Rainbow Electronics MAX1209 - Manual (Page 22)

MAX1209
Buffered External Reference
Drives Multiple ADCs
The buffered external reference mode allows for more
control over the MAX1209 reference voltage and allows
multiple converters to use a common reference. The
REFIN input impedance is >50M
Ω.
Figure 13 uses the MAX6029EUK21 precision 2.048V
reference as a common reference for multiple convert-
ers. The 2.048V output of the MAX6029 passes through
a one-pole, 10Hz lowpass filter to the MAX4230. The
MAX4230 buffers the 2.048V reference and provides
additional 10Hz lowpass filtering before its output is
applied to the REFIN input of the MAX1209.
12-Bit, 80Msps, 3.3V IF-Sampling ADC
22 ______________________________________________________________________________________
MAX1209
NOTE: ONE FRONT-END REFERENCE
CIRCUIT IS CAPABLE OF SOURCING 15mA
AND SINKING 30mA OF OUTPUT CURRENT.
*PLACE THE 1 µF REFP-to-REFN BYPASS CAPACITOR AS CLOSE TO THE DEVICE AS POSSIBLE.
16.2k Ω
0.1 µF
0.1 µF
1 µF
2
5
2.048V
2.048V
+3.3V
1
2
4
1
3
5
47 Ω
1.47k Ω
+3.3V
10 µF
6V
330 µF
6V
+3.3V
2.2 µF
2.2 µF
0.1 µF
1 µF* 10 µF
0.1 µF
0.1 µF
0.1 µF
REFP
REFN
COM
3
2
1 V DD
GND
REFIN
39
REFOUT
38
MAX1209
+3.3V
2.2 µF
2.2 µF
0.1 µF
1 µF* 10 µF
0.1 µF
0.1 µF
0.1 µF
REFP
REFN
COM
3
2
1 V
DD
GND
REFIN
39
REFOUT
38
MAX6029EUK21
MAX4230
Figure 13. External Buffered Reference Driving Multiple ADCs