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L6919C

2. Constant Current Operation

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

another OCP event is detected.

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

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

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 7 shows this working condition

Figure 7. Constant Current operation

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

off, the FAULT pin is driven high and the device stops working. Cycle the power supply to restart operation. The

maximum average current during the Constant-Current behavior results:

In this particular situation, the switching frequency results reduced. The ON time is the maximum allowed

age with respect to the load value, it can be simply considered that, for example, to have on OCP threshold

a) Maximum current for each phase

b) Output Characteristic

TonMAX

TonMAX

Ipeak

Vout

Iout

µA)

UVP

Droop effect

Ipea k

I

OCPx

V

IN

Vo ut

MIN

–

L

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

MAX

⋅

+

I

OCPx

V

IN

Vo ut

MIN

–

L

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

⋅⋅

+

==

I

M AX,TOT

2I

MA X

2I

OCPx

Ipe ak

I

OC P x

–

2

--------------------------------------

+





⋅

+

⋅

=

T

OFF

L

Ipe ak

I

OC P x

–

V

OUT

--------------------------------------

⋅

=

f

1

T

ON m a x

T

OFF

+

------------------------------------------

=