LTC3873_15 Datasheet, PDF (1/16 Pages) Linear Technology – Frequency Current Mode Boost/Flyback/SEPIC DC/DC Controller

LTC3873
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 _{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 Profile (1mm) ThinSOT}^TM _{and (0.75mm)}
2mm × 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, flyback 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 ×
3mm DFN packages.
PARAMETER
V_CC UV⁺
V_CC UV^–
LTC3873
8.4V
4V
LTC3873-5
3.9V
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
4.7μF
100V
X5R
7.5k
2.2nF
5V Output Nonisolated Telecom Power Supply
10μF
10V
X5R
0.1μF
V_IN
36V TO 72V
221k
D2
T1
•
D1
•
V_CC
I_TH NGATE
LTC3873
RUN/SS
GND
SW
IPRG
V_FB
12.1k
38.3k
M1
68mΩ
100μF
6.3V
X5R
s3
V_OUT
5V
2A MAX
3873 TA01a
Efficiency 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
V_IN = 72V
V_IN = 60V ₅₀₀
V_IN = 48V
V_IN = 36V
10
1000
LOAD CURRENT (mA)
3873 TA01b
3873fa
1