1. Infrared Transmitter and Receiver Block Design
3/29/05 Kevin Erickson

2. IR Transmitter Block Architecture
Infrared Emitter
Driver
16 bit serial data sent via Infrared Emitter
Digital Audio sampled at 44.1 kHz
16 bit serial data
ADC Block
The input is a series of 0’s and 1’s from the ADC block.
The output is infrared pulses of the 0’s and 1’s sent to a photodiode in the IR Receiver
3/29/05 Kevin Erickson

3. IR Transmitter Schematic
5 Volt supply to operate provided by transmitter power supply block
Digital audio data input from ADC block
D1 is an infrared emitting diode
R1 is a current limiting resistor thru the infrared emitter
C1 is a speed up capacitor
2 circuits needed
(left and right channel)
3/29/05 Kevin Erickson

4. IR Transmitter Key Component Selection
Infrared emitter
Ability to transmit 20 feet (high forward current)
Fast switching time
Current limiting resistor
Power and heat dissipation
Transistor
Ability to handle short bursts of 1A
3/29/05 Kevin Erickson

5. Infrared Transmitter Key Components
HDSL-4420 Infrared Emitter Characteristics
Peak Forward Current (pulse width 100μs): 500 mA
Continuous DC Forward Current: 100 mA
Power Dissipation: 100 mW
Transient Forward Current (10 ms Pulse): 1.0 A
Forward Voltage: – 1.70 V
Reverse Voltage: 5 – 20 V
Series Resistance: 2Ω
Viewing Angle: 24° (±12°)
Peak Wavelength: 850 – 900 nm
Optical Rise and Fall time: 40 ns
Bandwidth: 9 MHz
3/29/05 Kevin Erickson

6. IR Transmitter Key Component Selection
Current Limiting Resistor
20Ω carbon film resistor
½ Watt
3/29/05 Kevin Erickson

7. IR Transmitter Key Component Selection
2N7002 N-Channel Enhancement Mode FET
ID Maximum Drain Current – Continuous 115 mA
– Pulsed 800 mA
PD Maximum Power Dissipation: 200 mW
VDS(ON) Drain-Source On-Voltage: – 1.5 V
ID(ON) On-State Drain Current: – 2700 mA
ton Turn-On Time: 20 ns
toff Turn-Off Time: 20 ns
3/29/05 Kevin Erickson

8. Infrared Transmitter Bill of Materials
Item #
Qty
Manufacture ID Number
Attributes
Reference to Schematic
Cost 1 2
Agilient
HSDL-4420
Infrared emitter--880nm Peak emission
±12° Half angle
40ns Switching times D1
$1.32
Kemet
C315C473M5U5CA
0.047 μf Capacitor
50 Volt
± 10% tolerance C1
$0.36 3
Yageo
CFR-50JB-20R
20 Ohm carbon film resistor
½ Watt
1% tolerance R1
$0.02 4
CFR-25JB-1K0
1 kΩ Ohm carbon film resistor
¼ Watt
± 5% tolerance R2 5
CFR-25JB-22R
22 Ohm carbon film resistor R3 6
Fairchild Semi
2N7002
N-Channel Enhancement Mode FET
Power MOSFET gate drivers
10ns Switching times Q1
$0.50
Total
$2.24
3/29/05 Kevin Erickson

9. IR Receiver Block Architecture
16 bit serial data sent via Infrared Emitter
16 bit serial data to DAC block
Photodiode
Transimpedance
Amplifier
Comparator
DAC
Photodiode receives the infrared signal and converts the light signal to current
The transimpedance amplifier is needed to convert the current into an amplified voltage
Comparator is used to create the 5 Volt logic (0’s and 1’s) needed by the ADC block
3/29/05 Kevin Erickson

10. IR Receiver Schematic Transimpedance Amplifier Comparator Photodiode
2 circuits needed
(left and right channel)
Transimpedance Amplifier
Comparator
Photodiode
D1 is a photodiode (λ= nm)
U1 creates the transimpedance amplifier
U2 is a 5V comparator for 5V logic.
3/29/05 Kevin Erickson

11. IR Receiver Key Component Selection
Photodiode
Fast switching time
Able to receive infrared signal 20 feet away
Comparator
0-5 Volt logic output
3/29/05 Kevin Erickson

12. Infrared Transmitter Key Components
HDSL-5420 Photodiode Characteristics
Short Circuit Current: 4.3 μA
PhotoCurrent: 3.0 – 6.0 μA
Power Dissipation: 150 mW
Forward Voltage: 0.8 V
Series Resistance: 2000Ω
Viewing Angle: 28° (±14°)
Peak Wavelength: 850 – 900 nm
Optical Rise and Fall time: 7.5 ns
Bandwidth: 50 MHz
3/29/05 Kevin Erickson

13. IR Receiver Transimpedance Amplifier
Typical ISC = 4.3μA from photodiode spec. sheet
ISC
3/29/05 Kevin Erickson

14. Infrared Receiver Bill of Materials
Item #
Qty
Manufacture ID
Attributes
Reference to Schematic
Cost 1 2
HSDL-5420
875nm Peak emission
±14° Half angle
7.5ns Switching times D1
$1.08
LM741CN
General purpose op-amp U1 3
LMV331
5 Volt Comparator
5V logic output U2
$1.60 4
CFR-25JB-1M0
1 MΩ Ohm carbon film
¼ Watt
± 5% tolerance R1
$0.02
Total
$3.78
3/29/05 Kevin Erickson