ISL28023 Datasheet, PDF (35/55 Pages) Intersil Corporation – Bidirectional current sensing

ISL28023
The value of the two currents that are sourced from the part
during the temperature measurement are 100µA and 20µA. I₂
equal 100µA. The variable k is Boltzmann constant equal to
1.3806503*10^-23m²kg/S². The variable q is the electron
charge constant equal to = 1.6*10^-19C. The variable n is the
ideality factor of the temperature diode. A typical value is near 1.
The external temperature feature is a function of the Auxiliary
V_SHUNT conversion time as well as converter averaging. The
settings for the aforementioned registers directly impacts the
accuracy of the measurement and the timing.
ENTERING\EXITING THE EXTERNAL TEMPERATURE
MODE
Writing a 1 to D[0] of register 0xE2 will not configure the Aux
inputs to external temperature sense mode. The following series
of commands need to be sent to enable external temperature
sense functionality.
1. Power-down the ADC -- Set BitD[6] of register 0xD2 to 1.
2. Enable the Ext Temp bit -- Set BitD[0] of register 0xDE2 to 1.
3. Power ADC + and set measurement mode to temperature--
Set BitD[6] to 0 and set Bits[D2:0] to 6 for register 0xD2.
The external temperature feature is functional in both trigger and
continuous modes. Undoing the series of commands listed above
will exit the external temperature mode.
Measurement Registers
0XD6 READ V_SHUNT OUT (R)
The Read V_SHUNT Out register is a readable word register that
stores the signed measured digital value of the primary V_SHUNT
input of the DPM. Using Equation 2 to calculate the integer value
of the register, Equation 8 calculates the floating point measured
value for the primary V_SHUNT channel.
Vshunt Register _valuevshunt _LSB
(EQ. 8)
Vshunt_LSB is the numerical weight of each level for the V_SHUNT
channel, which equals 2.5µV.
0X8B READ V_OUT (R)
The Read V_OUT register is a readable word register that stores the
unsigned measured digital value of the primary V_BUS input of the
DPM. Using Equation 1 to calculate the integer value of the
register, Equation 9 calculates the floating point measured value
for the primary V_BUS channel.
Vbus Register _valuevbus _LSB
(EQ. 9)
Vbus_LSB is the numerical weight of each level for the V_BUS
channel. The Vbus_LSB equals 1mV for the 60V version of the
DPM and 250µV for the 12V version of the DPM.
0X8C READ I_OUT (R)
The Read I_OUT register is a readable word register that stores the
signed measured digital value of the current passing through the
primary channel’s shunt. The register uses the measured value
from V_SHUNT and the IOUT_CAL_GAIN register. Equation 10
yields the current for the primary channel.
Current Register _valueCurrent _LSB
(EQ. 10)
The Register_value is calculated using Equation 2 on page 31. The
Current_LSB is calculated using Equation 4 on page 33.
0XD8 READ PEAK MIN I_OUT (R)
0XD9 READ PEAK MAX I_OUT (R)
FIGURE 99. THE ISL28023 TRACKS MINIMUM AND MAXIMUM
AVERAGE CURRENT READINGS
The Read Peak Min/Max I_OUT registers are readable word
registers that store the minimum and maximum current value of
an averaging cycle for the current passing through the primary
shunt.
The min/max current tracking is enabled by setting the Peak
Detect Enable bit in the CONFIG_PEAK_DET (0xD7) register. The
current peak detect feature only works for the current register.
At the conclusion of each primary channel current, the DPM will
record and store the minimum and maximum values of the
current measured. The feature operates for both the trigger and
continuous modes. Disabling the Peak Detector Enable bit will
turn off the feature as well as clear the Read Peak Min/Max I_OUT
registers.
0X96 READ P_OUT (R)
The Read P_OUT register is a signed readable word register that
reports the digital value of the power from the primary channel.
The register uses the values from READ_IOUT and
READ_VSHUNT_OUT registers to calculate the power.
The units for the power register are in watts. The power can be
calculated using Equation 11.
Power Register _value  Power _LSB 40000
(EQ. 11)
The Register_value is calculated using Equation 2. The Power_LSB
can be calculated from Equation 12.
Power _LSB Current _LSBVbus _LSB
(EQ. 12)
The V_BUSLSB equals 1mV for the 60V version of the DPM and
250µV for the 12V version of the DPM. The Current_LSB is the
value yielded from Equation 4 on page 33.
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FN8389.5
March 18, 2016