UCC3884D ,Frequency Foldback Current Mode PWM ControllerMAXIMUM RATINGSVALUE UNITSupply voltage 15 VOutput sink current 1AOutput source current 0.5All othe ..
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UCC3884D
Frequency Foldback Current Mode PWM Controller
1FEATURES
DESCRIPTION
UCC3884
www.ti.com............................................................................................................................................. SLUS160C–AUGUST 1999–REVISED NOVEMBER 2008
Frequency Foldback Current Mode PWM Controller Frequency Foldback Reduces Operating
Frequency Under Fault Conditions The UCC3884isa high performance current mode
PWM controller intended for single ended switch•
Accurate Programmable Volt-Second Clampmode power supplies. The chip implements a•
Programmable Maximum Duty Cycle Clamp frequency foldback scheme that decreases the•
Oscillator Synchronization oscillator frequencyas the output voltage falls below
Overcurrent Protection a programmed value. This technique decreases the
average output current sourced intoa low impedance•
Shutdown With Full Soft Start load which can occur duringan output short circuitor•
Wide Gain Bandwidth Amplifier (GBW> 2.5 overload condition. Excessive short circuit currentis
MHz) more prevalentin high frequency converters where
the propagation delay and switch turn-off time forces•
Current Mode Operation minimum attainable duty cycle. An accurate•
Precision 5-V Reference volt-second clamp limits the duty cycle during lineor
load transient conditions which could otherwise
saturate the transformer. The volt-second clamp may
also be used with an external overvoltage protection
circuit to handle fault conditions such as current
sense disconnector current transformer saturation.
The frequency foldback, volt-second clamp,
cycle-by-cycle current limit, and overcurrent shutdown
providea rich setof protection features for usein
peak current-mode pulse width modulators.
OSCILLATOR SYNCHRONIZATION
