MAX1021 Datasheet, PDF(34/40 Page) Maxim Integrated Products – 10-Bit, Multichannel ADCs/DACs with FIFO, Temperature Sensing, and GPIO Ports

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MAX1021 Datasheet, PDF (34/40 Pages) Maxim Integrated Products – 10-Bit, Multichannel ADCs/DACs with FIFO, Temperature Sensing, and GPIO Ports

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10-Bit, Multichannel ADCs/DACs with FIFO,

Temperature Sensing, and GPIO Ports

DIN

SCLK

(CONVERSION BYTE)

(UP TO 514 INTERNALLY CLOCKED ACQUISITIONS AND CONVERSIONS)

DOUT

EOC

MSB1

tDOV

LSB1

MSB2

Figure 8. Clock Mode 10âThe command byte to the conversion register begins the acquisition (CNVST is not required).

zeros (NOP byte) between each conversion byte. If 2

NOP bytes follow a conversion byte, the analog cells

power down at the end of the second NOP. Set the

FBGON bit to one in the reset register to keep the inter-

nal bias block powered.

If reference mode 00 is requested, or if an external refer-

ence is selected, but a temperature measurement is

being requested, wait 45Âµs with CS high after writing the

conversion byte to extend the acquisition and allow the

internal reference to power up. To perform a temperature

measurement, write 24 bytes (192 cycles) of zeros after

the conversion byte. The temperature result appears on

DOUT during the last 2 bytes of the 192 cycles.

Temperature results are available in 12-bit format.

Conversion-Time Calculations

The conversion time for each scan is based on a num-

ber of different factors: conversion time per sample,

samples per result, results per scan, if a temperature

measurement is requested, and if the external refer-

ence is in use. Use the following formula to calculate

the total conversion time for an internally timed conver-

sion in clock mode 00 and 10 (see the Electrical

Characteristics, as applicable):

Total conversion time =

tCNV x nAVG x nSCAN + tTS + tINT-REF,SU

where:

tCNV = tDOV (where tDOV is dependent on clock mode

and reference mode selected)

nAVG = samples per result (amount of averaging)

nSCAN = number of times each channel is scanned; set

to one unless [SCAN1, SCAN0] = 10

tTS = time required for temperature measurement

(53.1Âµs); set to zero if temperature measurement is not

requested

tINT-REF,SU = tWU (external-reference wake-up); if a

conversion using the external reference is requested.

In clock mode 01, the total conversion time depends on

how long CNVST is held low or high. Conversion time in

externally clocked mode (CKSEL1, CKSEL0 = 11)

depends on the SCLK period and how long CS is held

high between each set of eight SCLK cycles. In clock

mode 01, the total conversion time does not include the

time required to turn on the internal reference.

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