Datasheet

AD5535B Data Sheet
Rev. A | Page 14 of 16
APPLICATIONS INFORMATION
MEMS MIRROR CONTROL APPLICATION
The AD5535B is targeted to all optical switching control systems
based on MEMS technology. The AD5535B 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 4 V. Each amplifier can output 550 µA and directly
drives the control actuators, which determine the position of
MEMS mirrors in optical switch applications.
The AD5535B is generally used in a closed-loop feedback system,
as shown in Figure 20, 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
4-to-1 multiplexer 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 14-bit monotonic
behavior and a 0 V to 200 V output range, coupled with its fast
serial interface, the AD5535B is ideally suited for controlling a
cluster of MEMS-based mirrors.
Figure 20. AD5535B in a MEMS-Based Optical Switch
IPC-221-COMPLIANT BOARD LAYOUT
The diagram in Figure 21 is a typical 2-layer printed circuit board
(PCB) layout for the AD5535B that complies with the specifications
outlined in IPC-221. Do not connect to the four corner balls
labeled as original no connects. Connect balls labeled as
additional no connects to AGND.
The routing shown in Figure 21 shows the feasibility of
connecting to the high voltage balls while complying with
the spacing requirements of IPC-221. Figure 21 also shows
the physical distances that are available.
Figure 21. Layout Guidelines to Comply with IPC-221
ADSP-21065L
AD5535B
OUTPUT RANGE
0V TO 200V
V
OUT
0
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
V
PP
V
+
REF_IN
V
OUT
31
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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
250µm RAD
SPACE = 405µm
100µm
250µm RAD
SPACE = 405µm
250µm RAD
SPACE = 433µm
100µm
250µm RAD
SPACE = 433µm
SPACE = 433µm
100µm
DETAIL A
A1 BALL PAD CORNER
1
1
1
ORIGINAL
NO CONNECTS
ADDITIONAL
NO CONNECTS
1
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