FEATURES
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LT1933
600mA, 500kHz Step-Down
Switching Regulator in SOT-
23 and DFN Packages
DESCRIPTION
The LT
®
1933 is a current mode PWM step-down DC/DC
converter with an internal 0.75A power switch, packaged
in a tiny 6-lead SOT-23. The wide input range of 3.6V
to 36V makes the LT1933 suitable for regulating power
from a wide variety of sources, including unregulated wall
transformers, 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
provides output disconnect, enabling easy power manage-
ment in battery-powered systems.
L,
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.
Wide Input Range: 3.6V to 36V
5V at 600mA from 16V to 36V Input
3.3V at 600mA from 12V to 36V Input
5V at 500mA from 6.3V to 36V Input
3.3V at 500mA from 4.5V to 36V Input
Fixed Frequency 500kHz Operation
Uses Tiny Capacitors and Inductors
Soft-Start
Internally Compensated
Low Shutdown Current: <2μA
Output Adjustable Down to 1.25V
Low Profile (1mm) SOT-23 (ThinSOT™) and
(2mm x 3mm x 0.75mm) 6-Pin DFN Packages
APPLICATIONS
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Automotive Battery Regulation
Industrial Control Supplies
Wall Transformer Regulation
Distributed Supply Regulation
Battery-Powered Equipment
TYPICAL APPLICATION
3.3V Step-Down Converter
95
V
IN
4.5V TO 36V
1N4148
V
IN
BOOST
LT1933
OFF ON
SHDN
GND
SW
FB
16.5k
2.2μF
10k
MBRM140
0.1μF
22μH
90
V
OUT
3.3V/500mA
EFFICIENCY (%)
85
V
OUT
= 3.3V
80
75
70
1933 TA01a
Efficiency
V
IN
= 12V
V
OUT
= 5V
22μF
65
0
100
200
300
400
LOAD CURRENT (mA)
500
600
1933 TA01b
1933fd
1
LT1933
ABSOLUTE MAXIMUM RATINGS
(Note 1)
Input Voltage (V
IN
) .....................................– 0.4V to 36V
BOOST Pin Voltage ..................................................43V
BOOST Pin Above SW Pin.........................................20V
SHDN
Pin ................................................... –0.4V to 36V
FB Voltage .................................................... –0.4V to 6V
Operating Temperature Range (Note 2)
LT1933E .................................................. –40°C to 85°C
LT1933I ................................................. –40°C to 125°C
LT1933H................................................. –40°C to 150°C
Maximum Junction Temperature
LT1933E, LT1933I ................................................ 125°C
LT1933H................................................................ 150°C
Storage Temperature Range................... –65°C to 150°C
Lead Temperature, S6 Package
(Soldering, 10 sec) ........................................... 300°C
PIN CONFIGURATION
TOP VIEW
TOP VIEW
BOOST 1
V
IN
2
SW 3
7
6 FB
5 GND
4
SHDN
BOOST 1
GND 2
FB 3
6 SW
5 V
IN
4
SHDN
DCB PACKAGE
6-LEAD (2mm
×
3mm) PLASTIC DFN
θ
JA
= 73.5°C/W,
θ
JC
= 12°C/W
EXPOSED PAD (PIN 7) IS GND, MUST BE SOLDERED TO PCB
S6 PACKAGE
6-LEAD PLASTIC TSOT-23
θ
JA
= 165°C/W,
θ
JC
= 102°C/W
ORDER INFORMATION
LEAD FREE FINISH
LT1933IDCB#PBF
LT1933HDCB#PBF
LT1933ES6#PBF
LT1933IS6#PBF
LT1933HS6#PBF
LEAD BASED FINISH
LT1933IDCB
LT1933HDCB
LT1933ES6
LT1933IS6
LT1933HS6
TAPE AND REEL
LT1933IDCB#TRPBF
LT1933HDCB#TRPBF
LT1933ES6#TRPBF
LT1933IS6#TRPBF
LT1933HS6#TRPBF
TAPE AND REEL
LT1933IDCB#TR
LT1933HDCB#TR
LT1933ES6#TR
LT1933IS6#TR
LT1933HS6#TR
PART MARKING
LCGM
LCGN
LTAGN
LTAGP
LTDDQ
PART MARKING
LCGM
LCGN
LTAGN
LTAGP
LTDDQ
PACKAGE DESCRIPTION
6-Lead (2mm
×
3mm) Plastic DFN
6-Lead (2mm
×
3mm) Plastic DFN
6-Lead Plastic TSOT-23
6-Lead Plastic TSOT-23
6-Lead Plastic TSOT-23
PACKAGE DESCRIPTION
6-Lead (2mm
×
3mm) Plastic DFN
6-Lead (2mm
×
3mm) Plastic DFN
6-Lead Plastic TSOT-23
6-Lead Plastic TSOT-23
6-Lead Plastic TSOT-23
TEMPERATURE RANGE
–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 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/
1933fd
2
LT1933
ELECTRICAL CHARACTERISTICS
PARAMETER
Undervoltage Lockout
Feedback Voltage
FB Pin Bias Current
Quiescent Current
Quiescent Current in Shutdown
Reference Line Regulation
Switching Frequency
Maximum Duty Cycle
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
34
0.01
I
SW
= 400mA
I
SW
= 400mA
2.3
0.3
50
0.1
1.9
18
(Note 3)
I
SW
= 400mA, S6 Package
I
SW
= 400mA, DCB6 Package
V
FB
= Measured V
REF
+ 10mV (Note 4)
Not Switching
V
SHDN
= 0V
V
IN
= 5V to 36V
V
FB
= 1.1V
V
FB
= 0V
l
l
l
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)
CONDITIONS
MIN
1.225
TYP
3.35
1.245
40
1.6
0.01
0.01
400
88
0.75
500
55
94
1.05
370
370
500
2
2.3
25
600
MAX
3.6
1.265
120
2.5
2
UNITS
V
V
nA
mA
μA
%/V
kHz
kHz
%
A
mV
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 LT1933E is guaranteed to meet performance specifications
from 0°C to 70°C. Specifications over the –40°C to 85°C operating
temperature range are assured by design, characterization and correlation
with statistical process controls. The LT1933I specifications are
guaranteed over the –40°C to 125°C temperature range. The LT1933H
specifications are guaranteed over the –40°C to 150°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.
1933fd
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LT1933
TYPICAL PERFORMANCE CHARACTERISTICS
Efficiency, V
OUT
= 5V
100
T
A
= 25°C
V
OUT
= 5V
V
IN
= 12V
EFFICIENCY (%)
100
Efficiency, V
OUT
= 3.3V
T
A
= 25°C
V
OUT
= 3.3V
V
IN
= 5V
V
IN
= 12V
V
IN
= 24V
70
SWITCH CURRENT LIMIT (mA)
1200
1000
800
600
400
200
0
Switch Current Limit
T
A
= 25°C
TYPICAL
90
EFFICIENCY (%)
90
MINIMUM
80
V
IN
= 24V
80
70
D1 = MBRM140
L1 = Toko D53LCB 33μH
0
100
300
400
LOAD CURRENT (mA)
200
500
600
1933 G01
60
60
0
100
200
D1 = MBRM140
L1 = Toko D53LCB 22μH
300
400
LOAD CURRENT (mA)
500
600
1933 G02
0
20
60
40
DUTY CYCLE (%)
80
100
1933 G03
Maximum Load Current
800
T
A
= 25°C
V
OUT
= 5V
LOAD CURRENT (mA)
800
Maximum Load Current
T
A
= 25°C
V
OUT
= 3.3V
SWITCH VOLTAGE (mV)
600
500
Switch Voltage Drop
LOAD CURRENT (mA)
700
L = 33μH
600
L = 22μH
500
700
L = 22μH
600
L = 15μH
500
T
A
= 25°C
400
T
A
= 85°C
300
200
100
T
A
= –40°C
400
400
0
5
15
20
10
INPUT VOLTAGE (V)
25
30
1933 G04
0
5
15
20
10
INPUT VOLTAGE (V)
25
30
1933 G05
0
0
0.1
0.3
0.2
0.4
SWITCH CURRENT (A)
0.5
0.6
1933 G06
Feedback Voltage
1.260
1.255
FEEDBACK VOLTAGE (V)
3.6
1.250
UVLO (V)
1.245
1.240
3.2
1.235
1.230
–50 –25
3.4
3.8
Undervoltage Lockout
600
SWITCHING FREQUENCY (kHz)
Switching Frequency
550
500
450
0
25 50 75 100 125 150
TEMPERATURE (°C)
1933 G07
3.0
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
1933 G08
400
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
1933 G09
1933fd
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LT1933
TYPICAL PERFORMANCE CHARACTERISTICS
Frequency Foldback
700
SWITCHING FREQUENCY (kHz)
600
SWITCH CURRENT LIMIT (A)
500
400
300
200
100
0
0.0
1.0
0.5
FB PIN VOLTAGE (V)
1.5
1933 G10
Soft-Start
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
0
2
3
1
SHDN
PIN VOLTAGE (V)
4
1933 G11
SHDN
Pin Current
200
T
A
= 25°C
T
A
= 25°C
T
A
= 25°C
DC = 30%
SHDN
PIN CURRENT (μA)
150
100
50
0
0
8
12
4
SHDN
PIN VOLTAGE (V)
16
1933 G12
Typical Minimum Input Voltage
8
V
OUT
= 5V
T
A
= 25°C
L = 33μH
INPUT VOLTAGE (V)
TO START
6.0
5.5
Typical Minimum Input Voltage
V
OUT
= 3.3V
T
A
= 25°C
L = 22μH
TO START
5.0
4.5
4.0
3.5
TO RUN
1.4
1.2
SWITCH CURRENT LIMIT (A)
1.0
0.8
0.6
0.4
0.2
Switch Current Limit
7
INPUT VOLTAGE (V)
6
TO RUN
5
4
1
10
100
LOAD CURRENT (mA)
1933 G13
3.0
1
10
100
LOAD CURRENT (mA)
1933 G14
0
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
1933 G15
Operating Waveforms
V
OUT1
1.8V
Operating Waveforms,
Discontinuous Mode
V
OUT1
1.8V
V
SW
10V/DIV
V
SW
10V/DIV
I
L
200mA/DIV
V
OUT2
1.2V
I
L
200mA/DIV
V
OUT2
1.2V
V
OUT
10mV/DIV
1933 G16
V
OUT
10mV/DIV
1933 G17
V
IN
= 12V, V
OUT
= 3.3V, I
OUT
= 400mA,
L = 22μH, C
OUT
= 22μF
V
IN
= 12V, V
OUT
= 3.3V, I
OUT
= 20mA,
L = 22μH, C
OUT
= 22μF
1933fd
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