LT1103 Datasheet, PDF (2/32 Pages) Linear Technology – Offline Switching Regulator

LT1103/LT1105
DESCRIPTION
200kHz maximum switching frequency to achieve high
power density. Performance at switching frequencies
above 100kHz may be degraded due to internal timing
constraints associated with fully isolated flyback mode.
Included are the oscillator, control, and protection cir-
cuitry such as current limit and overvoltage lockout.
Switch frequency and maximum duty cycle are adjustable.
Bootstrap circuitry draws 200µA for start-up of isolated
topologies. A 5V reference as well as a 15V gate bias are
available to power external primary-side circuitry. No
external current sense resistor is necessary with LT1103
because it is integrated with the high current switch. The
LT1105 brings out the input to the current limit amplifier
and requires the use of an external sense resistor.
The LT1103/LT1105 have unique features not found on
other offline switching regulators. Adaptive antisat switch
drive allows wide ranging load currents while maintaining
high efficiency. The external FET is protected from insuf-
ficient or excessive gate drive voltage with a drive detec-
tion circuit. An externally activated shutdown mode
reduces total supply current to less than 200µA, typical for
standby operation. Fully isolated and regulated outputs
can be generated in the optional isolated flyback mode
without the need for optocouplers or other isolated feed-
back paths.
WAR I G!
DANGEROUS AND LETHAL POTENTIALS ARE
PRESENT IN OFFLINE CIRCUITS!
BEFORE PROCEEDING ANY FURTHER, THE
READER IS WARNED THAT CAUTION MUST
BE USED IN THE CONSTRUCTION, TESTING
AND USE OF OFFLINE CIRCUITS. HIGH
VOLTAGE, AC LINE-CONNECTED POTENTIALS
ARE PRESENT IN THESE CIRCUITS. EXTREME
CAUTION MUST BE USED IN WORKING WITH
AND MAKING CONNECTIONS TO THESE
CIRCUITS. REPEAT: OFFLINE CIRCUITS
CONTAIN DANGEROUS, AC LINE-CONNECTED
HIGH VOLTAGE POTENTIALS. USE CAUTION.
ALL TESTING PERFORMED ON AN OFFLINE
CIRCUIT MUST BE DONE WITH AN ISOLATION
TRANSFORMER CONNECTED BETWEEN THE
OFFLINE CIRCUIT'S INPUT AND THE AC LINE.
USERS AND CONSTRUCTORS OF OFFLINE
CIRCUITS MUST OBSERVE THIS PRECAUTION
WHEN CONNECTING TEST EQUIPMENT TO
THE CIRCUIT TO AVOID ELECTRIC SHOCK.
REPEAT: AN ISOLATION TRANSFORMER
MUST BE CONNECTED BETWEEN THE CIRCUIT
INPUT AND THE AC LINE IF ANY TEST
EQUIPMENT IS TO BE CONNECTED.
ABSOLUTE MAXIMUM RATINGS (Note 1)
V_IN .......................................................................... 30V
V_SW Output Voltage (LT1103) ................................. 50V
V_SW Output Current (200ns)(LT1105) ................. ±1.5A
V_C, FB, OSC, SS ........................................................ 6V
I_LIM (LT1105) ........................................................... 3V
0VLO Input Current ............................................... 1mA
Lead Temperature (Soldering, 10 sec.)................ 300°C
Maximum Operating Ambient Temperature Range
LT1103C .............................................. 0°C to 70°C
LT1105C .............................................. 0°C to 70°C
Maximum Operating Junction Temperature Range
LT1103C ............................................. 0°C to 100°C
LT1105C ............................................ 0°C to 100°C
LT1105I ......................................... – 40°C to 125°C
Storage Temperature Range ................ –65°C to 150°C
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