MAX11612–MAX11617
Low-Power, 4-/8-/12-Channel, I
2
C,
12-Bit ADCs in Ultra-Small Packages
19
Maxim Integrated
When idle, the MAX11612–MAX11617 continuously wait
for a START condition followed by their slave address
(see the
Slave Address
section). Upon reading a valid
address byte, the MAX11612–MAX11617 power up.
The internal reference requires 10ms to wake up, so
when using the internal reference it should be powered
up 10ms prior to conversion or powered continuously.
Wake-up is invisible when using an external reference
or V
DD
as the reference.
Automatic shutdown results in dramatic power savings,
particularly at slow conversion rates and with internal
clock. For example, at a conversion rate of 10ksps, the
average supply current for the MAX11613 is 60µA (typ)
and drops to 6µA (typ) at 1ksps. At 0.1ksps the average
supply current is just 1µA, or a minuscule 3µW of power
consumption. See Average Supply Current vs. Conversion
Rate in the
Typical Operating Characteristics
section).
Reference Voltage
SEL[2:0] of the setup byte (Table 1) control the reference
and the AIN_/REF configuration (Table 6). When AIN_/REF
is configured to be a reference input or reference output
(SEL1 = 1), differential conversions on AIN_/REF appear
as if AIN_/REF is connected to GND (see note 2 of Table
4). Single-ended conversion in scan mode AIN_/REF is
ignored by the internal limiter, which sets the highest avail-
able channel at AIN2 or AIN10.
Internal Reference
The internal reference is 4.096V for the MAX11612/
MAX11614/MAX11616 and 2.048V for the MAX11613/
MAX11615/MAX11617. SEL1 of the setup byte controls
whether AIN_/REF is used for an analog input or a refer-
ence (Table 6). When AIN_/REF is configured to be an
internal reference output (SEL[2:1] = 11), decouple
AIN_/REF to GND with a 0.1µF capacitor and a 2kΩ
series resistor (see the
Typical Operating Circuit
). Once
powered up, the reference always remains on until recon-
figured. The internal reference requires 10ms to wake up
and is accessed using SEL0 (Table 6). When in shutdown,
the internal reference output is in a high-impedance state.
The reference should not be used to supply current for
external circuitry. The internal reference does not require an
external bypass capacitor and works best when left uncon-
nected (SEL1 = 0).
External Reference
The external reference can range from 1V to V
DD
. For
maximum conversion accuracy, the reference must be
able to deliver up to 40µA and have an output imped-
ance of 500kΩ or less. If the reference has a higher out-
put impedance or is noisy, bypass it to GND as close to
AIN_/REF as possible with a 0.1µF capacitor.
