EVAL-ADM1063LFEB AD [Analog Devices], EVAL-ADM1063LFEB Datasheet - Page 14

• Manufacturer Part Number: EVAL-ADM1063LFEB
• Description: Multisupply Supervisor/Sequencer with ADC and Temperature Monitoring
• Manufacturer: AD [Analog Devices]

ADM1063
INPUT COMPARATOR HYSTERESIS
The UV and OV comparators shown in Figure 22 are always
looking at VPn. To avoid chattering (multiple transitions when
the input is very close to the set threshold level), these compara-
tors have digitally programmable hysteresis. The hysteresis can
be programmed up to the values shown in Table 5.
The hysteresis is added after a supply voltage goes out of
tolerance. Therefore, the user can program the amount above
the UV threshold that the input must rise to before a UV fault is
deasserted. Similarly, the user can program the amount below
the OV threshold that an input must fall to before an OV fault
is deasserted.
The hysteresis figure is given by
where:
V
N
Note that N
hysteresis for the ranges are listed in Table 5.
INPUT GLITCH FILTERING
The final stage of the SFDs is a glitch filter. This block provides
time-domain filtering on the output of the SFD comparators.
This allows the user to remove any spurious transitions, such as
supply bounce at turn-on. The glitch filter function is additional
to the digitally programmable hysteresis of the SFD comparators.
The glitch filter timeout is programmable up to 100 µs.
For example, when the glitch filter timeout is 100 µs, any pulse
appearing on the input of the glitch filter block that is less than
100 µs in duration is prevented from appearing on the output of
the glitch filter block. Any input pulse that is longer than 100 µs
does appear on the output of the glitch filter block. The output
is delayed with respect to the input by 100 µs. The filtering
process is shown in Figure 23.
HYST
THRESH
V
is the desired hysteresis voltage.
HYST
is the decimal value of the 5-bit hysteresis code.
= V
THRESH
R
× N
has a maximum value of 31. The maximum
THRESH
/255
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SUPPLY SUPERVISION WITH VXn INPUTS
The VXn inputs have two functions. They can be used as either
supply fault detectors or digital logic inputs. When selected as an
analog (SFD) input, the VXn pins function similarly to the VH
and VPn pins. The primary difference is that the VXn pins have
only one input range: 0.573 V to 1.375 V. Therefore, these inputs
can directly supervise only the very low supplies. However, the
input impedance of the VXn pins is high, allowing an external
resistor divide network to be connected to the pin. Thus,
potentially any supply can be divided down into the input range
of the VXn pin and supervised. This enables the ADM1063 to
monitor other supplies such as +24 V, +48 V, and −5 V.
An additional supply supervision function is available when the
VXn pins are selected as digital inputs. In this case, the analog
function is available as a second detector on each of the dedi-
cated analog inputs, VP1 to VP4 and VH. The analog function
of VX1 is mapped to VP1, VX2 is mapped to VP2, and so on;
VX5 is mapped to VH. In this case, these SFDs can be viewed as
a secondary or warning SFD.
The secondary SFDs are fixed to the same input range as the
primary SFD. They are used to indicate warning levels rather
than failure levels. This allows faults and warnings to be gener-
ated on a single supply using only one pin. For example, if VP1
is set to output a fault when a 3.3 V supply drops to 3.0 V, VX1
can be set to output a warning at 3.1 V. Warning outputs are
available for readback from the status registers. They are also
OR’ e d together and fed into the SE, allowing warnings to generate
interrupts on the PDOs. Therefore, in the previous example, if
the supply drops to 3.1 V, a warning is generated and remedial
action can be taken before the supply drops out of tolerance.
T
T
THAN GLITCH FILTER TIMEOUT
PROGRAMMED
0
0
INPUT
TIMEOUT
INPUT PULSE SHORTER
T
T
GF
GF
OUTPUT
Figure 23. Input Glitch Filter Function
PROGRAMMED
THAN GLITCH FILTER TIMEOUT
T
T
0
0
TIMEOUT
INPUT PULSE LONGER
INPUT
T
T
GF
GF
OUTPUT