MAX1403EVKIT Maxim Integrated Products, MAX1403EVKIT Datasheet - Page 34

• Manufacturer Part Number: MAX1403EVKIT
• Description: EVAL KIT FOR MAX1403
• Manufacturer: Maxim Integrated Products

Specifications of MAX1403EVKIT

• Number Of Adc's: 1
• Number Of Bits: 18
• Sampling Rate (per Second): 480
• Data Interface: Serial
• Inputs Per Adc: 6 Single Ended
• Input Range: ±VREF/gain
• Power (typ) @ Conditions: 16.9mW @ 480SPS
• Voltage Supply Source: Analog and Digital
• Operating Temperature: 0°C ~ 70°C
• Utilized Ic / Part: MAX1403
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

+3V, 18-Bit, Low-Power, Multichannel,
Oversampling (Sigma-Delta) ADC
Figure 15. Thermocouple Application with MAX1403
Figure 16. 4–20mA Transmitter
34
THERMOCOUPLE
JUNCTION
______________________________________________________________________________________
SENSOR
+3V
+1.25V
R
R
C
GND
V+
SPI
4
ISOLATION
BARRIER
C
AIN1
REFIN+
REFIN-
AGND
AIN2
SPI
4
SWITCHING
NETWORK
µP/µC
MAX1403
DGND
SPI
BUFFER
3
GND
DAC
V+
PGA
R
GAIN
Low-power, single-supply operation, and easy interfac-
ing with optocouplers make the MAX1403 ideal for
loop-powered 4–20mA transmitters. Loop-powered
transmitters draw their power from the 4–20mA loop,
limiting the transmitter circuitry to a current budget of
4mA. Tolerances in the loop further limit this current
budget to 3.5mA. Since the MAX1403 consumes only
250µA, a total of 3.25mA remains to power the remain-
ing transmitter circuitry. Figure 16 shows a block dia-
gram for a loop-powered 4–20mA transmitter.
Tightly matched 200µA current sources compensate for
errors in 3-wire and 4-wire RTD configurations. In the 3-
wire configuration (Figure 17), the lead resistances
result in errors if only one current source is used. The
200µA will flow through R
between AIN1 and AIN2. An additional current source
compensates for this error by developing an equivalent
voltage across R
AIN1 and AIN2 is not affected by lead resistance. This
assumes both leads are of the same material and of
equal length (R
OUT2 have matching tempcos (5ppm/°C). Both current
sources will flow through R
mode voltage that will not affect the differential voltage
at AIN1 and AIN2. Using one of the current sources to
supply the reference voltage ensures a more accurate
ratiometric result.
R
R
OFST
FDBK
C
3-Wire and 4-Wire RTD Configurations
C
Loop-Powered, 4–20mA Transmitters
REGULATOR
L1
L2
VOLTAGE
, ensuring the differential voltage at
= R
L2
R
L1
Y
), and assumes OUT1 and
L3
developing a voltage error
, developing a common-
R
R
X
SENSE
4–20mA LOOP
INTERFACE
V
V
IN+
IN-