LT1766/LT1766-5
5.5V to 60V 1.5A, 200kHz
Step-Down Switching Regulator
FEATURES
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DESCRIPTION
The LT
®
1766/LT1766-5 are 200kHz monolithic buck switch-
ing regulators that accept input voltages up to 60V. A high
efficiency 1.5A, 0.2Ω switch is included on the die along
with all the necessary oscillator, control and logic circuitry.
A current mode control architecture delivers fast transient
response and excellent loop stability.
Special design techniques and a new high voltage process
achieve high efficiency over a wide input range. Efficiency
is maintained over a wide output current range by using the
output to bias the circuitry and by utilizing a supply boost
capacitor to saturate the power switch. Patented circuitry
maintains peak switch current over the full duty cycle range.
A shutdown pin reduces supply current to 25μA and the
device can be externally synchronized from 228kHz to
700kHz with logic-level inputs.
The LT1766/LT1766-5 are available in a 16-pin fused-lead
SSOP package or a TSSOP package with exposed backside
for improved thermal performance.
L,
LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and
ThinSOT is a trademark of Linear Technology Corporation. All other trademarks are the property
of their respective owners. Protected by U.S. Patents, including 6498466, 6531909.
Wide Input Range: 5.5V to 60V
1.5A Peak Switch Current
Constant 200kHz Switching Frequency
Saturating Switch Design: 0.2Ω
Peak Switch Current Rating Maintained Over
Full Duty Cycle Range
Low Effective Supply Current: 2.5mA
Low Shutdown Current: 25μA
1.2V Feedback Reference Voltage (LT1766)
5V Fixed Output (LT1766-5)
Easily Synchronizable
Cycle-by-Cycle Current Limiting
Small 16-Pin SSOP and Thermally Enhanced
TSSOP Packages
APPLICATIONS
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High Voltage, Industrial and Automotive
Portable Computers
Battery-Powered Systems
Battery Chargers
Distributed Power Systems
TYPICAL APPLICATION
5V Buck Converter
1N4148W
6
V
IN
*
5.5V TO 60V
4
2.2μF
†
100V
CERAMIC
OFF ON
15
14
BOOST
V
IN
LT1766
SHDN
SYNC
GND
BIAS
FB
V
C
10
12
15.4k
4.99k
SW
0.33μF
2
47μH
100
V
OUT
5V
1A
Efficiency vs Load Current
V
OUT
= 5V
L = 47μH
V
IN
= 12V
10MQ060N
+
90
EFFICIENCY (%)
V
IN
= 42V
80
100μF 10V
SOLID
TANTALUM
70
1, 8, 9, 16 11
2.2k
0.022μF
1766 TA01
60
220pF
50
0
0.25
0.75
1.00
0.50
LOAD CURRENT (A)
1.25
1766 TA02
*FOR INPUT VOLTAGES BELOW 7.5V, SOME RESTRICTIONS MAY APPLY
†
TDK C4532X7R2A225K
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LT1766/LT1766-5
ABSOLUTE MAXIMUM RATINGS
(Note 1)
Input Voltage (V
IN
) .................................................. 60V
BOOST Pin Above SW .............................................. 35V
BOOST Pin Voltage ................................................. 68V
SYNC, SENSE Voltage (LT1766-5) ............................. 7V
SHDN
Voltage ............................................................ 6V
BIAS Pin Voltage ..................................................... 30V
FB Pin Voltage/Current (LT1766) ................... 3.5V/2mA
Operating Junction Temperature Range
LT1766EFE/LT1766EFE-5/LT1766EGN/
LT1766EGN-5 (Note 8,10) ....................–40°C to 125°C
LT1766IFE/LT1766IFE-5/
LT1766IGN/LT1766IGN-5 (Note 8,10) ..–40°C to 125°C
LT1766HFE ..........................................–40°C to 140°C
Storage Temperature Range .................. –65°C to 150°C
Lead Temperature (Soldering, 10 sec) .................. 300°C
PIN CONFIGURATION
TOP VIEW
GND
SW
NC
V
IN
NC
BOOST
NC
GND
1
2
3
4
5
6
7
8
17
GND
16 GND
15
SHDN
14 SYNC
13 NC
12 FB/SENSE
11 V
C
10 BIAS
9
GND
GND
SW
NC
V
IN
NC
BOOST
NC
GND
1
2
3
4
5
6
7
8
TOP VIEW
16 GND
15
SHDN
14 SYNC
13 NC
12 FB/SENSE
11 V
C
10 BIAS
9
GND
FE PACKAGE
16-LEAD PLASTIC TSSOP
θ
JA
= 45°C,
θ
JC
(PIN 17) = 10°C/W
EXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCB
GN PACKAGE
16-LEAD PLASTIC SSOP
θ
JA
= 85°C,
θ
JC
(PIN 8) = 25°C/W
FOUR CORNER PINS SOLDERED TO GROUND PIN
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LT1766/LT1766-5
ORDER INFORMATION
LEAD FREE FINISH
LT1766EFE#PBF
LT1766IFE#PBF
LT1766HFE#PBF
LT1766EFE-5#PBF
LT1766IFE-5#PBF
LT1766EGN#PBF
LT1766IGN#PBF
LT1766EGN-5#PBF
LT1766IGN-5#PBF
LEAD BASED FINISH
LT1766EFE
LT1766IFE
LT1766HFE
LT1766EFE-5
LT1766IFE-5
LT1766EGN
LT1766IGN
LT1766EGN-5
LT1766IGN-5
TAPE AND REEL
LT1766EFE#TRPBF
LT1766IFE#TRPBF
LT1766HFE#TRPBF
LT1766EFE-5#TRPBF
LT1766IFE-5#TRPBF
LT1766EGN#TRPBF
LT1766IGN#TRPBF
LT1766EGN-5#TRPBF
LT1766IGN-5#TRPBF
TAPE AND REEL
LT1766EFE#TR
LT1766IFE#TR
LT1766HFE#TR
LT1766EFE-5#TR
LT1766IFE-5#TR
LT1766EGN#TR
LT1766IGN#TR
LT1766EGN-5#TR
LT1766IGN-5#TR
PART MARKING
1766EFE
1766IFE
1766HFE
1766EFE-5
1766IFE-5
1766
1766I
17665
1766I5
PART MARKING
1766EFE
1766IFE
1766HFE
1766EFE-5
1766IFE-5
1766
1766I
17665
1766I5
PACKAGE DESCRIPTION
16-Lead Plastic TSSOP
16-Lead Plastic TSSOP
16-Lead Plastic TSSOP
16-Lead Plastic TSSOP
16-Lead Plastic TSSOP
16-Lead Plastic SSOP
16-Lead Plastic SSOP
16-Lead Plastic SSOP
16-Lead Plastic SSOP
PACKAGE DESCRIPTION
16-Lead Plastic TSSOP
16-Lead Plastic TSSOP
16-Lead Plastic TSSOP
16-Lead Plastic TSSOP
16-Lead Plastic TSSOP
16-Lead Plastic SSOP
16-Lead Plastic SSOP
16-Lead Plastic SSOP
16-Lead Plastic SSOP
TEMPERATURE RANGE
0°C to 125°C
–40°C to 125°C
–40°C to 140°C
0°C to 125°C
–40°C to 125°C
0°C to 125°C
–40°C to 125°C
0°C to 125°C
–40°C to 125°C
TEMPERATURE RANGE
0°C to 125°C
–40°C to 85°C
–40°C to 140°C
0°C to 125°C
–40°C to 125°C
0°C to 125°C
–40°C to 125°C
0°C to 125°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/
(LT1766E/LT1766I Grade)
The
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denotes specifications which apply over the full operating temperature range, otherwise specifications are at T
J
= 25°C.
V
IN
= 15V, VC = 1.5V,
SHDN
= 1V, BOOST open circuit, SW open circuit, unless otherwise noted.
PARAMETER
Reference Voltage (V
REF
) (LT1766)
SENSE Voltage (LT1766-5)
SENSE Pin Resistance (LT1766-5)
FB Input Bias Current (LT1766)
Error Amp Voltage Gain
Error Amp g
m
V
C
to Switch g
m
EA Source Current
EA Sink Current
V
C
Switching Threshold
V
C
High Clamp
Switch Current Limit
FB = 1V or V
SENSE
= 4.1V
FB = 1.4V or V
SENSE
= 5.7V
Duty Cycle = 0
SHDN
= 1V
V
C
Open, Boost = V
IN
+ 5V, FB = 1V or V
SENSE
= 4.1V
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ELECTRICAL CHARACTERISTICS
CONDITIONS
5.5V ≤ V
IN
≤ 60V
V
OL
+ 0.2 ≤ V
C
≤ V
OH
– 0.2
5.5V ≤ V
IN
≤ 60V
V
OL
+ 0.2V ≤ V
C
≤ V
OH
– 0.2V
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MIN
1.204
1.195
4.94
4.90
9.5
TYP
1.219
5
13.8
–0.5
400
2000
1.7
MAX
1.234
1.243
5.06
5.10
19
–1.5
3000
4200
400
450
UNITS
V
V
V
V
kΩ
μA
V/V
μMho
μMho
A/V
μA
μA
V
V
(Notes 2, 9)
dl (V
C
) = ±10μA (Note 9)
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200
1500
1000
125
100
225
225
0.9
2.1
1.5
2
3
A
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LT1766/LT1766-5
(LT1766E/LT1766I Grade)
The
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denotes specifications which apply over the full operating temperature range, otherwise specifications are at T
J
= 25°C.
V
IN
= 15V, V
C
= 1.5V,
SHDN
= 1V, BOOST open circuit, SW open circuit, unless otherwise noted.
PARAMETER
Switch On-Resistance
Maximum Switch Duty Cycle
Switch Frequency
f
SW
Line Regulation
f
SW
Frequency Shifting Threshold
Minimum Input Voltage
Minimum Boost Voltage
Boost Current (Note 5)
Input Supply Current (I
VIN
)
Bias Supply Current (I
BIAS
)
Shutdown Supply Current
Lockout Threshold
Shutdown Thresholds
Minimum SYNC Amplitude
SYNC Frequency Range
SYNC Input Resistance
CONDITIONS
I
SW
= 1.5A, Boost = V
IN
+ 5V (Note 7)
FB = 1V or V
SENSE
= 4.1V
V
C
Set to Give DC = 50%
5.5V ≤ V
IN
≤ 60V
Df = 10kHz
(Note 3)
(Note 4) I
SW
≤ 1.5A
Boost = V
IN
+ 5V, I
SW
= 0.5A
Boost = V
IN
+ 5V, I
SW
= 1.5A
(Note 6) V
BIAS
= 5V
(Note 6) V
BIAS
= 5V
SHDN
= 0V, V
IN
≤ 60V, SW = 0V, V
C
Open
V
C
Open
V
C
Open, Shutting Down
V
C
Open, Starting Up
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ELECTRICAL CHARACTERISTICS
MIN
TYP
0.2
MAX
0.3
0.4
UNITS
Ω
Ω
%
%
93
90
184
172
96
200
200
0.05
0.8
4.6
1.8
12
45
1.4
2.9
25
5.5
3
25
70
2.2
4.2
75
200
2.53
0.6
0.6
2.2
700
20
216
228
0.15
kHz
kHz
%/V
V
V
V
mA
mA
mA
mA
μA
μA
V
V
V
V
kHz
kΩ
2.3
0.15
0.25
228
2.42
0.37
0.45
1.5
(LT1766H Grade)
The
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denotes specifications which apply over the full operating temperature range, otherwise specifications are at T
J
= 25°C.
V
IN
= 15V, V
C
= 1.5V,
SHDN
= 1V, BOOST open circuit, SW open circuit, unless otherwise noted.
PARAMETER
Reference Voltage (V
REF
)
FB Input Bias Current
Error Amp Voltage Gain
Error Amp g
m
V
C
to Switch g
m
EA Source Current
EA Sink Current
V
C
Switching Threshold
V
C
High Clamp
Switch Current Limit
Switch On Resistance
Maximum Switch Duty Cycle
Switch Frequency
FB = 1V or V
SENSE
= 4.1V
FB = 1.4V or V
SENSE
= 5.7V
Duty Cycle = 0
SHDN
= 1V
V
C
Open, Boost = V
IN
+ 5V, FB = 1V or V
SENSE
= 4.1V
I
SW
= 0.75A, Boost = V
IN
+ 5V (Note 7)
FB = 1V or V
SENSE
= 4.1V
V
C
Set to Give DC = 50%
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CONDITIONS
5.5V ≤ V
IN
≤ 60V
V
OL
+ 0.2 ≤ V
C
≤ V
OH
– 0.2
(Notes 2, 9)
dl (V
C
) = ±10μA (Note 9)
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MIN
1.204
1.175
200
1500
900
125
100
TYP
1.219
–0.5
400
2000
1.7
225
225
0.9
2.1
MAX
1.234
1.265
–1.5
3000
4200
400
450
UNITS
V
V
μA
V/V
μMho
μMho
A/V
μA
μA
V
V
0.75
2
0.2
3
0.3
0.8
A
Ω
Ω
%
%
93
90
184
135
96
200
200
216
228
kHz
kHz
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LT1766/LT1766-5
ELECTRICAL CHARACTERISTICS
(LT1766H Grade)
The
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denotes specifications which apply over the full operating temperature range, otherwise specifications are at T
J
= 25°C.
V
IN
= 15V, V
C
= 1.5V,
SHDN
= 1V, BOOST open circuit, SW open circuit, unless otherwise noted.
PARAMETER
f
SW
Line Regulation
f
SW
Frequency Shifting Threshold
Minimum Input Voltage
Minimum Boost Voltage
Boost Current (Note 5)
Input Supply Current (I
VIN
)
Bias Supply Current (I
BIAS
)
Shutdown Supply Current
Lockout Threshold
Shutdown Thresholds
Minimum SYNC Amplitude
SYNC Frequency Range
SYNC Input Resistance
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:
Gain is measured with a V
C
swing equal to 200mV above the low
clamp level to 200mV below the upper clamp level.
Note 3:
Minimum input voltage is not measured directly, but is guaranteed
by other tests. It is defined as the voltage where internal bias lines are still
regulated so that the reference voltage and oscillator remain constant.
Actual minimum input voltage to maintain a regulated output will depend
upon output voltage and load current. See Applications Information.
Note 4:
This is the minimum voltage across the boost capacitor needed to
guarantee full saturation of the internal power switch.
Note 5:
Boost current is the current flowing into the BOOST pin with the
pin held 5V above input voltage. It flows only during switch on time.
Note 6:
Input supply current is the quiescent current drawn by the input
pin when the BIAS pin is held at 5V with switching disabled. Bias supply
current is the current drawn by the BIAS pin when the BIAS pin is held
at 5V. Total input referred supply current is calculated by summing input
supply current (I
VIN
) with a fraction of bias supply current (I
BIAS
):
I
TOTAL
= I
VIN
+ (I
BIAS
)(V
OUT
/V
IN
)
with V
IN
= 15V, V
OUT
= 5V, I
VIN
= 1.4mA, I
BIAS
= 2.9mA, I
TOTAL
= 2.4mA.
CONDITIONS
5.5V ≤ V
IN
≤ 60V
Df = 10kHz
(Note 3)
(Note 4) I
SW
≤ 0.75A
Boost = V
IN
+ 5V, I
SW
= 0.5A
Boost = V
IN
+ 5V, I
SW
= 0.75A
(Note 6) V
BIAS
= 5V
(Note 6) V
BIAS
= 5V
SHDN
= 0V, V
IN
≤ 60V, SW = 0V, V
C
Open
V
C
Open
V
C
Open, Shutting Down
V
C
Open, Starting Up
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MIN
TYP
0.05
0.8
4.6
1.8
12
45
1.4
2.9
25
MAX
0.15
5.5
3
40
100
2.2
4.2
120
500
2.68
0.9
0.9
2.2
700
UNITS
%/V
V
V
V
mA
mA
mA
mA
μA
μA
V
V
V
V
kHz
kΩ
2.3
0.15
0.25
228
2.42
0.37
0.45
1.5
20
Note 7:
Switch on-resistance is calculated by dividing V
IN
to SW voltage
by the forced current. See Typical Performance Characteristics for the
graph of switch voltage at other currents.
Note 8:
The LT1766EGN, LT1766EGN-5, LT1766EFE and LT1766EFE-5
are guaranteed to meet performance specifications from 0°C to 125°C
junction temperature. Specifications over the –40°C to 125°C operating
junction temperature range are assured by design, characterization and
correlation with statistical process controls. The LT1766IGN, LT1766IGN-5,
LT1766IFE and LT1766IFE-5 are guaranteed over the full –40°C to 125°C
operating junction temperature range. The LT1766HGN and LT1766HFE are
guaranteed over the full –40°C to 140°C operating junction temperature
range.
Note 9:
Transconductance and voltage gain refer to the internal amplifier
exclusive of the voltage divider. To calculate gain and transconductance,
refer to the SENSE pin on fixed voltage parts. Divide the values shown by
the ratio V
OUT
/1.219.
Note 10:
This IC includes overtemperature protection that is intended
to protect the device during momentary overload conditions. Junction
temperature will exceed 140°C when overtemperature protection is active.
Continuous operation above the specified maximum operating junction
temperature may impair device reliability.
Note 11:
High junction temperatures degrade operating lifetimes.
Operating lifetime at junction temperatures between 125°C and 140°C is
derated to 1000 hours.
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