ISL28023 Datasheet, PDF (34/55 Pages) Intersil Corporation – Bidirectional current sensing

ISL28023
  ^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 Value
0
000 0000 0000 0000
0XD5 CONFIGURE VCHANNEL (R/W)
The Configure Vchannel 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 VCHANNEL REGISTER DEFINITION
BIT
NUMBER D[15:14] D[13:10] D[9:7]
D[6:3]
D[2:0]
Bit Name
N/A
AuxV
AuxV
V_BUS
V_BUS
Sample Conversion Sample Conversion
AVG
Time
AVG
Time
Default Value 00
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.
0XD7 CONFIGURE PEAK DETECTOR (R/W)
The Configure Peak Detector register is a read/writable byte
register that toggles the minimum and maximum current
tracking feature. A Peak Detect Enable bit setting of 1 enables
the current peak detect feature of the DPM. The feature is
discussed in more detail in “0xD8 Read Peak Min I_OUT (R)” on
page 35.
TABLE 20. 0xD7 CONFIGURE PEAK DETECTOR REGISTER DEFINITION
BIT
NUMBER
D[7:1]
D[0]
Bit Name
N/A
Peak Detect En
Default Value
0000 000
0
0XE2 CONFIGURE EXCITATION (R/W)
The Configure Excitation register is a read/writable byte register
that changes the measurement functionality of the auxiliary
V_SHUNT input.
TABLE 21. 0xE2 CONFIGURE EXCITATION REGISTER DEFINITION
BIT NUMBER
D[15:1]
D[0]
Bit Name
N/A
Ext Temp En
Default Value
0000 0000 0000 000
0
The default state of the register configures the auxiliary V_SHUNT
input to measure the differential voltage across the AUXP and
AUXM inputs. The maximum measurable voltage that can be
applied to the inputs is 80mV.
Setting the Ext Temp En bit to 1 activates the current sourcing
circuitry at the auxiliary V_SHUNT input. Connecting a diode
between AUXP and AUXM will enable external temperature
measurement functionality.
V BU S
VBUS_Vsense
V IN P
V IN M
CM = 0 to 60V
A UX V
AUX_Vsense
I²C
SM BUS
PM BUS
ADC
16-BIT
S M BC LK
To µC
S M BD A T
A0
A1
A2
E XT_TEM P_E N
20µA and/or 100µA
A UX P
CM = 0 to VCC
A UX M
FIGURE 98. SIMPLIFIED CIRCUIT DIAGRAM OF AN EXTERNAL
TEMPERATURE APPLICATION
The external temperature measurement mode forces two
currents (20µA/100µA) through the diode. The differential
voltage between the AUXP and AUXM pins for each current forced
are measured and stored by way of a sample and hold circuitry.
The timing for the two current measurement is 1µs. The
maximum voltage that can be measured between the auxiliary
Vshunt pins is ±VCC.
Upon completion of the two current measurements, the ADC
measures the difference between the two stored differential
voltage values. The measured value by the ADC yields the Vbe
voltage for the two currents. The maximum Vbe voltage that the
temperature circuit can measure is 80mV. The DPM stores the
measured value from the ADC in the READ_TEMPERATURE_1
register. Using Equation 2 to calculate the register signed integer
value, the Vbe voltage can be calculated using Equation 6.
Vbe Register _ValueAux_Vshunt _LSB
(EQ. 6)
Register_value is the READ_TEMPERATURE_1 signed integer
value. The Aux_Vshunt_LSB equals 10µV.
Equation 7 yields the absolute temperature from the current
measurements.
T


q
nk
^




Vbe
ln



I
I
2
1








273
(EQ. 7)
The Vbe value calculated in Equation 6 is used to calculate the
temperature in centigrade (°C).
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FN8389.5
March 18, 2016