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MAX1069_10 Datasheet, PDF (17/20 Pages) Maxim Integrated Products – 58.6ksps, 14-Bit, 2-Wire Serial ADC in a 14-Pin TSSOP
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58.6ksps, 14-Bit, 2-Wire Serial ADC
in a 14-Pin TSSOP
Internal Reference
The MAX1069 contains an internal 4.096V bandgap ref-
erence. This bandgap reference is connected to
REFADJ through a 5kΩ resistor. Bypass REFADJ with a
0.1µF capacitor to AGND. The MAX1069 reference
buffer has a unity gain to provide +4.096V at REF.
Bypass REF with a 10µF capacitor to AGND when the
internal reference is used (Figure 12).
The internal reference is adjustable to ±1.5% using the
Figure 13 circuit.
External Reference
For external reference operation, disable the internal
reference by connecting REFADJ to AVDD. During con-
version, an external reference at REF must deliver up to
100µA of DC load current and have an output imped-
ance of less than 10Ω.
For optimal performance, buffer the reference through
an op amp and bypass REF with a 10µF capacitor.
Consider the MAX1069’s equivalent input noise
(80µVRMS) when choosing a reference.
Transfer Function
The MAX1069 has a standard unipolar transfer function
with a valid analog input voltage range from VAGNDS to
VREF. Output data coding is binary with 1LSB =
(VREF/2N) where ‘N’ is the number of bits (14). Code
transitions occur halfway between successive-integer
SAR
ADC
REF
4.096V
AV = 1.0
MAX1069
5kΩ
4.096V
BANDGAP
REFERENCE
REF 13
10µF
REFADJ 12
0.1µF
DGND
1
AGND
9
Figure 12. Internal Reference
LSB values. Figure 14 shows the MAX1069 input/output
(I/O) transfer function.
Input Buffer
Most applications require an input buffer amplifier to
achieve 14-bit accuracy. If the input signal is multi-
plexed, the input channel should be switched immedi-
ately after acquisition, rather than near the end of or
MAX1069
AVDD 8
0.1µF
SAR
ADC
REF
4.096V
AV = 1.0
5kΩ
4.096V
BANDGAP
REFERENCE
REF 13
10µF
REFADJ 12
68kΩ
0.1µF
DGND
1
AGND
9
5.0V
100kΩ
POTENTIOMETER
150kΩ
Figure 13. Adjusting the Internal Reference
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