The UCC2833/5/ADJ family of positive linear series pass voltage regulators are tailored for low-drop-out applications where low quiescent power is important. Fabricated with a BiCMOS technology ideally suited for low input-to-output differential applications, the UCC2835 passes 3 A while requiring only 0.45 V of typical input voltage headroom (ensured 0.6-V dropout).
These regulators include reverse voltage sensing that prevents current in the reverse direction. Quiescent current is always less than 650 µA. These devices have been internally compensated in such a way that the need for a minimum output capacitor has been eliminated.
UCC2833 and UCC2835 versions are in 3-lead packages and have preset outputs at 3.3 V and 5.0 V respectively. The output voltage is regulated to 1.5% at room temperature. The UCC283ADJ version, in a 5-lead package, regulates the output voltage programmed by an external resistor ratio.
Short-circuit current is internally limited. The device responds to a sustained overcurrent condition by turning off after a tON time delay. The device then stays off for a period, tOFF, that is 32 times the tON delay. The device then begins pulsing on and off at the tON/(tON +tOFF) duty cycle of 3%. This drastically reduces the power dissipation during short-circuit and means heat sinks need only accommodate normal operation. On the
3-leaded versions of the device tON is fixed at 750 µs, on the adjustable 5-leaded versions an external capacitor sets the on time. The off time is always 32 × tON. The external timing control pin, CT, on the 5-leaded versions also serves as a shutdown input when pulled low.
Internal power dissipation is further controlled with thermal overload protection circuitry. Thermal shutdown occurs if the junction temperature exceeds 165°C. The chip remains off until the temperature has dropped 20°C.
The UCC283 series is specified for operation over the industrial range of 40°C to 85°C, and the UCC383 series is specified from 0°C to 70°C. These devices are available in 3- and 5-pin TO220 and TO263 power packages.
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