PAC1921 Datasheet, PDF (16/44 Pages) Microchip Technology – High-Side Current/Power Sensor

PAC1921
EQUATION 4-2: POWER LSB WEIGHT
1_LSB = -R---------^------------^------0---D---.----1--I----V----G--1------0--A----2----I--3--N------_---^--2---D-₆---------V--------3_------2-G-----V----A--------I-----N-----
Where:
0.1V = Maximum V_SENSE
voltage input
RΩ = R_SENSE resistor value
DI_GAIN = Digital current gain
32V/DV_GAIN = Maximum device bus
voltage input
DV_GAIN = Digital voltage gain
4.5.2
V_SENSE MEASUREMENT
When V_SENSE is selected as the measurement type,
free-run integration is used (see Section 4.7.3
“Free-Run Integration”). The V_SENSE voltage is digi-
tized and summed in the I_SUM Accumulator Registers,
The average is then taken at the end of the integration
period. Finally, digital gain is applied by adjusting the
parameter DI_GAIN. The upper 10-bit resultant value
represents the average V_SENSE voltage measured and
is used to drive the DAC. The PAC1921 should be kept
in the Integrate state for continuous output in this
mode. The value of one LSB in amps can be calculated
according to Equation 4-3.
EQUATION 4-3: V_SENSE LSB VALUE IN
AMPS
1_LSB = -R---------^--------1----^--0------20-D-----3.----1I----_--_V------G--2------₆--A--------I----N-----
Where:
0.1V = Maximum V_SENSE voltage input
RΩ = R_SENSE resistor value
DI_GAIN = Digital current gain
1023 x 2⁶ = FSR x scale offset
The value of one LSB in volts can be calculated accord-
ing to Equation 4-4.
EQUATION 4-4: V_SENSE LSB VALUE IN
VOLTS
1_LSB = -D-1------0--I-----2-0_----3--.G--1------_-V-A--------2I----N--₆---
Where:
0.1V = Maximum V_SENSE voltage input
DI_GAIN = Digital current gain
1023 x 2⁶ = FSR x scale offset
4.5.3
V_BUS MEASUREMENT
When V_BUS is selected as the measurement type,
free-run integration is used (see Section 4.7.3
“Free-Run Integration”). The V_BUS voltage is digi-
tized and summed in the V_SUM Accumulator Registers.
The average is taken at the end of the integration
period and digital gain is applied by adjusting the
parameter DV_GAIN. The upper 10-bit resultant value
represents the average V_BUS voltage measured and is
used to drive the DAC. The PAC1921 should be kept in
the Integrate state for continuous output in this mode.
The value of one LSB in volts can be calculated accord-
ing to Equation 4-5.
EQUATION 4-5: V_BUS LSB VALUE IN
VOLTS
1_LSB = -D---1------0V------2--3_----3--2--G-----V-_--A-------2-I------N₆----
Where:
1LSB = LSB value in volts
32/DV_GAIN = Maximum voltage
1023 x 2⁶ = FSR shifted 6 bits
4.6 OUT Pin and Measurement Type
The OUT pin is driven by a buffered 10-bit DAC. The
OUT pin signal is typically sent to an MCU with ADC
inputs to supply data for algorithms that cannot tolerate
the latencies inherent in embedded communications
buses. After a DAC update, the OUT pin can be polled
after t_SETTLE. The output voltage can also be
expressed as a result of the DAC, as shown in
Equation 4-6.
EQUATION 4-6: OUT PIN VALUE
OUT = _{1----0--D-2---3-A---}-C----2---₆-  OUTFSR
Where:
OUT = Output on OUT pin
DAC = value of the selected
measurement result registers
1023 x 2⁶ = FSR x scale offset
OUTFSR = Output FSR
DS20005293B-page 16
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