Linear Technology DC112A Quick setup guide

1
DEMO MANUAL DC112A
LT1328 IrDA Infrared
Receiver
DESCRIPTIO
U
This demonstration board implements the IrDA
®
stan-
dards for infrared data communications. It is a complete
transmitter/receiverforuseinSIR,FIRand4PPMinfrared
data links. The LT
®
1328 is a photodiode receiver that
supports IrDA data rates up to 4Mbps, as well as other
modulation methods such as Sharp-ASK and TV remote
control.ThisboardcanbeconfiguredforIrDA-SIR(Infra-
red Data Association Serial Infrared), IrDA-FIR (Infrared
Data Association Fast Infrared) and 4PPM (4MHz pulse-
position modulation).
The LT1328, in the SO-8 and MSOP packages, contains
all the necessary circuitry to convert current pulses from
an external photodiode to a digital TTL output, while
rejecting unwanted lower frequency interference. The
LT1328 requires only six external components to make
an IrDA compatible receiver. Figure 1 is a block diagram
of the LT1328. The preamp converts the photodiode
current into a voltage that trips the comparator. The
internal servo action suppresses only frequencies below
the R
gm
/C
FILT
pole. This highpass filtering attenuates
interfering signals, such as sunlight or incandescent and
fluorescent lamps, and is selectable at Pin 7 for low or
high data rates. The upper frequency limit for the servo
isset byan externalcapacitorC4. Thepole is foundby the
formula f(Hz) = 25[1/(2π• 60k • C4)]; a 330pF capacitor
for C4 will pass signals above 200kHz (FIR and 4PPM).
To lower the passband for SIR, move the jumper on the
demoboardfrom FIR,4PPM toSIR. Thistakes theMODE
pin (Pin 7) from ground to V
CC
, which switches C1 (on
Pin 3) in parallel with C4. The required filtering for V
BIAS
(Pin 8) is provided by C6, a 1000pF cap to ground. The
DATA pin (Pin 5) is the output of the comparator. The
quiescent, no signal state is a TTL HIGH; a TTL LOW
occurs when the photodiode receives light. Power re-
quirements for the LT1328 are minimal: a single 5V
supply and 2mA of quiescent current. The LT1328’s ease
of use and flexibility make it an ideal solution for numer-
ous other photodiode receiver applications. The LT1328
isavailablein the8-pinSO andthetinyMSOPpackage for
size-critical applications.
An IrDA transmitter is also provided on the demo board.
Figure 2 shows the LED driver circuit and the LT1328
receiver. The LED transmits light when the transmit input
pin on the demo board is high (5V), and is off when the
TransmitInputislow(0V).ThereceiveroutputistheDATA
pinonthe demo board (which is Pin 5 on the LT1328). The
Data pin is high for no received light and a TTL LOW for a
light pulse. To switch from SIR to the faster data rates, a
jumper is provided. Remote switching can be accom-
plished by removing the jumper and accessing the MODE
pin: TTL HIGH for SIR and TTL LOW for faster data rates.
Actual transmit and receive waveforms can be seen in
Figures 3, 4 and 5 for SIR, FIR and 4PPM, respectively.
The lower waveform in each photo is the transmit input
to the demo board. The upper waveform is the demo
board DATA pin (Pin 5 of the LT1328).
DEMO MANUAL DC112A
, LTC and LT are registered trademarks of Linear Technology Corporation.
IrDA is a registered trademark of the Infrared Data Association.
BOARD PHOTO
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2
DEMO MANUAL DC112A
PACKAGE AND SCHEMATIC DIAGRAMS
WWU
R3
6.3Ω
1/2W
R2
10k
5%
R1
100Ω
5%
D2
HSDL-4220
Q1
2N7002 Q2  2N7002
E5 GND
E6 TRANS
V
CC
DC112A TA02
1
2
3
4
8
7
6
5
IN
FILT

GND
SHDN
MODE
V
CC

DATA
C1
10nF
C6
1000pF
U1
LT1328CS8
DC112A TA01
C4
330pF C2
0.1µF
D1
BPV22NF

C3
10µF
FILTER
SWITCH E3 V
CC
E2 MODE
E4 DATA
E1 GND
+
V
CC
12
JP1
3
–+
R
FB

50k 1.5V
V
CC
R
IN

2k
D1
PHOTODIODE
TEMIC
BPV22NF
C1
10nF
IN1
8V
BIAS
65V
C3
10µF
V
CC
7MODE
5
DC112A BD
DATA
FILTER2
FILTER SWITCH3
GND4
PREAMP
DC SERVO
FILTER
g
m

60k
+
–
–
+
COMP
BIAS
C4
330pF
C6
1000pF
HIGH: SIR
LOW: FIR AND 4PPM
C2
0.1µF
+
Figure 1. LT1328 Block Diagram
Figure 2a. IrDA Receiver Figure 2b. IrDA Transmitter
1
2
3
4
IN
FILTER
FILTER SWITCH
GND
8
7
6
5
V
BIAS

MODE
V
CC

DATA
TOP VIEW
MS8 PACKAGE
8-LEAD PLASTIC MSOP
LT1328CMS8
1
2
3
4
8
7
6
5
TOP VIEW
S8 PACKAGE
8-LEAD PLASTIC SO
IN
FILTER

GND
VBIAS
MODE
VCC
DATA
FILTER
SWITCH
LT1328CS8
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3
DEMO MANUAL DC112A
REFERENCE
DESIGNATOR QUANTITY PART NUMBER DESCRIPTION VENDOR TELEPHONE
C1 1 12065C103KATMA 0.01µF 50V 20% X7R Capacitor AVX [phone]
C2 1 12065C104KATMA 0.1µF 50V 10% X7R Capacitor AVX [phone]
C3 1 TAJC106K016R 10µF 16V 10% Tantalum Capacitor AVX [phone]
C4 1 1206A331KATMA 330pF 50V 10% NPO Capacitor AVX [phone]
C6 1 12065C102KATMA 1000pF 50V 10% X7R Capacitor AVX [phone]
D1 1 BPV22NF Diode Temic [phone]
D2 1 HSDL-4220 LED Hewlett Packard [phone]
E1 to E6 6 1502-2 Turret Keystone [phone]
JP1 1 3801S-3-G1 3-Pin Header COMM CON [phone]
Q1, Q2 2 2N7002LTA Transistor Zetex [phone]
R1 1 CR32-101J-T 100Ω5% Resistor AVX [phone]
R2 1 CR32-103J-T 10k 5% Resistor AVX [phone]
R3 1 CRCW20106R8J 6.8Ω1/2W 5% Dale [phone]
U1 1 LT1328CS8 IC LTC [phone]
XJP1 1 CCIJ230-G Shunt COMM CON [phone]
PARTS LIST
OPERATIO
U
The most straightforward way of evaluating IR links with
the LT1328 demo board is to have a separate LED trans-
mitter, like that on DC112A, that can be placed a measured
distance from the receiver. If a second board is not
available, it is a simple matter to duplicate the transmitter
design shown in the schematic diagram (Figure 2). The
pulses to drive this transmitter can be obtained from a
suitable pulse generator that has a TTL output or from the
system that will use the IR link, if available. Use coax cable
and place a suitable termination on the input of the
transmitter board to ensure good pulse fidelity.
The onboard jumper must be set for the modulation
desired.The positionof thisjumper ismarkedon thedemo
board. For example, for IrDA-SIR modulation, set the
mode jumper to the SIR side.
Connect an oscilloscope to the appropriate output of the
demonstrationboardandapplya5Vpowersourcecapable
of supplying greater than 25mA to the V
CC
and either GND
pin (both ground pins are common).
Set the transmitter close to the receiver (≈1cm), input an
appropriate modulation signal to the trans input pin and
verify the basic operation of the receiver using the modu-
lation photographs (Figures 3, 4 and 5) as a guide.
You can then test the receiver over the desired range,
transmitter power, angle of incidence or other variables. It
is helpful to set up a space for an optical range that is clear
of obstacles, reflections and interference. Later, when the
basic operation of the IR link is established, the receiver
canbe tested againstany interference thatthefinal system
may encounter. For more sophisticated testing, a Bit Error
RateTest (BERT) set is usually required, as are the circuits
to modulate and demodulate the digital signals.
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4
DEMO MANUAL DC112A
OPERATIO
U
IrDA-SIR
Because SIR systems transmit a pulse for a zero and
nothing for a one (see Figure 3a), the two photographs
demonstrating the SIR modulation show a sequence of
zeros. In both photographs, the input data to the transmit-
terisshownonthebottomandtheoutputoftheIRreceiver
is shown on the top. Note that the receiver output is a TTL
LOWfor atransmittedlight pulse.Thetwo photos,Figures
3b and 3c, show received data at 1 meter and 1cm. There
is not much difference at distances in between.
0 1 0 0 1 1 0 1 0 
1328 F02a
NRZ DATA
IrDA-SIR HIGH = LIGHT TRANSMITTED
DATA RATES: 2400BAUD TO 115kBAUD
BIT INTERVAL: 417µs TO 8.7µs
PULSE WIDTH: 3/16 OF INTERVAL OR 1.63µs
TRANSMITTER
INPUT
RECEIVER
OUTPUT RECEIVER
OUTPUT
TRANSMITTER
INPUT
IrDA-SIR (1m) IrDA-SIR (1cm)
Figure 3. IrDA-SIR Modulation
3b 3c
3a
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5
DEMO MANUAL DC112A
OPERATIO
U
IrDA-FIR
With the exception of data rate and pulse width, FIR is very
similartoSIR(see Figure4a).Thesameprecautionsabout
interference from the other output apply to FIR and SIR.
The first FIR photo, Figure 4b, shows the receiver at a
range of 1 meter. The second photo, Figure 4c, shows the
receiver 1cm from the transmitter. Again, a detected light
pulse will make the receiver switch to a TTL LOW state.
TRANSMITTER
INPUT
RECEIVER
OUTPUT RECEIVER
OUTPUT
TRANSMITTER
INPUT
IrDA-FIR (1m) IrDA-FIR (1cm)
Figure 4. IrDA-FIR Modulation
0 1 0 0 1 1 0 1 0 
1328 F03a
NRZ DATA
IrDA-FIR HIGH = LIGHT TRANSMITTED
DATA RATES: FIXED AT 1.15MBAUD
BIT INTERVAL: 870ns
PULSE WIDTH: 1/4 OF INTERVAL OR 217ns
4a
4c4b
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6
DEMO MANUAL DC112A
OPERATIO
U
IrDA-4PPM
4Mbps pulse position modulation positions one pulse,
125ns wide in one of four data windows for every data bit
pair.Thefourdata windowsmakeupabitintervalof 500ns
(Figure 5a). By varying the distance from the demo board
0 1 0 0 1 1 0 1 0 
1328 F04a
NRZ DATA
IrDA 4PPM HIGH = LIGHT TRANSMITTED
DATA RATES: FIXED AT 4MBAUD
BIT INTERVAL: 500ns
PULSE WIDTH: 1/4 OF INTERVAL OR 125ns
DATA BIT
PAIR
00
01
10
11
4PPM DATA
SYMBOL
1000
0100
0010
0001
RECEIVER
OUTPUT
TRANSMITTER
INPUT
IrDA-4PPM (1m) IrDA-4PPM (1cm)
RECEIVER
OUTPUT
TRANSMITTER
INPUT
5a
Figure 5. IrDA-4PPM
to the transmitter, the LT1328’s output can be evaluated.
The first photo, Figure 5b, is when the receiver is 1 meter
from the transmitter. The second photo shows the 1cm
response.
5c5b
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7
DEMO MANUAL DC112A
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-
tationthattheinterconnectionofitscircuitsasdescribedhereinwillnotinfringeonexistingpatentrights.
PCB LAYOUT A D FIL


UW
Component Side
Component Side Silkscreen Component Side Solder Mask
Solder Side Silkscreen Solder Side Solder Side Solder Mask
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8
DEMO MANUAL DC112A
dc112af LT/GP 0197 500 • PRINTED IN USA
 LINEAR TECHNOLOGY CORPORATION 1997
PC FAB DRAWI G
U
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
●
[phone]
FAX: [phone]
●
TELEX: 499-3977
●
www.linear-tech.com
1.25
1.25
0.017
0.020
DC112 FAB
SYMBOL
A
B
C
D

DIAMETER
0.094
0.042
0.037
0.015
TOTAL HOLES
NUMBER
OF HOLES
6
2
7
2
17
NOTES:
1.MATERIAL: 2 LAYERS, 0.062" THICK, FR-4 GLASS EPOXY 2OZ COPPER CLAD 
2.ALL HOLES SHALL BE PLATED THROUGH
3.PLATE THROUGH HOLES WITH COPPER 0.0014 MIN THICKNESS. ALL HOLE
 SIZES IN HOLE TABLE ARE AFTER PLATING
4.SILKSCREEN: WHITE EPOXY NONCONDUCTIVE INK
5.FINISH: SMOBC
6.SOLDER MASK: LPI, GREEN
7.SCORING:
A
A
A
AA
BC
C
D
A
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