A
= 25°C
V
IN
= 12V
V
IN
= 7V
90
80
L = TOKO D52LC 47µH
T
A
= 25°C
V
IN
= 12V
EFFICIENCY (%)
EFFICIENCY (%)
70
V
IN
= 24V
60
50
40
30
0.1
V
IN
= 36V
V
FB
(V)
10
1
LOAD CURRENT (mA)
Top and Bottom Switch Current
Limits (V
FB
= 0V) vs Temperature
400
350
CURRENT LIMIT (mA)
BIAS CURRENT (µA)
300
V
IN
CURRENT (µA)
250
200
150
100
50
0
– 50 – 25
0
25 50 75 100 125 150
TEMPERATURE (°C)
3470 G04
SHDN Bias Current
vs Temperature
9
8
7
V
SHDN
= 36V
SHDN CURRENT (µA)
FB CURRENT (nA)
6
5
4
3
2
V
SHDN
= 2.5V
1
0
–50
–25
0
25
50
75 100 125 150
TEMPERATURE (°C)
3470 G07
4
U W
100
3470 G01
Efficiency, V
OUT
= 5V
1.260
V
FB
vs Temperature
1.255
70
V
IN
= 24V
60
50
V
IN
= 36V
1.250
1.245
40
30
0.1
10
1
LOAD CURRENT (mA)
100
3470 G02
1.240
–50
–25
75
0
25
50
TEMPERATURE (°C)
100
125
3470 G03
V
IN
Quiescent Current
vs Temperature
50
30
25
BIAS Quiescent Current
(Bias > 3V) vs Temperature
40
BIAS < 3V
30
20
15
10
5
0
–50
–25
20
BIAS > 3V
10
0
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
3470 G05
0
25
50
75
100 125 150
TEMPERATURE (°C)
3470 G06
FB Bias Current (V
FB
= 1V)
vs Temperature
60
50
40
30
20
10
0
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
3470 G08
3470fc
LT3470
TYPICAL PERFOR A CE CHARACTERISTICS
FB Bias Current (V
FB
= 0V)
vs Temperature
120
100
SWITCH V
CESAT
(mV)
FB CURRENT (µA)
80
60
40
20
0
–50 –25
200
150
100
50
0
–50 –25
SCHOTTKY V
F
(V)
0
25 50 75 100 125 150
TEMPERATURE (°C)
3470 G10
0
25 50 75 100 125 150
TEMPERATURE (°C)
3470 G09
Catch Diode V
F
(I
F
= 100mA)
vs Temperature
0.7
SCHOTTKY DIODE LEAKAGE (µA)
0.6
0.5
0.4
40
35
30
25
20
15
10
5
0
–50 –25
SWITCH V
CESAT
(mV)
SCHOTTKY V
F
(V)
0.3
0.2
0.1
0
–50
–25
0
25
50
75
100 125 150
TEMPERATURE (°C)
3470 G12
BOOST Pin Current
14
12
BOOST PIN CURRENT (mA)
SCHOTTKY V
F
(V)
10
8
6
4
2
0
0
100
300
SWITCH CURRENT (mA)
200
400
3470 G15
U W
Switch V
CESAT
(I
SW
= 100mA)
vs Temperature
300
250
Boost Diode V
F
(I
F
= 50mA)
vs Temperature
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
– 50 – 25
0
25 50 75 100 125 150
TEMPERATURE (°C)
3470 G11
Diode Leakage (V
R
= 36V)
vs Temperature
60
55
50
45
CATCH
BOOST
700
600
500
400
300
200
100
0
Switch V
CESAT
0
25 50 75 100 125 150
TEMPERATURE (°C)
3470 G13
0
100
300
SWITCH CURRENT (mA)
200
400
3470 G14
Catch Diode Forward Voltage
1.0
0.8
0.6
0.4
0.2
0
0
200
300
100
CATCH DIODE CURRENT (mA)
400
3470 G16
3470fc
5
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