Preliminary Technical Data

AD5535

Rev. PrE | Page 13 of 16

APPLICATIONS INFORMATION

MEMS MIRROR CONTROL APPLICATION

The AD5535 is targeted to all optical switching control systems

based on micro-electromechanical systems (MEMS)

technology. The AD5535 is a 32-channel, 14-bit DAC with

integrated high voltage amplifiers. The output amplifiers are

capable of generating an output range of 0 V to 200 V when

using a 4 V reference. The full-scale output voltage is

programmable from 50 V to 200 V using reference voltages

from 1 V to 4V. Each amplifier can output 700 µA and directly

drives the control actuators, which determine the position of

MEMS mirrors in optical switch applications.

The AD5535 is generally used in a closed-loop feedback system,

as shown in Figure 15, with a high resolution ADC and DSP.

The exact position of each mirror is measured using capacitive

sensors. The sensor outputs are multiplexed using an ADG739

to an 8-channel 14-bit ADC (AD7856). An alternative solution

is to multiplex using a 32-to-1 multiplexer (ADG732) into a

single-channel ADC (AD7671). The control loop is driven by an

ADSP-21065L, a 32-bit SHARC DSP with an SPI-compatible

SPORT interface. With its 14-bit monotonic behavior and 0 V to

200 V output range coupled with its fast serial interface, the

AD5535 is ideally suited for controlling a cluster of MEMS-

based mirrors.

ADSP21065L

AD5535

OUTPUT RANGE

0V TO 200V

14-BIT DAC

14-BIT DAC

REF198

(4.096V)

ACTUATORS

FOR

MEMS

MIRROR

ARRAY

SENSOR

+

4 TO 1 MUX

(ADG739)

OR

32 TO 1 MUX

(ADG732)

8-CHANNEL

ADC (AD7856)

OR

SINGLE

CHANNEL

ADC (AD7671)

+210V

+5V

–5V

REF_IN

Figure 15. AD5535 in a MEMS-Based Optical Switch

AD5535 BOARD LAYOUT TO ENSURE

COMPLIANCE WITH IPC-221 SPECIFICATION

The diagram in Figure 16 is a typical 2-layer printed circuit

board layout for the AD5535 complying with the specifications

outlined in IPC221. The four corner balls labeled as original no-

connects must remain, because no connections and no signals

should be connected to these balls. Balls labeled as additional

no-connects should be connected to AGND.

The routing shown in Figure 16 shows the feasibility of

connecting to the high voltage balls while complying with the

spacing requirements of IPC-221. Figure 17 shows the physical

distances that are available.

A

B

C

D

E

F

G

J

H

K

L

M

N

P

10

8

7

6

3

2

1

9

5

4

11 12 13 14

1.414mm

2mm

250

µm RAD

SPACE = 433

µm

100

µm

250

µm RAD

SPACE = 433

µm

SPACE = 433

µm

100

µm

DETAIL A

A1 BALL PAD CORNER

1

1

1

ORIGINAL

NO-CONNECTS

ADDITIONAL

NO-CONNECTS

1

Figure 16. Layout Guidelines to Comply with IPC-221