LTC3803-5_15 Datasheet, PDF (1/16 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
n _{VIN and VOUT Limited Only by External Components}
n _{4.8V Undervoltage Lockout Threshold}
n _{Operating Junction Temperature from –55°C to}
150°C
n _{Adjustable Slope Compensation}
n _{Internal Soft-Start}
n _{Constant Frequency 200kHz Operation}
n _{±1.5% Reference Accuracy}
n _{Current Mode Operation for Excellent Line and Load}
Transient Response
n _{No Minimum Load Requirement}
n _{Low Quiescent Current: 240μA}
n _{Low Profile (1mm) SOT-23 Package}
APPLICATIONS
n _{42V and 12V Automotive Power Supplies}
n _{Telecom Power Supplies}
n _{Auxiliary/Housekeeping Power Supplies}
n _{Power Over Ethernet}
L, LT, LTC, LTM, Burst Mode, Linear Technology and the Linear logo are registered trademarks
and ThinSOT and No R_SENSE are trademarks of Linear Technology Corporation. All other
trademarks are the property of their respective owners.
DESCRIPTION
The LTC^®3803-5 is a constant frequency current mode
flyback controller optimized for driving N-channel MOSFETs
in high input voltage applications. The LTC3803-5 operates
from inputs as low as 5V. 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 LTC3803-5 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 shunt regulator. An internal undervoltage lockout
shuts down the IC when the input voltage is too low to
provide sufficient gate drive to the external MOSFET.
The LTC3803-5 is available in a low profile (1mm) 6-lead
SOT-23 (ThinSOT™) package.
TYPICAL APPLICATION
Dual Output Wide Input Range Converter
V_IN
6V TO 50V
PDZ6.8B
22k
1μF
100V
×3
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
02
46
8 10 12
OUTPUT POWER (W)
38035 TA01b
38035fd
1