Datasheet

Mask
Window
RDY1
t1 t2
t3 t4
t0
RDY2
Counter
delay
EN1
EN2
NPOR
Counter
delay
NPOR
Mask Time
Counter
delay
NPOR
Mask Time
EN2
0V
RDY2
Case 2:
Case 1:
Mask
Window
LM26480
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SNVS543I JANUARY 2008REVISED MAY 2013
Figure 30. NPOR Mask Window
In Case 1, we see that case where EN2 and RDY2 are initiated after triggered programmable delay. To prevent
the nPOR being asserted again, a masked window (5 ms) counter delay is triggered off the EN2 rising edge.
NPOR is still held HIGH for the duration of the mask, whereupon the nPOR status afterwards will depend on the
status of both RDY1 and RDY2 lines.
In Case 2, we see the case where EN2 is initiated after the RDY1 triggered programmable delay, but RDY2
never goes HIGH (Buck2 never turns on). Normal operation operation of nPOR occurs wilth respect to EN1 and
RDY1, and the nPOR signal is held HIGH for the duration of the mask window. We see that nPOR goes LOW
after the masking window has timed out because it is now dependent on RDY1 and RDY2, where RDY2 is LOW.
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