MICRF002YM TR - Micrel - Datasheet.Company

March 2003 1 MICRF002/RF022

MICRF002/RF022 Micrel

MICRF002/RF022

300-440MHz QwikRadio™ASK Receiver

Final Information

Typical Application

SEL0SEL0 SWEN

VSSRF REFOSC

VSSRF SEL1

ANT CAGC

VDDRF WAKEB

VDDBB SHUT

CTH DO

NC VSSBB

0.047uF

4.8970MHz

Data

Output

MICRF002

4.7uF

+5V

12nH

12pF

68nH

1/4 Wave Monopole

315MHz 800bps On-Off Keyed Receiver

Features

• 300MHz to 440MHz frequency range

• Data-rate up to 10kbps (fixed-mode)

• Low Power Consumption

• 2.2mA fully operational (315MHz)

• 0.9µA in shutdown

• 220µA in polled operation (10:1 duty-cycle)

• Wake-up output flag to enable decoders and micropro-

cessors

• Very low RF reradiation at the antenna

• Highly integrated with extremely low external part count

Applications

• Automotive Remote Keyless Entry (RKE)

• Remote controls

• Remote fan and light control

• Garage door and gate openers

Micrel, Inc. • 1849 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 944-0970 • http://www.micrel.com

QwikRadio is a trademark of Micrel, Inc. The QwikRadio ICs were developed under a partnership agreement with AIT of Orlando, Florida.

General Description

The MICRF002 is a single chip ASK/OOK (ON-OFF Keyed)

RF receiver IC. This device is a true “antenna-in to data-out”

monolithic device. All RF and IF tuning is accomplished

automatically within the IC which eliminates manual tuning

and reduces production costs. The result is a highly reliable

yet low cost solution.

The MICRF002 is a fully featured part in 16-pin packaging,

the MICRF022 is the same part packaged in 8-pin packaging

with a reduced feature set (see “Ordering Information” for

more information).

The MICRF002 is an enhanced version of the MICRF001

and MICRF011. The MICRF002 provides two additional

functions over the MICRF001/011, (1) a Shutdown pin, which

may be used to turn the device off for duty-cycled operation,

and (2) a “Wake-up” output, which provides an output flag

indicating when an RF signal is present. These features make

the MICRF002 ideal for low and ultra-low power applications,

such as RKE and remote controls.

All IF filtering and post-detection (demodulator) data filtering

is provided within the MICRF002, so no external filters are

necessary. One of four demodulator filter bandwidths may be

selected externally by the user.

The MICRF002 offer two modes of operation; fixed-mode

(FIX) and sweep-mode (SWP). In fixed mode the MICRF002

functions as a conventional superhet receiver. In sweep

mode the MICRF002 employs a patented sweeping function

to sweep a wider RF spectrum. Fixed-mode provides better

selectivity and sensitivity performance and sweep mode

enables the MICRF002 to be used with low cost, imprecise

transmitters.

QwikRadio™

MICRF002/RF022 Micrel

MICRF002/RF022 2 March 2003

8-Pin Options

The standard 16-pin package allows complete control of all

configurable features. Some reduced function 8-pin versions

are also available, see “Ordering Information” above.

For high-volume applications additional customized 8-pin

devices can be produced. SWEN, SEL0 and SEL1 pins are

internally bonded to reduce the pin count. pin 6 may be

configured as either SHUT or WAKEB.

Pin Configuration

SEL0

SEL0 SWEN

VSSRF REFOSC

VSSRF SEL1

ANT CAGC

VDDRF WAKEB

VDDBB SHUT

CTH DO

NC VSSBB

MICRF002Bx

116

215

314

413

512

611

710

VSSRF REFOSC

ANT CAGC

VDDRF SHUT/WAKEB

CTH DO

MICRF022Bx-xxxx

Standard 16-Pin or 8-Pin SOP (M) Packages

Ordering Information

Demodulator WAKEB

Part Number Bandwidth Operating Mode Shutdown Output Flag Package

MICRF002BM User Programable Fixed or Sweep Yes Yes 16-Pin SOP

MICRF022BM-SW48 5000Hz Sweep No Yes 8-Pin SOP

MICRF022BM-FS12 1250Hz Fixed Yes No 8-Pin SOP

MICRF022BM-FS24 2500Hz Fixed Yes No 8-Pin SOP

MICRF022BM-FS48 5000Hz Fixed Yes No 8-Pin SOP

0LES1LES htdiwdnaBrotaludomeD

edoMpeewSedoMDEXIF

11 zH0005zH00001

01 zH0052zH0005

10 zH0521zH0052

00 zH526zH0521

Table 1. Nominal Demodulator Filter Bandwidth vs.

SEL0, SEL1 and Operating Mode

March 2003 3 MICRF002/RF022

MICRF002/RF022 Micrel

Pin Description

Pin Number Pin Number Pin Name Pin Function

16-Pin Pkg. 8-Pin Pkg.

1 SEL0 Bandwidth Selection Bit 0 (Digital Input): Used in conjunction with SEL1 to

set the desired demodulator filter bandwidth. See Table 1. Internally pulled-

up to VDDRF

2, 3 1 VSSRF RF Power Supply: Ground return to the RF section power supply.

4 2 ANT Antenna (Analog Input): For optimal performance the ANT pin should be

impedance matched to the antenna. See “Applications Information” for

information on input impedance and matching techniques

5 3 VDDRF RF Power Supply: Positive supply input for the RF section of the IC

6 VDDBB Base-Band Power Supply: Positive supply input for the baseband section

(digital section) of the IC

7 4 CTH Data Slicing Threshold Capacitor (Analog I/O): Capacitor connected to this

pin extracts the dc average value from the demodulated waveform which

becomes the reference for the internal data slicing comparator

8 NC Not internally connected

9 VSSBB Base-Band Power Supply: Ground return to the baseband section power

supply

10 5 DO Data Output (Digital Output)

11 6 SHUT Shutdown (Digital Input): Shutdown-mode logic-level control input. Pull low

to enable the receiver. Internally pulled-up to VDDRF

12 WAKEB Wakeup (Digital Output): Active-low output that indicates detection of an

incoming RF signal

13 7 CAGC Automatic Gain Control (Analog I/O): Connect an external capacitor to set

the attack/decay rate of the on-chip automatic gain control

14 SEL1 Bandwidth Selection Bit 1 (Digital Input): Used in conjunction with SEL0 to

set the desired demodulator filter bandwidth. See Table 1. Internally pulled-

up to VDDRF

15 8 REFOSC Reference Oscillator: Timing reference, sets the RF receive frequency.

16 SWEN Sweep-Mode Enable (Digital Input): Sweep- or Fixed-mode operation

control input. SWEN high= sweep mode; SWEN low = conventional

superheterodyne receiver. Internally pulled-up to VDDRF

MICRF002/RF022 Micrel

MICRF002/RF022 4 March 2003

Electrical Characteristics

VDDRF = VDDBB = VDD where +4.75V ≤ VDD ≤ 5.5V, VSS = 0V; CAGC = 4.7µF, CTH = 100nF; SEL0 = SEL1 = VSS; fixed mode ( SWEN

= VSS); fREFOSC = 4.8970MHz (equivalent to fRF = 315MHz); data-rate = 1kbps (Manchester encoded). TA = 25°C, bold values indicate

–40°C ≤ TA ≤ +85°C; current flow into device pins is positive; unless noted.

Symbol Parameter Condition Min Typ Max Units

IOP Operating Current continuous operation, fRF = 315MHz 2.2 3.2 mA

polled with 10:1 duty cycle, fRF = 315MHz 220 µA

continuous operation, fRF = 433.92MHz 3.5 mA

polled with 10:1 duty cycle, fRF = 433.92MHz 350 µA

ISTBY Standby Current VSHUT = VDD 0.9 µA

RF Section, IF Section

Receiver Sensitivity (Note 4) fRF = 315MHz –97 dBm

fRF = 433.92MHz –95 dBm

fIF IF Center Frequency Note 6 0.86 MHz

fBW IF Bandwidth Note 6 0.43 MHz

Maximum Receiver Input RSC = 50Ω–20 dBm

Spurious Reverse Isolation ANT pin, RSC = 50Ω, Note 5 30 µVrms

AGC Attack to Decay Ratio tATTACK ÷ tDECAY 0.1

AGC Leakage Current TA = +85°C±100 nA

Reference Oscillator

ZREFOSC Reference Oscillator Note 8 290 kΩ

Input Impedance

Reference Oscillator Source 5.2 uA

Current

Demodulator

ZCTH CTH Source Impedance Note 7 145 kΩ

IZCTH(leak) CTH Leakage Current TA = +85°C±100 nA

Demodulator Filter Bandwidth VSEL0 = VDD. VSEL1 = VDD 4000 Hz

Sweep Mode VSEL0 = VSS. VSEL1 = VDD 2000 Hz

(SWEN = VDD or OPEN) VSEL0 = VDD. VSEL1 = VSS 1000 Hz

Note 6 VSEL0 = VSS. VSEL1 = VSS 500 Hz

Demodulator Filter Bandwidth VSEL0 = VDD. VSEL1 = VDD 8000 Hz

Fixed Mode VSEL0 = VSS. VSEL1 = VDD 4000 Hz

(SWEN = VSS VSEL0 = VDD. VSEL1 = VSS 2000 Hz

Note 6 VSEL0 = VSS. VSEL1 = VSS 1000 Hz

Absolute Maximum Ratings (Note 1)

Supply Voltage (VDDRF, VDDBB) .................................... +7V

Input/Output Voltage (VI/O) ................. VSS–0.3 to VDD+0.3

Junction Temperature (TJ) ...................................... +150°C

Storage Temperature Range (TS) ............ –65°C to +150°C

Lead Temperature (soldering, 10 sec.) ................... +260°C

ESD Rating, Note 3

Operating Ratings (Note 2)

Supply Voltage (VDDRF, VDDBB) ................ +4.75V to +5.5V

RF Frequency Range ............................. 300MHz to 440Hz

Data Duty-Cycle ............................................... 20% to 80%

Reference Oscillator Input Range ............ 0.1VPP to 1.5VPP

Ambient Temperature (TA) ......................... –40°C to +85°C

March 2003 5 MICRF002/RF022

MICRF002/RF022 Micrel

Symbol Parameter Condition Min Typ Max Units

Digital/Control Section

VIN(high) Input-High Voltage SEL0, SEL1, SWEN 0.8 VDD

VIN(low) Input-Low Voltage SEL0, SEL1, SWEN 0.2 VDD

IOUT Output Current DO, WAKEB pins, push-pull 10 µA

VOUT(high) Output High Voltage DO, WAKEB pins, IOUT = –1µA0.9 VDD

VOUT(low) Output Low Voltage DO, WAKEB pins, IOUT = +1µA0.1 VDD

tR, tFOutput Rise and Fall Times DO, WAKEB pins, CLOAD = 15pF 10 µs

Note 1. Exceeding the absolute maximum rating may damage the device.

Note 2. The device is not guaranteed to function outside its operating rating.

Note 3. Devices are ESD sensitive, use appropriate ESD precautions. Meets class 1 ESD test requirements, (human body model HBM), in accor-

dance with MIL-STD-883C, method 3015. Do not operate or store near strong electrostatic fields.

Note 4: Sensitivity is defined as the average signal level measured at the input necessary to achieve 10-2 BER (bit error rate). The RF input is

assumed to be matched to 50Ω.

Note 5: Spurious reverse isolation represents the spurious components which appear on the RF input pin (ANT) measured into 50Ω with an input RF

matching network.

Note 6: Parameter scales linearly with reference oscillator frequency fT. For any reference oscillator frequency other than 4.8970MHz, compute

new parameter value as the ratio:

f MHz

4.8970MHz (parameter value at 4.8970MHz)

REFOSC

Note 7: Parameter scales inversely with reference oscillator frequency fT. For any reference oscillator frequency other than 4.8970MHz, compute

new parameter value as the ratio:

Note 8: Series resistance of the resonator (ceramic resonator or crystal) should be minimized to the extent possible. In cases where the resonator

series resistance is too great, the oscillator may oscillate at a diminished peak-to-peak level, or may fail to oscillate entirely. Micrel recom-

mends that series resistances for ceramic resonators and crystals not exceed 50Ohms and 100Ohms respectively. Refer to Application Hint

35 for crystal recommendations.

4.8970MHz

f MHz (parameter value at 4.8970MHz)

REFOSC

MICRF002/RF022 Micrel

MICRF002/RF022 6 March 2003

Typical Characteristics

1.5

3.0

4.5

6.0

250 300 350 400 450 500

CURRENT (mA)

FREQUENCY (MHz)

Supply Current

vs. Frequency

= 25°C

= 5V

Sweep Mode,

Continuous Operation

1.5

2.0

2.5

3.0

3.5

-40 -20 0 20 40 60 80 100

CURRENT (mA)

TEMPERATURE (°C)

Supply Current

vs. Temperature

f = 315MHz

= 5V

Sweep Mode,

Continuous Operation

March 2003 7 MICRF002/RF022

MICRF002/RF022 Micrel

Applications Information and Functional

Description

Refer to figure 1 “MICRF002 Block Diagram”. Identified in the

block diagram are the four sections of the IC: UHF

Downconverter, OOK Demodulator, Reference and Control,

and Wakeup. Also shown in the figure are two capacitors

(CTH, CAGC) and one timing component, usually a crystal or

ceramic resonator. With the exception of a supply decoupling

capacitor, and antenna impedance matching network, these

are the only external components needed by the MICRF002

to assemble a complete UHF receiver.

For optimal performance is highly recommended that the

MICRF002 is impedance matched to the antenna, the match-

ing network will add an additional two or three components.

Four control inputs are shown in the block diagram: SEL0,

SEL1, SWEN, and SHUT. Using these logic inputs, the user

can control the operating mode and selectable features of the

IC. These inputs are CMOS compatible, and are internally

pulled-up. IF Bandpass Filter Roll-off response of the IF Filter

is 5th order, while the demodulator data filter exhibits a 2nd

order response.

Design Steps

The following steps are the basic design steps for using the

MICRF002 receiver:

1). Select the operating mode (sweep or fixed)

2). Select the reference oscillator

3). Select the CTH capacitor

4). Select the CAGC capacitor

5). Select the demodulator filter bandwidth

Functional Diagram

Peak

Detector

AGC

Control

2nd Order

Programmable

Low-Pass Filter

5th Order

Band-Pass Filter

Programmable

Synthesizer

Control

Logic

Resettable

Counter

Reference

Oscillator

Cystal

Ceramic

Resonator

CAGC

ANT

SEL0

VDD

VSS

SEL1

SWEN

REFOSC

430kHz

Switched-

Capacitor

Resistor

WAKEB

CTH

MICRF002

Amp

Amp Compa-

rator

WakeupReference and Control

UHF Downconverter OOK Demodulator

SHUT

AGC

Figure 1. MICRF002 Block Diagram

Step 1: Selecting The Operating Mode

Fixed-Mode Operation

For applications where the transmit frequency is accurately

set (that is, applications where a SAW or crystal-based

transmitter is used) the MICRF002 may be configured as a

standard superheterodyne receiver (fixed mode). In fixed-

mode operation the RF bandwidth is narrower making the

receiver less susceptible to interfering signals. Fixed mode is

selected by connecting SWEN to ground.

Sweep-Mode Operation

When used in conjunction with low-cost L-C transmitters the

MICRF002 should be configured in sweep-mode. In sweep-

mode, while the topology is still superheterodyne, the LO

(local oscillator) is swept over a range of frequencies at rates

greater than the data rate. This technique effectively in-

creases the RF bandwidth of the MICRF002, allowing the

device to operate in applications where significant transmit-

ter-receiver frequency misalignment may exist. The transmit

frequency may vary up to ±0.5% over initial tolerance, aging,

and temperature. In sweep-mode a band approximately

1.5% around the nominal transmit frequency is captured. The

transmitter may drift up to ±0.5% without the need to retune

the receiver and without impacting system performance.

The swept-LO technique does not affect the IF bandwidth,

therefore noise performance is not degraded relative to fixed

mode. The IF bandwidth is 430kHz whether the device is

operating in fixed or sweep-mode.

Due to limitations imposed by the LO sweeping process, the

upper limit on data rate in sweep mode is approximately

5.0kbps.

Similar performance is not currently available with crystal-

based superheterodyne receivers which can operate only

with SAW- or crystal-based transmitters.

MICRF002/RF022 Micrel

MICRF002/RF022 8 March 2003

In sweep-mode, a range reduction will occur in installations

where there is a strong interferer in the swept RF band. This

is because the process indiscriminately includes all signals

within the sweep range. An MICRF002 may be used in place

of a superregenerative receiver in most applications.

Step 2: Selecting The Reference

Oscillator

All timing and tuning operations on the MICRF002 are de-

rived from the internal Colpitts reference oscillator. Timing

and tuning is controlled through the REFOSC pin in one of

three ways:

1. Connect a ceramic resonator

2. Connect a crystal

3. Drive this pin with an external timing signal

The specific reference frequency required is related to the

system transmit frequency and to the operating mode of the

receiver as set by the SWEN pin.

Crystal or Ceramic Resonator Selection

Do not use resonators with integral capacitors since capaci-

tors are included in the IC, also care should be taken to

ensure low ESR capacitors are selected. Application Hint 34

and Application Hint 35 provide additional information and

recommended sources for crystals and resonators.

If operating in fixed-mode, a crystal is recommended. In

sweep-mode either a crystal or ceramic resonator may be

used. When a crystal of ceramic resonator is used the

minimum voltage is 300mVPP. If using an externally applied

signal it should be AC-coupled and limited to the operating

range of 0.1VPP to 1.5VPP.

Selecting Reference Oscillator Frequency fT

(Fixed Mode)

As with any superheterodyne receiver, the mixing between

the internal LO (local oscillator) frequency fLO and the incom-

ing transmit frequency fTX ideally must equal the IF center

frequency. Equation 1 may be used to compute the appropri-

ate fLO for a given fTX:

(1)

f f 0.86 f

315

LO TX

=±







Frequencies fTX and fLO are in MHz. Note that two values of

fLO exist for any given fTX, distinguished as “high-side mixing”

and “low-side mixing.” High-side mixing results in an image

frequency above the frequency of interest and low-side

mixing results in a frequency below.

After choosing one of the two acceptable values of fLO, use

Equation 2 to compute the reference oscillator frequency fT:

(2)

64.5

TLO

Frequency fT is in MHz. Connect a crystal of frequency fT to

REFOSC on the MICRF002. Four-decimal-place accuracy

on the frequency is generally adequate. The following table

identifies fT for some common transmit frequencies when the

MICRF002 is operated in fixed mode.

timsnarT

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zHM513zHM0798.4

zHM093zHM0360.6

zHM814zHM3894.6

zHM29.334zHM8547.6

Table 2. Fixed Mode Recommended Reference

Oscillator Values For Typical Transmit Frequencies

(high-side mixing)

Selecting REFOSC Frequency fT

(Sweep Mode)

Selection of the reference oscillator frequency fT in sweep

mode is much simpler than in fixed mode due to the LO

sweeping process. Also, accuracy requirements of the fre-

quency reference component are significantly relaxed.

In sweep mode, fT is given by Equation 3:

(3)

64.25

TLO

In SWEEP mode a reference oscillator with frequency accu-

rate to two-decimal-places is generally adequate. A crystal

may be used and may be necessary in some cases if the

transmit frequency is particularly imprecise.

timsnarT

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rotallicsOecnerefeR

ycneuqerF

zHM513zHM88.4

zHM093zHM50.6

zHM814zHM84.6

zHM29.334zHM37.6

Table 3. Recommended Reference Oscillator Values

For Typical Transmit Frequencies (sweep-mode)

March 2003 9 MICRF002/RF022

MICRF002/RF022 Micrel

Step 3: Selecting The CTH Capacitor

Extraction of the dc value of the demodulated signal for

purposes of logic-level data slicing is accomplished using the

external threshold capacitor CTH and the on-chip switched-

capacitor “resistor” RSC, shown in the block diagram.

Slicing level time constant values vary somewhat with de-

coder type, data pattern, and data rate, but typically values

range from 5ms to 50ms. Optimization of the value of CTH is

required to maximize range.

Selecting Capacitor CTH

The first step in the process is selection of a data-slicing-level

time constant. This selection is strongly dependent on sys-

tem issues including system decode response time and data

code structure (that is, existence of data preamble, etc.). This

issue is covered in more detail in Application Note 22.

The effective resistance of RSC is listed in the electrical

characteristics table as 145kΩ at 315MHz, this value scales

linearly with frequency. Source impedance of the CTH pin at

other frequencies is given by equation (4), where fT is in MHz:

(4)

R 145k 4.8970

=Ω

τ of 5x the bit-rate is recommended. Assuming that a slicing

level time constant τ has been established, capacitor CTH

may be computed using equation

(5)

=τ

A standard ±20% X7R ceramic capacitor is generally suffi-

cient. Refer to Application Hint 42 for CTH and CAGC selection

examples.

Step 4: Selecting The CAGC Capacitor

The signal path has AGC (automatic gain control) to increase

input dynamic range. The attack time constant of the AGC is

set externally by the value of the CAGC capacitor connected

to the CAGC pin of the device. To maximize system range, it

is important to keep the AGC control voltage ripple low,

preferably under 10mVpp once the control voltage has at-

tained its quiescent value. For this reason capacitor values of

at least 0.47µF are recommended.

The AGC control voltage is carefully managed on-chip to

allow duty-cycle operation of the MICRF002. When the

device is placed into shutdown mode (SHUT pin pulled high),

the AGC capacitor floats to retain the voltage. When opera-

tion is resumed, only the voltage droop due to capacitor

leakage must be replenished. A relatively low-leakage ca-

pacitor is recommended when the devices are used in duty-

cycled operation.

To further enhance duty-cycled operation, the AGC push and

pull currents are boosted for approximately 10ms immedi-

ately after the device is taken out of shutdown. This compen-

sates for AGC capacitor voltage droop and reduces the time

to restore the correct AGC voltage. The current is boosted by

a factor of 45.

Selecting CAGC Capacitor in Continuous Mode

A CAGC capacitor in the range of 0.47µF to 4.7µF is typically

recommended. The value of the CAGC should be selected to

minimize the ripple on the AGC control voltage by using a

sufficiently large capacitor. However if the capacitor is too

large the AGC may react too slowly to incoming signals. AGC

settling time from a completely discharged (zero-volt) state is

given approximately by Equation 6:

(6)

∆t 1.333C 0.44

AGC

=−

where:

CAGC is in µF, and ∆t is in seconds.

Selecting CAGC Capacitor in Duty-Cycle Mode

Voltage droop across the CAGC capacitor during shutdown

should be replenished as quickly as possible after the IC is

enabled. As mentioned above, the MICRF002 boosts the

push-pull current by a factor of 45 immediately after start-up.

This fixed time period is based on the reference oscillator

frequency fT. The time is 10.9ms for fT = 6.00MHz, and varies

inversely with fT. The value of CAGC capacitor and the

duration of the shutdown time period should be selected such

that the droop can be replenished within this 10ms period.

Polarity of the droop is unknown, meaning the AGC voltage

could droop up or down. Worst-case from a recovery stand-

point is downward droop, since the AGC pull-up current is

1/10th magnitude of the pulldown current. The downward

droop is replenished according to the Equation 7:

(7)

AGC

=∆

∆

where:

I = AGC pullup current for the initial 10ms (67.5µA)

CAGC = AGC capacitor value

∆t = droop recovery time

∆V = droop voltage

For example, if user desires ∆t = 10ms and chooses a 4.7µF

CAGC, then the allowable droop is about 144mV. Using the

same equation with 200nA worst case pin leakage and

assuming 1µA of capacitor leakage in the same direction, the

maximum allowable ∆t (shutdown time) is about 0.56s for

droop recovery in 10ms.

The ratio of decay-to-attack time-constant is fixed at 10:1

(that is, the attack time constant is 1/10th of the decay time

constant). Generally the design value of 10:1 is adequate for

the vast majority of applications. If adjustment is required the

constant may be varied by adding a resistor in parallel with the

CAGC capacitor. The value of the resistor must be determined

on a case by case basis.

Step 5: Selecting The Demod Filter

Bandwidth

The inputs SEL0 and SEL1 control the demodulator filter

bandwidth in four binary steps (625Hz to 5000Hz in sweep,

1250Hz to 10000Hz in fixed mode), see Table 1. Bandwidth

must be selected according to the application. The demodu-

lator bandwidth should be set according to equation 8.

MICRF002/RF022 Micrel

MICRF002/RF022 10 March 2003

(8) Demoulator bandwidth = 0.65 / Shortest pulse-width

It should be noted that the values indicated in table 1 are

nominal values. The filter bandwidth scales linearly with

frequency so the exact value will depend on the operating

frequency. Refer to the “Electrical Characteristics” for the

exact filter bandwidthat a chosen frequency.

0LES1LES htdiwdnaBrotaludomeD

edoMpeewSedoMDEXIF

11 zH0005zH00001

01 zH0052zH0005

10 zH0521zH0052

00 zH526zH0521

Table 1. Nominal Demodulator Filter Bandwidth vs.

SEL0, SEL1 and Operating Mode

March 2003 11 MICRF002/RF022

MICRF002/RF022 Micrel

Additional Applications Information

In addition to the basic operation of the MICRF002 the

following enhancements can be made. In particilar it is

strongly recommended that the antenna impedance is

matched to the input of the IC.

Antenna Impedance Matching

As shown in table 4 the antenna pin input impedance is

frequency dependant.

The ANT pin can be matched to 50 Ohms with an L-type

circuit. That is, a shunt inductor from the RF input to ground

and another in series from the RF input to the antenna pin.

Inductor values may be different from table depending on

PCB material, PCB thickness, ground configuration, and how

long the traces are in the layout. Values shown were charac-

terized for a 0.031 thickness, FR4 board, solid ground plane

on bottom layer, and very short traces. MuRata and Coilcraft

wire wound 0603 or 0805 surface mount inductors were

tested, however any wire wound inductor with high SRF (self

resonance frequency) should do the job.

Shutdown Function

Duty-cycled operation of the MICRF002 (often referred to as

polling) is achieved by turning the MICRF002 on and off via

the SHUT pin. The shutdown function is controlled by a logic

state applied to the SHUT pin. When VSHUT is high, the

device goes into low-power standby mode. This pin is pulled

high internally, it must be externally pulled low to enable the

receiver.

ycneuqerF

)zHM(

)(

11Z 11SL

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)Hn(L

SEIRES

)Hn(

003661j–21925.0j–308.05127

503561j–21035.0j–008.05127

013361j–21635.0j–697.05127

513261j–31635.0j–197.05127

023061j–21345.0j–987.05186

523751j–21055.0j–287.02186

033551j-21655.0j–877.02186

533251j–21465.0j–077.02186

043051j-11275.0j–767.05165

543841j–11875.0j–267.05165

053541j–11685.0j–357.02165

553341j–11295.0j–847.02165

063141j–11795.0j–247.00165

563931j–11306.0j–537.00165

073731–01216.0j–237.02174

573531j–01916.0j–527.02174

083331j–01526.0j–817.00174

583131j–01136.0j–117.00174

093031j–01436.0j–707.00134

593821j–01146.0j–007.00134

004621j–01746.0j–296.00134

504421j–01356.0j–486.00193

014221j–01066.0j–576.00193

514021j–01766.0j–766.00193

024811j–01376.0j–856.00163

524711j–01776.0j–356.00163

034511j–01486.0j–346.00133

534411j–01786.0j–836.00133

044211j–8407.0j–536.02.833

j100

j25

∞

–j25 –j100

Table 4. Input Impedance Versus Frequency

SHUNT

SERIES

MICRF002/RF022 Micrel

MICRF002/RF022 12 March 2003

Power Supply Bypass Capacitors

VDDBB and VDDRF should be connected together directly at

the IC pins. Supply bypass capacitors are strongly

recommended. They should be connected to VDDBB and

VDDRF and should have the shortest possible lead lengths.

For best performance, connect VSSRF to VSSBB at the

power supply only (that is, keep VSSBB currents from flowing

through the VSSRF return path).

Increasing Selectivity With an Optional BandPass

Filter

For applications located in high ambient noise environments,

a fixed value band-pass network may be connected between

the ANT pin and VSSRF to provide additional receive selec-

tivity and input overload protection. A minimum input configu-

ration is included in figure 7a. it provides some filtering and

necessary overload protection.

Data Squelching

During quiet periods (no signal) the data output (DO pin)

transitions randomly with noise. Most decoders can

descriminate between this random noise and actual data but

for some system it does present a problem. There are three

possible approaches to reducing this output noise:

1). Analog squelch to raise the demodulator threshold

2). Digital squelch to disable the output when data is not

present

3). Output filter to filter the (high frequency) noise glitches on

the data output pin.

The simplest solution is add analog squelch by introducing a

small offset, or squelch voltage, on the CTH pin so that noise

does not trigger the internal comparator. Usually 20mV to

30mV is sufficient, and may be achieved by connecting a

several-megohm resistor from the CTH pin to either VSS or

VDD, depending on the desired offset polarity. Since the

MICRF002 has receiver AGC noise at the internal compara-

tor input is always the same, set by the AGC. The squelch

offset requirement does not change as the local noise strength

changes from installation to installation. Introducing squelch

will reduce sensitivity and also reduce range. Only introduce

an amount of offset sufficient to quiet the output. Typical

squelch resistor values range from 6.8MΩ to 10MΩ.

Wake-Up Function

The WAKEB output signal can be used to reduce system

power consumption by enabling the rest of a system when an

RF signal is present. The WAKEB is an output logic signal

which goes active low when the IC detects a constant RF

carrier. The wake-up function is unavailable when the IC is in

shutdown mode.

To activate the Wake-Up function, a received constant RF

carrier must be present for 128 counts or the internal system

clock. The internal system clock is derived from the reference

oscillator and is 1/256 the reference oscillator frequency. For

example:

fT = 6.4MHz

fS = fT/256 = 25kHz

PS = 1/fS = 0.04ms

128 counts x 0.04ms = 5.12ms

where:

fT = reference oscillator frequency

fS = system clock frequency

PS = system clock period

The Wake-Up counter will reset immediately after a detected

RF carrier drops. The duration of the Wake-Up signal output

is then determined by the required wake up time plus an

additional RF carrier on time interval to create a wake up

pulse output.

WAKEB Output Pulse Time = TWAKE + Additional RF

Carrier On Time

For designers who wish to use the wakeup function while

squelching the output, a positive squelching offset voltage

must be used. This simply requires that the squelch resistor

be connected to a voltage more positive than the quiescent

voltage on the CTH pin so that the data output is low in

absence of a transmission.

I/O Pin Interface Circuitry

Interface circuitry for the various I/O pins of the MICRF002

are diagrammed in Figures 1 through 6. The ESD protection

diodes at all input and output pins are not shown.

CTH Pin

6.9pF

PHI2B PHI1B

PHI1PHI2

CTH

Demodulator

Signal

2.85Vdc

VDDBB

VSSBB VSSBB

Figure 2. CTH Pin

Figure 2 illustrates the CTH-pin interface circuit. The CTH pin

is driven from a P-channel MOSFET source-follower with

approximately 10µA of bias. Transmission gates TG1 and

TG2 isolate the 6.9pF capacitor. Internal control signals

PHI1/PHI2 are related in a manner such that the impedance

across the transmission gates looks like a “resistance” of

approximately 100kΩ. The dc potential at the CTH pin is

approximately 1.6V

March 2003 13 MICRF002/RF022

MICRF002/RF022 Micrel

CAGC Pin

VDDBB

VSSBB

675µA

67.5µA

Compa-

rator

1.5µA

15µA

Timout

CAGC

Figure 3. CAGC Pin

Figure 3 illustrates the CAGC pin interface circuit. The AGC

control voltage is developed as an integrated current into a

capacitor CAGC. The attack current is nominally 15µA, while

the decay current is a 1/10th scaling of this, nominally 1.5µA,

making the attack/decay time constant ratio a fixed 10:1.

Signal gain of the RF/IF strip inside the IC diminishes as the

voltage at CAGC decreases. Modification of the attack/decay

ratio is possible by adding resistance from the CAGC pin to

either VDDBB or VSSBB, as desired.

Both the push and pull current sources are disabled during

shutdown, which maintains the voltage across CAGC, and

improves recovery time in duty-cycled applications. To fur-

ther improve duty-cycle recovery, both push and pull currents

are increased by 45 times for approximately 10ms after

release of the SHUT pin. This allows rapid recovery of any

voltage droop on CAGC while in shutdown.

DO and WAKEB Pins

VDDBB

VSSBB

Compa-

rator

10µA

Figure 4. DO and WAKEB Pins

The output stage for DO (digital output) and WAKEB (wakeup

output) is shown in Figure 4. The output is a 10µA push and

10µA pull switched-current stage. This output stage is ca-

pable of driving CMOS loads. An external buffer-driver is

recommended for driving high-capacitance loads.

REFOSC Pin

250Ω

200k

Active

Bias

REFOSC

30pF

30pF 30µA

VDDBB

VSSBB

Figure 5. REFOSC Pin

The REFOSC input circuit is shown in Figure 5. Input imped-

ance is high (200kΩ). This is a Colpitts oscillator with internal

30pF capacitors. This input is intended to work with standard

ceramic resonators connected from this pin to the VSSBB

pin, although a crystal may be used when greater frequency

accuracy is required. The nominal dc bias voltage on this pin

is 1.4V.

SEL0, SEL1, SWEN, and SHUT Pins

to Internal

Circuits

VDDBB

VSSBB

SEL0,

SEL1,

SWEN

VSSBB

SHUT Q4

Figure 6a. SEL0, SEL1, SWEN

to Internal

Circuits

VDDBB

VSSBB

SHUT

VSSBB

Figure 6b. SHUT

Control input circuitry is shown in Figures 6a and 6b. The

standard input is a logic inverter constructed with minimum

geometry MOSFETs (Q2, Q3). P-channel MOSFET Q1 is a

large channel length device which functions essentially as a

“weak” pullup to VDDBB. Typical pullup current is 5µA,

leading to an impedance to the VDDBB supply of typically

1MΩ.

MICRF002/RF022 Micrel

MICRF002/RF022 14 March 2003

Applications Example

315MHz Receiver/Decoder Application

Figure 7a illustrates a typical application for the MICRF002

UHF Receiver IC. This receiver operates continuously (not

duty cycled) in sweep mode, and features 6-bit address

decoding and two output code bits.

Operation in this example is at 315MHz, and may be custom-

ized by selection of the appropriate frequency reference (Y1),

and adjustment of the antenna length. The value of C4 would

also change if the optional input filter is used. Changes from

the 1kb/s data rate may require a change in the value of R1.

A bill of materials accompanies the schematic.

SEL0SEL0 SWEN

VSSRF REFOSC

VSSRF SEL1

ANT CAGC

VDDRF WAKEB

VDDBB SHUT

CTH DO

NC VSSBB

2.2µF

4.8970MHz

U1 MICRF002

4.7µF

Optional Filter

8.2pF, 16.6nH

pcb foil inductor

1in of 30mil trace

+5V

Supply

Input

4.7µF

A0 VDD

A1 VT

A2 OSC1

A3 OSC2

A4 DIN

A5 D11

A6 D10

A7 D9

U2 HT-12D

VSS D8

68k

Code Bit 0

Code Bit 1

(Analog)

Ground

Baseband

(Digital)

Ground

0.4 monopole

antenna (11.6in)

6-bit

address

Figure 7a. 315MHz, 1kbps On-Off Keyed Receiver/Decoder

metIrebmuNtraPrerutcafunaMnoitpircseD

1U200FRCIMlerciMreviecerFHU

2UD21-THketloHredocedcigol

1RCGM00.6ASCataruMrotanosercimareczHM00.6

1DDIL001XL-FSSxemuLDELder

1R %5W4/1k86

2RyahsiV%5W4/1k1

1CyahsiVroticapacmulatnatdeppidFµ7.4

3CyahsiVroticapacmulatnatdeppidFµ7.4

2CyahsiVroticapacmulatnatdeppidFµ2.2

4CyahsiVroticapaccimarecGOCFp2.8

Figure 7b. Bill of Material

rodneVenohpeleTXAF

yahsiV1626-862)302( —

ketloH6409-498)804(8380-498)804(

xemuL6665-872)008(4098-953)748(

ataruM4756-142)008(0303-634)077(

Figure 7c. Component Vendors

March 2003 15 MICRF002/RF022

MICRF002/RF022 Micrel

PCB Layout Information

The MICRF002 evaluation board was designed and charac-

terized using two sided 0.031 inch thick FR4 material with 1

ounce copper clad. If another type of printed circuit board

material were to be substituted, impedance matching and

characterization data stated in this document may not be

valid. The gerber files for this board can be downloaded from

the Micrel website at www.micrel.com.

PCB Silk Screen

PCB Component Side Layout

PCB Solder Side Layout

10k

C3(CTH)

0.047µF

0.1µF

4.7µF

C4(CAGC)

4.7µF

6.7458MHz

MICRF002

REF.OSC.

GND

SHUT

GND

JP2

(Not Placed)

WAKEB

SHUT

VSSBB

VDDRF

VDDBB

CTH

N/C

JP3

JP1

+5V

GND

RF INPUT

Z3 Z4

Squelch

Resistor

(Not Placed)

SWEN

REFOSC

SEL1

CAGC

SEL0

VSSRF

ANT

MICRF002/RF022 Micrel

MICRF002/RF022 16 March 2003

Package Information

45°

0°–8°

0.244 (6.20)

0.228 (5.79)

0.394 (10.00)

0.386 (9.80) SEATING

PLANE

0.020 (0.51)

REF 0.020 (0.51)

0.013 (0.33)

0.157 (3.99)

0.150 (3.81)

0.050 (1.27)

0.016 (0.40)

0.0648 (1.646)

0.0434 (1.102)

0.050 (1.27)

BSC

PIN 1

DIMENSIONS:

INCHES (MM)

0.0098 (0.249)

0.0040 (0.102)

16-Pin SOP (M)

45°

0°–8°

0.244 (6.20)

0.228 (5.79)

0.197 (5.0)

0.189 (4.8) SEATING

PLANE

0.026 (0.65)

MAX)

0.010 (0.25)

0.007 (0.18)

0.064 (1.63)

0.045 (1.14)

0.0098 (0.249)

0.0040 (0.102)

0.020 (0.51)

0.013 (0.33)

0.157 (3.99)

0.150 (3.81)

0.050 (1.27)

TYP

PIN 1

DIMENSIONS:

INCHES (MM)

0.050 (1.27)

0.016 (0.40)

8-Pin SOP (M)

MICREL, INC. 1849 FORTUNE DRIVE SAN JOSE, CA 95131 USA

TEL + 1 (408) 944-0800 FAX + 1 (408) 944-0970 WEB http://www.micrel.com

The information furnished by Micrel in this datasheet 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

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