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L6712A L6712

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

ON with a TON imposed by the control loop at the next available clock cycle and the device works in the

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 reset.

Figure 6 shows this working condition.

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

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

Figure 6. Constant Current operation

I

p eak

I

OCPx

V

IN

Vout

min

–

L

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

MAX

I

OCPx

V

IN

Vout

MIN

–

L

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

⋅⋅

+

=

⋅

+

=

I

MAX,TOT

2I

MAX

2I

OCPx

Ipea k

I

OCPx

–

2

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

+





⋅

=

⋅

=

T

OFF

L

Ipea k

I

OCPx

–

V

OUt

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

f

1

T

ONmax

T

OFF

+

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

=

⋅

=

a) Maximum current for each phase

b) Output Characteristic

TonMAX

TonMAX

Ipeak

Vout

Iout

µA)

µA)

UVP

Droop effect