lm5066pmhx National Semiconductor Corporation, lm5066pmhx Datasheet - Page 41

• Manufacturer Part Number: lm5066pmhx
• Description: High Voltage System Power Management And Protection Ic With Pmbus
• Manufacturer: National Semiconductor Corporation

Reading Input and Output Voltage
Coefficients for VIN and VOUT are fixed and are consistent
between read telemetry measurements (e.g., READ_VIN,
READ_AVG_VIN)
Reading Power
The power calculation of the LM5066 is a relative power cal-
culation meaning that full scale of the power register corre-
sponds to simultaneous full scale values in the current
register and voltage register such that the power register has
the following relationship based on decimal equivalents of the
register contents:
1. Determine m' based on full scale analog input and full scale
digital range:
2. Determine exponent R necessary to set m' to integer value m
with desired accuracy:
3. Final values
Step
1. Determine full scale power from known full scale of input
current and input voltage:
P
2. Determine m':
3. Optional: Determine exponent R necessary to set m' to integer
value m with desired accuracy:
4. Final values
IN_MAX
= V
IN_MAX
x I
IN_MAX
and
warning
Step
thresholds
(e.g.,
41
Select R to provide 16 bit accuracy for the integer value of m:
(4585 in this example):
R = -2
m = 4586
R = -2
b =0
Example
Example: 8.6A application with 3 mΩ shunt.
P
Select R to provide 16 bit accuracy for the integer value of m :
R = -4
m = 18103
R = -4
b = 0
IN_MAX
VIN_UV_WARN_LIMIT). Input and output voltage values are
read/written in Direct format with 12-bit resolution and a 21.8
mV LSB. An example of calculating the PMBus coefficients
for input voltage is shown below.
For this reason power coefficients will also vary depending on
the shunt value and must be calculated for each application.
The power LSB will vary depending on shunt value according
to 828 µW/Rsense for the 26mV range or 1.65 mW/Rsense
for the 50mV range.
= (89.3V) x (76 mV / 3 mΩ) = 2262W
Example
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