LT3493-3
1.2A, 750kHz Step-Down
Switching Regulator in
2mm
×
3mm DFN
FEATURES
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DESCRIPTIO
Wide Input Range: 6.8V 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 2mm
×
3mm
DFN-6 Package
The LT
®
3493-3 is a current mode PWM step-down DC/DC
converter with an internal 1.75A power switch. The wide
operating input range of 6.8V to 36V (40V maximum) makes
the LT3493-3 ideal for regulating power from a wide vari-
ety of sources, including unregulated wall transformers,
24V industrial supplies and automotive batteries. Its high
operating frequency allows the use of tiny, low cost induc-
tors 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.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
ThinSOT is a trademark of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
APPLICATIO S
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Automotive Battery Regulation
Industrial Control Supplies
Wall Transformer Regulation
Distributed Supply Regulation
Battery-Powered Equipment
TYPICAL APPLICATIO
3.3V Step-Down Converter
90
V
IN
6.8V TO 36V
ON OFF
V
IN
SHDN
BOOST
LT3493-3
SW
0.1µF 10µH
32.4k
22pF
V
OUT
3.3V
1.2A, V
IN
> 12V
1.1A, V
IN
> 8V
EFFICIENCY (%)
85
80
75
70
65
60
GND
FB
10µF
10k
1µF
3493-3 TA01a
55
50
0
U
Efficiency
V
IN
= 12V
V
OUT
= 3.3V
L = 10µH
0.2
0.8
0.4
0.6
LOAD CURRENT (A)
1.0
1.2
3493-3 TA01b
U
U
3493-3f
1
LT3493-3
ABSOLUTE
(Note 1)
AXI U
RATI GS
PACKAGE/ORDER I FOR ATIO
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-3 ........................................... –40°C to 85°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 PART NUMBER
LT3493EDCB-3
DCB PART MARKING
LCGJ
Order Options
Tape and Reel: Add #TR Lead Free: Add #PBF
Lead Free Tape and Reel: Add #TRPBF
Lead Free Part Marking:
http://www.linear.com/leadfree/
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
The
●
denotes 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
(Note 4)
Not Switching
V
SHDN
= 0V
V
IN
= 6.8V to 36V
V
FB
= 0.7V
V
FB
= 0V
●
●
●
CONDITIONS
MIN
6.8
6.2
765
TYP
6.5
780
50
1.9
0.01
0.007
MAX
36
6.8
795
150
2.5
2
815
UNITS
V
V
mV
nA
mA
µA
%/V
kHz
kHz
%
%
685
88
91
750
36
95
95
2
U
3493-3f
W
U
U
W W
W
LT3493-3
ELECTRICAL CHARACTERISTICS
The
●
denotes 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
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-3 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.
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 PERFOR A CE 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
U W
T
A
= 25°C unless otherwise noted.
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
3493-3 G01
3493-3 G02
3493-3f
3
LT3493-3
TYPICAL PERFOR A CE CHARACTERISTICS
Maximum Load Current,
V
OUT
= 5V, L = 8.2µH
1.60
1.50
TYPICAL
1.60
1.50
TYPICAL
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
1.40
1.30
1.20
MINIMUM
1.10
1.00
0.90
8
12
16
20
V
IN
(V)
24
28
3493-3 G04
1.40
1.30
1.20
1.10
1.00
0.90
8
12
16
20
V
IN
(V)
24
28
3493-3 G22
OUTPUT CURRENT (A)
Maximum Load Current,
V
OUT
= 3.3V, L = 10µH
1.60
1.50
TYPICAL
OUTPUT CURRENT (A)
1.40
V
CE(SW)
(mV)
1.30
MINIMUM
1.20
1.10
1.00
0.90
5
10
15
20
V
IN
(V)
3493-3 G21
300
250
200
150
100
50
0
T
A
= –40°C
UVLO (V)
Switching Frequency
800
780
SWITCHING FREQUENCY (kHz)
600
500
400
300
200
100
0
SWITCH CURRENT LIMIT (A)
760
FREQUENCY (kHz)
740
720
700
680
660
640
620
600
–50
–25
0
25
50
TEMPERATURE (°C)
75
100
3493-3 G09
4
U W
25
T
A
= 25°C unless otherwise noted.
Maximum Load Current,
V
OUT
= 3.3V, L = 4.7µH
1.60
1.50
TYPICAL
1.40
1.30
1.20
MINIMUM
1.10
1.00
0.90
5
10
15
20
V
IN
(V)
3493-3 G05
Maximum Load Current,
V
OUT
= 5V, L = 33µH
MINIMUM
25
30
Switch Voltage Drop
550
500
450
400
350
T
A
= 85°C
T
A
= 25°C
7.0
6.9
6.8
6.7
6.6
6.5
6.4
6.3
6.2
6.1
Undervoltage Lockout
30
0
0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8
SWITCH CURRENT (A)
3493-3 G06
6.0
–50
–25
0
25
50
TEMPERATURE (°C)
75
100
3493-3 G07
Frequency Foldback
800
700
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
Soft-Start
0
100 200 300 400 500 600 700 800
FEEDBACK VOLTAGE (mV)
3493-3 G11
0
0.25 0.50 0.75 1 1.25 1.50 1.75
SHDN PIN VOLTAGE (V)
2
3493-3 G13
3493-3f
LT3493-3
TYPICAL PERFOR A CE CHARACTERISTICS
SHDN Pin Current
50
45
SWITCH CURRENT LIMIT (A)
35
1.7
1.6
1.5
1.4
1.3
1.2
1.1
SWITCH CURRENT LIMIT (A)
40
I
SHDN
(µA)
30
25
20
15
10
5
0
0
2
4
6
8 10 12 14 16 18 20
V
SHDN
(V)
3493-3 G14
Operating Waveforms
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
3493-3 G19
U W
T
A
= 25°C unless otherwise noted.
Switch Current Limit
2.0
1.9
1.8
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
Switch Current Limit
1.0
–50
–25
0
25
50
TEMPERATURE (°C)
75
100
0
0
20
60
40
DUTY CYCLE (%)
80
100
3493-3 G18
3493-3 G17
Operating Waveforms,
Discontinuous Mode
V
SW
5V/DIV
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
3493-3 G20
3493-3f
5
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