Linear Technology DC112A Guida rapida alla configurazione

DEMO MANUAL DC112A

LT1328 IrDA Infrared

Receiver

DESCRIPTIO

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

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

, 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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DEMO MANUAL DC112A

PACKAGE AND SCHEMATIC DIAGRAMS

WWU

R3

6.3Ω

1/2W

R2

10k

R1

100Ω

D2

HSDL-4220

Q1

2N7002 Q2 

2N7002

E5 GND

E6 TRANS

DC112A TA02

1

2

3

8

7

6

IN

FILT



GND

SHDN

MODE



DATA

C1

10nF

C6

1000pF

U1

LT1328CS8

DC112A TA01

C4

330pF C2

0.1µF

D1

BPV22NF



C3

10µF

FILTER

SWITCH E3 V

E2 MODE

E4 DATA

E1 GND

JP1

–+



50k 1.5V



D1

PHOTODIODE

TEMIC

BPV22NF

C1

10nF

IN1

BIAS

65V

C3

10µF

7MODE

DC112A BD

DATA

FILTER2

FILTER SWITCH3

GND4

PREAMP

DC SERVO

FILTER



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

IN

FILTER

FILTER SWITCH

GND

8

7

6

BIAS



MODE



DATA

TOP VIEW

MS8 PACKAGE

8-LEAD PLASTIC MSOP

LT1328CMS8

1

2

3

8

7

6

TOP VIEW

S8 PACKAGE

8-LEAD PLASTIC SO

IN

FILTER



GND

VBIAS

MODE

VCC

DATA

FILTER

SWITCH

LT1328CS8

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DEMO MANUAL DC112A

REFERENCE

DESIGNATOR QUANTITY PART NUMBER DESCRIPTION VENDOR TELEPHONE

C1 1 12065C103KATMA 0.01µF 50V 20% X7R Capacitor AVX (803) 946-0362

C2 1 12065C104KATMA 0.1µF 50V 10% X7R Capacitor AVX (803) 946-0362

C3 1 TAJC106K016R 10µF 16V 10% Tantalum Capacitor AVX (207) 282-5111

C4 1 1206A331KATMA 330pF 50V 10% NPO Capacitor AVX (803) 946-0362

C6 1 12065C102KATMA 1000pF 50V 10% X7R Capacitor AVX (803) 946-0362

D1 1 BPV22NF Diode Temic (408) 970-5700

D2 1 HSDL-4220 LED Hewlett Packard (800) 235-0312

E1 to E6 6 1502-2 Turret Keystone (718) 956-8900

JP1 1 3801S-3-G1 3-Pin Header COMM CON (818) 301-4200

Q1, Q2 2 2N7002LTA Transistor Zetex (516) 543-7100

R1 1 CR32-101J-T 100Ω5% Resistor AVX (803) 946-0524

R2 1 CR32-103J-T 10k 5% Resistor AVX (803) 946-0524

R3 1 CRCW20106R8J 6.8Ω1/2W 5% Dale (408) 985-5733

U1 1 LT1328CS8 IC LTC (408) 432-1900

XJP1 1 CCIJ230-G Shunt COMM CON (818) 301-4200

PARTS LIST

OPERATIO

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

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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DEMO MANUAL DC112A

OPERATIO

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

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DEMO MANUAL DC112A

OPERATIO

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

4c4b

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DEMO MANUAL DC112A

OPERATIO

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

4PPM DATA

SYMBOL

1000

0100

0010

0001

RECEIVER

OUTPUT

TRANSMITTER

INPUT

IrDA-4PPM (1m) IrDA-4PPM (1cm)

RECEIVER

OUTPUT

TRANSMITTER

INPUT

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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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



Component Side

Component Side Silkscreen Component Side Solder Mask

Solder Side Silkscreen Solder Side Solder Side Solder Mask

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DEMO MANUAL DC112A

dc112af LT/GP 0197 500 • PRINTED IN USA

 LINEAR TECHNOLOGY CORPORATION 1997

PC FAB DRAWI G

Linear Technology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

●

(408)432-1900

FAX: (408) 434-0507

●

TELEX: 499-3977

●

www.linear-tech.com

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

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:

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