AVAGO HSDL-3211 Irdaâ® data compliant low power 1.15 mbit/s infrared transceiver Datasheet

HSDL-3211
IrDA® Data Compliant Low Power 1.15 Mbit/s
Infrared Transceiver
Data Sheet
Description
The HSDL-3211 is a new generation low profile high
speed infrared transceiver module that provides
interface between logic and IR signals for throughair, serial, half-duplex IR data-link. The module is fully
compliant to IrDA Physical Layer specification
version 1.4 low power from 9.6kbit/s to 1.152 Mbit/s
(MIR) and is IEC825-Class 1 Eye Safe.
Features
• Fully compliant to IrDA 1.4 physical layer low power specification from 9.6 kbit/s to 1.152 Mbit/s (MIR)
• Miniature package
– Height: 2.5 mm
– Width: 8.0 mm
– Depth: 3.0 mm
• No data rate switching required
• Typical link distance > 50 cm
The HSDL-3211 can be shutdown completely to
achieve very low power consumption. In the shutdown
mode, the PIN diode will be inactive and thus
producing very little photocurrent even under very
bright ambient light. It is also designed to interface
to input/output logic circuits as low as 1.8V. These
features are ideal for mobile devices that require low
power consumption.
• Guaranteed temperature performance, -25o to 85oC
– Critical parameters are guaranteed over temperature and supply
voltage
• Low power consumption
– Low shutdown current (1 nA typical)
– Complete shutdown of TXD, RXD, and PIN diode
• Withstands >100 mVp-p power supply ripple typically
• Excellent EMI performance
• Vcc supply 2.4 to 3.6 Volts
VCC
CX2
• Interfacing with I/O logic circuits as low as 1.8 V
CX4
• Lead-free package
CX1
GND (8)
VCC (6)
IOVCC (7)
• LED stuck-high protection
• Designed to accommodate light loss with cosmetic windows
SD (5)
RECEIVER
• IEC 825-class 1 eye safe
RXD (4)
Applications
SHIELD
HSDL-3211
TXD (3)
LED C (2)
R1
TRANSMITTER
LED A (1)
Vled
CX3
Figure 1. Functional block diagram of HSDL-3211.
8
7
6
5
4
3
2
Figure 2. Rear view diagram with pinout.
1
• Mobile telecom
– Mobile phones
– Smart phones
– Pagers
• Data communication
– Pocket PC handheld products
– Personal digital assistants
– Portable printers
• Digital imaging
– Digital cameras
– Photo-imaging printers
• Electronic wallet
• Small industrial & medical instrumentation
– General data collection devices
– Patient & pharmaceutical data collection devices
Application Support Information
The Application Engineering
Group is available to assist you
with the application design
associated with the HSDL-3211
infrared transceiver module. You
can contact them through your
local sales representatives for
additional details.
Order Information
Part Number
Packaging Type
Package
Quantity
HSDL-3211-021
Tape and Reel
Front View
2500
I/O Pins Configuration Table
Pin
Symbol
Description
I/O Type
Notes
1
LED A
LED Anode
I
1
2
LED C
LED Cathode
3
TXD
Transmit Data. Active High.
I
3
4
RXD
Receive Data. Active Low.
O
4
5
SD
Shutdown. Active High.
I
5
6
Vcc
Supply Voltage
6
7
IOVcc
Input/Output ASIC Vcc
7
8
GND
Ground
8
-
Shield
EMI Shield
9
2
Recommended Application Circuit Components
Component
Recommended Value
Notes
R1
3.9Ω ± 5%, 0.25 watt for 2.4 ≤ Vled < 2.7V
5.6Ω ± 5%, 0.25 watt for 2.7 ≤ Vled < 3.3V
10Ω ± 5%, 0.25 watt for 3.3 ≤ Vled < 4.2V
15Ω ± 5%, 0.25 watt for 4.2 ≤ Vled < 5.5V
CX1, CX4
0.47 µF ± 20%, X7R Ceramic
10
CX2, CX3
6.8 µF ± 20%, Tantalum
11
Notes:
1. Tied through external series resistor, R1, to regulated Vled from 2.4 to 5.5V. Please refer to table
below for recommended series resistor value.
2. Internally connected to LED driver. Leave this pin unconnected.
3. This pin is used to transmit serial data when SD pin is low. If this pin is held high for longer than
50 ms, the LED is turned off. Do NOT float this pin.
4. This pin is capable of driving a standard CMOS or TTL load. No external pull-up or pull-down
resistor is required. The pin is in tri-state when the transceiver is in shutdown mode. The receiver
output echoes transmitted signal.
5. The transceiver is in shutdown mode if this pin is high. Do NOT float this pin.
6. Regulated, 2.4 to 3.6 Volts.
7. Connect to ASIC logic controller Vcc voltage or supply voltage. The voltage at this pin must be
equal to or less than supply voltage.
8. Connect to system ground.
9. Connect to system ground via a low inductance trace. For best performance, do not connect
directly to the transceiver pin GND
10. CX1 must be placed within 0.7 cm of the HSDL-3211 to obtain optimum noise immunity.
11. In environments with noisy power supplies, including CX2, as shown in Figure 1, can enhance
supply ripple rejection performance.
2
Marking Information
The unit is marked with ‘yyww’
on the shield:
yy = year
ww = work week
CAUTIONS: The BiCMOS inherent to the design of this component increases the component’s
susceptibility to damage from electrostatic discharge (ESD). It is advised that normal static precautions
be taken in handling and assembly of this component to prevent damage and/or degradation which may
be induced by ESD.
Absolute Maximum Ratings
For implementations where case to ambient thermal resistance is ≤ 50°C/W.
Parameter
Symbol
Min.
Max.
Units
Storage Temperature
TS
-40
+100
°C
Operating Temperature
TA
-25
+85
°C
LED Anode Voltage
VLEDA
0
6.5
V
Supply Voltage
VCC
0
6.5
V
Input Voltage: TXD, SD/Mode
VI
0
6.5
V
Output Voltage: RXD
VO
0
6.5
V
DC LED Transmit Current
ILED (DC)
150
mA
Average Transmit Current
ILED (PK)
600
mA
Conditions
≤ 90 µs pulse width
≤ 25% duty cycle
Recommended Operating Conditions
Parameter
Symbol
Min.
Operating Temperature
TA
Supply Voltage
Input/Output Voltage
Logic Input Voltage
for TXD, SD/Mode
Receiver Input
Irradiance
LED (Logic High) Current
Pulse Amplitude
Receiver Data Rate
Max.
Units
-25
+85
°C
VCC
2.4
3.6
V
IOVcc
1.8
Vcc
V
Logic High
VIH
IOVcc – 0.5
IOVcc
V
Logic Low
VIL
0
0.4
V
Logic High
EIH, min
EIH, max
0.0081
500
mW/cm2
mW/cm2
Logic Low
EIL
0.3
µW/cm2
ILEDA
Typ.
150
0.0096
Conditions
9.6kbit/s ≤ in-band signals
≤1.152 Mbit/s [12]
For in-band signals [12]
mA
1.152
Mbit/s
Note :
12. An in-band optical signal is a pulse/sequence where the peak wavelength, λp, is defined as 850 ≤ λp ≤ 900 nm, and the pulse characteristics are
compliant with the IrDA Serial Infrared Physical Layer Link Specification v1.4.
3
Electrical & Optical Specifications
Specifications (Min. & Max. values) hold over the recommended operating conditions unless otherwise noted.
Unspecified test conditions may be anywhere in their operating range. All typical values (Typ.) are at 25°C, Vcc set to 3.0V
and IOVcc set to 1.8V unless otherwise noted.
Parameter
Symbol
Min.
Viewing Angle
2θ
30
Peak Sensitivity Wavelength
λp
Typ.
Max.
Units
Conditions
Receiver
°
880
nm
Logic High
VOH
IOVCC – 0.2
IOVCC
V
IOH = -200 µA, EI ≤ 0.3 µW/cm2
Logic Low
VOL
0
0.4
V
IOL = 200 µA, EI ≥ 8.1 µW/cm2
RXD Pulse Width (SIR)[13]
tPW (SIR)
1
4.0
µs
θ ≤ 15°, CL = 9 pF
RXD Pulse Width (MIR)[14]
tPW(MIR)
100
500
ns
θ ≤ 15°, CL = 9 pF
RXD Rise and Fall Times
tr, tf
25
ns
CL = 9 pF
Receiver Latency Time[15]
tL
25
50
µs
Receiver Wake Up Time[16]
tW
50
100
µs
RXD Output Voltage
Transmitter
IEH
10
Viewing Angle
2θ
30
Peak Wavelength
λp
875
nm
Spectral Line Half Width
∆λ
35
nm
High
IH
0.02
10
µA
VTXD ≥ VIH
Low
IL
-0.02
10
µA
0 ≤ VTXD ≤ VIL
mA
VTXD ≥ VIH, R1=5.6ohm, Vled=3.0V
TXD Input Current
-10
45
mW/sr
ILEDA= 150 mA, θ ≤ 15°, VTXD ≥ VIH,
VSD ≤ VIL, Ta=25°C
Radiant Intensity
60
150
°
LED ON Current
ILEDA
TXD Pulse Width (SIR)
tPW (SIR)
1.5
1.6
1.8
µs
tPW (TXD) = 1.6 µs at 115.2 kbit/s
TXD Pulse Width (MIR)
tPW(MIR)
148
217
260
ns
tPW (TXD) = 217 ns at 1.152 Mbit/s
Maximum Optical PW[17]
tPW(max.)
50
100
µs
TXD Rise and fall Time (Optical)
tr, tf
40
ns
tPW (TXD) = ns at 1.152 Mbit/s
LED Anode On-State Voltage
VON(LEDA)
1.6
2.0
V
ILEDA=150 mA, VTXD ≥VIH
Shutdown
ICC1
0.001
1
µA
VSD ≥ VIH, Ta= 25 °C
Idle
ICC2
0.4
1.0
mA
VSD ≤ VIL, VTXD ≤ VIL, EI=0
Transceiver
Supply Current
Notes:
13. For in-band signals from 9.6 kbit/s to 115.2 kbit/s, where 9 µW/cm2 ≤ EI ≤ 500 mW/cm2.
14. For in-band signals from 0.576 Mbit/s to 1.152 Mbit/s, where 22.5 µW/cm2 ≤ EI ≤ 500 mW/cm2.
15. Latency time is defined as the time from the last TxD light output pulse until the receiver has recovered full sensitivity.
16. Receiver wake up time is measured from Vcc power on or SD pin high to low transition to a valid RXD output.
17. The maximum optical PW is the maximum time the LED remains on when the TXD is constantly high. This is to prevent long turn on time of the LED
for eye safety protection.
4
tpw
tpw
VOH
LED ON
90%
90%
50%
50%
10%
VOL
10%
LED OFF
tf
tr
Figure 3. RxD output waveform.
tr
tf
Figure 4. LED optical waveform.
SD
TXD
RX
LIGHT
RXD
LED
tRW
tpw (MAX.)
Figure 5. TxD “Stuck On” protection waveform.
Figure 6. Receiver wakeup time waveform.
0.18
50
0.16
0.14
40
LOP (mW/Sr)
Iled (A)
0.12
0.10
0.08
0.06
30
20
0.04
10
0.02
0
1.4
1.5
1.6
1.7
1.8
VledA (V)
Figure 7. LED anode voltage vs. LED current.
5
0
0
0.05
0.1
0.15
0.2
lled (A)
Figure 8. LED current vs. radiant intensity.
HSDL-3211 Package Dimensions
2.0
0.8
0.4
6
HSDL-3211 Tape and Reel Dimensions
4.0 ± 0.1
Unit: mm
1.75 ± 0.1
1.5 ± 0.1
1.5 +0.10
POLARITY
Pin 8: GND
7.5 ± 0.1
16.0 ± 0.2
Pin 1: LEDA
0.4 ± 0.05
8.4 ± 0.1
Material of Carrier Tape: Conductive Polystyrene
Material of cover tape: PVC
Method of cover: Heat activated adhesive
3.4 ± 0.1
2.8 ± 0.1
8.0 ± 0.1
Progressive Direction
Empty
Parts Mounted
Leader
(400mm min)
(40mm min)
Empty
(40mm min)
Option # "B" "C" Quantity
021
330 80
2500
Unit: mm
Detail A
2.0 ± 0.5
B
C
13.0 ± 0.5
R1.0
LABEL
21 ± 0.8
Detail A
16.4
+2
0
2.0 ± 0.5
Note: The carrier tape is compliant to the packaging materials standards for ESD sensitive device, EIA-541
7
Moisture Proof Packaging
All HSDL-3211 options are
shipped in moisture proof
package. Once opened, moisture
absorption begins.
This part is compliant to JEDEC
Level 4.
Baking Conditions
If the parts are not stored in dry
conditions, they must be baked
before reflow to prevent damage
to the parts.
Package
UNITS IN A SEALED
MOISTURE-PROOF
PACKAGE
Temp.
Time
In reels
60°C
≥ 48 hours
In bulk
100°C
≥ 4 hours
125°C
≥ 2 hours
150°C
≥ 1 hour
Baking should only be done once.
PACKAGE IS
OPENED (UNSEALED)
Recommended Storage Conditions
ENVIRONMENT
LESS THAN 30°C,
AND LESS THAN
60% RH
YES
PACKAGE IS
OPENED LESS
THAN 72 HOURS
NO
PERFORM RECOMMENDED
BAKING CONDITIONS
Figure 9. Baking conditions chart.
8
10°C to 30°C
Relative Humidity
below 60% RH
Time from Unsealing to Soldering
After removal from the bag, the
parts should be soldered within
three days if stored at the recommended storage conditions. If
times longer than three days are
needed, the parts must be stored
in a dry box.
YES
NO BAKING
IS NECESSARY
Storage Temperature
NO
Recommended Reflow Profile
MAX. 260°C
T – TEMPERATURE – (°C)
255
R4
R3
230
220
200
180
R2
60 sec.
MAX.
ABOVE
220°C
160
R1
120
R5
80
25
0
50
100
150
200
250
300
t-TIME (SECONDS)
P1
HEAT
UP
P2
SOLDER PASTE DRY
P3
SOLDER
REFLOW
P4
COOL DOWN
Process Zone
Symbol
∆T
Maximum ∆T/∆time
Heat Up
P1, R1
25°C to 160°C
4°C/s
Solder Paste Dry
P2, R2
160°C to 200°C
0.5°C/s
P3, R3
200°C to 255°C (260°C at 10 seconds max)
4°C/s
P3, R4
255°C to 200°C
-6°C/s
P4, R5
200°C to 25°C
-6°C/s
Solder Reflow
Cool Down
The reflow profile is a straightline representation of a nominal
temperature profile for a convective reflow solder process. The
temperature profile is divided
into four process zones, each with
different ∆T/∆time temperature
change rates. The ∆T/∆time rates
are detailed in the above table.
The temperatures are measured
at the component to printed
circuit board connections.
In process zone P1, the PC board
and HSDL-3211 castellation pins
are heated to a temperature of
160°C to activate the flux in the
solder paste. The temperature
ramp up rate, R1, is limited to
4°C per second to allow for even
heating of both the PC board and
HSDL-3211 castellations.
9
Process zone P2 should be of
sufficient time duration (60 to
120 seconds) to dry the solder
paste. The temperature is raised
to a level just below the liquidus
point of the solder, usually 200° C
(392° F).
Process zone P3 is the solder
reflow zone. In zone P3, the
temperature is quickly raised
above the liquidus point of solder
to 255° C (491° F) for optimum
results. The dwell time above the
liquidus point of solder should be
between 20 and 60 seconds. It
usually takes about 20 seconds to
assure proper coalescing of the
solder balls into liquid solder and
the formation of good solder
connections. Beyond a dwell time
of 60 seconds, the intermetallic
growth within the solder connections becomes excessive, resulting in the formation of weak and
unreliable connections. The
temperature is then rapidly
reduced to a point below the
solidus temperature of the
solder, usually 200° C (392° F), to
allow the solder within the
connections to freeze solid.
Process zone P4 is the cool down
after solder freeze. The cool down
rate, R5, from the liquidus point
of the solder to 25° C (77° F)
should not exceed 6° C per second
maximum. This limitation is
necessary to allow the PC board
and HSDL-3211 castellations to
change dimensions evenly,
putting minimal stresses on the
HSDL-3211 transceiver.
Appendix A: SMT Assembly Application Note
Solder Pad, Mask and Metal Stencil Aperture
METAL STENCIL
FOR SOLDER PASTE
PRINTING
STENCIL APERTURE
LAND PATTERN
SOLDER MASK
PCB
Figure 10. Stencil and PCBA.
Recommended Land Pattern
SHIELD
SOLDER PAD
CL
1.35
MOUNTING
CENTER
1.25
2.05
0.10
0.775
1.75
FIDUCIAL
0.60
0.475
1.425
UNIT: mm
2.375
3.325
Figure 11. Stencil and PCBA.
10
Recommended Metal Solder
Stencil Aperture
It is recommended that only a
0.152 mm (0.006 inches) or a
0.127 mm (0.005 inches) thick
stencil be used for solder paste
printing. This is to ensure
adequate printed solder paste
volume and no shorting. See the
table below the drawing for
combinations of metal stencil
aperture and metal stencil
thickness that should be used.
Aperture opening for shield pad
is 2.7 mm x 1.25 mm as per land
pattern.
Adjacent Land Keepout and
Solder Mask Areas
Adjacent land keep-out is the
maximum space occupied by the
unit relative to the land pattern.
There should be no other SMD
components within this area.
APERTURES AS PER
LAND DIMENSIONS
t
w
l
Figure 12. Solder stencil aperature.
Stencil thickness, t (mm)
Aperture size (mm)
length, l
width, w
0.152 mm
2.60 ± 0.05
0.55 ± 0.05
0.127 mm
3.00 ± 0.05
0.55 ± 0.05
10.1
0.2
3.85
The minimum solder resist strip
width required to avoid solder
bridging adjacent pads is 0.2 mm.
It is recommended that two
fiducial crosses be place at midlength of the pads for unit
alignment.
SOLDER MASK
3.0
UNITS: mm
Note: Wet/Liquid PhotoImageable solder resist/mask is
recommended.
11
Figure 13. Adjacent land keepout and solder mask areas.
Appendix B: PCB Layout Suggestion
The following PCB layout guidelines should be followed to obtain
a good PSRR and EM immunity
resulting in good electrical
performance. Things to note:
4. Preferably a multi-layered
board should be used to
provide sufficient ground
plane. Use the layer underneath and near the transceiver
1. The ground plane should be
continuous under the part, but
should not extend under the
shield trace.
TOP LAYER
CONNECT THE METAL SHIELD AND MODULE
GROUND PIN TO BOTTOM GROUND LAYER.
2. The shield trace is a wide, low
inductance trace back to the
system ground. CX1, CX2,
CX3, and CX4 are optional
supply filter capacitors; they
may be left out if a clean
power supply is used.
3. Vled can be connected to
either unfiltered or unregulated power supply. If Vled
and Vcc share the same power
supply, CX3 need not be used
and the connections for CX1
and CX2 should be before the
current limiting resistor R1. In
a noisy environment, including
capacitor CX2 can enhance
supply rejection. CX1 is
generally a ceramic capacitor
of low inductance providing a
wide frequency response while
CX2 and CX3 are tantalum
capacitors of big volume and
fast frequency response. The
use of a tantalum capacitor is
more critical on the Vled line,
which carries a high current.
CX4 is an optional ceramic
capacitor, similar to CX1, for
the IOVcc line.
LAYER 2
CRITICAL GROUND PLANE ZONE. DO NOT
CONNECT DIRECTLY TO THE MODULE
GROUND PIN.
LAYER 3
KEEP DATA BUS AWAY FROM CRITICAL
GROUND PLANE ZONE.
BOTTOM LAYER (GND)
The area underneath the module
at the second layer, and 3 cm in
all directions around the module
is defined as the critical ground
plane zone. The ground plane
should be maximized in this
Figure 14. PCB layout suggestion.
12
module as Vcc, and sandwich
that layer between ground
connected board layers.
Refer to the diagram below for
an example of a 4 layer board.
zone. Refer to application note
AN1114 or the Avago IrDA Data
Link Design Guide for details.
The layout below is based on a
2-layer PCB.
Appendix C: General Application Guide for the HSDL-3211
Description
The HSDL-3211, a low-cost and
small form factor infrared transceiver, is designed to address the
mobile computing market such as
PDAs, as well as small-embedded
mobile products such as digital
cameras and cellular phones. It is
fully compliant to IrDA 1.4 low
power specification from 9.6 kb/s
to 1.152 Mb/s, and supports
HP-SIR and TV Remote modes.
The design of the HSDL-3211 also
includes the following unique
features:
• Low passive component count.
• Shutdown mode for low power
consumption requirement.
• Interface to input/output logic
circuits as low as 1.8V
Interface to Recommended I/O chips
The HSDL-3211’s TXD data input
is buffered to allow for CMOS
drive levels. No peaking circuit or
capacitor is required. Data rate
from 9.6 kb/s up to 1.152 Mb/s is
available at the RXD pin.
The block diagram below shows
how the IR port fits into a mobile
phone and PDA platform.
Selection of Resistor R1
Resistor R1 should be selected to
provide the appropriate peak
pulse LED current over different
ranges of Vcc as shown in the
table below.
Recommended R1
Vled
Intensity
Minimum Peak Pulse
LED Current
5.6Ω
3.0 V
45 mW/sr
150 mA
SPEAKER
AUDIO INTERFACE
DSP CORE
MICROPHONE
ASIC
CONTROLLER
RF INTERFACE
TRANSCEIVER
MOD/
DE-MODULATOR
IR
MICROCONTROLLER
USER INTERFACE
Figures 15. Mobile phone platform.
13
HSDL-3211
LCD
PANEL
RAM
IR
HSDL-3211
CPU
FOR EMBEDDED
APPLICATION
ROM
PCMCIA
CONTROLLER
TOUCH
PANEL
RS232C
DRIVER
Figure 16. PDA platform.
The link distance testing was
done using typical HSDL-3211
units with SMC’s FDC37C669
and FDC37N769 Super I/O
controllers. An IR link distance
of up to 75 cm was demonstrated
for SIR and MIR at full power.
14
COM
PORT
Appendix D: Window Designs for HSDL-3211
Optical port dimensions for
HSDL-3211
To ensure IrDA compliance, some
constraints on the height and
width of the window exist. The
minimum dimensions ensure
that the IrDA cone angles are met
without vignetting. The maximum dimensions minimize the
effects of stray light. The minimum size corresponds to a cone
angle of 30° and the maximum
size corresponds to a cone angle
of 60° .
In the figure below, X is the
width of the window, Y is the
OPAQUE
MATERIAL
height of the window and Z is the
distance from the HSDL-3211 to
the back of the window. The
distance from the center of the
LED lens to the center of the
photodiode lens, K, is 5.1mm.
The equations for computing the
window dimensions are as
follows:
X = K + 2*(Z+D)*tanA
Y = 2*(Z+D)*tanA
The above equations assume that
the thickness of the window is
negligible compared to the
distance of the module from the
back of the window (Z). If they are
IR TRANSPARENT WINDOW
Y
X
IR TRANSPARENT
WINDOW
K
Z
A
D
Figure 17. Window design diagram.
15
OPAQUE
MATERIAL
comparable, Z' replaces Z in the
above equation. Z' is defined as
Z' = Z + t/n
where ‘t’ is the thickness of the
window and ‘n’ is the refractive
index of the window material.
The depth of the LED image
inside the HSDL-3211, D, is
3.17mm. ‘A’ is the required half
angle for viewing. For IrDA
compliance, the minimum is 15°
and the maximum is 30° . Assuming the thickness of the window
to be negligible, the equations
result in the following tables and
graphs.
Aperture Width (x, mm)
Max.
Min.
Aperture Height (y, mm)
Max.
Min.
0
8.76
6.80
3.66
1.70
1
9.92
7.33
4.82
2.33
2
11.07
7.87
5.97
2.77
3
12.22
8.41
7.12
3.31
4
13.38
8.94
8.28
3.84
5
14.53
9.48
9.43
4.38
6
15.69
10.01
10.59
4.91
7
16.84
10.55
11.74
5.45
8
18.00
11.09
12.90
5.99
9
19.15
11.62
14.05
6.52
APERTURE WIDTH (X) vs. MODULE DEPTH
APERTURE HEIGHT (Y) vs. MODULE DEPTH
25
16
20
15
10
X MAX.
X MIN.
5
0
0
1
2
3
4
59 6
7
8
MODULE DEPTH (Z) – mm
Figure 18. Aperture width (X) vs. module depth.
16
APERTURE HEIGHT (Y) – mm
APERTURE WIDTH (X) – mm
Module Depth
(z) mm
14
12
10
8
6
4
Y MAX.
Y MIN.
2
0
0
1
2
3
4
59 6
7
8
MODULE DEPTH (Z) – mm
Figure 19. Aperture height (Y) vs. module depth.
Window Material
Almost any plastic material will
work as a window material.
Polycarbonate is recommended.
The surface finish of the plastic
should be smooth, without any
texture. An IR filter dye may be
used in the window to make it
look black to the eye, but the
total optical loss of the window
should be 10% or less for best
optical performance. Light loss
should be measured at 875 nm.
The recommended plastic
materials for use as a cosmetic
window are available from
General Electric Plastics.
Shape of the Window
From an optics standpoint, the
window should be flat. This
ensures that the window will not
alter either the radiation pattern
of the LED, or the receive pattern
of the photodiode.
If the window must be curved for
mechanical or industrial design
reasons, place the same curve on
the back side of the window that
has an identical radius as the
front side. While this will not
completely eliminate the lens
effect of the front curved surface,
it will significantly reduce the
effects. The amount of change in
the radiation pattern is dependent upon the material chosen
for the window, the radius of the
front and back curves, and the
distance from the back surface to
the transceiver. Once these items
are known, a lens design can be
made which will eliminate the
effect of the front surface curve.
The following drawings show the
effects of a curved window on the
radiation pattern. In all cases,
the center thickness of the
window is 1.5 mm, the window is
made of polycarbonate plastic,
and the distance from the
transceiver to the back surface of
the window is 3 mm.
Recommended Plastic Materials:
Material #
Light Transmission
Haze
Refractive Index
Lexan 141
88%
1%
1.586
Lexan 920A
85%
1%
1.586
Lexan 940A
85%
1%
1.586
Note: 920A and 940A are more flame retardant than 141.
Flat Window
(First Choice)
Figure 20. Shape of windows.
17
Curved Front and Back
(Second Choice)
Curved Front, Flat Back
(Do Not Use)
For product information and a complete list of distributors, please go to our web site:
www.avagotech.com
Avago, Avago Technologies, and the A logo are trademarks of Avago Technologies, Limited
in the United States and other countries.
Data subject to change. Copyright © 2006 Avago Technologies, Limited. All rights reserved.
5988-9887EN August 22, 2006
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