MAX11661_1111 Datasheet, PDF (25/28 Pages) Maxim Integrated Products – 500ksps, Low-Power, Serial 12-/10-/8-Bit ADCs

500ksps, Low-Power,
Serial 12-/10-/8-Bit ADCs
and stays within a given error band centered on the
resulting steady-state amplifier output level. The ADC
input sampling capacitor charges during the sampling
cycle, referred to as the acquisition period. During this
acquisition period, the settling time is affected by the
input resistance and the input sampling capacitance.
This error can be estimated by looking at the settling of
an RC time constant using the input capacitance and
the source impedance over the acquisition time period.
Figure 15 shows a typical application circuit. The
MAX4430, offering a settling time of 37ns at 16 bits, is
an excellent choice for this application. See the THD
vs. Input Resistance graph in the Typical Operating
Characteristics.
Choosing a Reference
For devices using an external reference, the choice of
the reference determines the output accuracy of the
ADC. An ideal voltage reference provides a perfect initial
accuracy and maintains the reference voltage indepen-
dent of changes in load current, temperature, and time.
Considerations in selecting a reference include initial
voltage accuracy, temperature drift, current source,
sink capability, quiescent current, and noise. Figure 15
shows a typical application circuit using the MAX6126
to provide the reference voltage. The MAX6033 and
MAX6043 are also excellent choices.
+5V
500I
AIN1
VDC
500I
AIN2
VDC
0.1µF
10µF
3V
100pF C0G
500I
4
5
MAX4430
3
2
1
-5V
0.1µF
10µF
0.1µF
10µF
10I
470pF
C0G CAPACITOR
470pF
C0G CAPACITOR
+5V
10µF
0.1µF
10µF
100pF C0G
500I
4
5
MAX4430
3
2
1
10I
-5V
0.1µF
10µF
0.1µF
VDD
AGND
V_OVDD
OVDD
0.1µF
10µF
AIN1
MAX11662
MAX11664
MAX11666
SCLK
AIN2
DOUT
CS
REF
CHSEL
EP
7 _OUTF
IN ²
6 _OUTS
MAX6126
4 _GNDS
NR ¹
3 _GND
SCK
MISO
CPU
SS
+5V
1µF
0.1µF
0.1µF
Figure 15. Typical Application Circuit
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