TMPSNSRD-RTD2 Microchip Technology, TMPSNSRD-RTD2 Datasheet - Page 15

• Manufacturer Part Number: TMPSNSRD-RTD2
• Description: BOARD RTD REFERENCE DESIGN
• Manufacturer: Microchip Technology

Specifications of TMPSNSRD-RTD2

• Sensor Type: Temperature
• Interface: USB
• Embedded: No
• Utilized Ic / Part: MCP3551, MCP9804
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Voltage - Supply: -
• Sensitivity: -
• Sensing Range: -
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Lead free / RoHS Compliant

Setting the DC Set Point for Sensor Circuit
A common DAC application is digitally controlling the set
point and/or calibration of parameters in a signal chain. The
fi gure below shows controlling the DC set point of a light
detector sensor using the MCP4728 12-bit quad DAC device.
The DAC provides 4096 output steps. If G = 1 and internal
reference voltage options are selected, then the internal
2.048 V
Setting the DC Set Point
Sensor Circuit Calibration using a DAC
REF
would produce 500 μV of resolution. If G = 2 is
R
6
R
V
V
Where Dn = Input Code (0 to 4095)
5
OUT
TRIP
R
4
= V
= V
R
G
RDY/BSY
3
X
REF
OUT
LDAC
= Gain Selection (x1 or x2)
SDA
SCL
V
V
DD
x Dn G
x R
DD
4096
1
2
3
4
5
1
R
MCP4728
+ R
Quad DAC
2
0.1 μF
⎩
⎨
⎧
To MCU
X
2
10 μF
10
9
8
7
6
Analog Outputs
V
V
V
V
V
SS
OUT
OUT
OUT
OUT
A
D
C
B
selected, the internal 2.048 V
resolution. If a smaller output step size is desired, the output
range would need to be reduced. So, using gain of 1 is a
better choice than using gain of 2 confi guration option for
smaller step size, but its full-scale range is one half of that
of the gain of 2. Using a voltage divider at the DAC output is
another method for obtaining a smaller step size.
Light
R
Light
Light
Light
R
R
R
1
R
R
1
1
1
R
R
R
R
R
SENSE
2
R
SENSE
2
SENSE
2
2
SENSE
V
V
V
V
V
DD
V
V
V
TRIP4
DD
DD
0.1 μF
DD
TRIP3
TRIP1
TRIP2
0.1 μF
0.1 μF
0.1 μF
REF
Signal Chain Design Guide
–
+
–
+
–
+
would produce 1 mV of
–
+
Comparator 1
Comparator 2
Comparator 3
Comparator 4
MCP6544(1/4)
MCP6544(2/4)
MCP6544(3/4)
MCP6544(4/4)
15