AD5750

Preliminary Technical Data

Rev. P

rC | Page 18 of 25

SOFTWARE CONTROL:

Software control is enabled by connecting the HW SELECT pin to ground. In software mode, the AD5750 is controlled over a versatile 3-

wire serial interface that operates at clock rates up to 30 MHz. It is compatible with SPI®, QSPI™, MICROWIRE™, and DSP standards The

input shift register is 16 bits wide. Data is loaded into the device MSB first as a 16-bit word under the control of a serial clock input,

SCLK. Data is clocked in on the falling edge of SCLK. The input register consists of 16 control bits as shown in Table 5. The timing

diagram for this operation is shown in Figure 2. The first 3 bits of the Input Register are used to set the hardware address of the AD5750

device on the PCB board. Up to 8 devices can be addressed per board.

Bits D11, D1, D0 must always be set to 0 during any write sequence.

Table 3. Input Shift Register Format

MSB

LSB

D15

D14

D13

D12

D11

D10

D9

D8

D7

D6

D5

D4

D3

D2

D1

D0

A2

A1

A0

R/

W

0

R3

R2

R1

R0

CLRSEL

OUTEN

CLEAR

RSEL

RESET

0

0

Table 6. Input Shift Register Decoded

Register

A2, A1, A0

Used in association with External Pins AD2, AD1, AD0 to determine which part is

being addressed by the system controller.

A2

A1

A0

Function

0

0

0

Addresses Part with pins AD2=0, AD1=0, AD0=0

0

0

1

Addresses Part with pins AD2=0, AD1=0, AD0=1

0

1

0

Addresses Part with pins AD2=0, AD1=1, AD0=0

0

1

1

Addresses Part with pins AD2=0, AD1=1, AD0=1

1

0

0

Addresses Part with pins AD2=1, AD1=0, AD0=0

1

0

1

Addresses Part with pins AD2=1, AD1=0, AD0=1

1

1

0

Addresses Part with pins AD2=1, AD1=1, AD0=0

1

1

1

Addresses Part with pins AD2=1, AD1=1, AD0=1

R/W

Indicates a read from or a write to the addressed register.

CLEAR

Software Clear Bit – Active High.

CLRSEL

Sets Clear Mode to zero scale or midscale. See Text.

CLRSEL

0

Clear to Zero Volts

1

Clear to Mid Scale in Unipolar Mode, Clear to Zero Scale in Bipolar Mode.

OUTEN

Output Enable Bit. This bit must be set to 1 to enable the outputs.

RSEL

Select Internal/External Current Sense Resistor.

RSEL

1

Select Internal Current Sense Resistor /*used with Range bits to select Range */

0

Select External Current Sense Resistor /*used with Range bits to select Range */

R3,R2,R1,R0

Selects output Configuration in conjunction with RSEL.

RSEL

R3

R2

R1

R0

Output Configuration

0

0

0

0

0

4-20MA

External Current Sense Resistor 15k ohm.

0

0

0

0

1

0-20MA

External Current Sense Resistor 15k ohm.

0

0

0

1

0

0-24MA

External Current Sense Resistor 15k ohm.

0

0

0

1

1

+/-20MA

External Current Sense Resistor 15k ohm.

0

0

1

0

0

+/-24MA

External Current Sense Resistor 15k ohm.

0

0

1

0

1

0-5V

0

0

1

1

0

0-10V

0

0

1

1

1

+/-5V

0

1

0

0

0

+/-10V

0

1

0

0

1

0-6.0V (20% over range)

0

1

0

1

0

0-12.0V (20% over range)

0

1

0

1

1

+/-6.0V (20% over range)