LT3493
1.2A, 750kHz Step-Down
Switching Regulator in
2mm
×
3mm DFN
FEATURES
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DESCRIPTION
The LT
®
3493 is a current mode PWM step-down DC/DC
converter with an internal 1.75A power switch. The wide
operating input range of 3.6V to 36V (40V maximum)
makes the LT3493 ideal for regulating power from a wide
variety of sources, including unregulated wall transform-
ers, 24V industrial supplies and automotive batteries.
Its high operating frequency allows the use of tiny, low
cost inductors and ceramic capacitors, resulting in low,
predictable output ripple.
Cycle-by-cycle current limit provides protection against
shorted outputs and soft-start eliminates input current
surge during start-up. The low current (<2μA) shutdown
mode provides output disconnect, enabling easy power
management in battery-powered systems.
L,
LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
Wide Input Range: 3.6V to 36V Operating,
40V Maximum
1.2A Output Current
Fixed Frequency Operation: 750kHz
Output Adjustable Down to 780mV
Short-Circuit Robust
Uses Tiny Capacitors and Inductors
Soft-Start
Internally Compensated
Low Shutdown Current: <2μA
Low V
CESAT
Switch: 330mV at 1A
Thermally Enhanced, Low Profile DFN Package
APPLICATIONS
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Automotive Battery Regulation
Industrial Control Supplies
Wall Transformer Regulation
Distributed Supply Regulation
Battery-Powered Equipment
TYPICAL APPLICATION
Efficiency
3.3V Step-Down Converter
V
IN
4.2V TO 36V
ON OFF
V
IN
SHDN
BOOST
LT3493
SW
32.4k
GND
1μF
FB
10k
22pF
10μF
0.1μF 10μH
V
OUT
3.3V
1.2A, V
IN
> 12V
0.95A, V
IN
> 5V
90
85
80
EFFICIENCY (%)
75
70
65
60
55
3493 TA01a
V
IN
= 12V
V
OUT
= 3.3V
L = 10μH
0
0.2
0.8
0.4
0.6
LOAD CURRENT (A)
1.0
1.2
50
3493 TA01b
3493fb
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LT3493
ABSOLUTE MAXIMUM RATINGS
(Note 1)
PIN CONFIGURATION
TOP VIEW
FB 1
GND 2
BOOST 3
7
6
SHDN
5 V
IN
4 SW
Input Voltage (V
IN
) ....................................................40V
BOOST Pin Voltage ..................................................50V
BOOST Pin Above SW Pin.........................................25V
SHDN
Pin ..................................................................40V
FB Voltage ...................................................................6V
Operating Temperature Range (Note 2)
LT3493E .............................................. –40°C to 85°C
LT3493I ............................................. –40°C to 125°C
Maximum Junction Temperature .......................... 125°C
Storage Temperature Range................... –65°C to 150°C
DCB PACKAGE
6-LEAD (2mm 3mm) PLASTIC DFN
T
JMAX
= 125°C,
θ
JA
= 64°C/W
EXPOSED PAD (PIN 7) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
LT3493EDCB#PBF
LT3493IDCB#PBF
LEAD BASED FINISH
LT3493EDCB
LT3493IDCB
TAPE AND REEL
LT3493EDCB#TRPBF
LT3493IDCB#TRPBF
TAPE AND REEL
LT3493EDCB#TR
LT3493IDCB#TR
PART MARKING
LCGG
LCGH
PART MARKING
LCGG
LCGH
PACKAGE DESCRIPTION
6-Lead (2mm
×
3mm) Plastic DFN
6-Lead (2mm
×
3mm) Plastic DFN
PACKAGE DESCRIPTION
6-Lead (2mm
×
3mm) Plastic DFN
6-Lead (2mm
×
3mm) Plastic DFN
TEMPERATURE RANGE
–40°C to 85°C
–40°C to 125°C
TEMPERATURE RANGE
–40°C to 85°C
–40°C to 125°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/
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 12V, V
BOOST
= 17V, unless otherwise noted. (Note 2)
PARAMETER
V
IN
Operating Range
Undervoltage Lockout
Feedback Voltage
FB Pin Bias Current
Quiescent Current
Quiescent Current in Shutdown
Reference Line Regulation
Switching Frequency
Maximum Duty Cycle
T
A
= 25°C
V
FB
= Measured V
REF
+ 10mV (Note 4)
Not Switching
V
SHDN
= 0V
V
IN
= 5V to 36V
V
FB
= 0.7V
V
FB
= 0V
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ELECTRICAL CHARACTERISTICS
CONDITIONS
MIN
3.6
3.1
765
TYP
3.4
780
50
1.9
0.01
0.007
MAX
36
3.6
795
150
2.5
2
815
UNITS
V
V
mV
nA
mA
μA
%/V
kHz
kHz
%
%
685
88
91
750
36
95
95
3493fb
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LT3493
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 12V, V
BOOST
= 17V, unless otherwise noted. (Note 2)
PARAMETER
Switch Current Limit
Switch V
CESAT
Switch Leakage Current
Minimum Boost Voltage Above Switch
BOOST Pin Current
SHDN
Input Voltage High
SHDN
Input Voltage Low
SHDN
Bias Current
V
SHDN
= 2.3V (Note 5)
V
SHDN
= 0V
6
0.01
I
SW
= 1A
I
SW
= 1A
2.3
0.3
15
0.1
1.85
30
CONDITIONS
(Note 3)
I
SW
= 1A
MIN
1.4
TYP
1.75
330
2
2.2
50
MAX
2.2
UNITS
A
mV
μA
V
mA
V
V
μA
μA
ELECTRICAL CHARACTERISTICS
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 LT3493E 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 LT3493I specifications are
guaranteed over the –40°C to 125°C temperature range.
Note 3:
Current limit guaranteed by design and/or correlation to static test.
Slope compensation reduces current limit at higher duty cycle.
Note 4:
Current flows out of pin.
Note 5:
Current flows into pin.
TYPICAL PERFORMANCE CHARACTERISTICS
Efficiency (V
OUT
= 5V, L = 10μH)
95
90
85
EFFICIENCY (%)
EFFICIENCY (%)
80
75
70
65
60
55
50
0
0.2
0.4
0.6
0.8
LOAD CURRENT (A)
V
IN
= 8V
V
IN
= 12V
V
IN
= 24V
1.0
1.2
3493 G01
T
A
= 25°C unless otherwise noted.
Efficiency (V
OUT
= 1.8V, L = 4.7μH)
80
75
70
65
60
55
50
0
0.2
0.4
0.6
0.8
LOAD CURRENT (A)
Efficiency (V
OUT
= 3.3V, L = 10μH)
90
85
80
75
70
65
60
55
50
0
0.2
0.4
0.6
0.8
LOAD CURRENT (A)
V
IN
= 8V
V
IN
= 12V
V
IN
= 24V
1.0
1.2
3493 G02
EFFICIENCY (%)
V
IN
= 5V
V
IN
= 12V
1.0
1.2
3493 G03
3493fb
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LT3493
TYPICAL PERFORMANCE CHARACTERISTICS
Maximum Load Current,
V
OUT
= 5V, L = 8.2μH
1.60
1.50
TYPICAL
OUTPUT CURRENT (A)
1.40
1.30
1.20
MINIMUM
1.10
1.00
0.90
8
12
16
20
V
IN
(V)
OUTPUT CURRENT (A)
1.40
1.30
1.20
1.10
1.00
0.90
8
12
16
20
V
IN
(V)
MINIMUM
1.60
1.50
TYPICAL
OUTPUT CURRENT (A)
1.40
1.30
1.20
MINIMUM
1.10
1.00
0.90
24
28
3493 G22
T
A
= 25°C unless otherwise noted.
Maximum Load Current,
V
OUT
= 3.3V, L = 4.7μH
1.60
1.50
TYPICAL
Maximum Load Current,
V
OUT
= 5V, L = 33μH
24
28
3493 G04
5
10
15
20
V
IN
(V)
25
30
3493 G05
Maximum Load Current,
V
OUT
= 3.3V, L = 10μH
1.60
1.50
OUTPUT CURRENT (A)
TYPICAL
1.40
V
CE(SW)
(mV)
1.30
MINIMUM
1.20
1.10
1.00
0.90
5
10
15
20
V
IN
(V)
3493 G21
Switch Voltage Drop
550
500
450
400
350
300
250
200
150
100
50
0
25
30
0
0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8
SWITCH CURRENT (A)
3493 G06
Undervoltage Lockout
4.00
3.90
T
A
= 85°C
T
A
= 25°C
T
A
= –40°C
UVLO (V)
3.80
3.70
3.60
3.50
3.40
3.30
3.20
3.10
3.00
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
3493 G08
Switching Frequency
800
780
SWITCHING FREQUENCY (kHz)
760
FREQUENCY (kHz)
740
720
700
680
660
640
620
600
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
3493 G09
Frequency Foldback
800
700
600
500
400
300
200
100
0
0
100 200 300 400 500 600 700 800
FEEDBACK VOLTAGE (mV)
3493 G11
Soft-Start
2.0
1.8
SWITCH CURRENT LIMIT (A)
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
0
0.25 0.50 0.75 1 1.25 1.50 1.75
SHDN
PIN VOLTAGE (V)
2
3493 G13
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LT3493
TYPICAL PERFORMANCE CHARACTERISTICS
SHDN
Pin Current
50
45
40
35
I
SHDN
(μA)
V
IN
(V)
V
IN
(V)
30
25
20
15
10
5
0
0
2
4
6
8 10 12 14 16 18 20
V
SHDN
(V)
3493 G14
T
A
= 25°C unless otherwise noted.
Typical Minimum Input Voltage
(V
OUT
= 3.3V)
5.5
5.3
5.1
4.9
TO START
Typical Minimum Input Voltage
(V
OUT
= 5V)
7.5
TO START
7.0
6.5
4.7
4.5
4.3
6.0
TO RUN
5.5
4.1
3.9
3.7
TO RUN
5.0
1
10
I
OUT
(mA)
3493 G15
3.5
100
1000
1
10
I
OUT
(mA)
3493 G16
100
1000
Switch Current Limit
2.0
1.9
SWITCH CURRENT LIMIT (A)
SWITCH CURRENT LIMIT (A)
1.8
1.7
1.6
1.5
1.4
1.3
1.2
1.1
1.0
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
3493 G17
Switch Current Limit
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
0
20
60
40
DUTY CYCLE (%)
80
100
3493 G18
Operating Waveforms
Operating Waveforms,
Discontinuous Mode
V
SW
5V/DIV
V
SW
5V/DIV
I
L
0.5A/DIV
0
V
OUT
20mV/DIV
V
IN
= 12V
V
OUT
= 3.3V
I
OUT
= 0.5A
L = 10μH
C
OUT
= 10μF
1μs/DIV
3493 G19
I
L
0.5A/DIV
0
V
OUT
20mV/DIV
V
IN
= 12V
V
OUT
= 3.3V
I
OUT
= 50mA
L = 10μH
C
OUT
= 10μF
1μs/DIV
3493 G20
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