Low-Power, Serial, 14-Bit DACs

with Voltage Output

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11

The MAX5170/MAX5172 accepts one 16-bit packet or

two 8-bit packets sent while

CS remains low. The

MAX5170/MAX5172 allow the following to be config-

ured:

• Clock edge on which serial data output (DOUT) is

clocked out

• State of the user-programmable logic output

• Configuration of the reset state.

Specific commands for setting these are shown in

Table 1.

The general timing diagram in Figure 4 illustrates how

the MAX5170/MAX5172 acquire data.

CS must go low

(SCLK). With

CS low, data is clocked into the register

on the rising edge of SCLK. The maximum serial clock

frequency guaranteed for proper operation is 10MHz

for MAX5170 and 6MHz for MAX5172. See Figure 5 for

a detailed timing diagram of the serial interface.

Serial Data Output (DOUT)

The serial-data output, DOUT, is the internal shift regis-

ter’s output and allows for daisy-chaining of multiple

devices as well as data readback (see

Applications

Information). By default upon start-up, data shifts out of

DOUT on the serial clock’s rising edge (Mode 0) and

provides a lag of 16 clock cycles, thus maintaining SPI,

QSPI, and MICROWIRE compatibility. However, if the

device is programmed for Mode 1, the output data lags

DIN by 16.5 clock cycles and is clocked out on the ser-

ial clock’s rising edge. During shutdown, DOUT retains

its last digital state prior to shutdown.

Load input register; DAC registers are updated (start-up DAC with new data).

1

0

Load input register; DAC registers are unchanged.

0

0

14-bit DAC data

14-bit DAC data

16-BIT SERIAL WORD

D11..................D0

C1

FUNCTION

C0

No operation (NOP).

1

1

0 0 x xxx xxxx xxxx

x x x xxx xxxx xxxx

Update DAC register from input register (start-up DAC with data previously

stored in the input registers).

0

1

UPO goes low (default).

1

1

1 0 0 xxx xxxx xxxx

0 1 x xxx xxxx xxxx

Mode 1, DOUT clocked out on SCLK’s rising edge.

1

1

1 1 0 xxx xxxx xxxx

1 0 1 xxx xxxx xxxx

UPO goes high.

1

1

Shut down DAC (provided

PDL = 1).

1

1

Mode 0, DOUT clocked out on SCLK’s falling edge (default).

1

1

1 1 1 xxx xxxx xxxx

SCLK

DIN

CS

MOSI

SCK

+5V

I/O

CPOL = 0, CPHA = 0

SPI/QSPI

PORT

SS

MAX5170

MAX5172

Figure 2. Connections for SPI and QSPI Interface

SCLK

DIN

CS

SK

SO

I/O

MICROWIRE

PORT

MAX5170

MAX5172

Figure 3. Connections for MICROWIRE Interface Standards

Table 1. Serial-Interface Programming Commands