Datasheet

ManualsBrandsTEXAS INSTRUMENTS ManualsData collecting ICsData acquisition IC - AD converter (ADC) External , Internal SOIC 20

TLV2556

SLAS355A – DECEMBER 2001 – REVISED SEPTEMBER 2002

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PRINCIPLES OF OPERATION

default mode

When the DATA IN pin is held high, the ADC goes into hardware default mode because the CFGR2 bits are all

programmed to the default values after 8 I/O CLOCKs. This means the ADC is programmed for an external

reference and pin 19 as EOC. In addition, channel AIN0 is selected. The first conversion is invalid therefore the

conversion result should be ignored. On the next cycle, AIN0 is sampled and converted. This mode of operation

is valid when CS

is toggled or held low after the first cycle.

To remove the device from hardware default mode, CFGR2 bit D0 must be reset to 0. Once this is done, the

host must program CFGR1 on the next cycle and disregard the result from the current cycle’s conversion.

data input

The data input is internally connected to an 8-bit serial-input address and control register. The register defines

the operation of the converter and the output data length. The host provides the input data byte with the MSB

first. Each data bit is clocked in on the rising edge of the I/O CLOCK sequence (see Table 2 for the data

input-register format).

Table 2. Command Set (CMR) and Configuration

01: 8-bit output length

X0: 12-bit output length

11: 16-bit output length (default)

0: MSB out first (default)

1: LSB out first

0: Unipolar binary (default)

1: Bipolar 2s complement

00: Internal 4.096 reference

01: Internal 2.048 reference

11: External reference (default)

0: Pin 19 output EOC (default)

1: Pin 19 output Int

0: Normal mode

(CFGR1 needs to be programmed)

1: Default mode enabled

(D[3:0] of CFGR1 and D[3:1] of

CFGR2 set to default)

SDI D[7:4]

Binary, HEX

COMMAND

0000b

0001b

0010b

0011b

0100b

0101b

0110b

0111b

1000b

1001b

1010b

1011b

1100b

1101b

1110b

1111b

SELECT analog input channel 0

SELECT analog input channel 1

SELECT analog input channel 2

SELECT analog input channel 3

SELECT analog input channel 4

SELECT analog input channel 5

SELECT analog input channel 6

SELECT analog input channel 7

SELECT analog input channel 8

SELECT analog input channel 9

SELECT analog input channel 10

SELECT TEST,

Voltage = (VREF+ + VREF–)/2

SELECT TEST, Voltage = REFM

SELECT TEST, Voltage = REFP

SW POWERDOWN (analog + reference)

ACCESS CFGR2

CONFIGURATION

CFGR1

SDI

D[3:0]

D[3:2]

CONFIGURATION

CFGR2

SDI

D[3:0]

D[3:2]