LTC3803-3 Datasheet, PDF (1/16 Pages) Linear Technology – Constant Frequency Current Mode Flyback DC/DC Controller in ThinSOT

LTC3803-3
Constant Frequency
Current Mode Flyback
DC/DC Controller in ThinSOT
FEATURES
■ _{VIN and VOUT Limited Only by External Components}
■ _{Adjustable Slope Compensation}
■ _{Internal Soft-Start}
■ _{–40°C to 125°C Operating Temperature Range}
■ _{Constant Frequency 300kHz Operation}
■ _{±1.5% Reference Accuracy}
■ _{Current Mode Operation for Excellent Line and Load}
Transient Response
■ _{No Minimum Load Requirement}
■ _{Low Quiescent Current: 240μA}
■ _{Low Profile (1mm) SOT-23 Package}
U
APPLICATIO S
■ _{Telecom Power Supplies}
■ _{42V and 12V Automotive Power Supplies}
■ _{Auxiliary/Housekeeping Power Supplies}
■ _{Power Over Ethernet Powered Devices}
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
ThinSOT is a trademark of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
DESCRIPTIO
The LTC^®3803-3 is a constant frequency current mode
flyback controller optimized for driving 6V-rated N-channel
MOSFETs in high input voltage applications. Constant
frequency operation is maintained down to very light
loads, resulting in less low frequency noise generation
over a wide range of load currents. Slope compensation
can be programmed with an external resistor.
The LTC3803-3 provides ±1.5% output voltage accuracy
and consumes only 240μA of quiescent current. Ground-
referenced current sensing allows LTC3803-3-based con-
verters to accept input supplies beyond the LTC3803-3’s
absolute maximum V_CC. A micropower hysteretic start-up
feature allows efficient operation at high input voltages.
For simplicity, the LTC3803-3 can also be powered from
a high V_IN through a resistor, due to its internal 9.4V shunt
regulator. An internal undervoltage lockout shuts down
the LTC3803-3 when the input voltage falls below 4.4V,
guaranteeing at least 4.4V of gate drive to the external
MOSFET.
The LTC3803-3 is available in a low profile (1mm) 6-lead
SOT-23 (ThinSOT^TM) package.
TYPICAL APPLICATIO
5V Output Nonisolated Telecom Housekeeping Power Supply
1μF
10V
X5R
82k
470pF
V_IN
36V TO 72V
10k
UPS840
T1
1μF ^•
100V
X5R
•
300μF*
6.3V
X5R
V_CC
I_TH/RUN NGATE
LTC3803-3
4.7k
GND SENSE
V_FB
FDC2512
68mΩ
150pF
200V
220Ω
V_OUT
5V
2A MAX
20k 105k
38033 TA01
T1: COOPER CTX02-15242
*THREE 100μF UNITS IN PARALLEL
Efficiency vs Load Current
100
V_OUT = 5V
95
90
85
80
75
70
65
60
V_IN = 36V
V_IN = 48V
55
V_IN = 60V
V_IN = 72V
50
250 500 750 1000 1250 1500 1750 2000
LOAD CURRENT (mA)
38033 TA02
38033fa
1