AME8570M Datasheet, PDF (12/25 Pages) Analog Microelectronics – Manual Reset Input Option

AME
AME8570M
n Applications Information
Supply Transients
These devices have a certain immunity to fast negative
going transients. In the following pages the graph titled
"Glitch Rejection" indicates the maximum allowable glitch
amplitude and duration to avoid triggering an unintended
reset. As shown in the graph shorter transients can have
larger amplitudes without triggering resets.
n Detailed Description
The AME8570M are designed to interface with the re-
set input of a microprocessor and to prevent code-execu-
tion 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
outputs 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 (V_TH)
2) The MRB pin pulled low
The reset will remain asserted for the prescribed reset
interval after:
1) V_IN rises above the thresholed (V_TH)
2) MRB goes high
µProcessor Supervisory
Manual Reset Input
The AME8570M 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).
(1) Normal MRB Signal (pulse width must ¡Ù1µS)
(2) MRB Noise Immunity (pulse width duration no reset
~ 100nS)
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 AME8570M family will reject negative going tran-
sients 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
between glitch amplitude and allowable glitch duration to
avoid unintended resets.
Accurate Output State at Low V_IN
With V_IN voltage on the order of the MOS transistor
threshold (<1.0V) the outputs of the AME8570M 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
V_IN is lower than the threshold voltage of the part.
12
Rev. A.14