Low-Power, Quad, 12-Bit

Voltage-Output DACs with Serial Interface

8

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SCLK

DIN

DOUT*

CS

SK

SO

SI*

I/O

MAX5500

MAX5501

MICROWIRE

PORT

*THE DOUT-SI CONNECTION IS NOT REQUIRED FOR WRITING TO THE

MAX5500/MAX5501, BUT CAN BE USED FOR READBACK PURPOSES.

Figure 2. Connections for MICROWIRE

Serial-Interface Configurations

The MAX5500/MAX5501s’ 3-wire serial interface is

compatible with both MICROWIRE (Figure 2) and

SPI/QSPI (Figure 3). The serial input word consists of

two address bits and two control bits followed by 12

data bits (MSB first), as shown in Figure 4. The 4-bit

address/control code determines the MAX5500/

MAX5501s’ response outlined in Table 1. The connec-

tion between DOUT and the serial-interface port is not

necessary, but may be used for data echo. Data held in

the shift register can be shifted out of DOUT and

returned to the µP for data verification.

The digital inputs of the MAX5500/MAX5501 are double

buffered. Depending on the command issued through the

serial interface, the input register(s) can be loaded without

affecting the DAC register(s), the DAC register(s) can be

loaded directly, or all four DAC registers can be updated

simultaneously from the input registers (Table 1).

Serial-Interface Description

The MAX5500/MAX5501 require 16 bits of serial data.

Table 1 lists the serial-interface programming com-

mands. For certain commands, the 12 data bits are

don’t-care bits. 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 com-

posed of two DAC address bits (A1, A0) and two control

bits (C1, C0), followed by the 12 data bits D11–D0

(Figure 4). The 4-bit address/control code determines:

• The register(s) to be updated

• The clock edge on which data is to be clocked out

through the serial-data output (DOUT)

• The state of the user-programmable logic output

(UPO)

• If the device is to enter shutdown mode (assuming

PDL is high)

• How the device is configured when exiting out of

shutdown mode

DOUT*

DIN

SCLK

CS

MISO*

MOSI

SCK

I/O

SPI/QSPI

PORT

SS

+5V

CPOL = 0, CPHA = 0

*THE DOUT-MISO CONNECTION IS NOT REQUIRED FOR WRITING TO THE

MAX5500/MAX5501, BUT CAN BE USED FOR READBACK PURPOSES.

MAX5500

MAX5501

Figure 3. Connections for SPI/QSPI

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

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

16 BITS OF SERIAL DATA

ADDRESS

BITS

CONTROL

BITS

DATA BITS

4 ADDRESS/

CONTROL BITS

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

A1

A0

C1

C0

12 DATA BITS

Figure 4. Serial-Data Format