+2.5V to +5.5V, Low-Power, Single/Dual,

8-Bit Voltage-Output DACs in µMAX Package

12

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Table 4. MAX550A Serial-Interface Programming Commands

COMMANDS LOADING DAC REGISTER

COMMANDS LOADING INPUT REGISTER ONLY

UNASSIGNED COMMANDS

Loaded Last

Loaded First

LDAC

CONTROL BYTE

COMMAND

(Commands executed on CS’s rising edge)

X

Update DAC register with current contents of

input register. Input register unchanged.

0

0

X

1

1

X

0

X

XXXXXXXX

X

Load DAC input register and update DAC register.

0

8-Bit DAC Data

1

X

1

1

X

0

X

XXXXXXXX

X

Load DAC input register and update DAC register.

X

8-Bit DAC Data

1

X

0

1

X

0

X

UB1

Pin 6

D7........D0

A0

A1

C0

C1

UB3

C2

UB2

X

Update DAC register with current contents of

input register. Input register unchanged.

X

0

X

0

1

X

0

X

X

Load DAC input register. DAC register unchanged.

X

8-Bit DAC Data

1

X

X

0

X

0

X

X

Unassigned operation

X

XXXXXXXX

0

X

X

X

X

X

1

X

Unassigned command

X

XXXXXXXX

0

X

X

0

X

0

X

DATA BYTE

COMMANDS UTILIZING THE ASYNCHRONOUS LOAD FUNCTION

X

After CS’s rising edge and on LDAC’s falling

edge, update DAC register with current contents

of input register. Input register unchanged.

1

XXXXXXXX

0

X

1

1

X

0

X

X

Load DAC input register. After CS’s rising edge

and on LDAC’s falling edge, update DAC register.

1

8-Bit DAC Data

1

X

1

1

X

0

X

COMMAND POWERING DOWN AND LOADING INPUT REGISTER ONLY

X

Load DAC input register and power down DAC.

X

8-Bit DAC Data

1

X

X

0

X

1

X

COMMANDS POWERING DOWN AND UPDATING DAC REGISTER

X

Load DAC input register, power down DAC, and

update DAC register.

X

8-Bit DAC Data

1

X

0

1

X

1

X

X

Load DAC input register, power down DAC, and

update DAC register.

0

8-Bit DAC Data

1

X

1

1

X

1

X

COMMAND POWERING DOWN AND UTILIZING THE ASYNCHRONOUS LOAD FUNCTION

X

Load DAC input register and power down DAC.

While powered down, on LDAC’s falling edge,

update DAC register.

1

8-Bit DAC Data

1

X

1

1

X

1

X

Table 5. Example Input Word

X = Don’t care

X = Don’t care

UB2

X

C2

0

UB3

X

C0

0

CONTROL BYTE

A0

1

Loaded First

A1

0

C1

1

D6

0

D4

0

D5

0

D2

0

DATA BYTE

D0

0

Loaded Last

D1

0

D3

0

D7

1

UB1

X