ADM1065
INPUTS
SUPPLY SUPERVISION
The ADM1065 has ten programmable inputs. Five of these are
dedicated supply fault detectors (SFDs). These dedicated inputs
are called VH and VP1–4 by default. The other five inputs are
labeled VX1-VX5 and have dual functionality. They can be used
as either supply fault detectors, with similar functionality to VH
and VP1–4, or CMOS/TTL-compatible logic inputs to the
devices. Therefore, the ADM1065 can have up to ten analog
inputs, a minimum of five analog inputs and five digital inputs,
or a combination. If an input is used as an analog input, it
cannot be used as a digital input. Therefore, a configuration
requiring ten analog inputs has no digital inputs available. Table
5 shows the details of each of the inputs.
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0
+
–
+
–
COMUV
VREF
FSELECT
COMOV
FAULT
FILTER
VPn
MID
LOW
RANGE
LOW
Figure 16. Supply Fault Detector Block
PROGRAMMING THE SUPPLY FAULT DETECTORS
The ADM1065 has up to ten supply fault detectors (SFDs) on its
ten input channels. These highly programmable reset generators
enable the supervision of up to ten supply voltages. The supplies
can be as low as 0.573 V and as high as 14.4 V. The inputs can be
configured to detect an undervoltage fault (the input voltage
droops below a preprogrammed value), an overvoltage fault (the
input voltage rises above a preprogrammed value) or an out-of-
window fault (undervoltage
or
overvoltage). The thresholds can
be programmed to an 8-bit resolution in registers provided in
the ADM1065. This translates to a voltage resolution that is
dependent on the range selected.
The resolution is given by
Step Size
=
Threshold Range
/255
Therefore, if the high range is selected on VH, the step size can
be calculated as follows:
(14.4 V 4.8 V)/255 = 37.6 mV
Table 4 lists the upper and lower limit of each available range,
the bottom of each range (V
B
), and the range itself (V
R
).
Table 4. Voltage Range Limits
Voltage Range (V)
0.573 to 1.375
1.25 to 3.00
2.5 to 6.0
4.8 to 14.4
V
B
(V)
0.573
1.25
2.5
4.8
V
R
(V)
0.802
1.75
3.5
9.6
The threshold value required is given by
V
T
= (
V
R
×
N
)/255 +
V
B
where:
V
T
is the desired threshold voltage (UV or OV).
V
R
is the voltage range.
N
is the decimal value of the 8-bit code.
V
B
is the bottom of the range.
Reversing the equation, the code for a desired threshold is
given by
N
= 255 × (
V
T
V
B
)/
V
R
For example, if the user wants to set a 5 V OV threshold on VP1,
the code to be programmed in the PS1OVTH register
(discussed in the AN-698 application note) is given by
N
= 255 × (5 2.5)/3.5
Therefore,
N
= 182 (1011 0110 or 0xB6).
Table 5. Input Functions, Thresholds, and Ranges
Input
Function
VH
High V Analog Input
VPn
Positive Analog Input
VXn
High Z Analog Input
Digital Input
Voltage Range (V)
2.5–6.0
4.8–14.4
0.573–1.375
1.25–3.00
2.5–6.0
0.573–1.375
0–5
Maximum Hysteresis
425 mV
1.16 V
97.5 mV
212 mV
425 mV
97.5 mV
N/A
Voltage Resolution (mV)
13.7
37.6
3.14
6.8
13.7
3.14
N/A
Glitch Filter (μs)
0–100
0–100
0–100
0–100
0–100
0–100
0–100