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

value.

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 driving high the OSC pin (Figure 19

shows this working condition).

crossed, all mosfets are turned off, the FAULT pin is driven high and the device stops working. Cycle the

power supply or the OUTEN pin to restart operation.

The maximum average current during the Constant-Current behavior results:

In this particular situation, the switching frequency for each phase results reduced. The ON time is the

ƒ

The transconductance resistor Rg can be designed considering that the device limits the bottom of the

inductor current ripple and also considering the additional current delivered during the quasi-constant-cur-

rent behavior as previously described in the worst case conditions.

Moreover, when designing D-VID compatible systems, the additional current due to the output filter charge

during dynamic VID transitions must be considered.

where

Figure 19. Constant Current operation

13.3 INDUCTOR SENSE (CS_SEL = SGND) OVER CURRENT

time: as a consequence of OCP detection, the device will turn OFF the HS mosfet and turns ON the LS

I

PEAK

I

OCPx

V

IN

Vout

MI N

–

L

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

MAX

⋅

+

I

OCPx

V

IN

Vou t

MIN

–

L

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

SW

⋅⋅

+

==

I

MAX,TOT

3I

MAX

⋅

3I

OCPx

Ip eak

I

OCPx

–

2

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

+

⎝⎠

⎛⎞

⋅

==

T

OFF

L

Ipea k

I

OCPx

–

V

out

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

⋅

=

1

T

onMax

T

OFF

+

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

=

Rg

I

OCPx max

()

⋅

I

OCTH min

()

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

=

I

OCPx

I

OUT OCP

()

3

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

I

PP

∆

2

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

–

I

D-VID

3

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

+

=

TonMAX

TonMAX

Ipeak

Vout

Iout

µA)

UVP

Droop effect

a) Maximum current for each phase

b) Output Characteristic