1
LT3470
3470f
Automotive Battery Regulation
Power for Portable Products
Distributed Supply Regulation
Industrial Supplies
Wall Transformer Regulation
Micropower Buck Regulator
with Integrated Boost and
Catch Diodes
Low Quiescent Current: 26
A at 12V
IN
to 3.3V
OUT
Integrated Boost and Catch Diodes
Input Range: 4V to 40V
Low Output Ripple: <10mV
< 1A 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 (1mm) ThinSOT Package
Efficiency and Power Loss vs Load Current
Burst Mode is a registered trademark of Linear Technology Corporation.
ThinSOT is a trademark of Linear Technology Corporation.
FEATURES
DESCRIPTIO
U
APPLICATIO S
U
TYPICAL APPLICATIO
U
The LT
3470 is a micropower step-down DC/DC converter
that integrates a 300mA power switch, catch diode and
boost diode into a low profile (1mm) ThinSOT
TM
package.
The LT3470 combines Burst Mode and continuous opera-
tion 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 26A
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.
LOAD CURRENT (mA)
30
EFFICIENCY (%)
POWER LOSS (mW)
40
60
80
90
0.1
10
100
3470 TA02
20
1
70
50
10
1
1000
100
10
0.1
V
IN
= 12V
V
IN
BOOST
LT3470
SW
SHDN
0.22F
22pF
22F
2.2F
V
IN
7V TO 40V
V
OUT
5V
200mA
604k
1%
200k
1%
33H
BIAS
FB
GND
OFF ON
, LTC and LT are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
2
LT3470
3470f
(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 ......................... 125C
Operating Temperature Range (Note 2) .. 40C to 85C
Storage Temperature Range ................. 65C to 150C
Lead Temperature (Soldering, 10 sec).................. 300C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ABSOLUTE AXI U RATI GS
W
W
W
U
PACKAGE/ORDER I FOR ATIO
U
U
W
SHDN 1
NC 2
V
IN
3
GND 4
8 FB
7 BIAS
6 BOOST
5 SW
TOP VIEW
TS8 PACKAGE
8-LEAD PLASTIC TSOT-23
ORDER PART
NUMBER
TS8 PART MARKING
T
JMAX
= 125C,
JA
= 140C/ W
LT3470ETS8
LT3470ITS8
LTBDM
LTBPW
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Minimum Input Voltage
4
V
Quiescent Current from V
IN
V
SHDN
= 0.2V
0.1
0.5
A
V
BIAS
= 3V, Not Switching
10
18
A
V
BIAS
= 0V, Not Switching
35
50
A
Quiescent Current from Bias
V
SHDN
= 0.2V
0.1
0.5
A
V
BIAS
= 3V, Not Switching
25
60
A
V
BIAS
= 0V, Not Switching
0.1
1.5
A
FB Comparator Trip Voltage
V
FB
Falling
1.228
1.250
1.265
V
FB Pin Bias Current (Note 3)
V
FB
= 1V
35
80
nA
35
150
nA
FB Voltage Line Regulation
4V < V
IN
< 40V
0.0006
0.01
%/V
Minimum Switch Off-Time (Note 5)
500
ns
Switch Leakage Current
0.7
1.5
A
Switch V
CESAT
I
SW
= 100mA
215
300
mV
Switch Top Current Limit
V
FB
= 0V
250
325
435
mA
Switch Bottom Current Limit
V
FB
= 0V
225
mA
The
denotes specifications which apply over the full operating temperature range, otherwise specifications are T
A
= 25C.
V
IN
= 10V, V
SHDN
= 10V, V
BOOST
= 15V, V
BIAS
= 3V unless otherwise specified.
ELECTRICAL CHARACTERISTICS
3
LT3470
3470f
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: The LT3470E is guaranteed to meet performance specifications
from 0C to 70C. Specifications over the 40C to 85C operating
temperature range are assured by design, characterization and correlation
with statistical process controls. The LT3470I specifications are
guaranteed over the 40C to 125C temperature range.
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Catch Schottky Drop
I
SH
= 100mA
630
775
mV
Catch Schottky Reverse Leakage
V
SW
= 10V
0.2
2
A
Boost Schottky Drop
I
SH
= 30mA
650
775
mV
Boost Schottky Reverse Leakage
V
SW
= 10V, V
BIAS
= 0V
0.2
2
A
Minimum Boost Voltage (Note 4)
1.7
2.2
V
BOOST Pin Current
I
SW
= 100mA
7
12
mA
SHDN Pin Current
V
SHDN
= 2.5V
1
5
A
SHDN Input Voltage High
2.5
V
SHDN Input Voltage Low
0.2
V
The
denotes specifications which apply over the full operating temperature range, otherwise specifications are T
A
= 25C.
V
IN
= 10V, V
SHDN
= 10V, V
BOOST
= 15V, V
BIAS
= 3V unless otherwise specified.
ELECTRICAL CHARACTERISTICS
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.
TYPICAL PERFOR A CE CHARACTERISTICS
U
W
Efficiency, V
OUT
= 5V
Efficiency, V
OUT
= 3.3V
V
FB
vs Temperature
LOAD CURRENT (mA)
50
EFFICIENCY (%)
70
90
40
60
80
0.1
10
100
3470 G01
30
1
L = TOKO D52LC 47H
T
A
= 25C
V
IN
= 7V
V
IN
= 12V
V
IN
= 36V
V
IN
= 24V
LOAD CURRENT (mA)
50
EFFICIENCY (%)
70
90
40
60
80
0.1
10
100
3470 G02
30
1
L = TOKO D52LC 47H
T
A
= 25C
V
IN
= 12V
V
IN
= 36V
V
IN
= 24V
TEMPERATURE (C)
50
1.240
V
FB
(V)
1.245
1.250
1.255
1.260
25
0
25
50
3470 G03
75
100
125
4
LT3470
3470f
TYPICAL PERFOR A CE CHARACTERISTICS
U
W
V
IN
Quiescent Current
vs Temperature
BIAS Quiescent Current
(Bias > 3V) vs Temperature
SHDN Bias Current
vs Temperature
FB Bias Current (V
FB
= 1V)
vs Temperature
Top and Bottom Switch Current
Limits (V
FB
= 0V) vs Temperature
TEMPERATURE (C)
50
CURRENT LIMIT (mA)
350
25
3470 G04
200
100
25
0
50
50
0
400
300
250
150
75
100
125
TEMPERATURE (C)
50
25
0
V
IN
CURRENT (
A)
20
50
0
50
75
3470 G05
10
40
30
25
100
125
BIAS < 3V
BIAS > 3V
TEMPERATURE (C)
50
BIAS CURRENT (
A)
20
25
30
25
75
3470 G06
15
10
25
0
50
100
125
5
0
TEMPERATURE (C)
50
0
SHDN CURRENT (
A)
1
3
4
5
50
9
3470 G07
2
0
25
75
100
25
125
6
7
8
V
SHDN
= 36V
V
SHDN
= 2.5V
TEMPERATURE (C)
50
25
0
FB CURRENT (nA)
20
50
0
50
75
3470 G08
10
40
30
25
100
125
FB Bias Current (V
FB
= 0V)
vs Temperature
TEMPERATURE (C)
50
FB CURRENT (
A)
80
100
120
25
75
3470 G09
60
40
25
0
50
100
125
20
0
Switch V
CESAT
(I
SW
= 100mA)
vs Temperature
Boost Diode V
F
(I
F
= 50mA)
vs Temperature
TEMPERATURE (C)
50
SWITCH V
CESAT
(mV)
200
250
300
25
75
3470 G10
150
100
25
0
50
100
125
50
0
TEMPERATURE (C)
50
SCHOTTKY V
F
(V)
0.7
25
3470 G11
0.4
0.2
25
0
50
0.1
0
0.8
0.6
0.5
0.3
75
100
125
Catch Diode V
F
(I
F
= 100mA)
vs Temperature
TEMPERATURE (C)
50
0.4
0.5
0.7
25
75
3470 G12
0.3
0.2
25
0
50
100
125
0.1
0
0.6
SCHOTTKY V
F
(V)
5
LT3470
3470f
TYPICAL PERFOR A CE CHARACTERISTICS
U
W
Switch V
CESAT
BOOST Pin Current
Catch Diode Forward Voltage
Boost Diode Forward Voltage
Diode Leakage (V
R
= 36V)
vs Temperature
Minimum Input Voltage, V
OUT
= 3.3V
Minimum Input Voltage, V
OUT
= 5V
TEMPERATURE (C)
50
25
0
SCHOTTKY DIODE LEAKAGE (
A)
10
25
0
50
75
3470 G13
5
20
15
25
100
125
BOOST
CATCH
SWITCH CURRENT (mA)
0
400
500
700
300
3470 G14
300
200
100
200
400
100
0
600
SWITCH V
CESAT
(mV)
SWITCH CURRENT (mA)
0
8
10
14
300
3470 G15
6
4
100
200
400
2
0
12
BOOST PIN CURRENT (mA)
CATCH DIODE CURRENT (mA)
0
SCHOTTKY V
F
(V)
0.4
0.6
400
3470 G16
0.2
0
100
200
300
1.0
0.8
BOOST DIODE CURRENT (mA)
0
SCHOTTKY V
F
(V)
500
600
700
200
3470 G17
400
300
0
50
100
150
100
200
900
800
LOAD CURRENT (mA)
0
3.0
INPUT VOLTAGE (V)
3.5
4.0
4.5
5.0
5.5
6.0
50
100
150
200
3470 G18
T
A
= 25C
V
IN
TO START
V
IN
TO RUN
LOAD CURRENT (mA)
0
INPUT VOLTAGE (V)
6
7
200
3470 G19
5
4
50
100
150
8
T
A
= 25C
V
IN
TO START
V
IN
TO RUN
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