LT1767/LT1767-1.8/
LT1767-2.5/LT1767-3.3/LT1767-5
Monolithic 1.5A, 1.25MHz
Step-Down Switching Regulators
FeaTures
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DescripTion
The
LT
®
1767
is a 1.25MHz monolithic buck switching
regulator. A high efficiency 1.5A, 0.22Ω switch is included
on the die together with all the control circuitry required
to complete a high frequency, current mode switching
regulator. Current mode control provides fast transient
response and excellent loop stability.
New design techniques achieve high efficiency at high
switching frequencies over a wide operating range. A
low dropout internal regulator maintains consistent per-
formance over a wide range of inputs from 24V systems
to Li-Ion batteries. An operating supply current of 1mA
improves efficiency, especially at lower output currents.
Shutdown reduces quiescent current to 6µA. Maximum
switch current remains constant at all duty cycles. Syn-
chronization allows an external logic level signal to increase
the internal oscillator from 1.5MHz to 2MHz.
The LT1767 is available in an 8-pin MSOP fused lead-frame
package and a low thermal resistance exposed pad package.
Full cycle-by-cycle current limit and thermal shutdown are
provided. High frequency operation allows the reduction
of input and output filtering components and permits the
use of chip inductors.
L,
LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks
of Linear Technology Corporation. All other trademarks are the property of their respective
owners. Protected by U.S. Patents, including 6611131, 6498466.
1.5A Switch in a Small MSOP Package
Constant 1.25MHz Switching Frequency
High Power Exposed Pad (MS8E) Package
Wide Operating Voltage Range: 3V to 25V
High Efficiency 0.22Ω Switch
1.2V Feedback Reference Voltage
Fixed Output Voltages of 1.8V, 2.5V, 3.3V, 5V
2% Overall Output Tolerance
Uses Low Profile Surface Mount Components
Low Shutdown Current: 6µA
Synchronizable to 2MHz
Current Mode Loop Control
Constant Maximum Switch Current Rating at All Duty
Cycles*
applicaTions
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DSL Modems
Portable Computers
Wall Adapters
Battery-Powered Systems
Distributed Power
Typical applicaTion
12V to 3.3V Step-Down Converter
D2
CMDSH-3
C2
0.1µF
V
IN
12V
V
IN
OPEN
OR
HIGH
= ON
SHDN
SYNC
BOOST
LT1767-3.3
FB
GND
V
C
C
C
1.5nF
D1
UPS120
C1
10µF
CERAMIC
V
SW
Efficiency vs Load Current
95
V
IN
= 10V
V
OUT
= 5V
90
EFFICIENCY (%)
L1
5µH
C3
2.2µF
CERAMIC
OUTPUT
3.3V
1.2A*
85
80
75
R
C
4.7k
70
0
0.2
*MAXIMUM OUTPUT CURRENT IS SUBJECT TO THERMAL DERATING.
0.4 0.6 0.8
1
LOAD CURRENT (A)
1.2
1.4
1767 TA01
1767 TA01a
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LT1767/LT1767-1.8/
LT1767-2.5/LT1767-3.3/LT1767-5
absoluTe MaxiMuM raTings
(Note 1)
Input Voltage ........................................................... 25V
BOOST Pin Above SW ............................................. 20V
Max BOOST Pin Voltage ............................................35V
SHDN
Pin ................................................................. 25V
FB Pin Voltage ........................................................... 6V
FB Pin Current......................................................... 1mA
SYNC Pin Current ................................................... 1mA
Operating Junction Temperature Range (Note 2)
LT1767E ........................................... – 40°C to 125°C
Storage Temperature Range ................. –65°C to 150°C
Lead Temperature (Soldering, 10 sec) ................ 300°C
pin conFiguraTion
TOP VIEW
BOOST
V
IN
SW
GND
1
2
3
4
8
7
6
5
SYNC
V
C
FB
SHDN
BOOST
V
IN
SW
GND
1
2
3
4
TOP VIEW
8
7
6
5
SYNC
V
C
FB
SHDN
MS8 PACKAGE
8-LEAD PLASTIC MSOP
T
JMAX
= 125°C,
θ
JA
= 110°C/W
GROUND PIN CONNECTED TO LARGE COPPER AREA
MS8E PACKAGE
8-LEAD PLASTIC MSOP
T
JMAX
= 125°C,
θ
JA
= 40°C/W
GROUND PIN CONNECTED TO LARGE COPPER AREA ON PCB
orDer inForMaTion
LEAD FREE FINISH
LT1767EMS8#PBF
LT1767EMS8-1.8#PBF
LT1767EMS8-2.5#PBF
LT1767EMS8-3.3#PBF
LT1767EMS8-5#PBF
LT1767EMS8E#PBF
LT1767EMS8E-1.8#PBF
LT1767EMS8E-2.5#PBF
LT1767EMS8E-3.3#PBF
LT1767EMS8E-5#PBF
TAPE AND REEL
LT1767EMS8#TRPBF
LT1767EMS8-1.8#TRPBF
LT1767EMS8-2.5#TRPBF
LT1767EMS8-3.3#TRPBF
LT1767EMS8-5#TRPBF
LT1767EMS8E#TRPBF
LT1767EMS8E-1.8#TRPBF
LT1767EMS8E-2.5#TRPBF
LT1767EMS8E-3.3#TRPBF
LT1767EMS8E-5#TRPBF
PART MARKING
LTLS
LTWG
LTWD
LTWE
LTWF
LTZG
LTZH
LTZJ
LTZK
LTZL
PACKAGE DESCRIPTION
8-Lead Plastic MSOP
8-Lead Plastic MSOP
8-Lead Plastic MSOP
8-Lead Plastic MSOP
8-Lead Plastic MSOP
8-Lead Plastic MSOP, Exposed Pad
8-Lead Plastic MSOP, Exposed Pad
8-Lead Plastic MSOP, Exposed Pad
8-Lead Plastic MSOP, Exposed Pad
8-Lead Plastic MSOP, Exposed Pad
TEMPERATURE RANGE
–40°C to 125°C
–40°C to 125°C
–40°C to 125°C
–40°C to 125°C
–40°C to 125°C
–40°C to 125°C
–40°C to 125°C
–40°C to 125°C
–40°C to 125°C
–40°C to 125°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
Consult LTC Marketing for information on nonstandard 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/
2
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LT1767/LT1767-1.8/
LT1767-2.5/LT1767-3.3/LT1767-5
elecTrical characTerisTics
The
l
denotes the specifications which apply over the full operating
PARAMETER
Maximum Switch Current Limit
Oscillator Frequency
Switch On Voltage Drop
V
IN
Undervoltage Lockout
V
IN
Supply Current
Shutdown Supply Current
Feedback Voltage
CONDITIONS
T
A
= 0°C to 125°C
T
A
= < 0°C
3.3V < V
IN
< 25V
l
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 15V, V
C
= 0.8V, Boost = V
IN
+ 5V,
SHDN,
SYNC and switch open
unless otherwise noted.
MIN
1.5
1.3
1.1
1.1
TYP
2
1.25
330
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MAX
3
3
1.4
1.5
400
500
2.73
1.3
20
45
1.218
1.224
1.836
2.55
3.366
5.1
–0.5
21
30
39
60
1300
160
180
UNITS
A
A
MHz
MHz
mV
mV
V
mA
µA
µA
V
V
V
V
V
V
µA
kΩ
kΩ
kΩ
kΩ
µMho
µA
µA
A/V
V
V
%
%
I
SW
= –1.5A, 0°C ≤ T
A
≤ 125°C and –1.3A, T
A
< 0°C
(Note 3)
V
FB
= V
NOM
+ 17%
V
SHDN
= 0V, V
IN
= 25V, V
SW
= 0V
3V < V
IN
< 25V, 0.4V < V
C
< 0.9V LT1767 (Adj)
(Note 3)
LT1767-1.8
LT1767-2.5
LT1767-3.3
LT1767-5
1.182
1.176
1.764
2.45
3.234
4.9
10.5
14.7
19
29
150
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2.47
2.6
1
6
1.2
1.8
2.5
3.3
5
–0.25
15
21
27.5
42
350
850
120
110
2.5
0.35
0.9
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FB Input Current
FB Input Resistance
LT1767 (Adj)
LT1767-1.8
LT1767-2.5
LT1767-3.3
LT1767-5
0.4V < V
C
< 0.9V
∆I
VC
= ±10µA
V
FB
= V
NOM
– 17%
V
FB
= V
NOM
+ 17%
Duty Cycle = 0%
V
C
= 1.2V, I
SW
= 400mA
Error Amp Voltage Gain
Error Amp Transconductance
V
C
Pin Source Current
V
C
Pin Sink Current
V
C
Pin to Switch Current Transconductance
V
C
Pin Minimum Switching Threshold
V
C
Pin 1.5A I
SW
Threshold
Maximum Switch Duty Cycle
Minimum Boost Voltage Above Switch
Boost Current
SHDN
Threshold Voltage
SHDN
Input Current (Shutting Down)
SHDN
Threshold Current Hysteresis
SYNC Threshold Voltage
SYNC Input Frequency
SYNC Pin Resistance
500
80
70
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85
80
90
1.8
10
30
2.7
15
45
1.40
–13
10
2.2
2
20
I
SW
= –1.5A, 0°C ≤ T
A
≤ 125°C and –1.3A, T
A
< 0°C
I
SW
= – 0.5A (Note 4)
I
SW
= –1.5A, 0°C ≤ T
A
≤ 125°C and –1.3A, T
A
< 0°C (Note 4)
SHDN
= 60mV Above Threshold
SHDN
= 100mV Below Threshold
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V
mA
mA
V
µA
µA
V
MHz
kΩ
1.27
–7
4
1.5
1.33
–10
7
1.5
I
SYNC
= 1mA
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elecTrical characTerisTics
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 LT1767E is guaranteed to meet performance specifications
from 0°C to 125°C. Specifications over the – 40°C to 125°C operating
junction temperature range are assured by design, characterization and
correlation with statistical process controls.
Note 3:
Minimum input voltage is defined as the voltage where the internal
regulator enters lockout. Actual minimum input voltage to maintain a
regulated output will depend on output voltage and load current. See
Applications Information.
Note 4:
Current flows into the BOOST pin only during the on period of the
switch cycle.
Typical perForMance characTerisTics
FB vs Temperature (Adj)
1.22
400
350
SWITCH VOLTAGE (mV)
T
A
= 25°C, unless otherwise noted.
Oscillator Frequency
1.50
1.45
1.40
FREQUENCY (MHz)
Switch On Voltage Drop
125°C
25°C
–40°C
1.21
FB VOLTAGE (V)
300
250
200
150
100
50
1.35
1.30
1.25
1.20
1.15
1.20
1.19
1.18
–50
–25
0
25
50
75
TEMPERATURE (°C)
100
125
1767 G01
0
0
1
0.5
SWITCH CURRENT (A)
1.5
1767 G02
1.10
–50
–25
0
25
50
75
TEMPERATURE (°C)
100
125
1767 G03
SHDN
Threshold vs Temperature
1.40
SHDN
Supply Current vs V
IN
7
6
V
IN
CURRENT (µA)
SHDN
I
P
Current vs Temperature
–12
–10
SHUTTING DOWN
SHDN
INPUT (µA)
SHDN
= 0V
1.38
SHDN THRESHOLD (V)
5
4
3
2
1
1.36
–8
–6
–4
–2
0
–50
STARTING UP
1.34
1.32
1.30
–50
–25
0
25
50
75
TEMPERATURE (°C)
100
125
0
0
5
10
15
V
IN
(V)
20
25
30
1767 G05
–25
0
25
50
75
TEMPERATURE (°C)
100
125
1767 G04
1767 G06
4
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LT1767-2.5/LT1767-3.3/LT1767-5
Typical perForMance characTerisTics
Minimum Input Voltage, 3.3V Out
Minimum Input Voltage, 3.3V Out
7.0
6.5
6.0
INPUT VOLTAGE (V)
V
IN
CURRENT (µA)
T
A
= 25°C, unless otherwise noted.
Input Supply Current
1200
SHDN
Supply Current
300
V
IN
= 15V
250
200
150
100
50
0
1000
V
IN
CURRENT (µA)
BOOST DIODE TIED TO V
OUT
BOOST DIODE TIED TO V
IN
5.5
5.0
4.5
4.0
3.5
3.0
2.5
1
TO RUN
TO START
800
600
400
200
0
MINIMUM
INPUT
VOLTAGE
10
100
LOAD CURRENT (mA)
1k
1767 G07
0
0.2
0.4 0.6 0.8
1
1.2
SHUTDOWN VOLTAGE (V)
1.4
0
5
10
15
20
INPUT VOLTAGE (V)
25
30
1767 G09
1767 G08
Current Limit Foldback
2.0
40
1.5
Maximum Load Current,
V
OUT
= 5V
1.5
Maximum Load Current,
V
OUT
= 2.5V
SWITCH PEAK CURRENT (A)
OUTPUT CURRENT (A)
SWITCH CURRENT
1.0
20
1.1
OUTPUT CURRENT (A)
1.5
30
1.3
FB INPUT CURRENT (µA)
L = 4.7µH
1.3
L = 4.7µH
1.1
L = 2.2µH
0.9
L = 2.2µH
L = 1.5µH
0.9
0.5
FB CURRENT
0
10
0.7
L = 1.5µH
0
0.2
0.4
0.6
0.8
FEEDBACK VOLTAGE (V)
1
0
1.2
1767 G10
0.5
0
5
10
15
INPUT VOLTAGE (V)
20
25
1767 G11
0.7
0
5
10
15
INPUT VOLTAGE (V)
20
25
1767 G12
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