MAX1497 Datasheet, PDF (26/33 Pages) Maxim Integrated Products – 3.5- and 4.5-Digit, Single-Chip ADCs with LED Drivers and μC Interface

3.5- and 4.5-Digit, Single-Chip ADCs with LED
Drivers and µC Interface
LED ADC RESULT
1 - - - - >4E1Fh
19,999 4E1Fh
2 0002h
1 0001h
0 0000h
- 0 FFFFh
- 1 FFFEh
- 2 FFFDh
-19,999 B1E0h
- 1 - - - - <B1E0h
-2V
-100µV 0 100µV
+2V
ANALOG INPUT VOLTAGE
Figure 17. MAX1499 Transfer Function, ±2V Range
LED ADC RESULT
1 - - - - 4E1Fh
19,999 4E1Fh
2 0002h
1 00001h
0 0000h
- 0 FFFFh
- 1 FFFEh
- 2 FFFDh
-19,999 B1E0h
- 1 - - - - <B1E0h
-200mV
-10µV 0 10µV
+200mV
ANALOG INPUT VOLTAGE
Figure 18. MAX1499 Transfer Function, ±200mV Range
LED ADC RESULT
1 - - - 7CFh
1999 7CFh
2 002h
1 001h
0 000h
- 0 FFFh
- 1 FFEh
- 2 FFDh
-1999 830h
- 1 - - - <830h
-200mV
-100µV 0 100µV
+200mV
ANALOG INPUT VOLTAGE
Figure 19. MAX1497 Transfer Function, ±200mV Range
LED ADC RESULT
1 - - - >7CFh
1999 7CFh
2 002h
1 001h
0 000h
- 0 FFFh
- 1 FFEh
- 2 FFDh
-1999 830h
- 1 - - - <830h
-2V
-1mV 0 1mV
+2V
ANALOG INPUT VOLTAGE
Figure 20. MAX1497 Transfer Function, ±2V Range
Thermocouple Measurement
Figure 16 shows a connection from a thermocouple to
the MAX1497/MAX1499. In this application, the
MAX1497/MAX1499 take advantage of the on-chip
input buffers that allow large source impedances on the
front end. The decoupling capacitors reduce noise
pickup from the thermocouple leads. To place the dif-
ferential voltage from the thermocouple at a suitable
common-mode voltage, the AIN- input of the MAX1497/
MAX1499 is biased to GND. Use an external tempera-
ture sensor, such as the DS75, and a µC to perform
cold-junction temperature compensation.
Transfer Functions
Figures 17–20 show the transfer functions of the
MAX1497/MAX1499. The output data is stored in the
ADC data register in two’s complement.
The transfer function for the MAX1499 with AIN+ - AIN-
≥ 0, RANGE = 0 is:
COUNTS
=
1.024


V_AIN+
V_REF+
−
−
V_AIN−
V_{REF −}


×
20,000
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