lm26480sqx-bf National Semiconductor Corporation, lm26480sqx-bf Datasheet - Page 17

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

The above diagram shows the simplest application of the
Power-On Reset, where both switcher enables are tied to-
gether. In Case 1, EN1 causes nPOR to transition LOW and
triggers the nPOR delay counter. If the power supply for
Buck2 does not come on within that period, nPOR will stay
LOW, indicating a power fail mode. Case 2 indicates the vice
NPOR with Counter Delay
17
versa scenario if Buck1 supply did not come on. In both cases
the nPOR remains LOW. Case 3 shows a typical application
of the Power-On Reset, where both switcher enables are tied
together. Even if RDY1 ramps up slightly faster than RDY2
(or vice versa), the nPOR signal will trigger a programmable
delay before going HIGH, as explained below.
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