____________Functional Description

The MAX132 integrates the input voltage for a fixed

period of time, then deintegrates a known reference

voltage and measures the time required to reach zero.

Good line rejection is achieved by setting the (input)

integration time equal to one 50Hz or 60Hz period. The

MAX132 has a 50Hz/60Hz mode selection bit that sets

the integration time to 655/545 clock periods, respec-

tively, so that 50Hz/60Hz rejection is obtained with a

32,768Hz crystal. The MAX132 is tested and guaran-

teed at a 16 conv/sec throughput rate. Figure 1 shows

the basic MAX132 application circuit, with component

values selected for 16 conv/sec .

For applications that don’t require 50Hz/60Hz rejection,

the MAX132 will operate up to 100 conv/sec at reduced

accuracy (typically 0.012% FSR nonlinearity, or ±13

bits). In these applications, the 50Hz mode is recom-

mended because of its longer (655 count) integration

time. See

Increased Speed section.

__________Analog Design Procedure

Input Voltage Range

and Input Protection

The recommended analog full-scale input range is

±512mV. Performance is tested and guaranteed at

±512mV full scale, corresponding to a 2µV/LSB resolu-

tion at 18 bits. Resolution is defined as follows:

which corresponds to 2µV/LSB resolution at 18 bits.

Consult the

Typical Operating Characteristics for Noise

vs. Number of Samples Averaged and other important

operating parameters. Note how accuracy depends on

common-mode input voltage (common mode is defined

here as

set the analog input full-scale between ±470mV and

±18-Bit ADC with Serial Interface

6

_______________________________________________________________________________________

Re

/

(

) /

,

solution Volts LSB

V

FS

IN

262 144

3k

3k

DOUT

DOUT

DGND

DGND

+5V

Figure 3. Load Circuits for Access Time

3k

3k

DOUT

DOUT

DGND

DGND

+5V

10pF

10pF

Figure 4. Load Circuits for Disable Time to Three-State

DIN

SCLK

CS

DOUT

P0–P3

MSB IN

B6–B1

LSB IN

LSB OUT

B6–B1

MSB OUT

Figure 2. Serial-Mode Timing