LTC3803
Constant Frequency
Current Mode Flyback
DC/DC Controller in ThinSOT
FEATURES DESCRIPTION
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V and V Limited Only by External Components
The LTC 3803 is a constant frequency current mode yback
IN OUT
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Adjustable Slope Compensation
controller optimized for driving N-channel MOSFETs in high
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Internal Soft-Start
input voltage applications. Constant frequency operation
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Constant Frequency 200kHz Operation
is maintained down to very light loads, resulting in less
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1.5% Reference Accuracy
low frequency noise generation over a wide range of load
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Current Mode Operation for Excellent Line and Load
currents. Slope compensation can be programmed with
Transient Response
an external resistor.
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No Minimum Load Requirement
The LTC3803 provides 1.5% output voltage accuracy and
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Low Quiescent Current: 240A
consumes only 240A of quiescent current. Ground-refer-
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Low Pro le (1mm) SOT-23 Package
enced current sensing allows LTC3803-based converters
to accept input supplies beyond the LTC3803s absolute
maximum V . A micropower hysteretic start-up feature
APPLICATIONS
CC
allows ef cient operation at high input voltages. For sim-
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Telecom Power Supplies
plicity, the LTC3803 can also be powered from a high V
IN
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42V and 12V Automotive Power Supplies
through a resistor, due to its internal shunt regulator. An
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Auxiliary/Housekeeping Power Supplies
internal undervoltage lockout shuts down the LTC3803
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Power Over Ethernet
when the input voltage is too low to provide suf cient
L, LT, LTC, LTM, Burst Mode, Linear Technology and the Linear logo are registered trademarks
gate drive to the external MOSFET.
and ThinSOT and No R are trademarks of Linear Technology Corporation. All other
SENSE
trademarks are the property of their respective owners.
The LTC3803 is available in a low pro le (1mm) 6-lead
SOT-23 (ThinSOT) package.
TYPICAL APPLICATION
5V Output Nonisolated Telecom Housekeeping Power Supply Ef ciency vs Load Current
90
V
IN
36V TO 72V
UPS840
V = 36V
IN
80
V
OUT
T1
5V
70
4.7F 300F* 2A MAX
V = 48V
IN
10k 100V 6.3V
60
X5R X5R
V = 60V
IN
10F
50
10V
V = 72V
IN
X5R
V
40
CC
I /RUN NGATE FDC2512
TH
30
56k
LTC3803
20
GND SENSE
0.0022F
V 10
FB
68m
0
20k 105k
1
0.1 10
3803 TA01
I (A)
OUT
T1: COOPER CTX02-15242
3803 TA02
*THREE 100F UNITS IN PARALLEL
3803fc
1
EFFICIENCY (%)LTC3803
ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION
(Note 1)
TOP VIEW
V to GND
CC
Low Impedance Source ........................... 0.3V to 8V I /RUN 1 6 NGATE
TH
GND 2 5 V
CC
Current Fed ........................................25mA into V *
CC
V 3 4 SENSE
FB
NGATE Voltage ............................................0.3V to V
CC
V , I /RUN Voltages............................... 0.3V to 3.5V S6 PACKAGE
FB TH
6-LEAD PLASTIC TSOT-23
SENSE Voltage ............................................. 0.3V to 1V
T = 150C, = 192C/W
JMAX JA
NGATE Peak Output Current (<10s) ......................... 1A
Operating Junction Temperature Range (Notes 2, 3)
LTC3803E, LTC3803I .......................... 40C to 125C
LTC3803H .......................................... 40C to 150C
LTC3803MP ....................................... 55C to 150C
Storage Temperature Range ...................65C to 150C
Lead Temperature (Soldering, 10 sec) .................. 300C
*LTC3803 internal clamp circuit self regulates V voltage to 9.5V.
CC
ORDER INFORMATION
LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE
LTC3803ES6#PBF LTC3803ES6#TRPBF LTACV 6-Lead Plastic TSOT-23 40C to 125C
LTC3803IS6#PBF LTC3803IS6#TRPBF LTBNC 6-Lead Plastic TSOT-23 40C to 125C
LTC3803HS6#PBF LTC3803HS6#TRPBF LTBNC 6-Lead Plastic TSOT-23 40C to 150C
LTC3803MPS6#PBF LTC3803MPS6#TRPBF LTBNC 6-Lead Plastic TSOT-23 55C to 150C
LEAD BASED FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE
LTC3803ES6 LTC3803ES6#TR LTACV 6-Lead Plastic TSOT-23 40C to 125C
LTC3803IS6 LTC3803IS6#TR LTBNC 6-Lead Plastic TSOT-23 40C to 125C
LTC3803HS6 LTC3803HS6#TR LTBNC 6-Lead Plastic TSOT-23 40C to 150C
LTC3803MPS6 LTC3803MPS6#TR LTBNC 6-Lead Plastic TSOT-23 55C to 150C
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.
For more information on lead free part marking, go to: