AD5533

–12–

REV. 0

Reset Function

The reset function on the AD5533 can be used to reset all nodes

on this device to their power-on-reset condition. This is imple-

mented by applying a low-going pulse of between 50 ns and 150 ns

to the

TRACK/RESET pin on the device. If the applied pulse

is less than 50 ns it is assumed to be a glitch and no operation

takes place. If the applied pulse is wider than 150 ns this pin adopts

output buffer and an acquisition on the channel will not occur

until a rising edge of

TRACK.

TRACK Function

Normally in SHA mode of operation,

TRACK is held high and

the channel begins to acquire when it is addressed. However, if

TRACK is low when the channel is addressed, V

to the output buffer and an acquisition on the channel will not

occur until a rising edge of

TRACK. At this stage the BUSY pin

will go low until the acquisition is complete, at which point the

DAC assumes control of the voltage to the output buffer and

This is useful in an application where the user wants to ramp up

not need to be acquired continuously while it is ramping up.

TRACK can be kept low and only when V

desired voltage is

TRACK brought high. At this stage, the

In the example shown, a desired voltage is required on the out-

put of the pin driver. This voltage is represented by one input to

a comparator. The microcontroller/microprocessor ramps up

ally acquired. When the desired voltage is reached on the output of

the pin driver, the comparator output switches. The

µC/µP then

knows what code is required to be input in order to obtain the

desired voltage at the DUT. The

TRACK input is now brought

has been acquired. When

BUSY goes high, the output buffer

MODES OF OPERATION

The AD5533 can be used in three different modes. These modes

are set by two mode bits, the first two bits in the serial word.

The 01 option (DAC Mode) is not available for the AD5533.

To avail of this mode refer to the AD5532 data sheet. If you

attempt to set up DAC mode, the AD5533 will enter a test-mode

and a 24-clock write will be necessary to clear this.

Table II. Modes of Operation

Mode Bit 1

Mode Bit 2

Operating Mode

0

0

SHA Mode

0

1

DAC Mode (Not Available)

1

0

Acquire and Readback

1

1

Readback

1. SHA Mode

In this standard mode a channel is addressed and that channel

or all channels). MSB is written first.

2. Acquire and Readback Mode

in a particular DAC register. The relevant channel is addressed

µs (max).

Following the acquisition, after the next falling edge of

SYNC

the data in the relevant DAC register is clocked out onto the

ignored. The full acquisition time must elapse before the DAC

register data can be clocked out.

3. Readback Mode

Again, this is a readback mode but no acquisition is performed.

The relevant channel is addressed (10-bit write, MSB first) and

on the next falling edge of

SYNC, the data in the relevant DAC

The user must allow 400 ns (min) between the last SCLK fall-

ing edge in the 10-bit write and the falling edge of

SYNC in

the 14-bit readback. The serial write and read words can be seen in

Figure 13.

This feature allows the user to read back the DAC register code

of any of the channels. Readback is useful if the system has been

calibrated and the user wants to know what code in the DAC

INTERFACES

SERIAL INTERFACE

The SER/

PAR pin is tied high to enable the serial interface and

to disable the parallel interface. The serial interface is controlled

by four pins as follows:

SYNC, D

Standard 3-wire interface pins. The

SYNC pin is shared

with the

CS function of the parallel interface.

Data Out pin for reading back the contents of the DAC regis-

ters. The data is clocked out on the rising edge of SCLK and

is valid on the falling edge of SCLK.

Cal Bit

The acquisition time is then 45

µs (typ) and accuracy may be

reduced.

Offset_Sel Bit

If this bit is set high, the offset channel is selected and Bits

A4–A0 are ignored.

Test Bit

This must be set low for correct operation of the part.

A4–A0

Used to address any one of the 32 channels (A4 = MSB of

address, A0 = LSB).