LTC3803-5 Datasheet, PDF (1/12 Pages) Linear Technology – Constant Frequency Current Mode Flyback DC/DC Controller in ThinSOT

LTC3803-5
Constant Frequency
Current Mode Flyback
DC/DC Controller in ThinSOT
FEATURES
■ _{VIN and VOUT Limited Only by External Components}
■ _{4.8V Undervoltage Lockout Threshold}
■ _{Operating Junction Temperature from –40°C to}
150°C
■ _{Adjustable Slope Compensation}
■ _{Internal Soft-Start}
■ _{Constant Frequency 200kHz 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
■ _{42V and 12V Automotive Power Supplies}
■ _{Telecom Power Supplies}
■ _{Auxiliary/Housekeeping Power Supplies}
■ _{Power Over Ethernet}
, LTC and LT are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
ThinSOT is a trademark of Linear Technology Corporation.
DESCRIPTIO
The LTC^®3803-5 is a constant frequency current mode
flyback controller optimized for driving 4.5V and 6V-rated
N-channel MOSFETs in high input voltage applications.
The LTC3803-5 operates from inputs as low as 5V. Con-
stant 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 LTC3803-5 provides ±1.5% output voltage accuracy
and consumes only 240µA of quiescent current. Ground-
referenced current sensing allows LTC3803-5-based con-
verters to accept input supplies beyond the LTC3803-5’s
absolute maximum V_CC. For simplicity, the LTC3803-5
can be powered from a high V_IN through a resistor, due to
its internal 8V shunt regulator. An internal undervoltage
lockout shuts down the IC when the input voltage falls
below 3.2V, guaranteeing at least 3.2V of gate drive to the
external MOSFET.
The LTC3803-5 is available in a low profile (1mm) 6-lead
SOT-23 (ThinSOT^TM) package.
TYPICAL APPLICATIO
Dual Output Wide Input Range Converter
V_IN
6V TO 50V
PDZ9.1B
22k
1µF
100V
3x
VPH5-0155 ^10MQ100N
MMBTA42
10nF
7.5k
8.06k
LTC3803-5
I_TH/RUN NGATE
GND
V_CC
V_FB
SENSE
0.1µF
57.6k
PHM25NQ10T
4.7k
0.012Ω
1µF
100V
1µF
100V
B3100
ALL CAPACITORS ARE X7R, TDK
13V/0.3A
20mA MIN
LOAD
22µF
10V
6.5V/1.2A
47µF
10V
38035 TA01
Efficiency and Power Loss
vs Output Power
90
V_IN = 8V
3.0
85 _{VIN = 12V}
2.5
80
2.0
V_IN = 24V
75
1.5
70
1.0
V_IN = 48V
65
0.5
60 ^{VIN = 12V}
0
2
4
6
8
OUTPUT POWER (W)
0
10 12
38035 TA01b
38035f
1