AN2683 datasheet(33/38 Pages) STMICROELECTRONICS

33 / 38 page

AN2683

Functional testing

33/38

where:

●

Top trace - L1 current 0.5 A/division

●

Bottom trace - output voltage 50 mV/division

4.4

Output current limit

Each output was loaded to its maximum rated load level. The load was increased in 10%

increments of the maximum rated load until the overcurrent limiting functioned. The level

was recorded.

After the overcurrent limit functioned, the load level was adjusted back the maximum rated

level and the input power was shut off and reapplied. The outputs resumed to normal

operation.

4.5

Output short circuit

Each output in turn was loaded to its maximum rated load level. A short was then applied to

the output at which time the overcurrent protection functioned. The opposite output

remained running. The short was then removed and the output remained latched off. The

input power was removed and then reapplied. The output resumed normal function. With

input power removed, each output in turn was shorted. Then input power was applied. The

shorted output's current limiting function operated while the non-shorted output ran

normally. The short was then removed and the input power was recycled. The output

resumed normal function.

4.6

Input under voltage lockout

With each output loaded to its nominal load level the input voltage was slowly increased

from 0 to 6 VDC and the output voltages were recorded. The input voltage was then slowly

increased from 6 to 8 VDC and the output voltages were recorded. The voltage at which the

device turns on is adjusted by the voltage divider consisting of R17 and R18 connected to

the SHDN pin(5). The typical turn-on threshold is 1.35 VDC and the device typically shuts

down with 0.85 VDC on the pin.

Table 8.

1.0 VDC output

Percent of maximum load (A)

130% (13.65)

Table 9.

1.8 VDC output

Percent of maximum load (A)

130% (3.25)

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