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ELM408 데이터시트 PDF




ELM에서 제조한 전자 부품 ELM408은 전자 산업 및 응용 분야에서
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부품번호 ELM408 기능
기능 Rotary Decoder
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ELM408 데이터시트, 핀배열, 회로
ELM408
Rotary Decoder - 2 wire Interface
Description
The ELM408 is an 8 pin integrated circuit that is
used to convert the output from a rotary encoder into
two signals (chip select, and up/down) that can be
used to control various devices. The low power
CMOS technology used ensures that only a very
small current is required over the entire 2.0 to 5.5
volt operating range.
There is no need for external filtering or
debounce circuits with the ELM408, as this is all
performed within the integrated circuit. After
debouncing the encoder signals, the ELM408
determines the direction of shaft rotation, and then
generates the appropriate outputs. A write sequence
can also be generated if the Write Enable input is at
a high level when the outputs are generated.
The ELM408 provides both 2x and 4x decoding
of a rotary encoder signal. See the Output
Waveforms section for more information.
Applications
• Digital audio potentiometer controls
• Variable voltage or temperature circuits
• Positioning controls
• Tuning circuits
Features
• Low power CMOS design
• Wide supply range – 2.0 to 5.5 volts
• Complete debouncing of the encoder inputs
• No external filtering needed
• 2x and 4x decoding
• Can generate a write sequence
• Startup delay timer
• High current drive outputs
Connection Diagram
PDIP and SOIC
(top view)
VDD 1
A2
B3
Write 4
Enable
8 VSS
7 CS
6 U/D
5 4x/2x
Block Diagram
VDD A
Debounce
2
Circuit
Direction
Output
VDD B
Decoding
Debounce
3
Circuit
Logic
7 CS
6 U/D
Rotary
Encoder
Write 4
Enable
5 4x/2x
ELM408DSA
Elm Electronics – Circuits for the Hobbyist
www.elmelectronics.com
1 of 10
Free Datasheet http://www.datasheet4u.com/




ELM408 pdf, 반도체, 판매, 대치품
ELM408
Absolute Maximum Ratings
Storage Temperature....................... -65°C to +150°C
Ambient Temperature with
Voltage Applied..................................-40°C to +85°C
Voltage on VDD with respect to VSS............ 0 to +6.5V
Voltage on any other pin with
respect to VSS........................... -0.3V to (VDD + 0.3V)
Note:
Stresses beyond those listed here will likely
damage this device. These values are given as a
design guideline only. The ability to operate to
these levels is neither inferred nor recommended.
Electrical Characteristics
All values are for operation at 25°C and a 5V supply, unless otherwise noted. For further information, refer to note 1 below.
Characteristic
Minimum Typical Maximum Units
Conditions
Supply voltage, VDD
2.0 5.0 5.5 V
VDD rate of rise
0.05
V/msec see note 2
Power on reset time
9 18 30 msec see note 3
Average supply current, IDD
0.6 1.1 mA VDD = 5.0V
0.2 0.3 mA VDD = 2.0V
Output low current
(sink)
VDD = 5.0V
VDD = 3.0V
10
5.0
mA VOL = 0.25V
mA VOL = 0.25V
Output high current
(source)
VDD = 5.0V
VDD = 3.0V
2.5
1.7
mA VOH = 4.75V
mA VOH = 2.75V
Debounce period
5.5 msec see note 4
Startup time delay
50 msec
Internal timing variation
1 4 % see note 5
Notes:
1. This integrated circuit is based on a Microchip Technology Inc. PIC12F5XX device. For more detailed
specifications, please refer to the Microchip documentation (www.microchip.com).
2. This spec must be met in order to ensure that a correct power on reset occurs. It is quite easily achieved
using most common types of supplies, but may be violated if one uses a slowly varying supply voltage, as
may be obtained through direct connection to solar cells, or some charge pump circuits.
3. The internal reset circuitry stops the ELM408 from doing anything during this period, so that the power
supplies and oscillators have time to stabilize. During this time, all pins behave like inputs.
4. Typical only - the actual period varies with the amount of noise present in the input signal.
5. All filtering, delay, and output timing is based on an internal master oscillator. The frequency of this oscillator
will vary with voltage and temperature. Values shown are typical maximums for 2.0V VDD 5.5V, and
temperatures of -40°C to +85°C
ELM408DSA
Elm Electronics – Circuits for the Hobbyist
www.elmelectronics.com
4 of 10
Free Datasheet http://www.datasheet4u.com/

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ELM408 전자부품, 판매, 대치품
ELM408
Output Waveforms
Once the ELM408 has some bounce-free signals
to work with, it can generate outputs based on them.
The output sequences that the ELM408 generates
depends on the direction of shaft rotation, and on the
level at the Write Enable input (pin 4). The direction
logic always assumes that the encoder is a standard
one, where the ‘A’ signal leads the ‘B’ for a clockwise
or ‘up’ rotation. Note that the level at pin 5 only
determines when the sequences are output, and does
not affect the waveshape or timing of them.
Figures 4 to 7 below show the sequences that the
ELM408 can generate. In all cases, the basic time
interval is 200 µsec (if it does not seem apparent).
Figures 4 and 5 show the two types of sequences that
would occur if the Write Enable is low (ie disabled).
The level at the U/D output when the CS signal goes
low determines whether the the controlled device will
count up (level is high), or down (level is low) when the
U/D pin next goes from low to high.
For many digital potentiometers, the level at the
U/D pin when the CS output returns high determines
whether the current setting of the digital potentiometer
is to be stored in non-volatile memory or not. If the
ELM408’s Write Enable input is high, then the U/D
output will be held high during the transition, causing a
write for many digital potentiometers. The resulting
waveforms are shown in Figures 6 and 7.
The logic to decode the motion of an encoder
shaft, and so decide when to provide output
sequences is not as simple as it would first appear.
Some authorities recommend simply monitoring an
input and when it changes, provide an output based on
the level of the other input. This does not always work,
as the encoder can output multiple signals from only
the ‘A’ or or only the ‘B’ contact if the shaft is moved
ever so slightly when at the detent or at the mid-point
position (between detents). Simply seeing one input
change is not sufficient to say that there is any
significant shaft rotation.
The ELM408 monitors both ‘A’ and ‘B’ transitions,
and determines the outputs based on the sequence in
which the transitions have occurred. This is a better
way to guarantee that the output signals are generated
properly. The internal logic also performs some self-
checking, and monitors for problems such as an output
pulse being initiated before the previous one had
completed, which might occur for some very fast
inputs (the second one will be ignored in this case).
The output of the ELM408 is a series of pulses, as
shown in Figures 8 and 9. The first figure shows 2x
CS
200
U/D µsec
Figure 4. Up (Clockwise) with
Write Enable = Low
CS
200
U/D µsec
Figure 5. Down (Counterclockwise) with
Write Enable = Low
CS
U/D 200
µsec
Figure 6. Up (Clockwise) with
Write Enable = High
CS
U/D 400
µsec
Figure 7. Down (Counterclockwise) with
Write Enable = High
ELM408DSA
Elm Electronics – Circuits for the Hobbyist
www.elmelectronics.com
7 of 10
Free Datasheet http://www.datasheet4u.com/

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