Datasheet

ADM1062
Rev. C | Page 15 of 36
INPUTS
SUPPLY SUPERVISION
The ADM1062 has 10 programmable inputs. Five of these are
dedicated supply fault detectors (SFDs). These dedicated inputs
are called VH and VPx (VP1 to VP4) by default. The other five
inputs are labeled VXx (VX1 to VX5) and have dual functionality.
They can be used either as SFDs, with functionality similar to VH
and VPx, or as CMOS-/TTL-compatible logic inputs to the device.
Therefore, the ADM1062 can have up to 10 analog inputs,
a minimum of five analog inputs and five digital inputs, or
a combination thereof. If an input is used as an analog input,
it cannot be used as a digital input. Therefore, a configuration
requiring 10 analog inputs has no available digital inputs. Table 6
shows the details of each input.
PROGRAMMING THE SUPPLY FAULT DETECTORS
The ADM1062 can have up to 10 SFDs on its 10 input channels.
These highly programmable reset generators enable the supervision
of up to 10 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 drops below a prepro-
grammed value), an overvoltage fault (the input voltage rises
above a preprogrammed value), or an out-of-window fault (the
input voltage is outside a preprogrammed range). The thresholds
can be programmed to an 8-bit resolution in registers provided in
the ADM1062. 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 − 6.0 V)/255 = 32.9 mV
Table 5 lists the upper and lower limits of each available range,
the bottom of each range (V
B
), and the range itself (V
R
).
Table 5. Voltage Range Limits
Voltage Range (V) V
B
(V) V
R
(V)
0.573 to 1.375 0.573 0.802
1.25 to 3.00 1.25 1.75
2.5 to 6.0 2.5 3.5
6.0 to 14.4 6.0 8.4
The threshold value required is given by
V
T
= (V
R
× N)/255 + V
B
where:
V
T
is the desired threshold voltage (undervoltage or overvoltage).
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 overvoltage threshold
on VP1, the code to be programmed in the PS1OVTH register
(as discussed in the AN-698 Application Note at www.analog.com)
is given by
N = 255 × (5 − 2.5)/3.5
Therefore, N = 182 (1011 0110 or 0xB6).
INPUT COMPARATOR HYSTERESIS
The UV and OV comparators shown in Figure 22 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 .
04433-023
+
–
+
–
UV
COMPARATOR
VREF
FAULT TYPE
SELECT
OV
COMPARATOR
FAULT
OUTPUT
GLITCH
FILTER
VPx
MID
LOW
RANGE
SELECT
ULTRA
LOW
Figure 22. Supply Fault Detector Block
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.
Table 6. Input Functions, Thresholds, and Ranges
Input Function Voltage Range (V) Maximum Hysteresis Voltage Resolution (mV) Glitch Filter (μs)
VH High Voltage Analog Input 2.5 to 6.0 425 mV 13.7 0 to 100
6.0 to 14.4 1.02 V 32.9 0 to 100
VPx Positive Analog Input 0.573 to 1.375 97.5 mV 3.14 0 to 100
1.25 to 3.00 212 mV 6.8 0 to 100
2.5 to 6.0 425 mV 13.7 0 to 100
VXx High-Z Analog Input 0.573 to 1.375 97.5 mV 3.14 0 to 100
Digital Input 0 to 5.0 N/A N/A 0 to 100