Manual
onto the bus. After reading all four channels, bring CS
high to release the parallel I/O. After waiting t
QUIET
,
pulse CONVST low to initiate the next conversion.
Reference
Bypass the reference inputs as indicated in Table 3.
Internal Reference
The internal reference supports all input ranges for the
MAX1338.
External Reference
Implement external-reference operation by overdriving
the internal reference voltage. Override the internal ref-
erence voltage by connecting a 2.0V to 3.0V external
reference at REF. The REF input impedance is typically
5kΩ. For more information about using an external ref-
erence, see the Transfer Functions section.
Transfer Functions
Digital Correction
Factory trim procedures digitally shift the transfer func-
tion to reduce bipolar zero-code offset to less than
±4 LSBs (typ). Depending on initial conditions, the
transfer function is shifted up or down, as required. The
maximum shift that any transfer function experiences is
64 codes, which can have a small effect at the
extremes of the transfer function, as shown in Figure 7.
MAX1338
14-Bit, 4-Channel, Software-Programmable,
Multiranging, Simultaneous-Sampling ADC
______________________________________________________________________________________ 17
CONVST
1
29
26
31
CH3
CH2
CH1
CH0
t
ACC
t
CONVST
SAMPLE
CLK
t
EOC
EOC
EOLC
D0–D13
2
27 28
30
t
CLKH
t
CLKL
t
CNTC
t
CLK
ONLY LAST PULSE SHOWN
CS
t
QUIET
t
RTC
t
RDH
t
RDL
t
CTR
t
EOCRD
t
EOLCRD
RD
t
REQ
Figure 6. Reading After a Conversion—External Clock
LOCATION
BYPASS
CAPACITORS
REFADC bypass capacitor to AGND 1nF
REFP1 bypass capacitor to AGND 0.1µF
REFN1 bypass capacitor to AGND 0.1µF
REFP1 to REFN1 capacitor 1.0µF
COM1 bypass capacitor to AGND 1.0µF || 0.1µF
Table 3. Reference Bypass Capacitors