Rainbow Electronics MAX534 User Manual

Page 10

MAX534

+5V, Low-Power, 8-Bit Quad DAC
with Rail-to-Rail Output Buffers

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For this command, the data bits are “Don't Cares.” As
an example, three MAX534s are daisy chained (A, B,
and C), and devices A and C need to be updated. The
36-bit-wide command would consist of one 12-bit word
for device C, followed by an NOP instruction for device
B and a third 12-bit word with data for device A. At

CS’s

rising edge, device B will not change state.

Set DOUT Phase—SCLK Rising (Mode 1)

The mode 1 command resets the serial-output DOUT to
transition at SCLK’s rising edge. Once this command is
issued, DOUT’s phase is latched and will not change
except on power-up or if the specific command to set
the phase to falling edge is issued.

This command also loads all DAC registers with the con-
tents of their respective input registers, and is identical to
the “

LDAC” command.

Set DOUT Phase—SCLK Falling (Mode 0, Default)

This command resets DOUT to transition at SCLK’s
falling edge. The same command also updates all DAC
registers with the contents of their respective input reg-
isters, identical to the “

LDAC” command.

LDAC Operation (Hardware)

LDAC is typically used in 4-wire interfaces (Figure 7).
This command is level sensitive, and allows asynchro-
nous hardware control of the DAC outputs. With

LDAC

low the DAC registers are transparent, and any time an
input register is updated, the DAC output immediately
follows.

Clear DACs with

CLR

Strobing the

CLR pin low causes an asynchronous

clear of input and DAC registers and sets all DAC out-
puts to zero. Similar to the

LDAC pin, CLR can be

invoked at any time, typically when the device is not
selected (

CS = H). When the DAC data is all zeros, this

function is equivalent to the “Update all DACs from Shift
Registers” command.

Serial Data Output

DOUT is the internal shift register’s output. DOUT can
be programmed to clock out data on SCLK’s falling
edge (mode 0) or rising edge (mode 1). In mode 0, out-
put data lags input data by 12.5 clock cycles, maintain-
ing compatibility with Microwire and SPI. In mode 1,
output data lags input data by 12 clock cycles. On
power-up, DOUT defaults to mode 0 timing. DOUT
never three-states; it always actively drives either high
or low and remains unchanged when

CS is high.

1 0

1 1

(

LDAC = x)

1 0

(

LDAC = x)

SCLK

DIN

I/0

MICROWIRE

PORT

MAX534

Figure 4. Connections for Microwire

DIN

SCLK

MOSI

SCK

I/0

SPI/QSPI

PORT

MAX534

Figure 5. Connections for SPI/QSPI