UCC386, UCC387, UCC388

LOW DROPOUT 200mA LINEAR REGULATOR

SLUS377B - JULY 1999 - REVISED MAY 2000

6

POST OFFICE BOX 655303

APPLICATION INFORMATION

maximum load recovery (continued)

CRITICAL LOAD CURRENT

vs

OUTPUT CAPACITANCE

100

0

40

80

120

160

200

20

60

140

180

UCC387

UCC386

CO - Output Capacitance - F

Figure 2.

using OFFB

The OFFB pin is used to turn the output of the LDO on or off from some external source. There are two things

to note when using this pin. The first is that after taking OFFB high (on), the LDO will require up to about 2 ms

to start and stabilize. The second item is that OFFB is designed to be driven from an open-drain-type output.

Internally, this pin is pulled high by a weak 100-nA current source, and will normally be at the input supply

voltage, so the driving circuitry must be able to withstand the voltage applied to the input of the regulator. Also,

depending upon load, if the OFFB pin is driven (overriding the internal pull-up) high with a fast edge signal, there

may be a brief pulse on the output, followed by no output, with the regulator coming on and stabilizing about

2 ms after the OFFB pin was driven high. This output pulse is never more than the normal output voltage of the

regulator and is about 200

µs in length.