regulator with internal power switch that draws only 12μA
typical DC supply current while maintaining a regulated
output voltage at no load.
The LTC7138 can supply up to 400mA load current and
features a programmable peak current limit that provides
a simple method for optimizing efficiency and for reduc-
ing output ripple and component size. The LTC7138’s
combination of Burst Mode
®
operation, integrated power
switch, low quiescent current, and programmable peak
current limit provides high efficiency over a broad range
of load currents.
With its wide input range of 4V to 140V and programmable
overvoltage lockout, the LTC7138 is a robust regulator
suited for regulating from a wide variety of power sources.
Additionally, the LTC7138 includes a precise run threshold
and soft-start feature to guarantee that the power system
start-up is well-controlled in any environment. A feedback
comparator output enables multiple LTC7138s to be con-
nected in parallel for higher current applications.
The LTC7138 is available in a thermally enhanced high
voltage-capable 16-lead MSE package with four missing pins.
L,
LT, LTC, LTM, Burst Mode, Linear Technology and the Linear logo are registered trademarks
of Linear Technology Corporation. All other trademarks are the property of their respective
owners.
n
n
n
n
n
n
n
n
n
n
Wide Operating Input Voltage Range: 4V to 140V
Internal Low Resistance Power MOSFET
No Compensation Required
Adjustable 100mA to 400mA Maximum Output
Current
Low Dropout Operation: 100% Duty Cycle
Low Quiescent Current: 12µA
Wide Output Range: 0.8V to V
IN
0.8V ±1% Feedback Voltage Reference
Precise RUN Pin Threshold
Internal or External Soft-Start
Programmable 1.8V, 3.3V, 5V or Adjustable Output
Few External Components Required
Programmable Input Overvoltage Lockout
Thermally Enhanced High Voltage MSOP Package
applicaTions
n
n
n
n
n
n
n
Industrial Control Supplies
Medical Devices
Distributed Power Systems
Portable Instruments
Battery-Operated Devices
Avionics
Automotive
Typical applicaTion
5V to 140V Input to 5V Output, 400mA Step-Down Regulator
V
IN
5V TO 140V C
IN
1µF
250V
L1
220µH
V
IN
LTC7138
ANODE
RUN
SS
V
PRG1
V
FB
OVLO
V
PRG2
GND
SW
V
OUT
5V
C
OUT
400mA
22µF
Efficiency and Power Loss vs Load Current
100
90
80
EFFICIENCY (%)
70
60
50
40
30
20
7138 TA01a
EFFICIENCY
POWER LOSS (mW)
1000
100
10
POWER LOSS
10
0
0.1
1
V
IN
= 12V
V
IN
= 48V
V
IN
= 140V
10
100
LOAD CURRENT (mA)
1
1000
7138f
7138 TA01b
For more information
www.linear.com/LTC7138
1
LTC7138
absoluTe MaxiMuM raTings
(Note 1)
pin conFiguraTion
TOP VIEW
SW 1
V
IN
3
FBO
V
PRG2
V
PRG1
GND
5
6
7
8
17
GND
16 ANODE
14 RUN
12
11
10
9
OVLO
I
SET
SS
V
FB
V
IN
Supply Voltage ................................... –0.3V to 140V
RUN Voltage............................................. –0.3V to 140V
SS, FBO, OVLO, I
SET
Voltages ...................... –0.3V to 6V
V
FB
, V
PRG1
, V
PRG2
Voltages ......................... –0.3V to 6V
Operating Junction Temperature Range (Notes 2, 3, 4)
LTC7138E, LTC7138I .......................... –40°C to 125°C
LTC7138H .......................................... –40°C to 150°C
LTC7138MP ....................................... –55°C to 150°C
Storage Temperature Range .................. –65°C to 150°C
Lead Temperature (Soldering, 10 sec)................... 300°C
MSE PACKAGE
VARIATION: MSE16 (12)
16-LEAD PLASTIC MSOP
T
JMAX
= 150°C,
θ
JA
= 40°C/W,
θ
JC
= 10°C/W
EXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCB
orDer inForMaTion
LEAD FREE FINISH
LTC7138EMSE#PBF
LTC7138IMSE#PBF
LTC7138HMSE#PBF
LTC7138MPMSE#PBF
TAPE AND REEL
LTC7138EMSE#TRPBF
LTC7138IMSE#TRPBF
LTC7138HMSE#TRPBF
LTC7138MPMSE#TRPBF
PART MARKING*
7138
7138
7138
7138
PACKAGE DESCRIPTION
16-Lead Plastic MSOP
16-Lead Plastic MSOP
16-Lead Plastic MSOP
16-Lead Plastic MSOP
TEMPERATURE RANGE
–40°C to 125°C
–40°C to 125°C
–40°C to 150°C
–55°C to 150°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/
The
l
denotes the specifications which apply over the specified operating
junction temperature range, otherwise specifications are at T
A
= 25°C (Note 2). V
IN
= 12V, unless otherwise noted.
SYMBOL
V
IN
V
OUT
UVLO
PARAMETER
Input Voltage Operating Range
Output Voltage Operating Range
V
IN
Undervoltage Lockout
DC Supply Current (Note 5)
Active Mode
Sleep Mode
Shutdown Mode
RUN Pin Threshold
V
IN
Rising
V
IN
Falling
Hysteresis
l
l
elecTrical characTerisTics
CONDITIONS
MIN
4
0.8
3.5
3.3
TYP
MAX
140
V
IN
UNITS
V
V
V
V
mV
µA
µA
µA
V
V
mV
nA
V
V
mV
7138f
Input Supply (V
IN
)
3.75
3.5
250
200
12
1.4
4.0
3.8
I
Q
No Load
V
RUN
= 0V
RUN Rising
RUN Falling
Hysteresis
RUN = 1.3V
OVLO Rising
OVLO Falling
Hysteresis
1.17
1.06
–10
1.17
1.06
400
22
6
1.25
1.14
10
1.25
1.14
V
RUN
I
RUN
V
OVLO
1.21
1.10
110
0
1.21
1.10
110
RUN Pin Leakage Current
OVLO Pin Threshold
2
For more information
www.linear.com/LTC7138
LTC7138
elecTrical characTerisTics
SYMBOL
V
FB(ADJ)
V
FBH
I
FB
V
FB(FIXED)
PARAMETER
Feedback Comparator Threshold
(Adjustable Output)
Feedback Comparator Hysteresis
(Adjustable Output)
Feedback Pin Current
Feedback Comparator Thresholds
(Fixed Output)
Output Supply (V
FB
)
V
FB
Rising, V
PRG1
= V
PRG2
= 0V
LTC7138E, LTC7138I
LTC7138H, LTC7138MP
V
FB
Falling, V
PRG1
= V
PRG2
= 0V
V
FB
= 1V, V
PRG1
= V
PRG2
= 0V
V
FB
Rising, V
PRG1
= SS, V
PRG2
= 0V
V
FB
Falling, V
PRG1
= SS, V
PRG2
= 0V
V
FB
Rising, V
PRG1
= 0V, V
PRG2
= SS
V
FB
Falling, V
PRG1
= 0V, V
PRG2
= SS
V
FB
Rising, V
PRG1
= V
PRG2
= SS
V
FB
Falling, V
PRG1
= V
PRG2
= SS
Operation
I
PEAK
I
VAL
R
ON
I
LSW
I
SS
t
INT(SS)
Peak Current Comparator Threshold
I
SET
Floating
100k Resistor from I
SET
to GND
I
SET
Shorted to GND
I
SET
Floating
100k Resistor from I
SET
to GND
I
SET
Shorted to GND
I
SW
= –100mA
V
IN
= 140V, SW = 0V
V
SS
< 2.5V
SS Pin Floating
4
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
The
l
denotes the specifications which apply over the specified operating
junction temperature range, otherwise specifications are at T
A
= 25°C (Note 2). V
IN
= 12V, unless otherwise noted.
CONDITIONS
MIN
TYP
MAX
UNITS
0.792
0.788
3
–10
4.94
4.91
3.25
3.23
1.78
1.77
540
270
140
50
45
45
0.800
0.800
5
0
5.015
4.985
3.31
3.29
1.81
1.80
610
310
170
60
60
60
1.8
0.1
5
1
0.808
0.812
9
10
5.09
5.06
3.37
3.35
1.84
1.83
680
350
200
70
70
75
1
6
V
V
mV
nA
V
V
V
V
V
V
mA
mA
mA
%
%
%
Ω
μA
μA
ms
Valley Current Comparator Threshold
Relative to I
PEAK
Power Switch On-Resistance
Switch Pin Leakage Current
Soft-Start Pin Pull-Up Current
Internal Soft-Start Time
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 LTC7138 is tested under pulsed load conditions such that
T
J
≈ T
A
. The LTC7138E is guaranteed to meet performance specifications
from 0°C to 85°C. Specifications over the –40°C to 125°C operating
junction temperature range are assured by design, characterization and
correlation with statistical process controls. The LTC7138I is guaranteed
over the –40°C to 125°C operating junction temperature range, the
LTC7138H is guaranteed over the –40°C to 150°C operating junction
temperature range and the LTC7138MP is tested and guaranteed over the
–55°C to 150°C operating junction temperature range.
High junction temperatures degrade operating lifetimes; operating lifetime
is derated for junction temperatures greater than 125°C. Note that the
maximum ambient temperature consistent with these specifications is
determined by specific operating conditions in conjunction with board
layout, the rated package thermal impedance and other environmental
factors.
Note 3:
The junction temperature (T
J
, in °C) is calculated from the ambient
temperature (T
A
, in °C) and power dissipation (P
D
, in Watts) according to
the formula:
T
J
= T
A
+ (P
D
•
θ
JA
)
where
θ
JA
is 40°C/W for the MSOP package.
Note that the maximum ambient temperature consistent with these
specifications is determined by specific operating conditions in
conjunction with board layout, the rated package thermal impedance and
other environmental factors.
Note 4:
This IC includes overtemperature protection that is intended to
protect the device during momentary overload conditions. The maximum
rated junction temperature will be exceeded when this protection is active.
Continuous operation above the specified absolute maximum operating
junction temperature may impair device reliability or permanently damage
the device. The overtemperature protection level is not production tested.
Note 5:
Dynamic supply current is higher due to the gate charge being
delivered at the switching frequency. See Applications Information.
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PCB Design
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