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APPLICATION INFORMATION

GENERAL FUNCTION

2 REF

CODE

0x1000

[V]

SERIAL INTERFACE

TMS320

DSP FSX

CLKX

DX

TLV5637

SCLK

DIN

CS

SPI

I/O

SCK

MOSI

TLV5637

SCLK

DIN

CS

Microwire

I/O

SK

SO

TLV5637

SCLK

DIN

CS

SERIAL CLOCK FREQUENCY AND UPDATE RATE

f

1

(t

+t

)

whmin

wlmin

=20MHz

f

=

updatemax

1

16(t

+t

)

whmin

wlmin

=1.25MHz

TLV5637

SLAS224C – JUNE 1999 – REVISED JUNE 2007

The TLV5637 is a dual 10-bit, single supply DAC, based on a resistor string architecture. It consists of a serial

interface, a speed and power-down control logic, a programmable internal reference, a resistor string, and a

rail-to-rail output buffer.

The output voltage (full scale determined by reference) is given by:

Where REF is the reference voltage and CODE is the digital input value in the range 0x000 to 0xFFF. Because

it is a 10-bit DAC, only D11 to D2 are used. D0 and D1 are ignored. A power-on reset initially puts the internal

latches to a defined state (all bits zero).

A falling edge of CS starts shifting the data bit-per-bit (starting with the MSB) to the internal register on the falling

edges of SCLK. After 16 bits have been transferred or CS rises, the content of the shift register is moved to the

target latches (DAC A, DAC B, BUFFER, CONTROL), depending on the control bits within the data word.

Figure 13 shows examples of how to connect the TLV5637 to TMS320, SPI, and Microwire.

Figure 13. Three-Wire Interface

Notes on SPI and Microwire: Before the controller starts the data transfer, the software has to generate a falling

edge on the I/O pin connected to CS. If the word width is 8 bits (SPI and Microwire), two write operations must

be performed to program the TLV5637. After the write operation(s), the holding registers or the control register

are updated automatically on the 16th positive clock edge.

The maximum serial clock frequency is given by:

The maximum update rate is:

Note that the maximum update rate is just a theoretical value for the serial interface, as the settling time of the

TLV5637 has to be considered as well.

10

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