TLC3574, TLC3578, TLC2574, TLC2578

5V ANALOG, 3/5V DIGITAL, 14/12BIT, 200KSPS, 4/8CHANNEL

SERIAL ANALOGTODIGITAL CONVERTERS WITH ±10V INPUTS

SLAS262C − OCTOBER 2000 − REVISED MAY 2003

19

POST OFFICE BOX 655303

circuit description (continued)

data format

INPUT DATA FORMAT (BINARY)

MSB

LSB

ID[15:12]

ID[11:0]

Command

Configuration data field or filled with zeros

OUTPUT DATA FORMAT (READ CONVERSION/FIFO)

TLC3574 and TLC3578

TLC2574 and TLC2578

MSB

LSB

MSB

LSB

OD[15:2]

OD[1:0]

OD[15:4]

OD[3:0]

Conversion result

Don’t Care

Conversion result

Don’t Care

14-BIT (TLC3574/78)

12-BIT (TLC2574/78)

Bipolar Input, Offset Binary: (BOB)

Negative full scale code = VFS− = 0000h, Vcode = −10 V

Midscale code = VBZS = 2000h, Vcode = 0 V

Positive full scale code = VFS+ = 3FFFh, Vcode = 10 V − 1 LSB

Bipolar Input, Binary 2s Complement: (BTC)

Negative full scale code = VFS− = 2000 h, Vcode = −10 V

Midscale code = VBZS = 0000h, Vcode = 0 V

Positive full scale code = VFS+ = 1FFFh, Vocde = 10 V − 1 LSB

Bipolar Offset Binary Output: (BOB)

Negative full scale code = 000h, Vcode = −10 V

Midscale code = 800h, Vcode = 0 V

Positive full scale code = FFFh, Vcode = 10 V − 1 LSB

Bipolar Input, Binary 2s Complement: (BTC)

Negative full scale code = 800 h, Vcode = −10 V

Midscale code = 000h, Vcode = 0 V

Positive full scale code = 7FFh, Vocde = 10 V − 1 LSB

operation description

The converter samples the selected analog input signal, then converts the sample into digital output according

to the selected output format. The converter has four digital input pins (SDI, SCLK, CS, and FS) and one digital

output pin (SDO) to communicate with the host device. SDI is a serial data input pin, SDO is a serial data output

pin, and SCLK is a serial clock from host device. This clock is used to clock the serial data transfer. It can also

be used as conversion clock source (see Table 2). CS and FS are used to start the operation. The converter

has a CSTART pin for external hardware sampling and conversion trigger, and INT/EOC for interrupt purpose.

device initialization

After power on, the status of EOC/INT is initially high, and the input data register is set to all zeros. The device

must be initialized before starting conversion. The initialization procedure depends on the working mode. The

first conversion result must be ignored after power on.

Hardware Default Mode: Nonprogrammed mode, default. After power on, two consecutive active cycles

last 16 SCLK at least. These cycles initialize the converter and load CFR register with 800h (bipolar offset binary

output code, normal long sampling, internal OSC, single-ended input, one-shot conversion mode, and EOC/INT

pin as INT). No additional software configuration is required.

Software Programmed Mode: Programmed. If the converter needs to be configured, The host must write

A000H into converters first after power on, then performs the WRITE CFR operation to configure the device.

start of operation cycle

Each operation consists of several actions that the converter takes according to the command from the host.

The operation cycle includes three periods: command period, sampling period, and conversion period. In the

command period, the device decodes the command from host. In the sampling period, the device samples the

selected analog signal according to the command. In the conversion period, the sample of the analog signal

is converted to digital format. The operation cycle starts from the command period, which is followed by one

or several sampling and conversion periods (depending on the setting), and finishes at the end of last

conversion period. The operation is initiated by the falling edge of CS or the rising edge of FS.