LTC3873-5 Datasheet, PDF (1/16 Pages) Linear Technology – No RSENSETM Constant Frequency Current Mode Boost/Flyback/SEPIC DC/DC Controller

LTC3873-5
No R_SENSE^TM 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 _{±1.5% Voltage Reference Accuracy}
n _{Current Mode Operation for Excellent Line and Load}
Transient Response
n _{4.1V Undervoltage Threshold for Logic Level}
MOSFET Applications
n _{Low Quiescent Current: 300μA}
n _{Low Profile (1mm) ThinSOT}^TM _{and (0.75mm)}
2mm × 3mm DFN Package
APPLICATIONS
n _{Telecom Power Supplies}
n _{Automotive Power Supplies}
n _{PoE Applications}
DESCRIPTION
The LTC^®3873-5 is a constant frequency current mode
controller for boost, flyback or SEPIC DC/DC converters
designed to drive an N-channel MOSFET for high input
and output voltage converter applications.
The LTC3873-5 provides ±1.5% output voltage accuracy
and consumes only 300μA quiescent current during nor-
mal operation and only 50μA during micropower start-up.
Using a 9.3V internal shunt regulator, the LTC3873-5 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. Soft-start can be programmed using
an external capacitor.
The LTC3873-5 is available in 8-lead ThinSOT and 2mm
× 3mm DFN packages.
PARAMETER
V_CC UV⁺
V_CC UV^–
LTC3873
8.4V
4V
LTC3873-5
4.1V
2.9V
L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
No R_SENSE and ThinSOT are trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
High Efficiency 5V Input, 12V Output Boost Converter
4.7nF
11.8k
47pF
12k
1nF
RUN/SS
I_TH
V_CC
LTC3873-5
IPRG
GND
SW
V_FB
NGATE
108k
10μH
10μF
22μF
V_IN
5V
V_OUT
12V
2A
38735 TA01a
Efficiency and Power Loss vs Load Current
100
90
80
70
60
50
40
30
20
10
0
10
10000
1000
100
100
I_OUT (mA)
10
1000
3873 TA01b
38735fb
1