LP2987, LP2988

SNVS004J – MARCH 1999 – REVISED APRIL 2013

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DETAILS OF ERR/RESET CIRCUIT OPERATION: (Refer to LP2987/8 Equivalent Circuit).

Figure 48. LP2987/8 Equivalent Circuit

The output of comparator U2 is the ERR/RESET flag. Since it is an open-collector output, it requires the use of a

controlled by the voltage applied to the non-inverting input.

The output of U1 (also an open-collector) will force the non-inverting input of U2 to go low whenever the

LP2987/8 regulated output drops about 5% below nominal.

U1's inverting input is also held at 1.23V. The other input samples the regulated output through a resistive divider

this voltage drops about 60 mV below 1.23V, the output of U1 will go low forcing the output of U2 low (which is

the ERROR state).

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