ADM1168 View Datasheet(PDF) - Analog Devices
Part Name
Description
Manufacturer
ADM1168 Datasheet PDF : 27 Pages
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ADM1168
Data Sheet
INPUT COMPARATOR HYSTERESIS
The UV and OV comparators shown in Figure 16 are always
monitoring VPx. To avoid chatter (multiple transitions when the
input is very close to the set threshold level), these comparators
have digitally programmable hysteresis. The hysteresis can be
programmed up to the values shown in Table 6.
The hysteresis is added after a supply voltage goes out of
tolerance. Therefore, the user can program the amount above
the undervoltage threshold to which the input must rise before
an undervoltage fault is deasserted. Similarly, the user can program
the amount below the overvoltage threshold to which an input
must fall before an overvoltage fault is deasserted.
The hysteresis value is given by
VHYST = VR × NTHRESH/255
where:
VHYST is the desired hysteresis voltage.
NTHRESH is the decimal value of the 5-bit hysteresis code.
Note that NTHRESH has a maximum value of 31. The maximum
hysteresis for the ranges is listed in Table 6.
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,
which allows the user to remove any spurious transitions such
as supply bounce at turn-on. The glitch filter function is in addition
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
appears 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 15.
INPUT PULSE SHORTER
THAN GLITCH FILTER TIMEOUT
INPUT PULSE LONGER
THAN GLITCH FILTER TIMEOUT
PROGRAMMED
TIMEOUT
PROGRAMMED
TIMEOUT
INPUT
t0
tGF
INPUT
t0
tGF
OUTPUT
OUTPUT
t0
tGF
t0
tGF
Figure 15. Input Glitch Filter Function
ULTRA
LOW
VPx
RANGE
SELECT
VREF
OV
+ COMPARATOR
–
GLITCH
FILTER
FAULT
OUTPUT
LOW
MID
+
–
UV
FAULT TYPE
COMPARATOR SELECT
Figure 16. Supply Fault Detector Block
Table 6. Input Functions, Thresholds, and Ranges
Input Function
Voltage Range (V)
VH High voltage analog input 2.5 to 6.0
6.0 to 14.4
VPx Positive analog input
0.573 to 1.375
1.25 to 3.00
2.5 to 6.0
VXx High-Z analog input
0.573 to 1.375
Digital input
0 to 5.0
Maximum Hysteresis
425 mV
1.02 V
97.5 mV
212 mV
425 mV
97.5 mV
Not applicable
Voltage Resolution (mV)
13.7
32.9
3.14
6.8
13.7
3.14
Not applicable
Glitch Filter (μs)
0 to 100
0 to 100
0 to 100
0 to 100
0 to 100
0 to 100
0 to 100
Rev. B | Page 12 of 27
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