EVAL-ADM1075EBZ View Datasheet(PDF) - Analog Devices
Part Name
Description
MFG CO.
EVAL-ADM1075EBZ
Analog Devices
'EVAL-ADM1075EBZ' PDF : 52 Pages View PDF
Data Sheet
ADM1075
The ADM1075 returns a single value corresponding to the
average voltage and current measured. When configured for
continuous mode, the power monitor continuously samples
voltage and current, making the most recent sample available
to be read. The ADC runs in continuous mode by default at
power-up.
The single-shot mode can be triggered in a number of ways.
The simplest is by selecting the single-shot mode using the
PMON_CONFIG command and writing to the CONVERT bit
using the PMON_CONTROL command. The CONVERT bit
can also be written as part of a PMBus group command. Using a
group command allows multiple devices to be written to as part
of the same I2C bus transaction, with all devices executing the
command when the stop condition appears on the bus. In this
way, several devices can be triggered to sample at the same time.
When the GPO1/ALERT1/CONV pin is set to the convert
(CONV) mode, an external hardware signal can be used to
trigger the single-shot sampling of one or more parts at the
same time.
Each time a current sense and input voltage measurement is
taken, a power calculation is performed, multiplying the two
measurements together. This can be read from the device using
the READ_PIN command, returning the input power.
At the same time, the calculated power value is added to a
power accumulator register that may increment a rollover
counter if the value exceeds the maximum accumulator value,
and that also increments a power sample counter.
The power accumulator and power sample counter are read
back using the same READ_EIN command to ensure that the
accumulated value and sample count are from the same point in
time. The bus host reading the data assigns a timestamp to show
when the data is read. By calculating the time difference between
consecutive uses of READ_EIN and determining the delta in
power consumed, it is possible for the host to determine the
total energy consumed over that period.
ISOLATION
Isolation is usually required in −48 V systems because there can
be a large voltage difference between different ground planes in
the system. The ADM1075 is referenced to −48 V, whereas the
MCU is usually referenced to 0 V. In almost all cases, the I2C signals
must be isolated. Any other ADM1075 digital input and output
signals that go to or come from the MCU must also be isolated.
Analog Devices, Inc., provide a range of digital isolators using
iCoupler® technology. iCoupler technology is based on chip
scale transformers rather than the LEDs and photodiodes used
in optocouplers. The ADuM1250 is a dual I2C isolator and can
be used in conjunction with the ADM1075 for I2C isolation.
In cases where more digital signals need to be isolated, the
ADuM3200 is a dual-channel digital isolator whereas the
ADuM5404 is a quad-channel isolator with isoPower®, an
integrated, isolated dc-to-dc converter.
–48V SIDE
(PRIMARY)
VDD1
100nF
5V
–48V
10kΩ
SDA
10kΩ
SCL
–48V
ADuM1250
ISOLATED SIDE
(SECONDARY)
VDD1 VDD2
SCL2 SDA2
SCL1 SCL2
GND1 GND2
SDA_ISO
5V_ISO
100nF
SCL_ISO GND_ISO
GND_ISO
Figure 54. ADuM1250 I2C Isolation
The ADuM1250 and ADuM3200 must be powered from both the
primary and secondary sides. The ADuM5404 only needs to be
powered from the secondary side and can provide power across
the isolation barrier via the integrated dc-to-dc converter. There-
fore, the ADuM5404 can be used to power the primary side of
the ADuM1250 if both are used on the board. Some extra care
is required if using the ADuM5404 to power the ADuM3200. If
the power at the secondary side is enabled by the ADM1075, the
isoPower solution may not work. Because isoPower is unpowered
in this case, the ADuM3200 outputs are in an undefined state. If
the SHDN input comes from the ADuM3200, it may be held
low, and the ADM1075 never turns on the FET or enables
power at the secondary side.
isoPower uses high frequency switching elements to transfer
power through its transformer. Special precautions must be
taken during printed circuit board (PCB) layout to meet
emissions standards. See the AN-0971 Application Note for
board layout recommendations.
Powering the iCouplers from the secondary side is usually
straightforward because there is often a suitable voltage rail
available. However, there is not always a suitable voltage rail
available on the primary side (−48 V side). If the ADuM5404 is
not used on the system, the ADuM1250 can be powered on the
primary side in a number of different ways.
If a voltage rail is available on the primary side (3.3 V or 5 V
referenced to VEE), that can be used to power the chip directly.
Otherwise, the ADM1075 shunt voltage and/or the −48 V
supply can be regulated down to power the part. A simple
emitter follower circuit achieves this, as shown in Figure 55.
12V (SHUNT) –48V RTN
20kΩ
1kΩ
0.33W
6V
20k
5V AUX
1µF
–48V
–48V
Figure 55. Powering iCoupler from −48 V Supply
Rev. D | Page 27 of 52
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