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LTC3873_15 Datasheet, PDF (1/16 Pages) Linear Technology – Frequency Current Mode Boost/Flyback/SEPIC DC/DC Controller | |||
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LTC3873
No RSENSETM Constant
Frequency Current Mode
Boost/Flyback/SEPIC
DC/DC Controller
FEATURES
n VIN and VOUT Limited Only by External Components
n Internal or Programmable External Soft-Start
n Constant Frequency 200kHz Operation
n Adjustable Current Limit
n Current Sense Resistor Optional
n Maximum 60V on SW Node with RDS(ON) Sensing
n ±1.5% Voltage Reference Accuracy
n Current Mode Operation for Excellent Line and Load
Transient Response
n Low Quiescent Current: 300μA
n Low Proï¬le (1mm) ThinSOTTM and (0.75mm)
2mm à 3mm DFN Package
APPLICATIONS
n Telecom Power Supplies
n 42V and 12V Automotive Power Supplies
n Portable Electronic Equipment
DESCRIPTION
The LTC®3873 is a constant frequency current mode,
boost, ï¬yback or SEPIC DC/DC controller that drives an
N-channel power MOSFET in high input and output volt-
age converter applications. Soft-start can be programmed
using an external capacitor.
The LTC3873 provides ±1.5% output voltage accuracy and
consumes only 300μA quiescent current during normal
operation and only 55μA during micropower start-up.
Using a 9.3V internal shunt regulator, the LTC3873 can
be powered from a high input voltage through a resistor
or it can be powered directly from a low impedance DC
voltage of 9V or less.
The LTC3873 is available in 8-lead ThinSOT and 2mm Ã
3mm DFN packages.
PARAMETER
VCC UV+
VCC UVâ
LTC3873
8.4V
4V
LTC3873-5
3.9V
2.9V
L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
No RSENSE and ThinSOT are trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
4.7μF
100V
X5R
7.5k
2.2nF
5V Output Nonisolated Telecom Power Supply
10μF
10V
X5R
0.1μF
VIN
36V TO 72V
221k
D2
T1
â¢
D1
â¢
VCC
ITH NGATE
LTC3873
RUN/SS
GND
SW
IPRG
VFB
12.1k
38.3k
M1
68mΩ
100μF
6.3V
X5R
s3
VOUT
5V
2A MAX
3873 TA01a
Efï¬ciency and Power Loss vs Load Current
100
3000
90
EFFICIENCY
80
2500
70
2000
60
50
40
30
20
10
0
10
POWER LOSS
1500
1000
VIN = 72V
VIN = 60V 500
VIN = 48V
VIN = 36V
10
1000
LOAD CURRENT (mA)
3873 TA01b
3873fa
1
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