Datasheet

ADM1069
Rev. C | Page 14 of 32
INPUTS
SUPPLY SUPERVISION
The ADM1069 has eight programmable inputs. Four of these
are dedicated supply fault detectors (SFDs). These dedicated
inputs are called VH and VPx (VP1 to VP3) by default. The
other four inputs are labeled VXx (VX1 to VX4) and have dual
functionality. They can be used either as SFDs, with functionality
similar to the VH and VPx, or as CMOS-/TTL-compatible logic
inputs to the device. Therefore, the ADM1069 can have up to
eight analog inputs, a minimum of four analog inputs and four
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 eight analog inputs has no available
digital inputs. Table 6 shows the details of each input.
PROGRAMMING THE SUPPLY FAULT DETECTORS
The ADM1069 can have up to eight SFDs on its eight input
channels. These highly programmable reset generators enable
the supervision of up to eight 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 preprogrammed 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 ADM1069. 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-721 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 compara-
tors have digitally programmable hysteresis. The hysteresis can
be programmed up to the values shown in Table 6.
04735-023
+
–
+
–
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