LT3837 Datasheet, PDF (1/28 Pages) Linear Technology – Isolated No-Opto Synchronous Flyback Controller

LT3837
Isolated No-Opto
Synchronous Flyback Controller
FEATURES
n _{Senses Output Voltage Directly from Primary Side}
Winding—No Optoisolator Required
n _{Synchronous Driver for High Efficiency}
n _{Supply Voltage Range 4.5V to 20V}
n _{Accurate Regulation Without User Trims}
n _{Programmable Switching Frequency from}
50kHz to 250kHz
n _{Synchronizable}
n _{Load Compensation}
n _{Undervoltage Lockout}
n _{Available in a Thermally Enhanced 16-Lead}
TSSOP Package
APPLICATIONS
n _{Isolated Medium Power (10W to 60W) Supplies}
n _{Instrumentation Power Supplies}
n _{Isolated Medical Supplies}
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
Protected by U.S. Patents including 6498466, 5841643.
DESCRIPTION
The LT^®3837 is an isolated switching regulator controller
designed for medium power flyback topologies. A typical
application is 10W to 60W with the part powered from a
DC supply.
The LT3837 is a current mode controller that regulates an
output voltage based on sensing the secondary voltage
via a transformer winding during flyback. This allows for
tight output regulation without the use of an optoisolator,
improving dynamic response and reliability. Synchronous
rectification increases converter efficiency and improves
output cross regulation in multiple output converters.
The LT3837 operates in forced continuous conduction
mode which improves cross regulation in multiple winding
applications. Switching frequency is user programmable
and can be externally synchronized. The part also has load
compensation, undervoltage lockout and soft-start circuitry.
The LT3837 is available in a thermally enhanced 16-pin
TSSOP package.
TYPICAL APPLICATION
9V –18V to 3.3V at 10A Isolated Converter
22.1k
2N3906
BAS16
22μF
3k
20k
3.3nF
V_CC
1nF
47pF
FB
UVLO
V_C
LT3837
OSC
100k
150k
12k
1.37k
0.1μF
SFST
PG
t_ON
SENSE⁺
ENDLY
PGDLY
R_CMP ^SENSE–
SG
C_CMP
GND
V_IN
86.6k
15k
10μF
2.2nF ^•
10Ω
100nH _{OUTPUT 3.3V/10A}
47μF s3
•
B0540W
10Ω
220μF
FMMT618
1μF
Si7336ADP
Si7852DP
FMMT718
8mΩ
330Ω
0.1μF
2.2nF
••
10k
15Ω
BAT54
3837 TA01
Efficiency vs Load Current
90
9V_IN
88
18V_IN
86
84
82
80
78
76
2 3 4 5 6 7 8 9 10
LOAD CURRENT (A)
3837 TA01b
Regulation vs Load Current
3.60
3.50
3.40
9V_IN
3.30
18V_IN
3.20
3.10
3.00
2 3 4 5 6 7 8 9 10
LOAD CURRENT (A)
3837 TA01c
3837fa
1