hedl-6443-it11 Avago Technologies, hedl-6443-it11 Datasheet - Page 3

• Manufacturer Part Number: hedl-6443-it11
• Description: Optical Incremental Housed Encoders
• Manufacturer: Avago Technologies

The HEDL-64XX translates rotary motion of a shaft into a
two or three channel digital output. The HEDL-64XX se-
ries has four key parts: a single light emitting diode (LED)
light source, a photodetector IC with a set of uniquely
configured photodiodes , a line drive IC and a pair of
lenses. The lens over the LED focuses light onto the code-
wheel. As the codewheel rotates, an alternating pattern
of light and dark corresponding to the pattern of the
codewheel falls upon the photodiodes.
This light is used to produce internal signals A and A’ , and
B and B’ .
As part of this “push-pull” detector system, these signals
are fed through comparators and line driver that are part
of the signal processing circuitry to produce the final
outputs for channels A and B and index.
Definitions
Count (N): For rotary motion, the number of bar and
window pairs or counts per revolution(CPR) of the code-
wheel. For linear motion, the number of bar and window
pairs per unit length (lines per inch[LPI] or lines per mm
[LPmm]).
One Cycle(C): 360 electrical degree(°e), 1 bar and win-
dow pair.
One Shaft Rotation: 360 mechanical degrees, N cycles
(rotary motion only).
Line Density: The number of reflective and non-reflec-
tive pairs per unit length, expressed as either lines per
inch(LPI) or lines per mm (LPmm).
LED
RESISTO
R
LENS
CODEWHEE
L
PHOTODIODE
S
SIGNA
L P ROCESSIN
G C IRCUITR
Y
Cycle error(∆C):: An indication of cycle uniformity. The
difference between an observed shaft angle which gives
rise to one electrical cycle and the nominal angular incre-
ment of 1/N of a revolution
Pulse Width (P): The number of the electrical degrees that
an output is high during one cycle, nominally 180°e or
1/2 a cycle.
Pulse Width Error(∆P): The deviation in electrical degrees
of the pulse width from its ideal value of 180°e.
State Width (S): The number of the electrical degrees be-
tween a transition in the output of the channel B. There
are 4 states per cycle, each nominally 90°e.
State Width Error (∆S): The deviation in electrical degrees
of each state width from its ideal value of 90°e.
Phase (f ): The number of electrical degrees between the
center of the high state on the channel A and the cen-
ter of the high state of channel B. This value is nominally
90°e.
Phase error (∆f ): The deviation in electrical degrees of the
phase from its ideal value of 90°e.
Position error (∆q):: The normalized angular difference
between the actual shaft position and the position indi-
cated by the encoder cycle count.
Index Pulse Width (Po): The number of electrical degrees
that an index is high during one full shaft rotation. This
value is nominally 90°e or ¼ cycle.
Gnd
Ch A
I
Ch A
Ch B
Ch B
I
Vcc