HSDL1100 HP [Agilent(Hewlett-Packard)], HSDL1100 Datasheet - Page 5

• Manufacturer Part Number: HSDL1100
• Description: General Application Guide for the HSDL-1100 4 Mb/s Infrared Transceiver
• Manufacturer: HP [Agilent(Hewlett-Packard)]

IOH = 6 mA in magnitude. LS/
HC241 and LS/HC244 are buffer
chips that can be used to drive the
TXD of the HSDL-1100.
Heat Dissipation for LEDA
The PC board must be designed to
dissipate heat from the HSDL-
1100’s LED. The junction tempera-
ture of the LED should be kept
below 125 C. The thermal resis-
tance of the PC board can be
minimized in order to keep
T
while operating up to 660 mA. For
typical applications, the LEDA pin
10 trace should be at least 38 mm
in area and no narrower than 2.5
mm at any point. Such a trace
should provide a thermal resis-
Table 3. Recommended Minimum Iih for a chosen ILED pulse
amplitude.
Table 5. LED Current
Table 4. Electrical Specifications.
ILED Pulse Amplitude (mA)
junction
LED Current Amplitude
(25% duty cycle) (mA)
Minimum Vih (V)
of the LED below 125 C
4.25
3.5
2.4
450
500
550
600
660
400
500
600
660
400
Maximum Pin 10 (Case) Temperature
2
R1 ( )
Recommended Minimum Iih (mA)
560
420
220
for the HSDL-1100 (degrees C)
tance of approximately 100 C/
Watt. The HSDL-1100 evaluation
board presents a thermal resis-
tance of approximately 100 C/Watt
for the LEDA pin 10 trace. An
opening in the solder mask for the
whole trace can be made to further
decrease the thermal resistance.
If you do not know your PC
board’s thermal resistance (deg C/
Watt), then the easiest way to
determine the maximum allowable
LED current is from maximum pin
10 = LEDA case temperature, see
Table 5. From the LED current
table you can see the maximum
pin10 lead temperature on the
HSDL-1100 for the #007 leadform.
A thermacouple can be placed on
101.3
3.2
4.0
4.8
5.3
98.4
95.3
92.1
88.7
83.0
CX2 (pF)
220
300
560
pin10 while operating the HSDL-
1100 transmitter in their PC board.
If the pin 10 temperature exceeds
the listed maximum temperature,
the PC board thermal resistance
must be reduced, or the LED
current must be reduced. The PC
board thermal resistance can be
reduced by increasing the metal
area of the pin10 trace on the PC
board, and by leaving it bare (no
epoxy glass over a section of that
trace).
For Example: If ILED = 550 mA,
then the PC board should be
designed so that the pin10 tempera-
ture does not exceed 92.1 C when
the PC board is enclosed in a
notebook or handy terminal box.
Interface to Recommended
I/O Chips
4 Mb/s Ir link distances of 1.3-1.95
meters between transmitter and
receiver have been demonstrated
using typical HSDL-1100 units, and
either the National Semiconductor
PC87108 I/O chip, the VLSI
VL82C147 I/O chip, or the SMC
FDC37C957 I/O chip. In reference
to the HSDL-1100 diagram on page
1 of this note, the TXD, RXD-A, and
RXD-B nodes can be connected
directly to the chosen I/O chip.
National Semiconductor
PC87108
For the National Semiconductor
PC87108 I/O chip, the Ir link can be
realized with the following connec-
tions:
Connect IRTX pin 39 of the
PC87108 to the I/O side of R1/CX2
labeled TXD on the diagram of
page 1.
Connect IRRX1 pin 38 of the
PC87108 to RXD-A (pin 8 of the
HSDL-1100).