PRELIMINARY TECHNICAL DATA

REV. PrF 09/2003

AD5380

–23–

Power-On-Reset

The AD5380 contains a power-on-reset generator and state-machine. The power-on-reset resets all registers to a

predefined state and the analog outputs are configured with a 100k impedance to ground. The

BUSY pin goes low

during the power-on-reset sequencing preventing data writes to the device.

Power-Down

The AD5380 contains a global power-down feature that puts all channels into a low power mode reducing both analog

and digital power consumption to 5uA. In power down mode the output amplifier can be configured as a high impedance

output or provide a 100k load to ground. The contents of all internal registers are retained in power-down mode. When

exiting power down the settling time of the amplifier will elapse before the outputs settle to their correct value.

AD5380 INTERFACES

The AD5380 contains both a parallel and serial interfaces. Furthermore, the serial interface can be programmed to be

either DSP,SPI,MICROWIRE or I2C compatible. The SER/

PAR pin selects parallel and serial interface modes. In

serial mode SPI/

I2C pin is used to select DSP,SPI,MICROWIRE or I2C interface mode.

The devices use an internal FIFO memory to allow high speed successive writes in parallel interface mode. The user can

continue writing new data to the device while write instructions are being executed. The

BUSY signal indicates the

current status of the device, going low while instructions in the FIFO are being executed. Up to 128 successive

intructions can be written to the FIFO at maximum speed in parallel mode. When the FIFO is full any further writes to

the device are ignored.

To minimize both the power consumption of the device and on-chip digital noise, the active interface only powers up

fully when the device is being written to, i.e. on the falling edge of

WR or on the falling edge of SYNC.

DSP, SPI, MICROWIRE COMPATIBLE SERIAL INTERFACES

The serial interface can be operated with a minimum of 3-wires in stand alone mode or 4-wires in daisy chain mode.

Daisy chaining allows many devices to be cascaded together to increase system channel count.The SER/

PAR pin must be

tied high and the SPI/

I2C (pin 97) should be tied high to enable the DSP,SPI,MICROWIRE compatible serial

interface. In serial interface mode the user does not need to drive the parallel input data pins. The serial interface is

control pins are as follows:

SYNC

SYNC

SYNC

SYNC

SYNC, DIN, SCLK - Standard 3-wire interface pins.

DCEN - Selects Stand-Alone Mode or Daisy-Chain Mode.

SDO - Data Out pin for Daisy-Chain Mode.

Figures 3 and 4 show the timing diagram for a serial write to the AD5380 in both Stand-Alone and Daisy-Chain Mode.

The 24-bit data word format for the serial interface in shown in Figure 9 below.

MSB

LSB

A

A

A

A

A/B R/W

W

W

W

W

A5 A4 A3 A 2 A 1 A 0 REG1 REG0 DB13 DB12 DB11 DB10 D B 9 D B 8 D B 7 D B 6 D B 5 D B 4 D B 3 D B 2 D B 1 D B 0

Figure 9 . AD5380, 40-Channel, 14-Bit DAC Serial Input Register Configuration

A/B When Toggle mode is enabled this selects whether the data write is to the A or B register, with Toggle disabled this

bit should be set to zero to select the A data register.

R/

W is the Read or Write control bit.

A5-A0 are used to Address the input channels .

REG1 & REG0 Select the register to which data is written as outlined in Table 1.

DB13-DB0 Contain the input data word.

X is a dont care condition.

Stand-Alone Mode

By connecting DCEN (Daisy-Chain Enable) pin low, Stand-Alone Mode is enabled. The serial interface works with

both a continuous and a noncontinuous serial clock. The first falling edge of

SYNC starts the write cycle and resets a

counter that counts the number of serial clocks to ensure that the correct number of bits are shifted into the serial shift

register. Any further edges on

SYNC except for a falling edge are ignored until 24 bits are clocked in. Once 24 bits

have been shifted in, the SCLK is ignored. In order for another serial transfer to take place the counter must be reset by

the falling edge of

SYNC.

Daisy-Chain Mode

For systems which contain several devices the SDO pin may be used to daisy-chain several devices together. This daisy-

chain mode can be useful in system diagnostics and reducing the number of serial interface lines.

By connecting DCEN (Daisy-Chain Enable) pin high, the Daisy-Chain Mode is enabled. The first falling edge of

SYNC

starts the write cycle. The SCLK is continuously applied to the input shift register when

SYNC is low. If more than 24