lm25066apsqx National Semiconductor Corporation, lm25066apsqx Datasheet - Page 41

• Manufacturer Part Number: lm25066apsqx
• Description: Lm25066a System Power Management And Protection Ic With Pmbus
• Manufacturer: National Semiconductor Corporation

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 = 6830, b = -310, 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
*READ_PIN, READ_AVG_PIN,
*READ_PIN, READ_AVG_PIN,
1. Determine full scale current and shunt value based on 29.98
mV across shunt at full scale.Use either:
or:
2. Determine m':
3. Determine exponent R necessary to set m' to integer value m: Select R to provide integer value of m:
4. Final values
MFR_PIN_OP_WARN_LIMIT
MFR_PIN_OP_WARN_LIMIT
MFR_IIN_OC_WARN_LIMIT
MFR_IIN_OC_WARN_LIMIT
*READ_IN, READ_AVG_IN
*READ_IN, READ_AVG_IN
READ_PEAK_PIN
READ_PEAK_PIN
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
41
Example: 122A application with 250 µΩ shunt.
R = -2
m = 3390
R = -2
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 25 mV current limit threshold (CL = GND).
In the 25mV range, the LSB value is 7.32 µV and the full scale
range is 30.2 mV. In the 46mV range (CL = VDD), the LSB
value is 14.64 µV and the full scale range in 60.4 mV.
Number of Data
Bytes
2
2
2
2
Example
13661 x R
6854 x R
736 x R
369 x R
m
S
S
S
S
S
in mΩ)
-5200
-3100
-3300
-1900
b
www.national.com
-2
-2
-2
-2
R
Units
W
W
A
A