13/34

L6710

1.

maximum output voltage, the output resulting voltage will start to drop after crossing. In this case, the de-

vice doesn't perform constant current limitation but only limits the maximum ON time following the previous

relationship. The output voltage follows the resulting characteristic (dotted in Figure 4b) until UVP is de-

µA

2.

CONSTANT CURRENT OPERATION

>35

µA).

The device enters in Quasi-Constant-Current operation: the low-side mosfets stays ON until the current

µA) skipping clock cycles. The high side mosfets can be turned

usual way until another OCP event is detected.

This means that the average current delivered can slightly increase also in Over Current condition since

the current ripple increases. In fact, the ON time increases due to the OFF time rise because of the current

When this happens, the device works in Constant Current and the output voltage decrease as the load

increase. Crossing the UVP threshold causes the device to latch (FAULT pin is driven high).

Figure 5 shows this working condition.

It can be observed that the peak current (Ipeak) is greater than the IOCPx but it can be determined as

follow:

The device works in Constant-Current, and the output voltage decreases as the load increase, until the

µA)

characteristic

µA)

Desired Output

characteristic and

UVP threshold

Resulting Output

characteristic

a) Maximum output Voltage

I

pea k

I

OCPx

V

IN

V out

mi n

–

L

------------------------------------- Ton

MAX

I

OCPx

V

IN

Vou t

MIN

–

L

-------------------------------------- 0.40 T

⋅⋅

+

=

⋅

+

=