MICRF302YML TR - MICROCHIP TECHNOLOGY

MICRF302

Parallel Encoder

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 M9999-032610-A

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.

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.

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

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

MICRF302YML XA02 -40ºC to +85ºC 10-pin 2.5mm × 2.5mm MLF®

Note:

1. MLF is a GREEN RoHS compliant package. Lead finish is NiPdAu. Mold compound is Halogen Free.

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Typical Application

MICRF302

ENCODER

DOUT

TRANSMITTER RECEIVER MCU

TXEN

Figure 1. RF Link

Figure 2. MICRF302 and Micrel Transmitter

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Pin Configur ation

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 10 Positive Supply

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Absolute Maximum Ratings(1)

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

Operating Ratings(2)

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 Min Typ Max Units

Operating Supply Current Fully Operational 130 200 µA

Standby Current 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 -10 0 +10 %

One bit time 0.9 1.0 1.1 ms

One packet time 98 ms

Delay between data packets 5 ms

Switch closure to TXEN (TD_TXEN) Does not depend on data rate <1 µs

Transmit Timeout(6) Does not depend on data rate 22.5 25 27.5 s

Transmit Enable to Data Out (TTXEN_DOUT) 36 40 44 ms

Pulse rejection (deglitch) by D0-D3 (Note 5) Does not depend on data rate 7.2 8 8.8 ms

Digital Section

Input Low Voltage D0 to D3 pins 0.1 VDD V

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 0.1 VDD V

Output Tr, Tf TXEN/DOUT pin, Cload = 15pF 10 µs

DOUT and TXEN, Output Current Source at 0.8 VDD

Sink at 0.2 VDD

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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Functional Diagram

Figure 3. MICRF302 Parallel Encoder Functional Diagram

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Functional Description

Overview

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.

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.

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.

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

PPROM Trim

The Poly-fuse Programmable Read-Only Memory stores

the MICRF302’s unique address (see the PPROM ID

block), as well as other necessary information.

Power-On Reset

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.

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.

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 inter-

packet delay, the packet is repeated, increasing the

probability of accurate detection at the receiver.

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MICRF302

ENCODER

DOUT

TRANSMITTER RECEIVER MCU

TXEN

Figure 4. Parallel Encoder / Decoder Configuration

PREAMBLE DEAD TIME SYNC ADDRESS DATA CRC

Figure 5. Data Transmission Packet Format

Operation Overview

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.

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 RF receiver-friendly

Manchester encoding

2. An industry-standard CRC (Cyclic Redundancy

Check) ensures that data is good before being

accepted by the decoder

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.

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

decoder wakeup and synchronization

2. Dead Time (3 bit-times) allows the receiver’s AGC

to increase its sensitivity

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.

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:

1. Its 50% duty cycle is very friendly to RF receivers.

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.

Manchester-coded data is shown here:

Figure 6. Manchester Coded Data

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MICRF302 Parallel Encoder Features

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.

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.

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-T i me 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%.

TX Enable

The MICRF302 TXEN is normally low and goes active-

high ~ 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).

TX Enable, SEL0=SEL1=VSS

Figure 7. TX Enable Output and Data Output

Figure 8. TX Enable Output and Data Output Zoom In

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MICRF211 and MICRF30 2 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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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 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 Assembl y

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Decoder and Encoder Test Configuration using a Micrel Transmitter and Receiver

Figure 13. Test Configuration

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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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Bill of Materials

TX112-MICRF302 KEYFOB Evaluation Board Bill of Materials

Item Quantity Reference Part PCB Footprint

1 1 ANTENNA ANTENNA ANTENNA_LOOP2

2 1 BT1 3 volts, BATTERYHOLDER 23MM/COINCELL/THM

3 1 C1 4.7uF 6.3V 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

10 1 C17 0.1µF 50V 0603

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

21 1 U1 MICRF112YMM 10P-MSOP

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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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

reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical impla

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.

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