MAX11612 Datasheet, PDF(18/22 Page) Maxim Integrated Products – 2.7V to 3.6V and 4.5V to 5.5V, Low-Power, 4-/8-/12-Channel, 2-Wire Serial, 12-Bit ADCs

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MAX11612 Datasheet, PDF (18/22 Pages) Maxim Integrated Products – 2.7V to 3.6V and 4.5V to 5.5V, Low-Power, 4-/8-/12-Channel, 2-Wire Serial, 12-Bit ADCs

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2.7V to 3.6V and 4.5V to 5.5V, Low-Power,

4-/8-/12-Channel, 2-Wire Serial, 12-Bit ADCs

Table 6. Reference Voltage, AIN_/REF, and REF Format

SEL2

SEL1

X = Donât care.

SEL0

REFERENCE

VOLTAGE

VDD

External reference

Internal reference

AIN_/REF

(MAX11612/

MAX11613/

MAX11616/

MAX11617)

Analog input

Reference input

Analog input

Reference output

REF

(MAX11614/

MAX11615)

Not connected

Reference input

Not connected

Reference output

INTERNAL

REFERENCE

STATE

Always off

Always on

Always off

Always on

When idle, the MAX11612âMAX11617 continuously wait

for a START condition followed by their slave address

(see the Slave Address section). Upon reading a valid

address byte, the MAX11612âMAX11617 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 VDD 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 60ÂµA (typ)

and drops to 6ÂµA (typ) at 1ksps. At 0.1ksps the average

supply current is just 1ÂµA, or a minuscule 3ÂµW 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 0.1ÂµF capacitor and a 2kÎ©

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 VDD. For

maximum conversion accuracy, the reference must be

able to deliver up to 40ÂµA and have an output imped-

put impedance or is noisy, bypass it to GND as close to

AIN_/REF as possible with a 0.1ÂµF capacitor.

OUTPUT CODE

11 . . . 111

11 . . . 110

11 . . . 101

FULL-SCALE

TRANSITION

MAX11612â

MAX11617

00 . . . 011

00 . . . 010

00 . . . 001

00 . . . 000

012 3

INPUT VOLTAGE (LSB)

Figure 12. Unipolar Transfer Function

FS = VREF

ZS = GND

1 LSB = VREF

4096

FS - 3/2 LSB

18 ______________________________________________________________________________________

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