Low-Power, 12-Bit Voltage-Output DAC

with Serial Interface

_______________________________________________________________________________________

7

SCLK

DIN

CS

SK

SO

I/O

MAX5302

MICROWIRE

PORT

Figure 2. Connections for MICROWIRE

DIN

SCLK

CS

MOSI

SCK

I/O

SPI/QSPI

PORT

SS

+5V

CPOL = 0, CPHA = 0

MAX5302

Figure 3. Connections for SPI/QSPI

Figure 4. Serial-Data Format

3 Control

Bits

12+1 Data Bits

D11 .....................................D0, S0

C2

C1

C0

Data Bits

MSB ................................LSB Sub-Bit

Control

Bits

16 Bits of Serial Data

MSB ..................................................................................LSB

S0

Table 1. Serial-Interface Programming Commands

X = Don’t care

16-BIT SERIAL WORD

01

1

X0

0

X0

1

X1

0

11

1

No operation (NOP)

Load input register; DAC register immediately updated (also exit shutdown).

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

MSB

LSB

FUNCTION

Load input register; DAC register unchanged.

C2

C1

C0

Update DAC register from input register (also exit shutdown; recall previ-

ous state).

Shutdown

XXXXXXXXXXXX

12 bits of data

12 bits of data

XXXXXXXXXXXX

XXXXXXXXXXXX

S0

0

0

X

X

X

by updating the DAC with new data. When powering up

the device or bringing it out of shutdown, allow 20µs for

the output to stabilize.

Serial-Interface Configurations

The MAX5302’s 3-wire serial interface is compatible

with both MICROWIRE (Figure 2) and SPI/QSPI (Figure 3).

The serial-input word consists of 3 control bits followed

by 12+1 data bits (MSB first), as shown in Figure 4. The

3-bit control code determines the MAX5302’s response

outlined in Table 1.

The MAX5302’s digital inputs are double buffered.

Depending on the command issued through the serial

interface, the input register can be loaded without

affecting the DAC register, the DAC register can be

loaded directly, or the DAC register can be updated

from the input register (Table 1).

Serial-Interface Description

The MAX5302 requires 16 bits of serial data. Table 1 lists

the serial-interface programming commands. For certain

commands, the 12+1 data bits are “don’t cares.” Data is

sent MSB first and can be sent in two 8-bit packets or

one 16-bit word (CS must remain low until 16 bits are

transferred). The serial data is composed of 3 control