ADS1148IPWR datasheet(36/100 Pages) TI2

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8000h

8001h

FFFFh

0000h

0001h

7FFEh

7FFFh

±FS

‡ ‡ ‡

±FS

± 1

Input Voltage VIN

±FS

± 1

ADS1146, ADS1147, ADS1148

SBAS453G – JULY 2009 – REVISED AUGUST 2016

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Product Folder Links: ADS1146 ADS1147 ADS1148

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Programming (continued)

9.5.1.7 SPI Communication During Power-Down Mode

When the START pin is low or the device is in power-down mode, only the RDATA, RDATAC, SDATAC,

WAKEUP, and NOP commands can be issued. The RDATA command can be used to repeatedly read the last

conversion result during power-down mode. Other commands do not function because the internal clock is shut

down to save power during power-down mode.

9.5.2 Data Format

The device provides 16 bits of data in binary twos complement format. The size of one code (LSB) is calculated

using Equation 20.

1 LSB = (2 × VREF / Gain) / 2

16 = +FS / 215

(20)

A positive full-scale (FS) input [VIN ≥ (+FS – 1 LSB) = (VREF / Gain – 1 LSB)] produces an output code of 7FFFh

and a negative full-scale input (VIN ≤ –FS = –VREF / Gain) produces an output code of 8000h. The output clips at

these codes for signals that exceed full-scale. Table 14 summarizes the ideal output codes for different input

signals.

(1)

Excludes effects of noise, linearity, offset, and gain errors.

Table 14. Ideal Output Code vs Input Signal

INPUT SIGNAL, VIN

(AINP – AINN)

IDEAL OUTPUT CODE(1)

≥ FS (215 – 1) / 215

7FFFh

FS / 215

0001h

0000h

–FS / 215

FFFFh

≤ –FS

8000h

Figure 45 shows the mapping of the analog input signal to the output codes.

Figure 45. Code Transition Diagram

ADS1148IPWR Datasheet(PDF) 36 Page - Texas Instruments

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