adm1075-2aruz-rl7 Analog Devices, Inc., adm1075-2aruz-rl7 Datasheet - Page 35

• Manufacturer Part Number: adm1075-2aruz-rl7
• Description: −48 V Hot Swap Controller And Digital Power Monitor With Pmbus Interface
• Manufacturer: Analog Devices, Inc.

Data Sheet
Table 7. PMBus Conversion to Real-World Coefficients
Coefficient
m
b
R
Example 3
The READ_VIN command returns a direct format value of 1726.
The ADC_V pin is shorted to the OV pin, which is connected
to the input supply via an 820 kΩ/11 kΩ resistor divider.
To convert this value to the input voltage, use Equation 2
This corresponds to 0.635 V at the ADC_V pin. To obtain the
input voltage, this must be amplified by the resistor divider ratio,
Example 4
The PIN_OP_WARN_LIMIT command requires a power limit
value expressed in direct format.
If the required power limit is 350 W and the sense resistor is
1 mΩ, the first step is to determine the m coefficient. Assuming
an
divider on VIN scales down the power limit referenced to the
ADC input. Assuming a 49 kΩ and 1 kΩ resistor divider on
VIN, this gives a scaling factor of 0.02.
Using Equation 1,
Writing a value of 5984 with the PIN_OP_WARN_LIMIT
command sets an overpower warning at 350 W.
VOLTAGE AND CURRENT CONVERSION USING
LSB VALUES
The direct format voltage and current values returned by the
READ_VIN, READ_VOUT, and READ_IOUT commands, and
the corresponding peak versions are the actual data output
directly from the
currents are a 12-bit ADC output code, they can also be
converted to real-world values with knowledge of the size of the
LSB on the ADC.
The m, b, and R coefficients defined for the PMBus conversion
are required to be whole integers by the standard and have
therefore been rounded off slightly. Using this alternative
method, with the exact LSB values, can provide slightly more
accurate numerical conversions.
ADM1075-1
X = 1/27,169 × (1726 × 10
X = 0.635 V
X = 0.635 V × (820 kΩ + 11 kΩ)/11 kΩ = 47.99 V
Y = (8549 × (350 × 0.02)) × 10
Y = 5984.3 = 5984 (rounded to the nearest integer)
device, m = 8549 × 1 = 8549. The resistor
ADM1075
Voltage (V)
27,169
0
−1
ADC. Because the voltages and
1
– 0)
−1
ADM1075-1
806 × R
20,475
−1
SENSE
Rev. 0 | Page 35 of 52
Current (A)
ADM1075-2
404 × R
20,475
−1
To convert an ADC code to current in amperes, the following
formulas can be used:
where:
V
LSB
LSB
I
I
R
To convert an ADC code to a voltage, the following formula can
be used:
where:
V
V
LSB
To convert a current in amperes to a 12-bit value, the following
formulas can be used (round the result to the nearest integer):
where:
V
I
R
I
LSB
LSB
To convert a voltage to a 12-bit value, the following formula can
be used (round the result to the nearest integer):
where:
V
V
LSB
ADC
OUT
A
CODE
SENSE
SENSE
SENSE
M
ADC
SENSE
CODE
A
SENSE
is the current value in amperes.
is the voltage value in volts.
is the measured value in volts.
25mV
50mV
INPUTV
25mV
50mV
INPUTV
is the 12-bit ADC code.
is the measured current value in amperes.
V
I
V
V
I
V
is the 12-bit ADC code.
is the 12-bit ADC code.
OUT
CODE
is the value of the sense resistor in milliohms.
is the value of the sense resistor in milliohms.
is the 12-bit ADC code.
= (V
= (V
SENSE
M
SENSE
CODE
= 12.4 μV.
= 24.77 μV.
= 12.4 μV.
= 24.77 μV.
= LSB
= V
= 368 μV.
= 368 μV.
= 2048 + ( V
= ( V
SENSE+
SENSE+
= LSB
= I
SENSE
A
INPUTV
× R
A
) − (V
) − (V
/ LSB
/( R
xmV
ADM1075-1
8549 × R
0
−1
SENSE
SENSE
× ( V
× ( I
INPUTV
SENSE−
SENSE−
SENSE
× 0.001
ADC
× 0.001)
ADC
/ LSB
) − 0.5
Power (W)—Resistor Scaled
SENSE
).
).
− 2048)
+ 0.5)
xmV
)
ADM1075-2
4279 × R
0
−1
ADM1075
SENSE