LT3694/LT3694-1
36V, 2.6A Monolithic Buck
Regulator With Dual LDO
FEATURES DESCRIPTION
?
n
Wide Input Range: 4V to 36V
The LT 3694/LT3694-1 are monolithic, current mode
n
Overvoltage Shutdown Protects Circuit Through
DC/DC converters with dual, low dropout regulator con-
70V Transients
trollers. The switching converter is a step-down converter
n
2.6A Output Switching Regulator with Internal
capable of generating up to 2.6A at its output. Each regu-
Power Switch
lator has independent track/soft-start circuits simplifying
n
Dual, Low Dropout, Linear Regulator Controllers
power supply sequencing and interfacing with micro-
with Programmable Current Limit
controllers and DSPs.
n
Tracking/Soft-Start Inputs and Power Good Output
The switching frequency is set with a single resistor with a
Simplify Soft-Start and Supply Sequencing
range of 250kHz to 2.5MHz. The high switching frequency
n
Uses Small Inductors and Ceramic Capacitors
permits the use of small inductors and ceramic capacitors
n
V = 0.75V (Buck and LDOs)
OUT(MIN)
leading to very small triple output solutions. The constant-
n
Adjustable 250kHz to 2.5MHz Switching Frequency
switching frequency, combined with low impedance ce-
n
Accurate Enable Threshold Allows User
ramic capacitors, results in low, predictable output ripple.
Programmable Undervoltage Lockout
Protection circuitry senses the current in the power switch
n
Options for Clock Synchronization (LT3694) or Clock
and external Schottky catch diode to protect the LT3694
Output to Enable Synchronization to Other Switching
against short-circuit conditions. Frequency foldback and
Regulators (LT3694-1)
thermal shutdown provide additional protection.
n
Thermally Enhanced 28-Lead 4mm ? 5mm QFN and
With its wide input voltage range of 4V to 36V, the LT3694
20-Lead TSSOP Packages
regulates a broad array of power sources from 4-cell batteries
APPLICATIONS
and 5V logic rails to unregulated wall transformers, lead acid
batteries and distributed power supplies. The LT3694 can be
n
Automotive
synchronized to an external clock with the SYNC pin while
n
Industrial
the LT3694-1 offers a CLKOUT pin allowing other DC/DC
n
DSL and Cable Modems
converters to synchronize to the LT3694-1 clock.
n
Distributed Power Regulation
L, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks
n
Wall Transformer Regulation
of Linear Technology Corporation. All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
V
IN Efficiency at V = 3.3V
OUT
4.5V TO 36V
4.7?F
EN/UVLO V BIAS BST
IN
100
0.22?F
f = 800kHz
SW
4.7?H
OUT1
TRK/SS1 SW
3.3V V = 4.5V
IN
90
1.7A
TRK/SS2
1nF B340A
34k V = 12V
IN
DA
TRK/SS3
FB1
0.1? 47?F V = 36V
LT3694 80 IN
330pF
OUT1 LIM2
41.2k
10k
V
C1
DRV2
OUT2
70
LIM3 OUT1
2.5V
0.1?
450mA
DRV3
24.9k
OUT3
2.2?F 60
FB2
1.8V
SYNC 450mA
15.4k
2.2?F
50
10.7k
PGOOD FB3
0 1 2 3
51.1k
11k I (A)
RT OUT
GND
36941 TA01b
f = 800kHz
SW 36941 TA01a
36941fb
1
EFFICIENCY (%)LT3694/LT3694-1
36V, 2.6A Monolithic Buck
Regulator With Dual LDO
FEATURES DESCRIPTION
?
n
Wide Input Range: 4V to 36V
The LT 3694/LT3694-1 are monolithic, current mode
n
Overvoltage Shutdown Protects Circuit Through
DC/DC converters with dual, low dropout regulator con-
70V Transients
trollers. The switching converter is a step-down converter
n
2.6A Output Switching Regulator with Internal
capable of generating up to 2.6A at its output. Each regu-
Power Switch
lator has independent track/soft-start circuits simplifying
n
Dual, Low Dropout, Linear Regulator Controllers
power supply sequencing and interfacing with micro-
with Programmable Current Limit
controllers and DSPs.
n
Tracking/Soft-Start Inputs and Power Good Output
The switching frequency is set with a single resistor with a
Simplify Soft-Start and Supply Sequencing
range of 250kHz to 2.5MHz. The high switching frequency
n
Uses Small Inductors and Ceramic Capacitors
permits the use of small inductors and ceramic capacitors
n
V = 0.75V (Buck and LDOs)
OUT(MIN)
leading to very small triple output solutions. The constant-
n
Adjustable 250kHz to 2.5MHz Switching Frequency
switching frequency, combined with low impedance ce-
n
Accurate Enable Threshold Allows User
ramic capacitors, results in low, predictable output ripple.
Programmable Undervoltage Lockout
Protection circuitry senses the current in the power switch
n
Options for Clock Synchronization (LT3694) or Clock
and external Schottky catch diode to protect the LT3694
Output to Enable Synchronization to Other Switching
against short-circuit conditions. Frequency foldback and
Regulators (LT3694-1)
thermal shutdown provide additional protection.
n
Thermally Enhanced 28-Lead 4mm ? 5mm QFN and
With its wide input voltage range of 4V to 36V, the LT3694
20-Lead TSSOP Packages
regulates a broad array of power sources from 4-cell batteries
APPLICATIONS
and 5V logic rails to unregulated wall transformers, lead acid
batteries and distributed power supplies. The LT3694 can be
n
Automotive
synchronized to an external clock with the SYNC pin while
n
Industrial
the LT3694-1 offers a CLKOUT pin allowing other DC/DC
n
DSL and Cable Modems
converters to synchronize to the LT3694-1 clock.
n
Distributed Power Regulation
L, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks
n
Wall Transformer Regulation
of Linear Technology Corporation. All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
V
IN Efficiency at V = 3.3V
OUT
4.5V TO 36V
4.7?F
EN/UVLO V BIAS BST
IN
100
0.22?F
f = 800kHz
SW
4.7?H
OUT1
TRK/SS1 SW
3.3V V = 4.5V
IN
90
1.7A
TRK/SS2
1nF B340A
34k V = 12V
IN
DA
TRK/SS3
FB1
0.1O 47?F V = 36V
LT3694 80 IN
330pF
OUT1 LIM2
41.2k
10k
V
C1
DRV2
OUT2
70
LIM3 OUT1
2.5V
0.1O
450mA
DRV3
24.9k
OUT3
2.2?F 60
FB2
1.8V
SYNC 450mA
15.4k
2.2?F
50
10.7k
PGOOD FB3
0 1 2 3
51.1k
11k I (A)
RT OUT
GND
36941 TA01b
f = 800kHz
SW 36941 TA01a
36941fb
1
EFFICIENCY (%)LT3694/LT3694-1
ABSOLUTE MAXIMUM RATINGS (Note 1)
V , EN/UVLO (Note 6) ............................... ?0.3V to 70V Operating Junction Temperature Range (Notes 2 and 5)
IN
BST ...........................................................................55V LT3694E ............................................. ?40?C to 125?C
BST Above SW ..........................................................25V LT3694I .............................................. ?40?C to 125?C
PGOOD ......................................................................16V Storage Temperature Range ................... ?65?C to 150?C
TRK/SS, V , FB, RT, SYNC Pins ...................................6V Lead Temperature (Soldering, 10 Sec)
C
BIAS, LIM2, LIM3 Pins ...............................................7V (TSSOP Only) ................................................... 300?C
PIN CONFIGURATION
TOP VIEW
TOP VIEW
V 1 20 SW
IN
28 27 26 25 24 23
EN/UVLO 2 19 DA
EN/UVLO 1 22 DA
SYNC(CLKOUT) 3 18 BST
SYNC (CLKOUT)
2 21 BST
PGOOD 4 17 BIAS
PGOOD 3 20 BIAS
29
RT 5 16 V
RT 4 19 V
21 C1
C1
GND
GND
TRK/SS1 5 18 FB1 TRK/SS1 6 15 FB1
TRK/SS2 6 17 TRK/SS3
TRK/SS2 7 14 TRK/SS3
FB2 7 16
FB3
FB2 8 13 FB3
8
DRV2 15 DRV3
DRV2 9 12 DRV3
9 10 11 12 13 14
LIM2 10 11 LIM3
FE PACKAGE
20-LEAD PLASTIC TSSOP
UFD PACKAGE
? = 38?C/W
28-LEAD (4mm ? 5mm) PLASTIC QFN JA
EXPOSED PAD (PIN 21) IS GND, MUST BE SOLDERED TO PCB
? = 34?C/W
JA
LT3694-1 PINOUT IS SHOWN IN PARENTHESIS
EXPOSED PAD (PIN 29) IS GND, MUST BE SOLDERED TO PCB
LT3694-1 PINOUT IS SHOWN IN PARENTHESIS
ORDER INFORMATION
LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE
LT3694EUFD#PBF LT3694EUFD#TRPBF 3694 28-Lead (4mm ? 5mm) Plastic QFN ?40?C to 125?C
LT3694IUFD#PBF LT3694IUFD#TRPBF 3694 ?40?C to 125?C
28-Lead (4mm ? 5mm) Plastic QFN
LT3694EFE#PBF LT3694EFE#TRPBF LT3694FE 20-Lead Plastic TSSOP ?40?C to 125?C
LT3694IFE#PBF LT3694IFE#TRPBF LT3694FE 20-Lead Plastic TSSOP ?40?C to 125?C
LT3694-1EUFD#PBF LT3694-1EUFD#TRPBF 36941 28-Lead (4mm ? 5mm) Plastic QFN ?40?C to 125?C
LT3694-1IUFD#PBF LT3694-1IUFD#TRPBF 36941 28-Lead (4mm ? 5mm) Plastic QFN ?40?C to 125?C
LT3694-1EFE#PBF LT3694-1EFE#TRPBF LT3694FE-1 20-Lead Plastic TSSOP ?40?C to 125?C
LT3694-1IFE#PBF LT3694-1IFE#TRPBF LT3694FE-1 20-Lead Plastic TSSOP ?40?C to 125?C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
Consult LTC Marketing for information on non-standard lead based finish parts.
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/
36941fb
2
LIM2 V
IN
GND V
IN
GND GND
GND
GND
GND
SW
LIM3 SWLT3694/LT3694-1
36V, 2.6A Monolithic Buck
Regulator With Dual LDO
FEATURES DESCRIPTION
?
n
Wide Input Range: 4V to 36V
The LT 3694/LT3694-1 are monolithic, current mode
n
Overvoltage Shutdown Protects Circuit Through
DC/DC converters with dual, low dropout regulator con-
70V Transients
trollers. The switching converter is a step-down converter
n
2.6A Output Switching Regulator with Internal
capable of generating up to 2.6A at its output. Each regu-
Power Switch
lator has independent track/soft-start circuits simplifying
n
Dual, Low Dropout, Linear Regulator Controllers
power supply sequencing and interfacing with micro-
with Programmable Current Limit
controllers and DSPs.
n
Tracking/Soft-Start Inputs and Power Good Output
The switching frequency is set with a single resistor with a
Simplify Soft-Start and Supply Sequencing
range of 250kHz to 2.5MHz. The high switching frequency
n
Uses Small Inductors and Ceramic Capacitors
permits the use of small inductors and ceramic capacitors
n
V = 0.75V (Buck and LDOs)
OUT(MIN)
leading to very small triple output solutions. The constant-
n
Adjustable 250kHz to 2.5MHz Switching Frequency
switching frequency, combined with low impedance ce-
n
Accurate Enable Threshold Allows User
ramic capacitors, results in low, predictable output ripple.
Programmable Undervoltage Lockout
Protection circuitry senses the current in the power switch
n
Options for Clock Synchronization (LT3694) or Clock
and external Schottky catch diode to protect the LT3694
Output to Enable Synchronization to Other Switching
against short-circuit conditions. Frequency foldback and
Regulators (LT3694-1)
thermal shutdown provide additional protection.
n
Thermally Enhanced 28-Lead 4mm ? 5mm QFN and
With its wide input voltage range of 4V to 36V, the LT3694
20-Lead TSSOP Packages
regulates a broad array of power sources from 4-cell batteries
APPLICATIONS
and 5V logic rails to unregulated wall transformers, lead acid
batteries and distributed power supplies. The LT3694 can be
n
Automotive
synchronized to an external clock with the SYNC pin while
n
Industrial
the LT3694-1 offers a CLKOUT pin allowing other DC/DC
n
DSL and Cable Modems
converters to synchronize to the LT3694-1 clock.
n
Distributed Power Regulation
L, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks
n
Wall Transformer Regulation
of Linear Technology Corporation. All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
V
IN Efficiency at V = 3.3V
OUT
4.5V TO 36V
4.7?F
EN/UVLO V BIAS BST
IN
100
0.22?F
f = 800kHz
SW
4.7?H
OUT1
TRK/SS1 SW
3.3V V = 4.5V
IN
90
1.7A
TRK/SS2
1nF B340A
34k V = 12V
IN
DA
TRK/SS3
FB1
0.1O 47?F V = 36V
LT3694 80 IN
330pF
OUT1 LIM2
41.2k
10k
V
C1
DRV2
OUT2
70
LIM3 OUT1
2.5V
0.1O
450mA
DRV3
24.9k
OUT3
2.2?F 60
FB2
1.8V
SYNC 450mA
15.4k
2.2?F
50
10.7k
PGOOD FB3
0 1 2 3
51.1k
11k I (A)
RT OUT
GND
36941 TA01b
f = 800kHz
SW 36941 TA01a
36941fb
1
EFFICIENCY (%)LT3694/LT3694-1
36V, 2.6A Monolithic Buck
Regulator With Dual LDO
FEATURES DESCRIPTION
?
n
Wide Input Range: 4V to 36V
The LT 3694/LT3694-1 are monolithic, current mode
n
Overvoltage Shutdown Protects Circuit Through
DC/DC converters with dual, low dropout regulator con-
70V Transients
trollers. The switching converter is a step-down converter
n
2.6A Output Switching Regulator with Internal
capable of generating up to 2.6A at its output. Each regu-
Power Switch
lator has independent track/soft-start circuits simplifying
n
Dual, Low Dropout, Linear Regulator Controllers
power supply sequencing and interfacing with micro-
with Programmable Current Limit
controllers and DSPs.
n
Tracking/Soft-Start Inputs and Power Good Output
The switching frequency is set with a single resistor with a
Simplify Soft-Start and Supply Sequencing
range of 250kHz to 2.5MHz. The high switching frequency
n
Uses Small Inductors and Ceramic Capacitors
permits the use of small inductors and ceramic capacitors
n
V = 0.75V (Buck and LDOs)
OUT(MIN)
leading to very small triple output solutions. The constant-
n
Adjustable 250kHz to 2.5MHz Switching Frequency
switching frequency, combined with low impedance ce-
n
Accurate Enable Threshold Allows User
ramic capacitors, results in low, predictable output ripple.
Programmable Undervoltage Lockout
Protection circuitry senses the current in the power switch
n
Options for Clock Synchronization (LT3694) or Clock
and external Schottky catch diode to protect the LT3694
Output to Enable Synchronization to Other Switching
against short-circuit conditions. Frequency foldback and
Regulators (LT3694-1)
thermal shutdown provide additional protection.
n
Thermally Enhanced 28-Lead 4mm ? 5mm QFN and
With its wide input voltage range of 4V to 36V, the LT3694
20-Lead TSSOP Packages
regulates a broad array of power sources from 4-cell batteries
APPLICATIONS
and 5V logic rails to unregulated wall transformers, lead acid
batteries and distributed power supplies. The LT3694 can be
n
Automotive
synchronized to an external clock with the SYNC pin while
n
Industrial
the LT3694-1 offers a CLKOUT pin allowing other DC/DC
n
DSL and Cable Modems
converters to synchronize to the LT3694-1 clock.
n
Distributed Power Regulation
L, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks
n
Wall Transformer Regulation
of Linear Technology Corporation. All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
V
IN Efficiency at V = 3.3V
OUT
4.5V TO 36V
4.7?F
EN/UVLO V BIAS BST
IN
100
0.22?F
f = 800kHz
SW
4.7?H
OUT1
TRK/SS1 SW
3.3V V = 4.5V
IN
90
1.7A
TRK/SS2
1nF B340A
34k V = 12V
IN
DA
TRK/SS3
FB1
0.1O 47?F V = 36V
LT3694 80 IN
330pF
OUT1 LIM2
41.2k
10k
V
C1
DRV2
OUT2
70
LIM3 OUT1
2.5V
0.1O
450mA
DRV3
24.9k
OUT3
2.2?F 60
FB2
1.8V
SYNC 450mA
15.4k
2.2?F
50
10.7k
PGOOD FB3
0 1 2 3
51.1k
11k I (A)
RT OUT
GND
36941 TA01b
f = 800kHz
SW 36941 TA01a
36941fb
1
EFFICIENCY (%)LT3694/LT3694-1
ABSOLUTE MAXIMUM RATINGS (Note 1)
V , EN/UVLO (Note 6) ............................... ?0.3V to 70V Operating Junction Temperature Range (Notes 2 and 5)
IN
BST ...........................................................................55V LT3694E ............................................. ?40?C to 125?C
BST Above SW ..........................................................25V LT3694I .............................................. ?40?C to 125?C
PGOOD ......................................................................16V Storage Temperature Range ................... ?65?C to 150?C
TRK/SS, V , FB, RT, SYNC Pins ...................................6V Lead Temperature (Soldering, 10 Sec)
C
BIAS, LIM2, LIM3 Pins ...............................................7V (TSSOP Only) ................................................... 300?C
PIN CONFIGURATION
TOP VIEW
TOP VIEW
V 1 20 SW
IN
28 27 26 25 24 23
EN/UVLO 2 19 DA
EN/UVLO 1 22 DA
SYNC(CLKOUT) 3 18 BST
SYNC (CLKOUT)
2 21 BST
PGOOD 4 17 BIAS
PGOOD 3 20 BIAS
29
RT 5 16 V
RT 4 19 V
21 C1
C1
GND
GND
TRK/SS1 5 18 FB1 TRK/SS1 6 15 FB1
TRK/SS2 6 17 TRK/SS3
TRK/SS2 7 14 TRK/SS3
FB2 7 16
FB3
FB2 8 13 FB3
8
DRV2 15 DRV3
DRV2 9 12 DRV3
9 10 11 12 13 14
LIM2 10 11 LIM3
FE PACKAGE
20-LEAD PLASTIC TSSOP
UFD PACKAGE
? = 38?C/W
28-LEAD (4mm ? 5mm) PLASTIC QFN JA
EXPOSED PAD (PIN 21) IS GND, MUST BE SOLDERED TO PCB
? = 34?C/W
JA
LT3694-1 PINOUT IS SHOWN IN PARENTHESIS
EXPOSED PAD (PIN 29) IS GND, MUST BE SOLDERED TO PCB
LT3694-1 PINOUT IS SHOWN IN PARENTHESIS
ORDER INFORMATION
LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE
LT3694EUFD#PBF LT3694EUFD#TRPBF 3694 28-Lead (4mm ? 5mm) Plastic QFN ?40?C to 125?C
LT3694IUFD#PBF LT3694IUFD#TRPBF 3694 ?40?C to 125?C
28-Lead (4mm ? 5mm) Plastic QFN
LT3694EFE#PBF LT3694EFE#TRPBF LT3694FE 20-Lead Plastic TSSOP ?40?C to 125?C
LT3694IFE#PBF LT3694IFE#TRPBF LT3694FE 20-Lead Plastic TSSOP ?40?C to 125?C
LT3694-1EUFD#PBF LT3694-1EUFD#TRPBF 36941 28-Lead (4mm ? 5mm) Plastic QFN ?40?C to 125?C
LT3694-1IUFD#PBF LT3694-1IUFD#TRPBF 36941 28-Lead (4mm ? 5mm) Plastic QFN ?40?C to 125?C
LT3694-1EFE#PBF LT3694-1EFE#TRPBF LT3694FE-1 20-Lead Plastic TSSOP ?40?C to 125?C
LT3694-1IFE#PBF LT3694-1IFE#TRPBF LT3694FE-1 20-Lead Plastic TSSOP ?40?C to 125?C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
Consult LTC Marketing for information on non-standard lead based finish parts.
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/
36941fb
2
LIM2 V
IN
GND V
IN
GND GND
GND
GND
GND
SW
LIM3 SWLT3694/LT3694-1
ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T = 25?C, V = 12V, V = 3V, unless otherwise noted. (Notes 2, 9)
A IN BIAS
PARAMETER CONDITIONS MIN TYP MAX UNITS
l
V Internal Undervoltage Lockout 3.5 3.8 4 V
IN
l
Overvoltage Shutdown Threshold 36 38 40 V
Input Quiescent Current Not Switching 1 2 mA
Bias Quiescent Current Not Switching 2 3.5 mA
Shutdown Current V = 0.1V 0.1 2 ?A
EN/UVLO
EN/UVLO Threshold, Bias On 350 500 mV
l
EN/UVLO Threshold, Switching On 1.16 1.2 1.23 V
Reference Voltage Line Regulation 5V < V < 36V 0.01 %/V
IN
Switching Frequency R = 40.2k l 0.9 1.0 1.1 MHz
T
SYNC Input Frequency Range LT3694 Only l 0.25 2.5 MHz
l
V , SYNC LT3694 Only 1.5 V
IH
l
V , SYNC LT3694 Only 0.35 V
IL
l
V , CLKOUT I = ?50?A, LT3694-1 Only 1.6 2.6 V
OH CLKOUT
V , CLKOUT I = 50?A, LT3694-1 Only l 0.3 V
OL CLKOUT
PGOOD Output Voltage Low I = 250?A 0.2 0.4 V
PGOOD
PGOOD Leakage V = 2V 10 1000 nA
PGOOD
PGOOD Threshold (Relative to V ) (Note 8) 86 90 94 %
FB
Switching Regulator
Feedback Pin Voltage l 735 750 765 mV
Feedback Pin Bias Current l ?50 ?500 nA
Error Amplifier Transconductance 350 ?S
Error Amplifier Voltage Gain 600 V/V
TRK/SS Pull-Up Current ?2 ?3 ?4 ?A
TRK/SS Threshold to Start Switching 35 50 70 mV
V Source Current V = 0.6V ?20 ?A
C1 C
V Sink Current V = 0.6V 28 ?A
C1 C
V Clamp Voltage 2 V
C1
V Switching Threshold 0.75 V
C1
V to Switch Current Gain 3.6 A/V
C1
Switch Leakage Current V = 36V 0.01 10 ?A
IN
Minimum Boost Voltage Above Switch (Note 4) 1.8 2.5 V
l
Switch Current Limit (Note 3) (Note 3) 10% Duty Cycle 3.5 4.9 6 A
Switch V I = 3A 600 mV
CESAT SW1
BST Operating Current I = 3A 60 mA
SW1
V , BST Diode I = 100mA 0.8 V
F BST
I BST Diode V ? V = 36V 1 ?A
L BST BIAS
l
DA Current Limit 2.6 3.6 4.5 A
l
Minimum Switch Off-Time 140 ns
36941fb
3LT3694/LT3694-1
36V, 2.6A Monolithic Buck
Regulator With Dual LDO
FEATURES DESCRIPTION
?
n
Wide Input Range: 4V to 36V
The LT 3694/LT3694-1 are monolithic, current mode
n
Overvoltage Shutdown Protects Circuit Through
DC/DC converters with dual, low dropout regulator con-
70V Transients
trollers. The switching converter is a step-down converter
n
2.6A Output Switching Regulator with Internal
capable of generating up to 2.6A at its output. Each regu-
Power Switch
lator has independent track/soft-start circuits simplifying
n
Dual, Low Dropout, Linear Regulator Controllers
power supply sequencing and interfacing with micro-
with Programmable Current Limit
controllers and DSPs.
n
Tracking/Soft-Start Inputs and Power Good Output
The switching frequency is set with a single resistor with a
Simplify Soft-Start and Supply Sequencing
range of 250kHz to 2.5MHz. The high switching frequency
n
Uses Small Inductors and Ceramic Capacitors
permits the use of small inductors and ceramic capacitors
n
V = 0.75V (Buck and LDOs)
OUT(MIN)
leading to very small triple output solutions. The constant-
n
Adjustable 250kHz to 2.5MHz Switching Frequency
switching frequency, combined with low impedance ce-
n
Accurate Enable Threshold Allows User
ramic capacitors, results in low, predictable output ripple.
Programmable Undervoltage Lockout
Protection circuitry senses the current in the power switch
n
Options for Clock Synchronization (LT3694) or Clock
and external Schottky catch diode to protect the LT3694
Output to Enable Synchronization to Other Switching
against short-circuit conditions. Frequency foldback and
Regulators (LT3694-1)
thermal shutdown provide additional protection.
n
Thermally Enhanced 28-Lead 4mm ? 5mm QFN and
With its wide input voltage range of 4V to 36V, the LT3694
20-Lead TSSOP Packages
regulates a broad array of power sources from 4-cell batteries
APPLICATIONS
and 5V logic rails to unregulated wall transformers, lead acid
batteries and distributed power supplies. The LT3694 can be
n
Automotive
synchronized to an external clock with the SYNC pin while
n
Industrial
the LT3694-1 offers a CLKOUT pin allowing other DC/DC
n
DSL and Cable Modems
converters to synchronize to the LT3694-1 clock.
n
Distributed Power Regulation
L, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks
n
Wall Transformer Regulation
of Linear Technology Corporation. All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
V
IN Efficiency at V = 3.3V
OUT
4.5V TO 36V
4.7?F
EN/UVLO V BIAS BST
IN
100
0.22?F
f = 800kHz
SW
4.7?H
OUT1
TRK/SS1 SW
3.3V V = 4.5V
IN
90
1.7A
TRK/SS2
1nF B340A
34k V = 12V
IN
DA
TRK/SS3
FB1
0.1O 47?F V = 36V
LT3694 80 IN
330pF
OUT1 LIM2
41.2k
10k
V
C1
DRV2
OUT2
70
LIM3 OUT1
2.5V
0.1O
450mA
DRV3
24.9k
OUT3
2.2?F 60
FB2
1.8V
SYNC 450mA
15.4k
2.2?F
50
10.7k
PGOOD FB3
0 1 2 3
51.1k
11k I (A)
RT OUT
GND
36941 TA01b
f = 800kHz
SW 36941 TA01a
36941fb
1
EFFICIENCY (%)LT3694/LT3694-1
36V, 2.6A Monolithic Buck
Regulator With Dual LDO
FEATURES DESCRIPTION
?
n
Wide Input Range: 4V to 36V
The LT 3694/LT3694-1 are monolithic, current mode
n
Overvoltage Shutdown Protects Circuit Through
DC/DC converters with dual, low dropout regulator con-
70V Transients
trollers. The switching converter is a step-down converter
n
2.6A Output Switching Regulator with Internal
capable of generating up to 2.6A at its output. Each regu-
Power Switch
lator has independent track/soft-start circuits simplifying
n
Dual, Low Dropout, Linear Regulator Controllers
power supply sequencing and interfacing with micro-
with Programmable Current Limit
controllers and DSPs.
n
Tracking/Soft-Start Inputs and Power Good Output
The switching frequency is set with a single resistor with a
Simplify Soft-Start and Supply Sequencing
range of 250kHz to 2.5MHz. The high switching frequency
n
Uses Small Inductors and Ceramic Capacitors
permits the use of small inductors and ceramic capacitors
n
V = 0.75V (Buck and LDOs)
OUT(MIN)
leading to very small triple output solutions. The constant-
n
Adjustable 250kHz to 2.5MHz Switching Frequency
switching frequency, combined with low impedance ce-
n
Accurate Enable Threshold Allows User
ramic capacitors, results in low, predictable output ripple.
Programmable Undervoltage Lockout
Protection circuitry senses the current in the power switch
n
Options for Clock Synchronization (LT3694) or Clock
and external Schottky catch diode to protect the LT3694
Output to Enable Synchronization to Other Switching
against short-circuit conditions. Frequency foldback and
Regulators (LT3694-1)
thermal shutdown provide additional protection.
n
Thermally Enhanced 28-Lead 4mm ? 5mm QFN and
With its wide input voltage range of 4V to 36V, the LT3694
20-Lead TSSOP Packages
regulates a broad array of power sources from 4-cell batteries
APPLICATIONS
and 5V logic rails to unregulated wall transformers, lead acid
batteries and distributed power supplies. The LT3694 can be
n
Automotive
synchronized to an external clock with the SYNC pin while
n
Industrial
the LT3694-1 offers a CLKOUT pin allowing other DC/DC
n
DSL and Cable Modems
converters to synchronize to the LT3694-1 clock.
n
Distributed Power Regulation
L, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks
n
Wall Transformer Regulation
of Linear Technology Corporation. All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
V
IN Efficiency at V = 3.3V
OUT
4.5V TO 36V
4.7?F
EN/UVLO V BIAS BST
IN
100
0.22?F
f = 800kHz
SW
4.7?H
OUT1
TRK/SS1 SW
3.3V V = 4.5V
IN
90
1.7A
TRK/SS2
1nF B340A
34k V = 12V
IN
DA
TRK/SS3
FB1
0.1O 47?F V = 36V
LT3694 80 IN
330pF
OUT1 LIM2
41.2k
10k
V
C1
DRV2
OUT2
70
LIM3 OUT1
2.5V
0.1O
450mA
DRV3
24.9k
OUT3
2.2?F 60
FB2
1.8V
SYNC 450mA
15.4k
2.2?F
50
10.7k
PGOOD FB3
0 1 2 3
51.1k
11k I (A)
RT OUT
GND
36941 TA01b
f = 800kHz
SW 36941 TA01a
36941fb
1
EFFICIENCY (%)LT3694/LT3694-1
ABSOLUTE MAXIMUM RATINGS (Note 1)
V , EN/UVLO (Note 6) ............................... ?0.3V to 70V Operating Junction Temperature Range (Notes 2 and 5)
IN
BST ...........................................................................55V LT3694E ............................................. ?40?C to 125?C
BST Above SW ..........................................................25V LT3694I .............................................. ?40?C to 125?C
PGOOD ......................................................................16V Storage Temperature Range ................... ?65?C to 150?C
TRK/SS, V , FB, RT, SYNC Pins ...................................6V Lead Temperature (Soldering, 10 Sec)
C
BIAS, LIM2, LIM3 Pins ...............................................7V (TSSOP Only) ................................................... 300?C
PIN CONFIGURATION
TOP VIEW
TOP VIEW
V 1 20 SW
IN
28 27 26 25 24 23
EN/UVLO 2 19 DA
EN/UVLO 1 22 DA
SYNC(CLKOUT) 3 18 BST
SYNC (CLKOUT)
2 21 BST
PGOOD 4 17 BIAS
PGOOD 3 20 BIAS
29
RT 5 16 V
RT 4 19 V
21 C1
C1
GND
GND
TRK/SS1 5 18 FB1 TRK/SS1 6 15 FB1
TRK/SS2 6 17 TRK/SS3
TRK/SS2 7 14 TRK/SS3
FB2 7 16
FB3
FB2 8 13 FB3
8
DRV2 15 DRV3
DRV2 9 12 DRV3
9 10 11 12 13 14
LIM2 10 11 LIM3
FE PACKAGE
20-LEAD PLASTIC TSSOP
UFD PACKAGE
? = 38?C/W
28-LEAD (4mm ? 5mm) PLASTIC QFN JA
EXPOSED PAD (PIN 21) IS GND, MUST BE SOLDERED TO PCB
? = 34?C/W
JA
LT3694-1 PINOUT IS SHOWN IN PARENTHESIS
EXPOSED PAD (PIN 29) IS GND, MUST BE SOLDERED TO PCB
LT3694-1 PINOUT IS SHOWN IN PARENTHESIS
ORDER INFORMATION
LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE
LT3694EUFD#PBF LT3694EUFD#TRPBF 3694 28-Lead (4mm ? 5mm) Plastic QFN ?40?C to 125?C
LT3694IUFD#PBF LT3694IUFD#TRPBF 3694 ?40?C to 125?C
28-Lead (4mm ? 5mm) Plastic QFN
LT3694EFE#PBF LT3694EFE#TRPBF LT3694FE 20-Lead Plastic TSSOP ?40?C to 125?C
LT3694IFE#PBF LT3694IFE#TRPBF LT3694FE 20-Lead Plastic TSSOP ?40?C to 125?C
LT3694-1EUFD#PBF LT3694-1EUFD#TRPBF 36941 28-Lead (4mm ? 5mm) Plastic QFN ?40?C to 125?C
LT3694-1IUFD#PBF LT3694-1IUFD#TRPBF 36941 28-Lead (4mm ? 5mm) Plastic QFN ?40?C to 125?C
LT3694-1EFE#PBF LT3694-1EFE#TRPBF LT3694FE-1 20-Lead Plastic TSSOP ?40?C to 125?C
LT3694-1IFE#PBF LT3694-1IFE#TRPBF LT3694FE-1 20-Lead Plastic TSSOP ?40?C to 125?C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
Consult LTC Marketing for information on non-standard lead based finish parts.
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/
36941fb
2
LIM2 V
IN
GND V
IN
GND GND
GND
GND
GND
SW
LIM3 SWLT3694/LT3694-1
36V, 2.6A Monolithic Buck
Regulator With Dual LDO
FEATURES DESCRIPTION
?
n
Wide Input Range: 4V to 36V
The LT 3694/LT3694-1 are monolithic, current mode
n
Overvoltage Shutdown Protects Circuit Through
DC/DC converters with dual, low dropout regulator con-
70V Transients
trollers. The switching converter is a step-down converter
n
2.6A Output Switching Regulator with Internal
capable of generating up to 2.6A at its output. Each regu-
Power Switch
lator has independent track/soft-start circuits simplifying
n
Dual, Low Dropout, Linear Regulator Controllers
power supply sequencing and interfacing with micro-
with Programmable Current Limit
controllers and DSPs.
n
Tracking/Soft-Start Inputs and Power Good Output
The switching frequency is set with a single resistor with a
Simplify Soft-Start and Supply Sequencing
range of 250kHz to 2.5MHz. The high switching frequency
n
Uses Small Inductors and Ceramic Capacitors
permits the use of small inductors and ceramic capacitors
n
V = 0.75V (Buck and LDOs)
OUT(MIN)
leading to very small triple output solutions. The constant-
n
Adjustable 250kHz to 2.5MHz Switching Frequency
switching frequency, combined with low impedance ce-
n
Accurate Enable Threshold Allows User
ramic capacitors, results in low, predictable output ripple.
Programmable Undervoltage Lockout
Protection circuitry senses the current in the power switch
n
Options for Clock Synchronization (LT3694) or Clock
and external Schottky catch diode to protect the LT3694
Output to Enable Synchronization to Other Switching
against short-circuit conditions. Frequency foldback and
Regulators (LT3694-1)
thermal shutdown provide additional protection.
n
Thermally Enhanced 28-Lead 4mm ? 5mm QFN and
With its wide input voltage range of 4V to 36V, the LT3694
20-Lead TSSOP Packages
regulates a broad array of power sources from 4-cell batteries
APPLICATIONS
and 5V logic rails to unregulated wall transformers, lead acid
batteries and distributed power supplies. The LT3694 can be
n
Automotive
synchronized to an external clock with the SYNC pin while
n
Industrial
the LT3694-1 offers a CLKOUT pin allowing other DC/DC
n
DSL and Cable Modems
converters to synchronize to the LT3694-1 clock.
n
Distributed Power Regulation
L, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks
n
Wall Transformer Regulation
of Linear Technology Corporation. All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
V
IN Efficiency at V = 3.3V
OUT
4.5V TO 36V
4.7?F
EN/UVLO V BIAS BST
IN
100
0.22?F
f = 800kHz
SW
4.7?H
OUT1
TRK/SS1 SW
3.3V V = 4.5V
IN
90
1.7A
TRK/SS2
1nF B340A
34k V = 12V
IN
DA
TRK/SS3
FB1
0.1O 47?F V = 36V
LT3694 80 IN
330pF
OUT1 LIM2
41.2k
10k
V
C1
DRV2
OUT2
70
LIM3 OUT1
2.5V
0.1O
450mA
DRV3
24.9k
OUT3
2.2?F 60
FB2
1.8V
SYNC 450mA
15.4k
2.2?F
50
10.7k
PGOOD FB3
0 1 2 3
51.1k
11k I (A)
RT OUT
GND
36941 TA01b
f = 800kHz
SW 36941 TA01a
36941fb
1
EFFICIENCY (%)LT3694/LT3694-1
36V, 2.6A Monolithic Buck
Regulator With Dual LDO
FEATURES DESCRIPTION
?
n
Wide Input Range: 4V to 36V
The LT 3694/LT3694-1 are monolithic, current mode
n
Overvoltage Shutdown Protects Circuit Through
DC/DC converters with dual, low dropout regulator con-
70V Transients
trollers. The switching converter is a step-down converter
n
2.6A Output Switching Regulator with Internal
capable of generating up to 2.6A at its output. Each regu-
Power Switch
lator has independent track/soft-start circuits simplifying
n
Dual, Low Dropout, Linear Regulator Controllers
power supply sequencing and interfacing with micro-
with Programmable Current Limit
controllers and DSPs.
n
Tracking/Soft-Start Inputs and Power Good Output
The switching frequency is set with a single resistor with a
Simplify Soft-Start and Supply Sequencing
range of 250kHz to 2.5MHz. The high switching frequency
n
Uses Small Inductors and Ceramic Capacitors
permits the use of small inductors and ceramic capacitors
n
V = 0.75V (Buck and LDOs)
OUT(MIN)
leading to very small triple output solutions. The constant-
n
Adjustable 250kHz to 2.5MHz Switching Frequency
switching frequency, combined with low impedance ce-
n
Accurate Enable Threshold Allows User
ramic capacitors, results in low, predictable output ripple.
Programmable Undervoltage Lockout
Protection circuitry senses the current in the power switch
n
Options for Clock Synchronization (LT3694) or Clock
and external Schottky catch diode to protect the LT3694
Output to Enable Synchronization to Other Switching
against short-circuit conditions. Frequency foldback and
Regulators (LT3694-1)
thermal shutdown provide additional protection.
n
Thermally Enhanced 28-Lead 4mm ? 5mm QFN and
With its wide input voltage range of 4V to 36V, the LT3694
20-Lead TSSOP Packages
regulates a broad array of power sources from 4-cell batteries
APPLICATIONS
and 5V logic rails to unregulated wall transformers, lead acid
batteries and distributed power supplies. The LT3694 can be
n
Automotive
synchronized to an external clock with the SYNC pin while
n
Industrial
the LT3694-1 offers a CLKOUT pin allowing other DC/DC
n
DSL and Cable Modems
converters to synchronize to the LT3694-1 clock.
n
Distributed Power Regulation
L, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks
n
Wall Transformer Regulation
of Linear Technology Corporation. All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
V
IN Efficiency at V = 3.3V
OUT
4.5V TO 36V
4.7?F
EN/UVLO V BIAS BST
IN
100
0.22?F
f = 800kHz
SW
4.7?H
OUT1
TRK/SS1 SW
3.3V V = 4.5V
IN
90
1.7A
TRK/SS2
1nF B340A
34k V = 12V
IN
DA
TRK/SS3
FB1
0.1O 47?F V = 36V
LT3694 80 IN
330pF
OUT1 LIM2
41.2k
10k
V
C1
DRV2
OUT2
70
LIM3 OUT1
2.5V
0.1O
450mA
DRV3
24.9k
OUT3
2.2?F 60
FB2
1.8V
SYNC 450mA
15.4k
2.2?F
50
10.7k
PGOOD FB3
0 1 2 3
51.1k
11k I (A)
RT OUT
GND
36941 TA01b
f = 800kHz
SW 36941 TA01a
36941fb
1
EFFICIENCY (%)LT3694/LT3694-1
ABSOLUTE MAXIMUM RATINGS (Note 1)
V , EN/UVLO (Note 6) ............................... ?0.3V to 70V Operating Junction Temperature Range (Notes 2 and 5)
IN
BST ...........................................................................55V LT3694E ............................................. ?40?C to 125?C
BST Above SW ..........................................................25V LT3694I .............................................. ?40?C to 125?C
PGOOD ......................................................................16V Storage Temperature Range ................... ?65?C to 150?C
TRK/SS, V , FB, RT, SYNC Pins ...................................6V Lead Temperature (Soldering, 10 Sec)
C
BIAS, LIM2, LIM3 Pins ...............................................7V (TSSOP Only) ................................................... 300?C
PIN CONFIGURATION
TOP VIEW
TOP VIEW
V 1 20 SW
IN
28 27 26 25 24 23
EN/UVLO 2 19 DA
EN/UVLO 1 22 DA
SYNC(CLKOUT) 3 18 BST
SYNC (CLKOUT)
2 21 BST
PGOOD 4 17 BIAS
PGOOD 3 20 BIAS
29
RT 5 16 V
RT 4 19 V
21 C1
C1
GND
GND
TRK/SS1 5 18 FB1 TRK/SS1 6 15 FB1
TRK/SS2 6 17 TRK/SS3
TRK/SS2 7 14 TRK/SS3
FB2 7 16
FB3
FB2 8 13 FB3
8
DRV2 15 DRV3
DRV2 9 12 DRV3
9 10 11 12 13 14
LIM2 10 11 LIM3
FE PACKAGE
20-LEAD PLASTIC TSSOP
UFD PACKAGE
? = 38?C/W
28-LEAD (4mm ? 5mm) PLASTIC QFN JA
EXPOSED PAD (PIN 21) IS GND, MUST BE SOLDERED TO PCB
? = 34?C/W
JA
LT3694-1 PINOUT IS SHOWN IN PARENTHESIS
EXPOSED PAD (PIN 29) IS GND, MUST BE SOLDERED TO PCB
LT3694-1 PINOUT IS SHOWN IN PARENTHESIS
ORDER INFORMATION
LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE
LT3694EUFD#PBF LT3694EUFD#TRPBF 3694 28-Lead (4mm ? 5mm) Plastic QFN ?40?C to 125?C
LT3694IUFD#PBF LT3694IUFD#TRPBF 3694 ?40?C to 125?C
28-Lead (4mm ? 5mm) Plastic QFN
LT3694EFE#PBF LT3694EFE#TRPBF LT3694FE 20-Lead Plastic TSSOP ?40?C to 125?C
LT3694IFE#PBF LT3694IFE#TRPBF LT3694FE 20-Lead Plastic TSSOP ?40?C to 125?C
LT3694-1EUFD#PBF LT3694-1EUFD#TRPBF 36941 28-Lead (4mm ? 5mm) Plastic QFN ?40?C to 125?C
LT3694-1IUFD#PBF LT3694-1IUFD#TRPBF 36941 28-Lead (4mm ? 5mm) Plastic QFN ?40?C to 125?C
LT3694-1EFE#PBF LT3694-1EFE#TRPBF LT3694FE-1 20-Lead Plastic TSSOP ?40?C to 125?C
LT3694-1IFE#PBF LT3694-1IFE#TRPBF LT3694FE-1 20-Lead Plastic TSSOP ?40?C to 125?C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
Consult LTC Marketing for information on non-standard lead based finish parts.
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/
36941fb
2
LIM2 V
IN
GND V
IN
GND GND
GND
GND
GND
SW
LIM3 SWLT3694/LT3694-1
ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T = 25?C, V = 12V, V = 3V, unless otherwise noted. (Notes 2, 9)
A IN BIAS
PARAMETER CONDITIONS MIN TYP MAX UNITS
l
V Internal Undervoltage Lockout 3.5 3.8 4 V
IN
l
Overvoltage Shutdown Threshold 36 38 40 V
Input Quiescent Current Not Switching 1 2 mA
Bias Quiescent Current Not Switching 2 3.5 mA
Shutdown Current V = 0.1V 0.1 2 ?A
EN/UVLO
EN/UVLO Threshold, Bias On 350 500 mV
l
EN/UVLO Threshold, Switching On 1.16 1.2 1.23 V
Reference Voltage Line Regulation 5V < V < 36V 0.01 %/V
IN
Switching Frequency R = 40.2k l 0.9 1.0 1.1 MHz
T
SYNC Input Frequency Range LT3694 Only l 0.25 2.5 MHz
l
V , SYNC LT3694 Only 1.5 V
IH
l
V , SYNC LT3694 Only 0.35 V
IL
l
V , CLKOUT I = ?50?A, LT3694-1 Only 1.6 2.6 V
OH CLKOUT
V , CLKOUT I = 50?A, LT3694-1 Only l 0.3 V
OL CLKOUT
PGOOD Output Voltage Low I = 250?A 0.2 0.4 V
PGOOD
PGOOD Leakage V = 2V 10 1000 nA
PGOOD
PGOOD Threshold (Relative to V ) (Note 8) 86 90 94 %
FB
Switching Regulator
Feedback Pin Voltage l 735 750 765 mV
Feedback Pin Bias Current l ?50 ?500 nA
Error Amplifier Transconductance 350 ?S
Error Amplifier Voltage Gain 600 V/V
TRK/SS Pull-Up Current ?2 ?3 ?4 ?A
TRK/SS Threshold to Start Switching 35 50 70 mV
V Source Current V = 0.6V ?20 ?A
C1 C
V Sink Current V = 0.6V 28 ?A
C1 C
V Clamp Voltage 2 V
C1
V Switching Threshold 0.75 V
C1
V to Switch Current Gain 3.6 A/V
C1
Switch Leakage Current V = 36V 0.01 10 ?A
IN
Minimum Boost Voltage Above Switch (Note 4) 1.8 2.5 V
l
Switch Current Limit (Note 3) (Note 3) 10% Duty Cycle 3.5 4.9 6 A
Switch V I = 3A 600 mV
CESAT SW1
BST Operating Current I = 3A 60 mA
SW1
V , BST Diode I = 100mA 0.8 V
F BST
I BST Diode V ? V = 36V 1 ?A
L BST BIAS
l
DA Current Limit 2.6 3.6 4.5 A
l
Minimum Switch Off-Time 140 ns
36941fb
3