ISL28025 Datasheet, PDF (27/48 Pages) Intersil Corporation – Precision Digital Power Monitor with Real Time Alerts

ISL28025
TABLE 16. PRIMARY V_SHUNT CONVERSION TIMES DEFINED
Config_Ichannel: D[2:0]
CONVERSION TIME
0
0
0
64µs
0
0
1
128µs
0
1
0
256µs
0
1
1
512µs
1
0
X
1.024ms
1
1
X
2.048ms
SHUNT VOLTAGE SAMPLE AVERAGE D[6:3]
The Shunt Voltage Sample Average bits set the number of
averaging samples for a unique sampling time. The DPM records
all samples and outputs the average resultant to the voltage
shunt register. Table 17 defines the list of selectable averages
the DPM can be set to. The shaded row indicates the default
setting.
TABLE 17. PRIMARY V_SHUNT NUMBER OF SAMPLES TO AVERAGE
DEFINED
AVG[3:0]
CONVERTER AVERAGES
0000
1
0001
2
0010
4
0011
8
0100
16
0101
32
0110
64
0111
128
1000
256
1001
512
1010
1024
1011
2048
11XX
4096
0X38 IOUT CALIBRATION GAIN (R/W)
The IOUT Calibration Gain register is a read/writable word
register that is used to calculate current and power
measurements for the primary channel of the DPM. When the
register is programmed, the DPM calculates the current and
power based on the primary channels V_BUS and V_SHUNT
measurements. The calculation resultant is stored in the
READ_IOUT and READ_POUT registers.
The calibration register value can be calculated as follows:
1. Calculate the full-scale current range that is desired. This can
be calculated using Equation 3.
Current _FS
Vshunt _FS
R _shunt
(EQ. 3)
R_shunt is the value of the shunt resistor. Vshunt_FS is the full
scale range of the primary channel, which equals 80mV.
2. From the current full-scale range, the current LSB can be
calculated using Equation 4. Current full-scale is the outcome
from Equation 3.
Current _LSB
Current _FS
ADC _res
(EQ. 4)
ADC_res is the resolution of shunt voltage reading. The output
of the ADC is a signed 15 bit binary number. Therefore, the
ADC_res value equals 2¹⁵ or 32768.
From Equation 4, the calibration resistor value can be calculated
using Equation 5. The resolution of the math that is processed
internally in the DPM is 2048 or 11 bits of resolution. The V_SHUNT
LSB is set to 2.5µV. Equation 5 yields a 15-bit binary number that
can be written to the calibration register. The calibration register
format is represented in Table 18.
  ^CalRegval
integer



Math _resVshunt _LSB
Current_LSBR_shunt



CalReg_val
integer


0.00512
Current_LSBR_shunt
^{}
(EQ. 5)
TABLE 18. 0x38 IOUT_CAL_GAIN DEFINITION
BIT
NUMBER
D[15]
D[14:0]
Bit Name
N/A
IOUT_CAL_GAIN
Default
0
Value
000 0000 0000 0000
0XD5 CONFIGURE V_CHANNEL (R/W)
The Configure V_CHANNEL register is a read/writable word register
that configures the ADC measurement acquisition settings for
the primary and auxiliary voltage bus inputs.
TABLE 19. 0xD5 CONFIGURE V_CHANNEL REGISTER DEFINITION
BIT
NUMBER D[15:14] D[13:10]
D[9:7]
D[6:3]
D[2:0]
Bit Name N/A
AuxV
Sample
AVG
AuxV
V_BUS
V_BUS
Conversion Sample Conversion
Time
AVG
Time
Default
00
Value
00 00
11 1
000 0
111
The ADC configuration of the sampling average and conversion
time settings for V_BUS and AuxV channels have the same setting
choices as the V_SHUNT primary and auxiliary channels.
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FN8388.4
February 19, 2016