lm5066pmhx National Semiconductor Corporation, lm5066pmhx Datasheet - Page 40

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

www.national.com
Care must be taken to adjust the exponent coefficient, R, such
that the value of m remains within the range of -32768 to
+32767. For example, if a 5 mΩ sense resistor is used, the
correct coefficients for the READ_IIN command with CL =
VDD would be m = 5359, b = -120, R = -1.
A Note on the "b" Coefficient
Since b coefficients represent offset, for simplification b is set
to zero in the following discussions.
Reading Current
The current register actually displays a value equivalent to a
voltage across the user specified sense resistor, R
1. Determine full scale current and shunt value based on 38.0
mV across shunt at full scale:
or:
2. Determine m':
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:
4. Final values
*READ_PIN, READ_AVG_PIN,
*READ_PIN, READ_AVG_PIN,
MFR_PIN_OP_WARN_LIMIT
MFR_PIN_OP_WARN_LIMIT
*READ_IIN, READ_AVG_IIN
MFR_IIN_OC_WARN_LIMIT
*READ_IIN, READ_AVG_IIN
MFR_IIN_OC_WARN_LIMIT
READ_PIN_PEAK
READ_PIN_PEAK
Commands
TABLE 42. Current and Power Telemetry and Warning Conversion Coefficients (R
Step
Condition
CL = GND
CL = GND
CL = VDD
CL = VDD
S
. The co-
DIRECT
DIRECT
DIRECT
DIRECT
Format
40
Example: 8.6A application with 3 mΩ shunt.
R = -1
m = 3233
R = -1
b = 0
efficients 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.
Data Bytes
Number of
2
2
2
2
10753 x R
Example
5405 x R
1204 x R
605 x R
m
S
S
S
S
S
in mΩ)
-1200
-6000
-8000
-600
b
-2
-2
-3
-3
R
Units
W
W
A
A