adm1069ast-reel Analog Devices, Inc., adm1069ast-reel Datasheet - Page 22

• Manufacturer Part Number: adm1069ast-reel
• Description: Super Sequencer With Margining Control
• Manufacturer: Analog Devices, Inc.

ADM1069
VOLTAGE READBACK
The ADM1069 has an on-board 12-bit accurate ADC for
voltage readback over the SMBus. The ADC has an 8-channel
analog mux on the front end. The eight channels consist of the
eight SFD inputs,VH, VPn (VP1 to VP3), and VXn (VX1 to
VX4). Any or all of these inputs can be selected to be read, in
turn, by the ADC. The circuit controlling this operation is
called round-robin. The round-robin circuit can be selected to
run through its loop of conversions just once or continuously.
Averaging is also provided for each channel. In this case, the
round-robin circuit runs through its loop of conversions 16
times before returning a result for each channel. At the end of
this cycle, the results are all written to the output registers.
The ADC samples single-sided inputs with respect to the AGND
pin. A 0 V input gives out Code 0, and an input equal to the
voltage on REFIN gives out full code (4095 decimal).
The inputs to the ADC come directly from the VXn pins and
from the back of the input attenuators on the VPn and VH pins,
as shown in Figure 29 and Figure 30.
The voltage at the input pin can be derived from the following
equation:
The ADC input voltage ranges for the SFD input ranges are
listed in Table 9.
V =
VPn/VH
ADC
4095
VXn
Code
Figure 30. ADC Reading on VPn/VH Pins
Figure 29. ADC Reading on VXn Pins
ATTENUATION NETWORK
(DEPENDS ON RANGE SELECTED)
NO ATTENUATION
× Attenuation Factor × 2.048 V
2.048V VREF
12-BIT
ADC
2.048V VREF
12-BIT
ADC
DIGITIZED
VOLTAGE
READING
DIGITIZED
VOLTAGE
READING
Rev. A | Page 22 of 36
Table 9. ADC Input Voltage Ranges
SFD Input
Range (V)
0.573 to 1.375
1.25 to 3
2.5 to 6
6.0 to 14.4
1
The normal way to supply the reference to the ADC on the
REFIN pin is to simply connect the REFOUT pin to the REFIN
pin. REFOUT provides a 2.048 V reference. As such, the
supervising range covers less than half the normal ADC range.
It is possible, however, to provide the ADC with a more
accurate external reference for improved readback accuracy.
Supplies can also be connected to the input pins purely for ADC
readback, even though they could go above the expected super-
visory range limits (but not above 6 V, because this violates the
absolute maximum ratings on these pins). For instance, a 1.5 V
supply connected to the VX1 pin can be correctly read out as an
ADC code of approximately 3/4 full scale, but it always sits
above any supervisory limits that can be set on that pin. The
maximum setting for the REFIN pin is 2.048 V.
SUPPLY SUPERVISION WITH THE ADC
In addition to the readback capability, a further level of supervi-
sion is provided by the on-chip 12-bit ADC. The ADM1069 has
limit registers that the user can program to a maximum or
minimum allowable threshold. Exceeding the threshold generates
a warning that can either be read back from the status registers
or input into the SE to determine what sequencing action the
ADM1069 should take. Only one register is provided for each
input channel, so a UV or OV threshold (but not both) can be
set for a given channel. The round-robin circuit can be enabled
via an SMBus write, or it can be programmed to turn on in any
state in the SE program. For example, it can be set to start after
a power-up sequence is complete and all supplies are known to
be within expected tolerance limits.
Note that a latency is built into this supervision, dictated by the
conversion time of the ADC. With all 12 channels selected, the
total time for the round-robin operation (averaging off) is
approximately 6 ms (500 μs per channel selected). Supervision
using the ADC, therefore, does not provide the same real time
response as the SFDs.
The upper limit is the absolute maximum allowed voltage on these pins.
Attenuation
Factor
1
2.181
4.363
10.472
ADC Input Voltage
Range (V)
0 to 2.048
0 to 4.46
0 to 6.0
0 to 14.4
1
1