Selecting Standby or Shutdown Mode

The MAX1165/MAX1166 have a selectable standby or

low-power shutdown mode. In standby mode, the

ADC’s internal reference and reference buffer do not

power down between conversions, eliminating the need

to wait for the reference to power up before performing

the next conversion. Shutdown mode powers down the

reference and reference buffer after completing a con-

version. The reference and reference buffer require a

power up and settle from shutdown.

The state of R/C at the second falling edge of CS

selects which power-down mode the MAX1165/

MAX1166 enter upon conversion completion. Holding

R/C low causes the MAX1165/MAX1166 to enter stand-

by mode. The reference and buffer are left on after the

conversion completes. R/C high causes the MAX1165/

MAX1166 to enter shutdown mode and shut down the

reference and buffer after conversion (Figures 5 and 6).

When using an external reference, set the REF power-

down bit high for lowest current operation.

Standby Mode

While in standby mode, the supply current is reduced

to less than 1mA (typ). The next falling edge of CS with

R/C low causes the MAX1165/MAX1166 to exit standby

mode and begin acquisition. The reference and refer-

ence buffer remain active to allow quick turn-on time.

Standby mode allows significant power savings while

running at the maximum sample rate.

Shutdown Mode

In shutdown mode, the reference and reference buffer

are shut down between conversions. Shutdown mode

reduces supply current to 0.5µA (typ) immediately after

the conversion. The falling edge of CS with R/C low

causes the reference and buffer to wake up and enter

acquisition mode. To achieve 16-bit accuracy, allow

reference to wake up.

Internal and External Reference

Internal Reference

The internal reference of the MAX1165/MAX1166 is

internally buffered to provide +4.096V output at REF.

Bypass REF to AGND and REFADJ to AGND with 4.7µF

and 0.1µF, respectively.

Fine adjustments can be made to the internal reference

voltage by sinking or sourcing current at REFADJ. The

input impedance of REFADJ is nominally 5kΩ. The

internal reference voltage is adjustable to ±1.5% with

the circuit of Figure 7.

External Reference

An external reference can be placed at either the input

(REFADJ) or the output (REF) of the MAX1165/

MAX1166s’ internal buffer amplifier. When connecting an

Low-Power, 16-Bit Analog-to-Digital Converter

with Parallel Interface

10

______________________________________________________________________________________

CS

REF

AND

BUFFER

REF POWER-

DOWN BIT

ACQUISITION

CONVERSION

DATA

OUT

R/C

EOC

Figure 5. Selecting Standby Mode

REF POWER-

DOWN BIT

ACQUISITION

CONVERSION

DATA

OUT

CS

REF

AND

BUFFER

R/C

EOC

Figure 6. Selecting Shutdown Mode

MAX1165

MAX1166

REFADJ

+5V

100kΩ

150kΩ

68kΩ

0.1µF

Figure 7. MAX1165/MAX1166 Reference Adjust Circuit