LT1241 Series
High Speed Current Mode
Pulse Width Modulators
FEATURES
DESCRIPTION
The LT ®1241 series devices are 8-pin, fixed frequency,
current mode, pulse width modulators. They are improved
plug compatible versions of the industry standard UC1842
series. These devices have both improved speed and
lower quiescent current. The LT1241 series is optimized
for off-line and DC/DC converter applications. They con-
tain a temperature-compensated reference, high gain
error amplifier, current sensing comparator and a high
current totem pole output stage ideally suited to driv-
ing power MOSFETs. Start-up current has been reduced
to less than 250µA. Cross-conduction current spikes in
the output stage have been eliminated, making 500kHz
operation practical. Several new features have been incor-
porated. Leading edge blanking has been added to the
current sense comparator. Trims have been added to the
oscillator circuit for both frequency and sink current, and
both of these parameters are tightly specified. The out-
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Low Start-Up Current: < 250µA
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50ns Current Sense Delay
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Current Mode Operation: To 500kHz
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Pin Compatible with UC1842 Series
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Undervoltage Lockout with Hysteresis
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No Cross-Conduction Current
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Trimmed Bandgap Reference
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1A Totem Pole Output
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Trimmed Oscillator Frequency and Sink Current
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Active Pull-Down on Reference and Output During
Undervoltage Lockout
High Level Output Clamp: 18V
Current Sense Leading Edge Blanking
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APPLICATIONS
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Off-Line Converters
DC/DC Converters
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put stage is clamped to a maximum V
on state. The output and the reference output are actively
pulled low during undervoltage lockout.
of 18V in the
OUT
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