Micrel MICRF302 Parallel encoder Datasheet

MICRF302
Parallel Encoder
General Description
The MICRF302 is a parallel encoder which works with
QwikRadio® family radios to significantly shorten design
time for RF products. The part is easy to use, provides
more communication distance, and it is extremely stable
over operating temperature and operating voltage range.
QwikRadio®
Features
• Small form factor: 10-pin MLF® package
• Wide operating voltage range: 1.8 V to 3.6 V
• Low current consumption: 130µA operating, 0.1µA
Standby
• On-chip clock generation requires no external
components
• Unique 20-bit internal address allows up to 1 million
combinations to differentiate from adjacent encoders.
• Selectable data rates: 0.6, 1, 3, 4.8kbps
• 8-bit industry-standard CRC provides robust data
protection
• On-chip pullup resistors
• On-chip deglitch makes it easy to use low-cost switches
The MICRF302 Parallel Encoder makes the transmission
of encoding data simple. This device encodes data from
four input pins, which have internal pull-up resistors and
deglitching circuitry. These inputs can be connected to
switches or external circuitry. The MICRF302 outputs
encoded data serially, and can be connected directly to
any QwikRadio® transmitter without any additional
components.
The MICRF302 gives communication reliability through
built-in CRC (cyclic redundancy check). The MICRF302
needs no external components for clock generation.
Unlike other encoders on the market, there is no shift in
performance with associated changes in operating
temperature nor operating voltage. The internal clock
provides stable data operations over a wide temperature
range of -40°C to +85°C. MICRF302 can operate from
1.8 V to 3.6 V. The MICRF302 is battery friendly, and will
work with alkaline, NiCd, NiMh, lithium ion, or lithium
batteries.
Applications
•
•
•
•
•
•
•
•
•
•
Light switches
Appliance controls
Christmas lights
Fan and HVAC switches
Remote half switches
Garage door openers
Remote controls
Toys
Lawn watering sensors
Robust, unidirectional, low cost, low power, low data
rate communications links
_________________________________________________________________________________________________
Ordering Information
Part Number
Marking Code
Temperature Range
Package
XA02
-40ºC to +85ºC
10-pin 2.5mm × 2.5mm MLF®
MICRF302YML
Note:
1. MLF is a GREEN RoHS compliant package. Lead finish is NiPdAu. Mold compound is Halogen Free.
QwikRadio is a registered trademark of Micrel, Inc.
MLF and MicroLead Frame are registered trademark of Amkor Technology
Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
March 2010
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Micrel, Inc.
MICRF302
Typical Application
D0
D1
D2
D3
DOUT
MICRF302
ENCODER
TXEN
TRANSMITTER
RECEIVER
DO
MCU
Figure 1. RF Link
Figure 2. MICRF302 and Micrel Transmitter
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MICRF302
Pin Configuration
®
10-Pin MLF Package
Pin Description
Pin Number
Pin Name
Pin Function
D3
1
Switch Input 3
D2
2
Switch Input 2
D1
3
Switch Input 1
D0
4
Switch Input 0
Typical applications connect D0-D3 to ground with a push-button switch. Unused
switch inputs can just be left unconnected.
D0-D3 are deglitched by the MICRF302; pulses shorter than 8 ms are rejected.
VSS
5
Negative Supply (Ground)
SEL0
6
Data rate select 0
SEL1
7
Data rate select 1
The data rate select pins must be connected to VDD or VSS, and select the data rate
as follows:
00: 600 bps
01: 1 kpbs
10: 3 kbps
11: 4.8 kbps
TXEN
8
Transmitter Enable
The active-high enable turns on a companion transmitter 40 ms before baseband data
transmission starts. This delay allows the Transmitter’s PLLs to lock.
DOUT
9
RF Baseband Data Output
Data from the MICRF302 is Manchester-coded.
VDD
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Positive Supply
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MICRF302
Absolute Maximum Ratings(1)
Operating Ratings(2)
Supply Voltage (VDD) ……………………...…-0.3 V to +4 V
Voltage on Any Pin................... VSS - 0.3 V to VDD + 0.3 V
Junction Temperature ................................-55°C to +150°C
Storage Temperature .................................-65°C to +150°C
Lead Temperature (soldering, 10 s)......................... +300°C
ESD Rating(3) ......................................................... 2kV HBM
Supply Voltage (VDD)...................................... 1.8 V to 3.6 V
Ambient/junction Temperature.....................-40°C to +85°C
Electrical Characteristics
VIN = 3.3V; TA = 25°C, bold values indicate –40°C ≤ TA ≤ +85°C, unless noted.
Parameter
Condition
Operating Supply Current
Standby Current
Min
Typ
Max
Units
Fully Operational
130
200
µA
Chip Disabled
0.3
1
µA
Analog Section
MICRF302 Parallel Encoder Timing (Note 4)
On-chip oscillator frequency accuracy
Does not depend on data rate
One bit time
-10
0
+10
%
0.9
1.0
1.1
ms
One packet time
98
ms
Delay between data packets
5
ms
<1
µs
Switch closure to TXEN (TD_TXEN)
Does not depend on data rate
(6)
Does not depend on data rate
Transmit Timeout
Transmit Enable to Data Out (TTXEN_DOUT)
Pulse rejection (deglitch) by D0-D3 (Note 5)
Does not depend on data rate
22.5
25
27.5
s
36
40
44
ms
7.2
8
8.8
ms
0.1 VDD
V
Digital Section
Input Low Voltage
D0 to D3 pins
Input High Voltage
D0 to D3 pins
0.9 VDD
V
Output High Voltage
TXEN/DOUT pin, 1µA Load
0.9 VDD
V
Output Low Voltage
TXEN/DOUT pin, 1µA Load
Output Tr, Tf
TXEN/DOUT pin, Cload = 15pF
10
µs
DOUT and TXEN, Output Current
Source at 0.8 VDD
3
mA
Sink at 0.2 VDD
10
0.1 VDD
V
Notes:
1. Exceeding the absolute maximum rating may damage the device
2. The device is not guaranteed to function outside its operating rating
3. This device is ESD sensitive
4. Timing numbers are for a data rate of 1 kbps. Except where shown, all data timing scales linearly with the data rate.
5. In this context, deglitching refers to the D0-D3 pins’ ability to reject high- or low-going glitches. Deglitching makes it much easier to use low-cost
push-to-make switches which have inherently noisy contacts.
6. Guaranteed by design.
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MICRF302
Functional Diagram
Figure 3. MICRF302 Parallel Encoder Functional Diagram
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MICRF302
Functional Description
PPROM Trim
Overview
The Poly-fuse Programmable Read-Only Memory stores
the MICRF302’s unique address (see the PPROM ID
block), as well as other necessary information.
The MICRF302 is an encoder that prepares data for
transmission across an RF link. It is a parallel encoder,
meaning that it provides multiple parallel inputs for
connection to low-cost push-button switches.
Power-On Reset
The MICRF302 encoder translates push button closures,
any combination of D0 to D3, into baseband packets
using a set of internal logic blocks, which we describe
here. Please refer to the Functional Diagram while
reading the following paragraphs.
This self-contained, on-chip reset generator manages
the behavior of the MICRF302 when power is initially
applied, for example when a battery is inserted into the
transmitter. The POR sequencer and PPROM control
logic powers up the PPROM, loads important information
into internal registers, powers down the PPROM, and
then puts the whole chip into its standby state, ready for
the first button push event.
Switch Deglitch and Register
When a button is pushed, the switch input is deglitched
to remove transient pulses shorter than 8 ms. The state
of the buttons is frozen and registered prior to
transmission. If multiple buttons are pushed within one
deglitch/sample time, their active levels will all be
included in the transmitted data.
Packet Multiplexor
The packet multiplexor chooses the appropriate
information for the MICRF302 to build and transmit a
packet. Under direction of the encoder state machine,
packet generation, packet assembly logic, the packet
multiplexor serializes the entire packet. The packet
consists of: preamble, dead time, sync field, address,
and data. The packet multiplexor feeds into CRC
generation and data mux sections. CRF Generation
computes the industry-standard 8-bit CRC. The data
mux chooses the right information to be sent to the
transmitter. The data mux also ensures that the DOUT
pin is inactive when no packet transmission is in
progress.
Power Management
Immediately after any switch closure, the MICRF302
wakes from its standby (low-power) state and asserts
the TXEN output to start the RF transmitter. The Power
Management circuitry keeps the MICRF302 active
during packet transmission, then supervises the
transition back to the standby state.
Clock Oscillator
The on-chip, trimmed oscillator is started by the Power
Management logic after startup (button press). It times
all internal events and sets the bit rate of the baseband
data via the clock generator. The clock oscillator
maintains its set frequency with a tolerance of ±10%
over process, voltage, and temperature variations
March 2010
Inter-Packet Delay
Getting its timing information from the Clock Generator,
the inter-packet delay block inserts the correct delay
between the four packets in a set. After each interpacket delay, the packet is repeated, increasing the
probability of accurate detection at the receiver.
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MICRF302
D0
D1
D2
D3
DOUT
MICRF302
ENCODER
TXEN
TRANSMITTER
DO
RECEIVER
MCU
Figure 4. Parallel Encoder / Decoder Configuration
PREAMBLE
DEAD TIME
SYNC
ADDRESS
DATA
CRC
Figure 5. Data Transmission Packet Format
decoder wakeup and synchronization
Operation Overview
2. Dead Time (3 bit-times) allows the receiver’s AGC
to increase its sensitivity
The Figure 4 shows the basic operation of a parallel
encoder/decoder configuration. When a button is pushed
(known as a push event), the MICRF302 Encoder sends
packets of data to the transmitter. Each packet contains
encoded data bits, suitable for transmission across an ASK
or FSK RF communications channel. The receiver
demodulates the baseband information from the RF carrier,
which is then decoded by the MCU.
3. Sync (four bits, 1111) identifies the end of the
preamble and the start of the payload
4. DEVADR—20 bits of Device Address—identifies
one unique Encoder that’s transmitting. decoders
compare the DEVADR field against their own value
and only accept the packet if a match is found. The
20-bit device address is programmed at the factory
to a unique value for each part.
Data Transmission
In any communications link we must be sure that the
decoder puts out what the encoder puts in. Lost data is
acceptable when the encoder and decoder are out of range,
but incorrect data is completely unacceptable when the
encoder and decoder are within range. Micrel’s MICRF302
uses an error management hierarchy to prevent bad data
getting through the link:
1. Data is encoded using
Manchester encoding
RF
5. Data (8 bits) carries the “real” information within the
packet.
6. CRC—Cyclic Redundancy Check—(8 bits) lets the
Decoder check for errors in the packet
Data Format
Manchester-coded data has two distinguishing features that
make it an excellent choice for low-cost RF data exchange:
receiver-friendly
1. Its 50% duty cycle is very friendly to RF receivers.
2. An industry-standard CRC (Cyclic Redundancy
Check) ensures that data is good before being
accepted by the decoder
2. It always has a transition at the center of every bit
(Figure 6). This certainty of a transition simplifies the
decoder’s task of recovering the encoder’s clock
rate and then actually decoding the data stream.
3. Data is sent in packets. Each packet has a
preamble, sync field, and a payload. Packets are
sent in groups of four. So even though four identical
packets are transmitted, a single valid packet
received by the Decoder is sufficient to change the
Decoder’s outputs. Please see operating manual of
the MICRF302 for details.
Manchester-coded data is shown here:
Packet Format
Each data packet consists of a number of fields, shown in
Figure 5. A packet consists of six fields:
1. Preamble (32 bits, all zero) is for receiver and
March 2010
Figure 6. Manchester Coded Data
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MICRF302
MICRF302 Parallel Encoder Features
TX Enable
The MICRF302 TXEN is normally low and goes activehigh ~ 40 ms before data is seen at the output (Figure 7,
8) and remains high until D0-D3 is deactivated or the
internal MICRF302 time out has elapsed (Figure 9).
Transmit Timeout
The MICRF302 implements a 25-second (nominal)
transmit timeout timer. If a user pushes an MICRF302
button and holds it down, transmission of packets (in
repeated groups of four) will continue for no more than
25 seconds. Afterwards, the MICRF302 shuts down and
waits to be restarted by another button push. The button
must be released before it can be pushed again to
restart packet transmission.
TX Enable, SEL0=SEL1=VSS
The purpose of the transmit timeout is to prevent battery
drain and unnecessary transmission where a user might,
for example, sit on a remote control.
Preamble/Dead-Time/Sync Format
The MICRF302 sends a lengthy amount of information at
the start of the packet to help the decoder synchronize to
the incoming data stream. The format is as followed:
1. 32 zeros
2. Three-bit dead time of no Manchester-coded
data. This allows the MICRF302 to be used with
receivers whose AGC benefits from the
presence of a dead time.
Figure 7. TX Enable Output and Data Output
3. Four ones (1111) mark the end of the preamble,
dead time, and sync. The bit following the last
one of the four is the first data bit of the 20-bit
DEVADR field.
Inter-Packet Delay
The delay (dead time, no Manchester-coded data)
between subsequent packets is always eight bit-times.
Important: Encoder Bit-Time Variation
The frequency of the MICRF302’s on-chip oscillator
varies by ±10% over supply voltage, temperature, and
manufacturing tolerances. It is important to remember
that this means that the MICRF302 Encoder’s bit time
does not vary by ±10%; it varies as follows. Consider an
MICRF302 Encoder set to transmit at a nominal rate of
1 kHz, with a nominal bit-time of 1 ms. The transmit
frequency will then fall in the range of 900 Hz to 1.1 kHz.
The corresponding bit-times are 1.111 ms to 0.909 ms.
This actually corresponds to a variation in bit-time of –
9.1% to +11.1%. It is critical that the decoder
accommodate incoming data streams whose bit-times
fall within this range, not ±10%.
March 2010
Figure 8. TX Enable Output and Data Output Zoom In
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MICRF302
MICRF211 and MICRF302 Data Output
Figure 9. MICRF302 Time
Figure 10. Micrel Receiver Example Receiving MICRF302
Data Output
Figure 10 is an example of an RF link when a Micrel
MICRF211 radio receiver is used to receive and
demodulate a transmitted MICRF302 baseband signal.
The MICRF302 Tester or the TX112-MICRF302
KEYFOB can be used to transmit the MICRF302
baseband signal.
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MICRF302
Application Information
Example: Four Button Transmitter using MICRF302 Encoder and MICRF112 Transmitter Device
Figure 11. TX112-MICRF302 KEYFOB Evaluation Board Schematic
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MICRF302
MICRF302 Decoder Board Assembly
MICRF302 Decoder, Figure 12 uses a QwikRadio®
receiver to receive the MICRF302 protocol. The data
output of the receiver will go to a Microchip PIC16F689
that has been programmed to decode the MICRF302
protocol. Further details about the design and operation
of the decoder/encoder (Figure 16) are available in the
MICRF302 Encoder/Decoder Users Guide. Design files
are available upon request.
Figure 12. MICRF302 Decoder Assembly
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MICRF302
Decoder and Encoder Test Configuration using a Micrel Transmitter and Receiver
Figure 13. Test Configuration
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MICRF302
PCB Board Layout
Figure 16. TX112-MICRF302 KEYFOB Evaluation Board,
Bottom View
Figure 14. TX112-MICRF302 Evaluation Board Assembly
Figure 15. TX112-MICRF302 KEYFOB Evaluation Board,
Top View
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MICRF302
Bill of Materials
TX112-MICRF302 KEYFOB Evaluation Board Bill of Materials
Item
Quantity
Reference
Part
1
1
ANTENNA
2
1
BT1
3 volts, BATTERYHOLDER 23MM/COINCELL/THM
3
1
C1
4.7uF 6.3V
ANTENNA
PCB Footprint
ANTENNA_LOOP2
0805
4
1
C2
100pF 50V
0603
5
1
C4
1pF
0603
6
1
C5
22pF 50V
0603
7
3
C6
Not Placed
0603
C11
Not Placed
0603
C16
Not Placed
0603
8
1
C7
3.9pF
0603
9
2
C13
10pF
0603
C14
10pF
0603
0.1µF 50V
0603
10
1
C17
11
2
JPR1
0 OHMS
0402
JPR3
0 OHMS
0402
12
1
JPR2
0 OHMS NP
0402
13
1
L1
680nH
0805
14
1
L3
33nH
0603
15
1
L4
0 OHMS
0603
16
1
R1
(NC)
0402
17
1
R2
100K
0402
18
1
R4
100K
0402
19
1
R7
0 OHMS/ TBD
0603
20
4
S1
SW PUSHBUTTON
SW/PB/KEYBOARD
S2
SW PUSHBUTTON
SW/PB/KEYBOARD
S3
SW PUSHBUTTON
SW/PB/KEYBOARD
S4
SW PUSHBUTTON
SW/PB/KEYBOARD
MICRF112YMM
10P-MSOP
21
1
U1
22
1
U2
MICRF302
10P-MLF
23
1
Y1
13.560MHz
See MICRF112 Data
Sheet
Note:
1. Resistor, +/-5%, Vishay or equivalent.
2. Capacitor, ceramic, +/-5% Vishay, Murata or equivalent.
3. Inductors, 0603, 0805 Coilcraft CS series, wire wound, 5% or equivalent.
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MICRF302
Package Information
10-Pin MLF® (ML)
MICREL, INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA
TEL +1 (408) 944-0800 FAX +1 (408) 474-1000 WEB http://www.micrel.com
The information furnished by Micrel in this data sheet is believed to be accurate and reliable. However, no responsibility is assumed by Micrel for its
use. Micrel reserves the right to change circuitry and specifications at any time without notification to the customer.
Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product
can reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical implant
into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user. A
Purchaser’s use or sale of Micrel Products for use in life support appliances, devices or systems is a Purchaser’s own risk and Purchaser agrees to fully
indemnify Micrel for any damages resulting from such use or sale.
© 2008 Micrel, Incorporated.
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