HEDS9140F00 AVAGO TECH, HEDS9140F00 Datasheet - Page 2

• Manufacturer Part Number: HEDS9140F00
• Manufacturer: AVAGO TECH

Block Diagram
2
The HEDS-9040 and 9140 have two channel quadrature
outputs plus a third channel index output. This index
output is a 90 electrical degree high true index pulse
which is generated once for each full rotation of the
codewheel.
The HEDS-9040 is designed for use with a HEDX-614X
codewheel which has an optical radius of 23.36 mm
(0.920 inch). The HEDS-9140 is designed for use with a
HEDx-5x4x codewheel which has an optical radius of
11.00 mm (0.433 inch).
The quadrature signals and the index pulse are accessed
through five 0.025 inch square pins located on 0.1 inch
centers.
Standard resolutions between 256 and 2000 counts per
revolution are available. Consult local Avago sales repre-
sentatives for other resolutions.
Applications
The HEDS-9040 and 9140 provide sophisticated motion
control detection at a low cost, making them ideal for
high volume applications. Typical applications include
printers, plotters, tape drives, and industrial and factory
automation equipment.
Note: Avago Technologies encoders are not recommend-
ed for use in safety critical applications. Eg. ABS braking
systems, power steering, life support systems and critical
care medical equipment. Please contact sales represen-
tative if more clarification is needed.
Theory of Operation
The HEDS-9040 and 9140 are emitter/detector modules.
Coupled with a codewheel, these modules translate the
rotary motion of a shaft into a three-channel digital out-
put.
As seen in the block diagram, the modules contain a
single Light Emitting Diode (LED) as its light source. The
light is collimated into a parallel beam by means of a
single polycarbonate lens located directly over the LED.
Opposite the emitter is the integrated detector circuit.
This IC consists of multiple sets of photodetectors and
the signal processing circuitry necessary to produce the
digital waveforms.
The codewheel rotates between the e mitter and d etector,
causing the light beam to be interrupted by the pattern
of spaces and bars on the codewheel. The photodiodes
which detect these interruptions are arranged in a pat-
tern that corresponds to the radius and design of the
codewheel. These detectors are also spaced such that a
light period on one pair of detectors corresponds to a
dark period on the adjacent pair of detectors. The photo-
diode outputs are then fed through the signal process-
ing circuitry resulting in A, A, B, B, I and I. Comparators
receive these signals and produce the final outputs for
channels A and B. Due to this integrated phasing tech-
nique, the digital output of channel A is in quadrature
with that of channel B (90 degrees out of phase).
The output of the comparator for I and I is sent to the in-
dex processing circuitry along with the outputs of chan-
nels A and B. The final output of channel I is an index
pulse P
the codewheel. This output P
nally 90 electrical degrees), high true index pulse which
is coincident with the low states of channels A and B.
O
which is generated once for each full rotation of
O
is a one state width (nomi-