AD5382
DATA
REGISTER
A
DAC
REGISTER
V
14-BIT DAC
OUT
DATA
REGISTER
B
INPUT
DATA REGISTER
INPUT
LDAC
CONTROL INPUT
A/B
Figure 42. Toggle Mode Function
+5V
OUTPUT RANGE
0–200V
0.01µF
REF
REF
AVDD
OUT
IN
VO1
8-CHANNEL ADC
14-BIT DAC
G = 50 ACTUATORS
FOR MEMS
MIRROR
(AD7856)
OR
SINGLE CHANNEL
ADC (AD7671)
SENSOR
AND
MULTIPLEXER
ARRAY
14-BIT DAC
G = 50
VO31
AD5382
ADSP-21065L
Figure 43. AD5382 in a MEMS Based Optical Switch
THERMAL MONITOR FUNCTION
AD5382 IN A MEMS BASED OPTICAL SWITCH
The AD5382 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 40 mA.
Operating the AD5382 at 5 V leads to a power dissipation of
200 mW per shorted amplifier. With five channels shorted, this
leads to an extra watt of power dissipation. For the 100-lead
LQFP, the θJA is typically 44°C/W.
In their feed-forward control paths, MEMS based optical
switches require high resolution DACs that offer high channel
density with 14-bit monotonic behavior. The 32-channel, 14-bit
AD5382 DAC satisfies these requirements. In the circuit in
Figure 43, the 0 V to 5 V outputs of the AD5382 are amplified to
achieve an output range of 0 V to 200 V, which is 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
resolution ADC in determining the mirror position. The control
loop is closed and driven by an ADSP-21065L, a 32-bit SHARC®
DSP with an SPI compatible SPORT interface. The ADSP-
21065L writes data to the DAC, controls the multiplexer, and
reads data from the ADC via the serial interface.
The thermal monitor is enabled by the user via CR8 in the
control register. The output amplifiers on the AD5382 are
automatically powered down if the die temperature exceeds
approximately 130°C. After a thermal shutdown has occurred,
the user can re-enable the part by executing a soft power-up if
the temperature has dropped below 130°C or by turning off the
thermal monitor function via the control register.
Rev. 0 | Page 35 of 40
ADI [ ADI ]
