AME8570 datasheet(9/17 Pages) AME

9 / 17 page

AME, Inc.

Rev. A.01

AME8570

µProcessor Supervisory

n Detailed Description

The AME8570 are designed to interface with the reset

input of a microprocessor and to prevent code-execution

errors due to power up, power down, and other power

supply errors.

Reset Output

Each output pin in the family can be configured to be

either push-pull or open-drain. In addition each output may

be either active high or active low. Active high reset out-

puts are denoted as RESET. Active low reset outputs

are denoted as RESETB. The selection guide on this

data sheet shows all possible combinations of output

driver configuration.

A reset will be asserted if any of two things happen:

1) V

IN drops below the threshold (VTH)

2) The MRB pin is pulled low.

The reset will remain asserted for the prescribed reset

interval after:

1) V

IN rises above the threshold (VTH)

2) MRB goes high

Manual Reset Input

The AME8570 feature a manual reset feature (MRB).

A logic low on the MRB pin asserts a reset. The reset

remains asserted as long as the MRB pin remains low.

After the MRB pin transitions to a high state the reset

remains asserted for the prescribed reset interval (T

D2).

The MRB pin is internally pulled up to V

IN by a 100K

resistor. It is internally debounced to reject switching

transients.

The MRB pin is ESD protected by diodes connected

to V

IN and GND. So the MRB pin should never be driven

higher than V

IN or lower than GND.

Glitch Rejection

The AME8570 family will reject negative going transients

on the V

IN line to some extent. The smaller the duration

of the transient the larger its amplitude may be without

triggering a reset. The "Glitch Rejection" chart in the

graphs section of this datasheet shows the relation be-

tween glitch amplitude and allowable glitch duration to

avoid unintended resets.

Accurate Output State at Low V

With V

IN voltage on the order of the MOS transistor

threshold (<1.0V) the outputs of the AME8570 may be-

come undefined. For parts with active low output

(RESETB) a resistor placed between RESETB and GND

on the order of 100K will ensure that the RESETB output

stays low when V

IN is lower than the threshold voltage of

the part. In a like manner a resistor on the order of 100K

when placed between RESET and V

IN will ensure parts

with active high output (RESET) will remain high when

IN is lower than the threshold voltage of the part.

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