LT3500
Monolithic 2A Step-Down
Regulator Plus Linear
Regulator/Controller
FEATURES DESCRIPTION
?
n
Wide Input Range: 3V to 36V Operating,
The LT 3500 is a current mode PWM step-down DC/DC
40V Maximum
converter with an internal 2.3A switch. The wide input range
n
Short-Circuit Protected Over Full Input Range
of 3V to 40V makes the LT3500 suitable for regulating
n
2A Output Current Capability
power from a wide variety of sources, including automo-
n
Adjustable/Synchronizable Fixed Frequency
tive batteries, 24V industrial supplies and unregulated
Operation from 250kHz to 2.2MHz
wall adapters.
n
Soft-Start/Tracking Capability
Resistor-programmable 250kHz to 2.2MHz frequency
n
Output Adjustable Down to 0.8V
range and synchronization capability enable optimization
n
Adjustable Linear Regulator/Driver with 13mA
between ef? ciency and external component size. Cycle-
Output Capability
by-cycle current limit, frequency foldback and thermal
n
Power Good Comparator with Complimentary
shutdown provide protection against a shorted output.
Outputs
The soft-start feature controls the ramp rate of the output
n
Low Shutdown Current: 12?A
voltage, eliminating input current surge during start-up,
n
Thermally Enhanced 3mm ? 3mm DFN or 16-Pin
and also provides output tracking.
MSOP Package
The LT3500 contains an internal NPN transistor with feed-
APPLICATIONS
back control which can be con? gured as a linear regulator
or as a linear regulator controller.
n
Automotive Battery Regulation
n
Industrial Control
The LT3500?s low current shutdown mode (<12?A) enables
n
Wall Transformer Regulation
easy power management in battery-powered systems.
n
Distributed Power Regulation
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
Dual Step-Down Converters
Switching Converter Ef? ciency Output Voltage Ripple
90
V
IN
V BST
IN
6V TO 36V
85
0.47?F
2.2?F
LT3500
6.8?H
V
OUT1
80 V = 5V AT 1A
OUT1
SW 5V
AC COUPLED
1A
B240A
SHDN 75 2mV/DIV
42.2k
SS 22?F
70
0.47?F
FB
PG
8.06k
65
PG
V = 3.3V AT 1A
OUT2
AC COUPLED
60
R SYNC LDRV
2mV/DIV
T/
V = 12V
IN
V 55
53.6k C
I = 0A
1k
OUT2
V
330pF 24.9k OUT2 FREQUENCY = 800kHz
50
LFB 3.3V
3500 TA01c
500ns/DIV
0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0
40.2k 1A
8.06k 22?F
LOAD CURRENT (A)
3500 TA01b
3500 TA01a
3500fc
1
EFFICIENCY (%)LT3500
Monolithic 2A Step-Down
Regulator Plus Linear
Regulator/Controller
FEATURES DESCRIPTION
?
n
Wide Input Range: 3V to 36V Operating,
The LT 3500 is a current mode PWM step-down DC/DC
40V Maximum
converter with an internal 2.3A switch. The wide input range
n
Short-Circuit Protected Over Full Input Range
of 3V to 40V makes the LT3500 suitable for regulating
n
2A Output Current Capability
power from a wide variety of sources, including automo-
n
Adjustable/Synchronizable Fixed Frequency
tive batteries, 24V industrial supplies and unregulated
Operation from 250kHz to 2.2MHz
wall adapters.
n
Soft-Start/Tracking Capability
Resistor-programmable 250kHz to 2.2MHz frequency
n
Output Adjustable Down to 0.8V
range and synchronization capability enable optimization
n
Adjustable Linear Regulator/Driver with 13mA
between ef? ciency and external component size. Cycle-
Output Capability
by-cycle current limit, frequency foldback and thermal
n
Power Good Comparator with Complimentary
shutdown provide protection against a shorted output.
Outputs
The soft-start feature controls the ramp rate of the output
n
Low Shutdown Current: 12?A
voltage, eliminating input current surge during start-up,
n
Thermally Enhanced 3mm ? 3mm DFN or 16-Pin
and also provides output tracking.
MSOP Package
The LT3500 contains an internal NPN transistor with feed-
APPLICATIONS
back control which can be con? gured as a linear regulator
or as a linear regulator controller.
n
Automotive Battery Regulation
n
Industrial Control
The LT3500?s low current shutdown mode (<12?A) enables
n
Wall Transformer Regulation
easy power management in battery-powered systems.
n
Distributed Power Regulation
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
Dual Step-Down Converters
Switching Converter Ef? ciency Output Voltage Ripple
90
V
IN
V BST
IN
6V TO 36V
85
0.47?F
2.2?F
LT3500
6.8?H
V
OUT1
80 V = 5V AT 1A
OUT1
SW 5V
AC COUPLED
1A
B240A
SHDN 75 2mV/DIV
42.2k
SS 22?F
70
0.47?F
FB
PG
8.06k
65
PG
V = 3.3V AT 1A
OUT2
AC COUPLED
60
R SYNC LDRV
2mV/DIV
T/
V = 12V
IN
V 55
53.6k C
I = 0A
1k
OUT2
V
330pF 24.9k OUT2 FREQUENCY = 800kHz
50
LFB 3.3V
3500 TA01c
500ns/DIV
0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0
40.2k 1A
8.06k 22?F
LOAD CURRENT (A)
3500 TA01b
3500 TA01a
3500fc
1
EFFICIENCY (%)LT3500
(Note 1)
ABSOLUTE MAXIMUM RATINGS
V , PG, PG Operating .................................... 40V/?0.3V Operating Junction Temperature Range
IN
SW ............................................................................. V LT3500EDD (Note 2) .......................... ?40?C to 125?C
IN
BST ................................................................ 55V/?0.3V LT3500IDD (Note 2) ........................... ?40?C to 125?C
BST Pin Above SW ....................................................25V LT3500HDD (Note 2).......................... ?40?C to 150?C
LDRV, SHDN ..............................................................15V LT3500EMSE (Note 2)........................ ?40?C to 125?C
FB, LFB, R /SYNC .......................................................5V LT3500IMSE (Note 3) ........................ ?40?C to 125?C
T
SS, V ......................................................................2.5V LT3500HMSE (Note 2) ....................... ?40?C to 150?C
C
Storage Temperature Range ................... ?65?C to 150?C
PIN CONFIGURATION
TOP VIEW
TOP VIEW
V 1 12 SW
1
IN NC1 16 NC16
V 2 15 SW
2 11 BST IN
SHDN
3
SHDN 14 BST
3 LDRV
SS 10
SS 4 13 LDRV
13
17
5
PG 12 LFB
4 LFB
PG 9
V 6 11 FB
C
5 FB
V 8
C 7
R /SYNC 10 PG
T
NC8 8 9 NC9
6 7
R /SYNC PG
T
MSE PACKAGE
DD PACKAGE
16-LEAD PLASTIC MSE
12-LEAD (3mm ? 3mm) PLASTIC DFN
? = 45?C/W, ? = 10?C/W
JA JC(PAD)
? = 45?C/W, ? = 10?C/W
JA JC(PAD)
EXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCB
EXPOSED PAD (PIN 13) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE
LT3500EDD#PBF LT3500EDD#TRPBF LCRN 12-Lead (3mm ? 3mm) Plastic DFN ?40?C to 125?C
LT3500IDD#PBF LT3500IDD#TRPBF LCRN 12-Lead (3mm ? 3mm) Plastic DFN ?40?C to 125?C
LT3500HDD#PBF LT3500HDD#TRPBF LDCY 12-Lead (3mm ? 3mm) Plastic DFN ?40?C to 150?C
LT3500EMSE#PBF LT3500EMSE#TRPBF 3500 16-Lead Plastic MSE ?40?C to 125?C
LT3500IMSE#PBF LT3500IMSE#TRPBF 3500 16-Lead Plastic MSE ?40?C to 125?C
LT3500HMSE#PBF LT3500HMSE#TRPBF 3500 16-Lead Plastic MSE ?40?C to 150?C
Consult LTC Marketing for parts speci? ed with wider operating temperature ranges. *The temperature grade is identi? ed by a label on the shipping container.
Consult LTC Marketing for information on non-standard lead based ? nish parts.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/
For more information on tape and reel speci? cations, go to: http://www.linear.com/tapeandreel/
3500fc
2LT3500
Monolithic 2A Step-Down
Regulator Plus Linear
Regulator/Controller
FEATURES DESCRIPTION
?
n
Wide Input Range: 3V to 36V Operating,
The LT 3500 is a current mode PWM step-down DC/DC
40V Maximum
converter with an internal 2.3A switch. The wide input range
n
Short-Circuit Protected Over Full Input Range
of 3V to 40V makes the LT3500 suitable for regulating
n
2A Output Current Capability
power from a wide variety of sources, including automo-
n
Adjustable/Synchronizable Fixed Frequency
tive batteries, 24V industrial supplies and unregulated
Operation from 250kHz to 2.2MHz
wall adapters.
n
Soft-Start/Tracking Capability
Resistor-programmable 250kHz to 2.2MHz frequency
n
Output Adjustable Down to 0.8V
range and synchronization capability enable optimization
n
Adjustable Linear Regulator/Driver with 13mA
between ef? ciency and external component size. Cycle-
Output Capability
by-cycle current limit, frequency foldback and thermal
n
Power Good Comparator with Complimentary
shutdown provide protection against a shorted output.
Outputs
The soft-start feature controls the ramp rate of the output
n
Low Shutdown Current: 12?A
voltage, eliminating input current surge during start-up,
n
Thermally Enhanced 3mm ? 3mm DFN or 16-Pin
and also provides output tracking.
MSOP Package
The LT3500 contains an internal NPN transistor with feed-
APPLICATIONS
back control which can be con? gured as a linear regulator
or as a linear regulator controller.
n
Automotive Battery Regulation
n
Industrial Control
The LT3500?s low current shutdown mode (<12?A) enables
n
Wall Transformer Regulation
easy power management in battery-powered systems.
n
Distributed Power Regulation
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
Dual Step-Down Converters
Switching Converter Ef? ciency Output Voltage Ripple
90
V
IN
V BST
IN
6V TO 36V
85
0.47?F
2.2?F
LT3500
6.8?H
V
OUT1
80 V = 5V AT 1A
OUT1
SW 5V
AC COUPLED
1A
B240A
SHDN 75 2mV/DIV
42.2k
SS 22?F
70
0.47?F
FB
PG
8.06k
65
PG
V = 3.3V AT 1A
OUT2
AC COUPLED
60
R SYNC LDRV
2mV/DIV
T/
V = 12V
IN
V 55
53.6k C
I = 0A
1k
OUT2
V
330pF 24.9k OUT2 FREQUENCY = 800kHz
50
LFB 3.3V
3500 TA01c
500ns/DIV
0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0
40.2k 1A
8.06k 22?F
LOAD CURRENT (A)
3500 TA01b
3500 TA01a
3500fc
1
EFFICIENCY (%)LT3500
Monolithic 2A Step-Down
Regulator Plus Linear
Regulator/Controller
FEATURES DESCRIPTION
?
n
Wide Input Range: 3V to 36V Operating,
The LT 3500 is a current mode PWM step-down DC/DC
40V Maximum
converter with an internal 2.3A switch. The wide input range
n
Short-Circuit Protected Over Full Input Range
of 3V to 40V makes the LT3500 suitable for regulating
n
2A Output Current Capability
power from a wide variety of sources, including automo-
n
Adjustable/Synchronizable Fixed Frequency
tive batteries, 24V industrial supplies and unregulated
Operation from 250kHz to 2.2MHz
wall adapters.
n
Soft-Start/Tracking Capability
Resistor-programmable 250kHz to 2.2MHz frequency
n
Output Adjustable Down to 0.8V
range and synchronization capability enable optimization
n
Adjustable Linear Regulator/Driver with 13mA
between ef? ciency and external component size. Cycle-
Output Capability
by-cycle current limit, frequency foldback and thermal
n
Power Good Comparator with Complimentary
shutdown provide protection against a shorted output.
Outputs
The soft-start feature controls the ramp rate of the output
n
Low Shutdown Current: 12?A
voltage, eliminating input current surge during start-up,
n
Thermally Enhanced 3mm ? 3mm DFN or 16-Pin
and also provides output tracking.
MSOP Package
The LT3500 contains an internal NPN transistor with feed-
APPLICATIONS
back control which can be con? gured as a linear regulator
or as a linear regulator controller.
n
Automotive Battery Regulation
n
Industrial Control
The LT3500?s low current shutdown mode (<12?A) enables
n
Wall Transformer Regulation
easy power management in battery-powered systems.
n
Distributed Power Regulation
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
Dual Step-Down Converters
Switching Converter Ef? ciency Output Voltage Ripple
90
V
IN
V BST
IN
6V TO 36V
85
0.47?F
2.2?F
LT3500
6.8?H
V
OUT1
80 V = 5V AT 1A
OUT1
SW 5V
AC COUPLED
1A
B240A
SHDN 75 2mV/DIV
42.2k
SS 22?F
70
0.47?F
FB
PG
8.06k
65
PG
V = 3.3V AT 1A
OUT2
AC COUPLED
60
R SYNC LDRV
2mV/DIV
T/
V = 12V
IN
V 55
53.6k C
I = 0A
1k
OUT2
V
330pF 24.9k OUT2 FREQUENCY = 800kHz
50
LFB 3.3V
3500 TA01c
500ns/DIV
0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0
40.2k 1A
8.06k 22?F
LOAD CURRENT (A)
3500 TA01b
3500 TA01a
3500fc
1
EFFICIENCY (%)LT3500
(Note 1)
ABSOLUTE MAXIMUM RATINGS
V , PG, PG Operating .................................... 40V/?0.3V Operating Junction Temperature Range
IN
SW ............................................................................. V LT3500EDD (Note 2) .......................... ?40?C to 125?C
IN
BST ................................................................ 55V/?0.3V LT3500IDD (Note 2) ........................... ?40?C to 125?C
BST Pin Above SW ....................................................25V LT3500HDD (Note 2).......................... ?40?C to 150?C
LDRV, SHDN ..............................................................15V LT3500EMSE (Note 2)........................ ?40?C to 125?C
FB, LFB, R /SYNC .......................................................5V LT3500IMSE (Note 3) ........................ ?40?C to 125?C
T
SS, V ......................................................................2.5V LT3500HMSE (Note 2) ....................... ?40?C to 150?C
C
Storage Temperature Range ................... ?65?C to 150?C
PIN CONFIGURATION
TOP VIEW
TOP VIEW
V 1 12 SW
1
IN NC1 16 NC16
V 2 15 SW
2 11 BST IN
SHDN
3
SHDN 14 BST
3 LDRV
SS 10
SS 4 13 LDRV
13
17
5
PG 12 LFB
4 LFB
PG 9
V 6 11 FB
C
5 FB
V 8
C 7
R /SYNC 10 PG
T
NC8 8 9 NC9
6 7
R /SYNC PG
T
MSE PACKAGE
DD PACKAGE
16-LEAD PLASTIC MSE
12-LEAD (3mm ? 3mm) PLASTIC DFN
? = 45?C/W, ? = 10?C/W
JA JC(PAD)
? = 45?C/W, ? = 10?C/W
JA JC(PAD)
EXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCB
EXPOSED PAD (PIN 13) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE
LT3500EDD#PBF LT3500EDD#TRPBF LCRN 12-Lead (3mm ? 3mm) Plastic DFN ?40?C to 125?C
LT3500IDD#PBF LT3500IDD#TRPBF LCRN 12-Lead (3mm ? 3mm) Plastic DFN ?40?C to 125?C
LT3500HDD#PBF LT3500HDD#TRPBF LDCY 12-Lead (3mm ? 3mm) Plastic DFN ?40?C to 150?C
LT3500EMSE#PBF LT3500EMSE#TRPBF 3500 16-Lead Plastic MSE ?40?C to 125?C
LT3500IMSE#PBF LT3500IMSE#TRPBF 3500 16-Lead Plastic MSE ?40?C to 125?C
LT3500HMSE#PBF LT3500HMSE#TRPBF 3500 16-Lead Plastic MSE ?40?C to 150?C
Consult LTC Marketing for parts speci? ed with wider operating temperature ranges. *The temperature grade is identi? ed by a label on the shipping container.
Consult LTC Marketing for information on non-standard lead based ? nish parts.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/
For more information on tape and reel speci? cations, go to: http://www.linear.com/tapeandreel/
3500fc
2LT3500
The ELECTRICAL CHARACTERISTICS l denotes the speci? cations which apply over the full operating
temperature range, otherwise speci? cations are at T = 25?C. V = 15V, V = 2V, unless otherwise speci? ed.
J VIN RT/SYNC
PARAMETER CONDITIONS MIN TYP MAX UNITS
SHDN Threshold l 710 760 780 mV
SHDN Source Current V = 0.62V 1.5 2.5 3.5 ?A
SHDN
SHDN Current Hysterisis 1.25 2 3.25 ?A
l
Minimum Input Voltage (Note 3) V = 0V 2.4 2.8 V
FB
Supply Shutdown Current V = 0V l 12 30 ?A
SHDN
Supply Quiescent Current V = 0.9V 2.5 3.5 mA
FB
FB Voltage V = 1V l 0.784 0.8 0.816 V
VC
V = 0.8V to 1.6V, V = 3V to 40V l 0.776 0.8 0.824 V
VC IN
FB Bias Current V = 0.8V, V = 1V 50 150 nA
FB VC
Error Ampli? er g V = 1V, I = ?10?A 150 250 350 ?mho
m VC VC
Error Ampli? er Source Current V = 0.6V, V = 1V 12 16 20 ?A
FB VC
Error Ampli? er Sink Current V = 1V, V = 1V 14 18 22 ?A
FB VC
Error Ampli? er High Clamp V = 0.6V 1.8 2.0 2.2 V
FB
Error Ampli? er Switching Threshold V = 0.6V 0.6 0.8 1.0 V
FB
SS Source Current V = 0.4V, V = 0.9V 2.25 2.75 3.75 ?A
SS FB
SS Sink Current V = 0V, V = 2V 300 600 900 ?A
FB SS
SS POR Sink Current (Note 4) V = 0V, V = 2V, Cycle SHDN 400 600 800 ?A
FB SS
SS POR Threshold 50 100 150 mV
SS to FB Offset (V ? V)V = V , V = 0.4V 70 100 120 mV
SS FB VC FS SS
PG/PG Leakage V = 0.9V, V /V = 40V 0.1 1 ?A
FB PG PG
PG/PG Threshold (Rising) V = 0.4V 0.685 0.708 0.730 V
PG
PG/PG Hysteresis (Falling) V = 0.4V 20 30 40 mV
PG
PG Sink Current V = 0.4V, V = 0.7V 250 500 750 ?A
PG FB
PG Sink Current V = 0.4V, V = 0.9V 500 800 1100 ?A
PG FB
R /SYNC Reference Voltage V = 0.9V, R = 15k 0.75 0.850 0.975 V
T FB RT/SYNC
Switching Frequency R = 90.9k 450 500 550 kHz
RT/SYNC
R = 90.9k l 425 500 625 kHz
RT/SYNC
R = 15k 2 2.4 2.8 MHz
RT/SYNC
l
SYNC Frequency Range 250 2500 kHz
Minimum Switch On Time V = 0.7V, R = 90.9k 140 ns
FB RT/SYNC
Minimum Switch Off Time V = 0.7V, R = 90.9k 120 ns
FB RT/SYNC
Switch Leakage Current V = 0V 1 10 ?A
SW
Switch Saturation Voltage I = 2A, V = 18V, V = 0.7V 450 mV
SW BST FB
Switch Peak Current DD Package V = 18V, V = 0.7V 2.3 2.8 3.5 A
BST FB
l 2.1 2.8 3.5 A
Switch Peak Current MSE Package V = 18V, V = 0.7V 2.3 2.9 3.5 A
BST FB
l
2.1 2.9 3.7 A
Boost Current I = 2A, V = 20V, V = 0.7V 20 30 45 mA
SW BST FB
Minimum Boost Voltage (Note 5) I = 2A, V = 0.7V 2.2 3 V
SW FB
3500fc
3LT3500
Monolithic 2A Step-Down
Regulator Plus Linear
Regulator/Controller
FEATURES DESCRIPTION
?
n
Wide Input Range: 3V to 36V Operating,
The LT 3500 is a current mode PWM step-down DC/DC
40V Maximum
converter with an internal 2.3A switch. The wide input range
n
Short-Circuit Protected Over Full Input Range
of 3V to 40V makes the LT3500 suitable for regulating
n
2A Output Current Capability
power from a wide variety of sources, including automo-
n
Adjustable/Synchronizable Fixed Frequency
tive batteries, 24V industrial supplies and unregulated
Operation from 250kHz to 2.2MHz
wall adapters.
n
Soft-Start/Tracking Capability
Resistor-programmable 250kHz to 2.2MHz frequency
n
Output Adjustable Down to 0.8V
range and synchronization capability enable optimization
n
Adjustable Linear Regulator/Driver with 13mA
between ef? ciency and external component size. Cycle-
Output Capability
by-cycle current limit, frequency foldback and thermal
n
Power Good Comparator with Complimentary
shutdown provide protection against a shorted output.
Outputs
The soft-start feature controls the ramp rate of the output
n
Low Shutdown Current: 12?A
voltage, eliminating input current surge during start-up,
n
Thermally Enhanced 3mm ? 3mm DFN or 16-Pin
and also provides output tracking.
MSOP Package
The LT3500 contains an internal NPN transistor with feed-
APPLICATIONS
back control which can be con? gured as a linear regulator
or as a linear regulator controller.
n
Automotive Battery Regulation
n
Industrial Control
The LT3500?s low current shutdown mode (<12?A) enables
n
Wall Transformer Regulation
easy power management in battery-powered systems.
n
Distributed Power Regulation
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
Dual Step-Down Converters
Switching Converter Ef? ciency Output Voltage Ripple
90
V
IN
V BST
IN
6V TO 36V
85
0.47?F
2.2?F
LT3500
6.8?H
V
OUT1
80 V = 5V AT 1A
OUT1
SW 5V
AC COUPLED
1A
B240A
SHDN 75 2mV/DIV
42.2k
SS 22?F
70
0.47?F
FB
PG
8.06k
65
PG
V = 3.3V AT 1A
OUT2
AC COUPLED
60
R SYNC LDRV
2mV/DIV
T/
V = 12V
IN
V 55
53.6k C
I = 0A
1k
OUT2
V
330pF 24.9k OUT2 FREQUENCY = 800kHz
50
LFB 3.3V
3500 TA01c
500ns/DIV
0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0
40.2k 1A
8.06k 22?F
LOAD CURRENT (A)
3500 TA01b
3500 TA01a
3500fc
1
EFFICIENCY (%)LT3500
Monolithic 2A Step-Down
Regulator Plus Linear
Regulator/Controller
FEATURES DESCRIPTION
?
n
Wide Input Range: 3V to 36V Operating,
The LT 3500 is a current mode PWM step-down DC/DC
40V Maximum
converter with an internal 2.3A switch. The wide input range
n
Short-Circuit Protected Over Full Input Range
of 3V to 40V makes the LT3500 suitable for regulating
n
2A Output Current Capability
power from a wide variety of sources, including automo-
n
Adjustable/Synchronizable Fixed Frequency
tive batteries, 24V industrial supplies and unregulated
Operation from 250kHz to 2.2MHz
wall adapters.
n
Soft-Start/Tracking Capability
Resistor-programmable 250kHz to 2.2MHz frequency
n
Output Adjustable Down to 0.8V
range and synchronization capability enable optimization
n
Adjustable Linear Regulator/Driver with 13mA
between ef? ciency and external component size. Cycle-
Output Capability
by-cycle current limit, frequency foldback and thermal
n
Power Good Comparator with Complimentary
shutdown provide protection against a shorted output.
Outputs
The soft-start feature controls the ramp rate of the output
n
Low Shutdown Current: 12?A
voltage, eliminating input current surge during start-up,
n
Thermally Enhanced 3mm ? 3mm DFN or 16-Pin
and also provides output tracking.
MSOP Package
The LT3500 contains an internal NPN transistor with feed-
APPLICATIONS
back control which can be con? gured as a linear regulator
or as a linear regulator controller.
n
Automotive Battery Regulation
n
Industrial Control
The LT3500?s low current shutdown mode (<12?A) enables
n
Wall Transformer Regulation
easy power management in battery-powered systems.
n
Distributed Power Regulation
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
Dual Step-Down Converters
Switching Converter Ef? ciency Output Voltage Ripple
90
V
IN
V BST
IN
6V TO 36V
85
0.47?F
2.2?F
LT3500
6.8?H
V
OUT1
80 V = 5V AT 1A
OUT1
SW 5V
AC COUPLED
1A
B240A
SHDN 75 2mV/DIV
42.2k
SS 22?F
70
0.47?F
FB
PG
8.06k
65
PG
V = 3.3V AT 1A
OUT2
AC COUPLED
60
R SYNC LDRV
2mV/DIV
T/
V = 12V
IN
V 55
53.6k C
I = 0A
1k
OUT2
V
330pF 24.9k OUT2 FREQUENCY = 800kHz
50
LFB 3.3V
3500 TA01c
500ns/DIV
0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0
40.2k 1A
8.06k 22?F
LOAD CURRENT (A)
3500 TA01b
3500 TA01a
3500fc
1
EFFICIENCY (%)LT3500
(Note 1)
ABSOLUTE MAXIMUM RATINGS
V , PG, PG Operating .................................... 40V/?0.3V Operating Junction Temperature Range
IN
SW ............................................................................. V LT3500EDD (Note 2) .......................... ?40?C to 125?C
IN
BST ................................................................ 55V/?0.3V LT3500IDD (Note 2) ........................... ?40?C to 125?C
BST Pin Above SW ....................................................25V LT3500HDD (Note 2).......................... ?40?C to 150?C
LDRV, SHDN ..............................................................15V LT3500EMSE (Note 2)........................ ?40?C to 125?C
FB, LFB, R /SYNC .......................................................5V LT3500IMSE (Note 3) ........................ ?40?C to 125?C
T
SS, V ......................................................................2.5V LT3500HMSE (Note 2) ....................... ?40?C to 150?C
C
Storage Temperature Range ................... ?65?C to 150?C
PIN CONFIGURATION
TOP VIEW
TOP VIEW
V 1 12 SW
1
IN NC1 16 NC16
V 2 15 SW
2 11 BST IN
SHDN
3
SHDN 14 BST
3 LDRV
SS 10
SS 4 13 LDRV
13
17
5
PG 12 LFB
4 LFB
PG 9
V 6 11 FB
C
5 FB
V 8
C 7
R /SYNC 10 PG
T
NC8 8 9 NC9
6 7
R /SYNC PG
T
MSE PACKAGE
DD PACKAGE
16-LEAD PLASTIC MSE
12-LEAD (3mm ? 3mm) PLASTIC DFN
? = 45?C/W, ? = 10?C/W
JA JC(PAD)
? = 45?C/W, ? = 10?C/W
JA JC(PAD)
EXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCB
EXPOSED PAD (PIN 13) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE
LT3500EDD#PBF LT3500EDD#TRPBF LCRN 12-Lead (3mm ? 3mm) Plastic DFN ?40?C to 125?C
LT3500IDD#PBF LT3500IDD#TRPBF LCRN 12-Lead (3mm ? 3mm) Plastic DFN ?40?C to 125?C
LT3500HDD#PBF LT3500HDD#TRPBF LDCY 12-Lead (3mm ? 3mm) Plastic DFN ?40?C to 150?C
LT3500EMSE#PBF LT3500EMSE#TRPBF 3500 16-Lead Plastic MSE ?40?C to 125?C
LT3500IMSE#PBF LT3500IMSE#TRPBF 3500 16-Lead Plastic MSE ?40?C to 125?C
LT3500HMSE#PBF LT3500HMSE#TRPBF 3500 16-Lead Plastic MSE ?40?C to 150?C
Consult LTC Marketing for parts speci? ed with wider operating temperature ranges. *The temperature grade is identi? ed by a label on the shipping container.
Consult LTC Marketing for information on non-standard lead based ? nish parts.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/
For more information on tape and reel speci? cations, go to: http://www.linear.com/tapeandreel/
3500fc
2LT3500
Monolithic 2A Step-Down
Regulator Plus Linear
Regulator/Controller
FEATURES DESCRIPTION
?
n
Wide Input Range: 3V to 36V Operating,
The LT 3500 is a current mode PWM step-down DC/DC
40V Maximum
converter with an internal 2.3A switch. The wide input range
n
Short-Circuit Protected Over Full Input Range
of 3V to 40V makes the LT3500 suitable for regulating
n
2A Output Current Capability
power from a wide variety of sources, including automo-
n
Adjustable/Synchronizable Fixed Frequency
tive batteries, 24V industrial supplies and unregulated
Operation from 250kHz to 2.2MHz
wall adapters.
n
Soft-Start/Tracking Capability
Resistor-programmable 250kHz to 2.2MHz frequency
n
Output Adjustable Down to 0.8V
range and synchronization capability enable optimization
n
Adjustable Linear Regulator/Driver with 13mA
between ef? ciency and external component size. Cycle-
Output Capability
by-cycle current limit, frequency foldback and thermal
n
Power Good Comparator with Complimentary
shutdown provide protection against a shorted output.
Outputs
The soft-start feature controls the ramp rate of the output
n
Low Shutdown Current: 12?A
voltage, eliminating input current surge during start-up,
n
Thermally Enhanced 3mm ? 3mm DFN or 16-Pin
and also provides output tracking.
MSOP Package
The LT3500 contains an internal NPN transistor with feed-
APPLICATIONS
back control which can be con? gured as a linear regulator
or as a linear regulator controller.
n
Automotive Battery Regulation
n
Industrial Control
The LT3500?s low current shutdown mode (<12?A) enables
n
Wall Transformer Regulation
easy power management in battery-powered systems.
n
Distributed Power Regulation
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
Dual Step-Down Converters
Switching Converter Ef? ciency Output Voltage Ripple
90
V
IN
V BST
IN
6V TO 36V
85
0.47?F
2.2?F
LT3500
6.8?H
V
OUT1
80 V = 5V AT 1A
OUT1
SW 5V
AC COUPLED
1A
B240A
SHDN 75 2mV/DIV
42.2k
SS 22?F
70
0.47?F
FB
PG
8.06k
65
PG
V = 3.3V AT 1A
OUT2
AC COUPLED
60
R SYNC LDRV
2mV/DIV
T/
V = 12V
IN
V 55
53.6k C
I = 0A
1k
OUT2
V
330pF 24.9k OUT2 FREQUENCY = 800kHz
50
LFB 3.3V
3500 TA01c
500ns/DIV
0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0
40.2k 1A
8.06k 22?F
LOAD CURRENT (A)
3500 TA01b
3500 TA01a
3500fc
1
EFFICIENCY (%)LT3500
Monolithic 2A Step-Down
Regulator Plus Linear
Regulator/Controller
FEATURES DESCRIPTION
?
n
Wide Input Range: 3V to 36V Operating,
The LT 3500 is a current mode PWM step-down DC/DC
40V Maximum
converter with an internal 2.3A switch. The wide input range
n
Short-Circuit Protected Over Full Input Range
of 3V to 40V makes the LT3500 suitable for regulating
n
2A Output Current Capability
power from a wide variety of sources, including automo-
n
Adjustable/Synchronizable Fixed Frequency
tive batteries, 24V industrial supplies and unregulated
Operation from 250kHz to 2.2MHz
wall adapters.
n
Soft-Start/Tracking Capability
Resistor-programmable 250kHz to 2.2MHz frequency
n
Output Adjustable Down to 0.8V
range and synchronization capability enable optimization
n
Adjustable Linear Regulator/Driver with 13mA
between ef? ciency and external component size. Cycle-
Output Capability
by-cycle current limit, frequency foldback and thermal
n
Power Good Comparator with Complimentary
shutdown provide protection against a shorted output.
Outputs
The soft-start feature controls the ramp rate of the output
n
Low Shutdown Current: 12?A
voltage, eliminating input current surge during start-up,
n
Thermally Enhanced 3mm ? 3mm DFN or 16-Pin
and also provides output tracking.
MSOP Package
The LT3500 contains an internal NPN transistor with feed-
APPLICATIONS
back control which can be con? gured as a linear regulator
or as a linear regulator controller.
n
Automotive Battery Regulation
n
Industrial Control
The LT3500?s low current shutdown mode (<12?A) enables
n
Wall Transformer Regulation
easy power management in battery-powered systems.
n
Distributed Power Regulation
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
Dual Step-Down Converters
Switching Converter Ef? ciency Output Voltage Ripple
90
V
IN
V BST
IN
6V TO 36V
85
0.47?F
2.2?F
LT3500
6.8?H
V
OUT1
80 V = 5V AT 1A
OUT1
SW 5V
AC COUPLED
1A
B240A
SHDN 75 2mV/DIV
42.2k
SS 22?F
70
0.47?F
FB
PG
8.06k
65
PG
V = 3.3V AT 1A
OUT2
AC COUPLED
60
R SYNC LDRV
2mV/DIV
T/
V = 12V
IN
V 55
53.6k C
I = 0A
1k
OUT2
V
330pF 24.9k OUT2 FREQUENCY = 800kHz
50
LFB 3.3V
3500 TA01c
500ns/DIV
0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0
40.2k 1A
8.06k 22?F
LOAD CURRENT (A)
3500 TA01b
3500 TA01a
3500fc
1
EFFICIENCY (%)LT3500
(Note 1)
ABSOLUTE MAXIMUM RATINGS
V , PG, PG Operating .................................... 40V/?0.3V Operating Junction Temperature Range
IN
SW ............................................................................. V LT3500EDD (Note 2) .......................... ?40?C to 125?C
IN
BST ................................................................ 55V/?0.3V LT3500IDD (Note 2) ........................... ?40?C to 125?C
BST Pin Above SW ....................................................25V LT3500HDD (Note 2).......................... ?40?C to 150?C
LDRV, SHDN ..............................................................15V LT3500EMSE (Note 2)........................ ?40?C to 125?C
FB, LFB, R /SYNC .......................................................5V LT3500IMSE (Note 3) ........................ ?40?C to 125?C
T
SS, V ......................................................................2.5V LT3500HMSE (Note 2) ....................... ?40?C to 150?C
C
Storage Temperature Range ................... ?65?C to 150?C
PIN CONFIGURATION
TOP VIEW
TOP VIEW
V 1 12 SW
1
IN NC1 16 NC16
V 2 15 SW
2 11 BST IN
SHDN
3
SHDN 14 BST
3 LDRV
SS 10
SS 4 13 LDRV
13
17
5
PG 12 LFB
4 LFB
PG 9
V 6 11 FB
C
5 FB
V 8
C 7
R /SYNC 10 PG
T
NC8 8 9 NC9
6 7
R /SYNC PG
T
MSE PACKAGE
DD PACKAGE
16-LEAD PLASTIC MSE
12-LEAD (3mm ? 3mm) PLASTIC DFN
? = 45?C/W, ? = 10?C/W
JA JC(PAD)
? = 45?C/W, ? = 10?C/W
JA JC(PAD)
EXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCB
EXPOSED PAD (PIN 13) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE
LT3500EDD#PBF LT3500EDD#TRPBF LCRN 12-Lead (3mm ? 3mm) Plastic DFN ?40?C to 125?C
LT3500IDD#PBF LT3500IDD#TRPBF LCRN 12-Lead (3mm ? 3mm) Plastic DFN ?40?C to 125?C
LT3500HDD#PBF LT3500HDD#TRPBF LDCY 12-Lead (3mm ? 3mm) Plastic DFN ?40?C to 150?C
LT3500EMSE#PBF LT3500EMSE#TRPBF 3500 16-Lead Plastic MSE ?40?C to 125?C
LT3500IMSE#PBF LT3500IMSE#TRPBF 3500 16-Lead Plastic MSE ?40?C to 125?C
LT3500HMSE#PBF LT3500HMSE#TRPBF 3500 16-Lead Plastic MSE ?40?C to 150?C
Consult LTC Marketing for parts speci? ed with wider operating temperature ranges. *The temperature grade is identi? ed by a label on the shipping container.
Consult LTC Marketing for information on non-standard lead based ? nish parts.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/
For more information on tape and reel speci? cations, go to: http://www.linear.com/tapeandreel/
3500fc
2LT3500
The ELECTRICAL CHARACTERISTICS l denotes the speci? cations which apply over the full operating
temperature range, otherwise speci? cations are at T = 25?C. V = 15V, V = 2V, unless otherwise speci? ed.
J VIN RT/SYNC
PARAMETER CONDITIONS MIN TYP MAX UNITS
SHDN Threshold l 710 760 780 mV
SHDN Source Current V = 0.62V 1.5 2.5 3.5 ?A
SHDN
SHDN Current Hysterisis 1.25 2 3.25 ?A
l
Minimum Input Voltage (Note 3) V = 0V 2.4 2.8 V
FB
Supply Shutdown Current V = 0V l 12 30 ?A
SHDN
Supply Quiescent Current V = 0.9V 2.5 3.5 mA
FB
FB Voltage V = 1V l 0.784 0.8 0.816 V
VC
V = 0.8V to 1.6V, V = 3V to 40V l 0.776 0.8 0.824 V
VC IN
FB Bias Current V = 0.8V, V = 1V 50 150 nA
FB VC
Error Ampli? er g V = 1V, I = ?10?A 150 250 350 ?mho
m VC VC
Error Ampli? er Source Current V = 0.6V, V = 1V 12 16 20 ?A
FB VC
Error Ampli? er Sink Current V = 1V, V = 1V 14 18 22 ?A
FB VC
Error Ampli? er High Clamp V = 0.6V 1.8 2.0 2.2 V
FB
Error Ampli? er Switching Threshold V = 0.6V 0.6 0.8 1.0 V
FB
SS Source Current V = 0.4V, V = 0.9V 2.25 2.75 3.75 ?A
SS FB
SS Sink Current V = 0V, V = 2V 300 600 900 ?A
FB SS
SS POR Sink Current (Note 4) V = 0V, V = 2V, Cycle SHDN 400 600 800 ?A
FB SS
SS POR Threshold 50 100 150 mV
SS to FB Offset (V ? V)V = V , V = 0.4V 70 100 120 mV
SS FB VC FS SS
PG/PG Leakage V = 0.9V, V /V = 40V 0.1 1 ?A
FB PG PG
PG/PG Threshold (Rising) V = 0.4V 0.685 0.708 0.730 V
PG
PG/PG Hysteresis (Falling) V = 0.4V 20 30 40 mV
PG
PG Sink Current V = 0.4V, V = 0.7V 250 500 750 ?A
PG FB
PG Sink Current V = 0.4V, V = 0.9V 500 800 1100 ?A
PG FB
R /SYNC Reference Voltage V = 0.9V, R = 15k 0.75 0.850 0.975 V
T FB RT/SYNC
Switching Frequency R = 90.9k 450 500 550 kHz
RT/SYNC
R = 90.9k l 425 500 625 kHz
RT/SYNC
R = 15k 2 2.4 2.8 MHz
RT/SYNC
l
SYNC Frequency Range 250 2500 kHz
Minimum Switch On Time V = 0.7V, R = 90.9k 140 ns
FB RT/SYNC
Minimum Switch Off Time V = 0.7V, R = 90.9k 120 ns
FB RT/SYNC
Switch Leakage Current V = 0V 1 10 ?A
SW
Switch Saturation Voltage I = 2A, V = 18V, V = 0.7V 450 mV
SW BST FB
Switch Peak Current DD Package V = 18V, V = 0.7V 2.3 2.8 3.5 A
BST FB
l 2.1 2.8 3.5 A
Switch Peak Current MSE Package V = 18V, V = 0.7V 2.3 2.9 3.5 A
BST FB
l
2.1 2.9 3.7 A
Boost Current I = 2A, V = 20V, V = 0.7V 20 30 45 mA
SW BST FB
Minimum Boost Voltage (Note 5) I = 2A, V = 0.7V 2.2 3 V
SW FB
3500fc
3