21
HFBR-24X6 Low-Cost 125 MHz
Receiver
Description
The HFBR-24X6 fiber optic
receiver is designed to operate
with the Avago HFBR-14XX fiber
optic transmitters and 50/125
µm, 62.5/125 µm, 100/140 µm
and 200 µm HCS
®
fiber optic
cable. Consistent coupling into
the receiver is assured by the
lensed optical system (Figure 1).
Response does not vary with fiber
size for core diameters of 100 µm
or less.
The receiver output is an analog
signal which allows follow-on
circuitry to be optimized for a
variety of distance/data rate
requirements. Low-cost external
components can be used to convert
the analog output to logic
compatible signal levels for various
data formats and data rates up to
175 MBd. This distance/data rate
tradeoff results in increased optical
power budget at lower data rates
which can be used for additional
distance or splices.
The HFBR-24X6 receiver contains
a PIN photodiode and low noise
transimpedance pre-amplifier
integrated circuit. The HFBR-24X6
receives an optical signal and
converts it to an analog voltage.
The output is a buffered emitter-
follower. Because the signal
amplitude from the HFBR-24X6
receiver is much larger than from a
simple PIN photodiode, it is less
susceptible to EMI, especially at
high signaling rates. For very noisy
environments, the conductive or
metal port option is recommended.
A receiver dynamic range of 23 dB
over temperature is achievable
(assuming 10
-9
BER).
The frequency response is typically
dc to 125 MHz. Although the
HFBR-24X6 is an analog receiver,
it is compatible with digital
systems. Please refer to
Application Bulletin 78 for simple
and inexpensive circuits that
operate at 155 MBd or higher.
The recommended ac coupled
receiver circuit is shown in Figure
12. It is essential that a 10 ohm
resistor be connected between pin
6 and the power supply, and a 0.1
µF ceramic bypass capacitor be
connected between the power
supply and ground. In addition, pin
6 should be filtered to protect the
Figure 11. Simplified schematic diagram.
Housed Product
Unhoused Product
receiver from noisy host systems.
Refer to AN 1038, 1065, or AB 78
for details.
CAUTION: The small junction sizes inherent to the design of these components increase the components’
susceptibility to damage from electrostatic discharge (ESD). It is advised that normal static precautions be
taken in handling and assembly of these components to prevent damage and/or degradation which may be
induced by ESD.
PIN FUNCTION
1
2*
3
4*
SIGNAL
V
EE
V
CC
V
EE
BIAS & FILTER
CIRCUITS
V
CC
V
OUT
V
EE
6
2
3, 7
POSITIVE
SUPPLY
ANALOG
SIGNAL
NEGATIVE
SUPPLY
5.0
mA
300 pF
PIN NO. 1
INDICATOR
BOTTOM VIEW
6
2
3 & 7
V
CC
ANALOG
SIGNAL
V
EE
PIN FUNCTION
1†
2
3*
4†
5†
6
7*
8†
* PINS 3 AND 7 ARE ELECTRICALLY
CONNECTED TO THE HEADER.
† PINS 1, 4, 5, AND 8 ARE ISOLATED FROM
THE INTERNAL CIRCUITRY, BUT ARE
ELECTRICALLY CONNECTED TO EACH OTHER.
N.C.
SIGNAL
V
EE
N.C.
N.C.
V
CC
V
EE
N.C.
1
4
3
2
8
5
6
7
