ADBMS1818CSWAZ-R7 datasheet(31/92 Pages) AD

31 / 92 page

Data Sheet

ADBMS1818

THEORY OF OPERATION

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Rev. B | 31 of 92

Undervoltage and Overvoltage Monitoring

Whenever the C inputs are measured, the results are compared

to undervoltage and overvoltage thresholds stored in the memory.

If the reading of a cell is above the overvoltage limit, a bit in the

memory is set as a flag. Similarly, measurement results below the

undervoltage limit cause a flag to be set. The overvoltage and

undervoltage thresholds are stored in Configuration Register Group

A. The flags are stored in Status Register Group B and Auxiliary

Auxiliary (GPIO) Measurements (ADAX

Command)

The ADAX command initiates the measurement of the GPIO inputs.

This command has options to select which GPIO input to measure

(GPIO1 to GPIO9) and which ADC mode to use. The ADAX

command also measures the 2nd reference. There are options in

the ADAX command to measure subsets of the GPIOs and the

2nd reference separately or to measure all nine GPIOs and the

2nd reference in a single command. See the Commands section

for the ADAX command format. All auxiliary measurements are

relative to the V– pin voltage. This command can be used to read

external temperatures by connecting temperature sensors to the

GPIOs. These sensors can be powered from the 2nd reference,

which is also measured by the ADAX command, resulting in precise

ratiometric measurements.

Figure 57 shows the timing of the ADAX command measuring

all nine GPIOs and the 2nd reference. All 10 measurements are

carried out on ADC1 alone. The 2nd reference is measured after

GPIO5 and before GPIO6.

Table 23 shows the conversion time for the ADAX command meas-

uring all nine GPIOs and the 2nd reference. t10C indicates the total

conversion time.

Figure 57. Timing for ADAX Command Measuring All GPIOs and 2nd Reference

Table 23. Conversion and Synchronization Times for ADAX Command Measuring All GPIOs and 2nd Reference in Different Modes

Mode

Conversion Times (μs)

Synchronization Time (μs)

t1M

t2M

t9M

t10M

t10C

tSKEW

27 kHz

104

431

478

1825

420

14 kHz

163

693

769

2116

682

7 kHz

145

279

1217

1350

3862

1205

3 kHz

261

512

2264

2514

5025

2253

2 kHz

494

977

4358

4841

7353

4347

1 kHz

960

1908

8547

9496

12,007

8536

422 Hz

1890

3770

16,926

18,805

21,316

16,915

26 Hz

29,818

59,624

268,271

298,078

335,498

268,260

ADBMS1818CSWAZ-R7 数据表(PDF) 31 Page - Analog Devices

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