MAX1497 Maxim, MAX1497 Datasheet - Page 26

• Manufacturer Part Number: MAX1497
• Description: 3.5- and 4.5-Digit / Single-Chip ADCs with LED Drivers and C Interface
• Manufacturer: Maxim

3.5- and 4.5-Digit, Single-Chip ADCs with LED
Drivers and µC Interface
The MAX1497/MAX1499 feature data-hold circuitry.
When activated (HOLD bit = 1), the device displays the
current reading on the LED.
The MAX1499 features a low-battery detection input.
When the voltage at LOWBATT drops below 2.048V
(typ), the LOWBATT bit of the status register goes high.
Connect the differential inputs of the MAX1497/MAX1499
to the bridge network of the strain gauge. In
the analog supply voltage powers the bridge network
and the MAX1497/MAX1499 along with the reference
voltage. The MAX1497/MAX1499 handle an analog input
voltage range of ±200mV and ±2V full scale. The ana-
log/reference inputs of the parts allow the analog input
range to have an absolute value of anywhere between
-2.2V and +2.2V.
Figure 16
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
Figure
26
- 1 - - - -
-19,999
1 - - - -
19,999
LED
______________________________________________________________________________________
17. MAX1499 Transfer Function, ±2V Range
- 0
- 1
- 2
2
1
0
ADC RESULT
>4E1Fh
4E1Fh
0002h
0001h
0000h
FFFFh
FFFEh
FFFDh
B1E0h
<B1E0h
shows a connection from a thermocouple to
Thermocouple Measurement
Strain-Gauge Measurement
-2V
ANALOG INPUT VOLTAGE
-100µV 100µV
0
Low Battery
Figure
+2V
Hold
15,
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.
Figures 17–20
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:
The transfer function for the MAX1499 with AIN+ - AIN-
< 0, RANGE = 0 is:
The transfer function for the MAX1497 with AIN+ - AIN-
≥ 0, RANGE = 0 is:
The transfer function for the MAX1497 with AIN+ - AIN-
< 0, RANGE = 0 is:
Figure
- 1 - - - -
-19,999
1 - - - -
19,999
LED
COUNTS
- 0
- 1
- 2
18. MAX1499 Transfer Function, ±200mV Range
2
1
0
COUNTS
COUNTS
ADC RESULT
4E1Fh
4E1Fh
0002h
00001h
0000h
FFFFh
FFFEh
FFFDh
B1E0h
<B1E0h
=
=
show the transfer functions of the
1 024
.
=
-200mV
1 024
.
1 024
.



V
V



REF
AIN
V



V
REF
AIN
V
V
ANALOG INPUT VOLTAGE
+
+
REF
AIN
-10µV
−
−
+
+
Transfer Functions
V
V
+
+
−
−
REF
AIN
−
−
V
V
0
V
V
REF
AIN
REF
10µV
−
AIN
−
−
−
−
−
×

 ×

20 000
×
,
2000
20 000
+200mV
,

 +




1