lm26480sqx-bf National Semiconductor Corporation, lm26480sqx-bf Datasheet - Page 18

• Manufacturer Part Number: lm26480sqx-bf
• Description: Lm26480 Externally Programmable Dual High-current Step-down Dc/dc And Dual Linear Regulators
• Manufacturer: National Semiconductor Corporation

www.national.com
The above timing diagram details the Power Good with delay
with respect to the enable signals EN1, and EN2. The RDY1,
RDY2 are internal signals derived from the output of two com-
parators. Each comparator has been trimmed as follows:
The circuits for EN1 and RDY1 are symmetrical to EN2 and
RDY2, so each reference to EN1 and RDY1 will also work for
EN2 and RDY2 and vice versa.
Comparator Level
HIGH
LOW
Buck Supply Level
Greater than 91%
Less than 82%
Faults Occurring in Counter Delay After Startup
18
If EN1 and RDY1 signals are High at time t1, then the RDY1
signal rising edge triggers the programmable delay counter
(50 μs, 50 ms, 100 ms, 200 ms). This delay forces nPOR LOW
between time interval t1 and t2. NPOR is then pulled high after
the programmable delay is completed. Now if EN2 and RDY2
are initiated during this interval the nPOR signal ignores this
event.
If either RDY1or RDY2 were to go LOW at t3 then the pro-
grammable delay is triggered again.
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