Datasheet

10
R
=
P¶
m
P¶=
4095
I
IN_MAX
I
IN_MAX
=
38.0 mV
R
S
LM5066
SNVS655G –JUNE 2011–REVISED FEBRUARY 2013 www.ti.com
READING CURRENT
The current register actually displays a value equivalent to a voltage across the user specified sense resistor, R
S
.
The coefficients enable the data output to be converted to amps. The values shown in the example are based on
having the device programmed for a 26 mV current limit threshold (CL = VDD). In the 26mV range, the LSB
value is 9.3 µV and the full scale range is 38.0 mV. In the 50mV range (CL = GND), the LSB value is 18.5 µV
and the full scale range in 76.0 mV.
Step Example
1. Determine full scale current and shunt value based on 38.0 mV Example: 8.6A application with 3 mΩ shunt.
across shunt at full scale:
(39)
(38)
or:
2. Determine m':
(41)
(40)
3. Determine exponent R necessary to set m' to integer value m: Select R to provide 16 bit accuracy for the integer value of m:
(42)
(43)
R = -1
4. Final values m = 3233
R = -1
b = 0
READING INPUT AND OUTPUT VOLTAGE
Coefficients for VIN and VOUT are fixed and are consistent between read telemetry measurements (for example,
READ_VIN, READ_AVG_VIN) and warning thresholds (for example, 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.
Step Example
1. Determine m' based on full scale analog input and full scale digital
range:
(45)
(44)
2. Determine exponent R necessary to set m' to integer value m with Select R to provide 16 bit accuracy for the integer value of m: (4585
desired accuracy: in this example):
(47)
(46)
R = -2
3. Final values m = 4586
R = -2
b =0
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