AME, Inc.
mProcessor Supervisory
AME8570
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.
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 (TD2).
The MRB pin is internally pulled up to VIN by a 100K
resistor. It is internally debounced to reject switching
transients.
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.
The MRB pin is ESD protected by diodes connected
to VIN and GND. So the MRB pin should never be driven
higher than VIN or lower thanGND.
A reset will be asserted if any of two things happen:
1) VIN drops below the threshold (VTH)
2) The MRB pin is pulled low.
Glitch Rejection
TheAME8570 family will reject negative going transients
on the VIN 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.
The reset will remain asserted for the prescribed reset
interval after:
1) VIN rises above the threshold (VTH)
2) MRB goes high
Accurate Output State at Low VIN
With VIN 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 andGND
on the order of 100K will ensure that the RESETB output
stays low when VIN 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 VIN will ensure parts
with active high output (RESET) will remain high when
VIN is lower than the threshold voltage of the part.
9
Rev. A.01
AME [ ANALOG MICROELECTRONICS ]
