TLV2548-EP

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SLAS668 – OCTOBER 2009

OUTPUT DATA FORMAT CONVERSION

MSB

LSB

D15

−D4

D3

−D0

Conversion result

Don’t care

OD[11:0]

The output data format is binary (unipolar straight binary).

Binary

Zero scale code = 000h, Vcode = VREFM.

Full scale code = FFFh, Vcode = VREFP

− 1 LSB

Control and Timing

Power Up and Initialization Requirements

•

Determine processor type by writing A000h to the TLV2548 (CS must be toggled).

•

Configure the device (CS must make a high-to-low transition, then can be held low if in DSP mode;

i.e., active FS).

The first conversion after power up or resuming from power down is not valid.

Start of the Cycle

•

When FS is not used (FS = 1 at the falling edge of CS), the falling edge of CS is the start of the cycle.

•

When FS is used (FS is an active signal from a DSP), the falling edge of FS is the start of the cycle.

First 4-MSBs: The Command Register (CMR)

The TLV2548 has a 4-bit command set (see Table 3) plus a 12-bit configuration data field. Most of the

commands require only the first 4 MSBs, i.e., without the 12-bit data field.

The valid commands are listed in Table 3.

Table 3. TLV2548 Command Set(1)

SDI D(15

−12) BINARY

COMMAND

0000b

0h

Select analog input channel 0

0001b

1h

Select analog input channel 1

0010b

2h

Select analog input channel 2

0011b

3h

Select analog input channel 3

0100b

4h

Select analog input channel 4

0101b

5h

Select analog input channel 5

0110b

6h

Select analog input channel 6

0111b

7h

Select analog input channel 7

1000b

8h

SW power down (analog + reference)

1001b

9h

Read CFR register data shown as SDO D(11-0)

Write CFR followed by 12–bit data, e.g., 0A100h means external reference,

1010b

Ah plus data

short sampling, SCLK/4, single shot, INT

1011b

Bh

Select test, voltage = (REFP+REFM)/2

1100b

Ch

Select test, voltage = REFM

1101b

Dh

Select test, voltage = REFP

1110b

Eh

FIFO read, FIFO contents shown as SDO D(15-4), D(3-0) = 0000

1111b

Fh plus data

Reserved

(1)

The status of the CFR can be read with a read CFR command when the device is programmed for one–shot conversion mode

(CFR D[6,5] = 00).

Copyright © 2009, Texas Instruments Incorporated

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