PRELIMINARY TECHNICAL DATA

REV. PrF 09/2003

–32–

AD5380

Thermal Monitor Function

The AD5380 contains a temperature shutdown function to protect the chip in case multiple outputs are shorted. The

short circuit current of each output amplifier is typically 40mA. Operating the AD5380 at 5V leads to a power dissipa-

tion of 200mW / shorted amplifier. With 5 channels shorted this leads to an extra watt of power dissipation. For the

The thermal monitor is enabled by the user via CR8 in the control register. The output amplifiers on the AD5380 are

thermal monitor function via the control register.

INPUT

REGISTER

DATA

REGISTER

A

DAC

REGISTER

14-BIT DAC

LDAC

CONTROL INPUT

DATA

REGISTER

B

VOUT

INPUT

DATA

A/B

Figure 20. Toggle Mode Function

AD5380 in a MEMS Based Optical Optical Switch

MEMS based optical switches have a requirement for high resolution DACs in their feedforward control path that offer

high channel density with 14-bit monotonic behaviour. The AD5380, 40-channel, 14-bit DAC in a 100lead LQFP pack-

age satisifies these requirements. In the circuit shown in Figure 19, the 0V–5V outputs of the AD5380 are amplified to

achieve an output range of 0V–200V used to control actuators that determine the position of MEMS mirrors in an optical

switch. The exact position of each mirror is measured using sensors. The sensor outputs are multiplexed into a high reso-

lution ADC in determining the mirror position. The control loop is closed and driven by an ADSP-21065L, a 32-bit

data from the ADC via the serial interface.

14-BitDA C

VO 1

Actuators

For

MEMS

Mirror

A rray

Sensor

+

Multiplexer

8-C hannelAD C

(A D 7856)

A D 5380

14-BitDA C

VO 40

.

.

.

.

.

.

.

.

A D SP21065L

REFIN

OutputR ange

0-200V

OR

Single C hannel

AD C (A D 7671)

+5V

AVDD

REFO UT

.

.

.

.

G=50

G=50

0.01uF

Figure 19 . AD5380 in a MEMS based Optical Switch