MICRF022BM-SW48中文资料

Typical Application

Data

315MHz 800bps On-Off Keyed Receiver

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

Micrel, Inc. 1849 Fortune Drive San Jose, CA 95131 USA tel + 1 (408) 944-0800 fax + 1 (408) 944-0970

March 20031MICRF002/RF022

Ordering Information

Part NumberMICRF002BMMICRF022BM-SW48MICRF022BM-FS12MICRF022BM-FS24MICRF022BM-FS48

Demodulator

BandwidthUser Programable

5000Hz1250Hz2500Hz5000Hz

Operating ModeFixed or Sweep

SweepFixedFixedFixed

Shutdown

YesNoYesYesYes

WAKEBOutput Flag

YesYesNoNoNo

Package16-Pin SOP8-Pin SOP8-Pin SOP8-Pin SOP8-Pin SOP

Pin Configuration

SEL0VSSRFVSSRFANTVDDRFVDDBBCTHNCSWENREFOSCSEL1CAGC

WAKEBSHUTDOVSSBB

REFOSCCAGCSHUT/WAKEBDO

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

8-Pin Options

The standard 16-pin package allows complete control of allconfigurable features. Some reduced function 8-pin versionsare also available, see “Ordering Information” above.

For high-volume applications additional customized 8-pindevices can be produced. SWEN, SEL0 and SEL1 pins areinternally bonded to reduce the pin count. pin 6 may beconfigured as either SHUT or WAKEB.

SEL01010

SEL11100

DemodulatorBandwidthSweepMode5000Hz2500Hz1250Hz625Hz

FIXEDMode10000Hz5000Hz2500Hz1250Hz

Table 1. Nominal Demodulator Filter Bandwidth vs.

SEL0, SEL1 and Operating Mode

MICRF002/RF0222March 2003

Pin Description

Pin Number

16-Pin Pkg.

1

Pin Number8-Pin Pkg.

Pin NameSEL0

Pin Function

Bandwidth Selection Bit 0 (Digital Input): Used in conjunction with SEL1 toset the desired demodulator filter bandwidth. See Table 1. Internally pulled-up to VDDRF

RF Power Supply: Ground return to the RF section power supply.Antenna (Analog Input): For optimal performance the ANT pin should beimpedance matched to the antenna. See “Applications Information” forinformation on input impedance and matching techniques

RF Power Supply: Positive supply input for the RF section of the ICBase-Band Power Supply: Positive supply input for the baseband section(digital section) of the IC

Data Slicing Threshold Capacitor (Analog I/O): Capacitor connected to thispin extracts the dc average value from the demodulated waveform whichbecomes the reference for the internal data slicing comparatorNot internally connected

Base-Band Power Supply: Ground return to the baseband section powersupply

Data Output (Digital Output)

Shutdown (Digital Input): Shutdown-mode logic-level control input. Pull lowto enable the receiver. Internally pulled-up to VDDRF

Wakeup (Digital Output): Active-low output that indicates detection of anincoming RF signal

Automatic Gain Control (Analog I/O): Connect an external capacitor to setthe attack/decay rate of the on-chip automatic gain control

Bandwidth Selection Bit 1 (Digital Input): Used in conjunction with SEL0 toset the desired demodulator filter bandwidth. See Table 1. Internally pulled-up to VDDRF

Reference Oscillator: Timing reference, sets the RF receive frequency.Sweep-Mode Enable (Digital Input): Sweep- or Fixed-mode operationcontrol input. SWEN high= sweep mode; SWEN low = conventionalsuperheterodyne receiver. Internally pulled-up to VDDRF

2, 34

12

VSSRFANT

567

3VDDRFVDDBB

4CTH

891011121314

756

NCVSSBBDOSHUTWAKEBCAGCSEL1

1516

8REFOSCSWEN

March 20033MICRF002/RF022

Absolute Maximum Ratings (Note 1)

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

Input/Output Voltage (VI/O).................VSS–0.3 to VDD+0.3Junction Temperature (TJ)......................................+150°CStorage Temperature Range (TS)............–65°C to +150°CLead Temperature (soldering, 10 sec.)...................+260°CESD Rating, Note 3

Operating Ratings (Note 2)

Supply Voltage (VDDRF, VDDBB)................+4.75V to +5.5VRF Frequency Range.............................300MHz to 440HzData Duty-Cycle...............................................20% to 80%Reference Oscillator Input Range............0.1VPP to 1.5VPPAmbient Temperature (TA).........................–40°C to +85°C

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.SymbolIOP

ParameterOperating Current

Condition

continuous operation, fRF = 315MHzpolled with 10:1 duty cycle, fRF = 315MHzcontinuous operation, fRF = 433.92MHzpolled with 10:1 duty cycle, fRF = 433.92MHz

ISTBY

Standby Current

VSHUT = VDDfRF = 315MHzfRF = 433.92MHz

fIFfBW

IF Center FrequencyIF Bandwidth

Maximum Receiver InputSpurious Reverse IsolationAGC Attack to Decay RatioAGC Leakage Current

Note 6Note 6RSC = 50

ANT pin, RSC = 50 , Note 5tATTACK ÷ tDECAYTA = +85°C

RF Section, IF Section

Receiver Sensitivity (Note 4)

–97–950.860.43–20300.1±100

nAdBmdBmMHzMHzdBmµVrms

Min

Typ2.22203.53500.9

Max3.2

UnitsmAµAmAµAµA

Reference OscillatorZREFOSC

Reference OscillatorInput Impedance

Reference Oscillator SourceCurrent

Note 8

2905.2

k uA

DemodulatorZCTHIZCTH(leak)

CTH Source ImpedanceCTH Leakage CurrentDemodulator Filter BandwidthSweep Mode

(SWEN = VDD or OPEN)Note 6

Demodulator Filter BandwidthFixed Mode(SWEN = VSSNote 6

Note 7TA = +85°C

VSEL0 = VDD. VSEL1 = VDDVSEL0 = VSS. VSEL1 = VDDVSEL0 = VDD. VSEL1 = VSSVSEL0 = VSS. VSEL1 = VSSVSEL0 = VDD. VSEL1 = VDDVSEL0 = VSS. VSEL1 = VDDVSEL0 = VDD. VSEL1 = VSSVSEL0 = VSS. VSEL1 = VSS

145±1004000200010005008000400020001000

k nAHzHzHzHzHzHzHzHz

MICRF002/RF0224March 2003

Symbol

Parameter

Condition

Min

Typ

Max

Digital/Control SectionVIN(high)VIN(low)IOUTVOUT(high)VOUT(low)tR, tF

Note 1.Note 2.Note 3.Note 4:Note 5:Note 6:

Units

Input-High VoltageInput-Low VoltageOutput CurrentOutput High VoltageOutput Low VoltageOutput Rise and Fall Times

SEL0, SEL1, SWENSEL0, SEL1, SWENDO, WAKEB pins, push-pullDO, WAKEB pins, IOUT = –1µADO, WAKEB pins, IOUT = +1µADO, WAKEB pins, CLOAD = 15pF

10

0.90.2

10

0.8

VDDVDDµAVDD

0.1

VDDµs

Exceeding the absolute maximum rating may damage the device.The device is not guaranteed to function outside its operating rating.

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.

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 50 .

Spurious reverse isolation represents the spurious components which appear on the RF input pin (ANT) measured into 50 with an input RFmatching network.

Parameter scales linearly with reference oscillator frequency fT. For any reference oscillator frequency other than 4.8970MHz, computenew parameter value as the ratio:

fREFOSCMHz

×(parameter value at 4.8970MHz)

4.8970MHz

Note 7:

T. For any reference oscillator frequency other than 4.8970MHz, computenew parameter value as the ratio:

4.8970MHz

×(parameter value at 4.8970MHz)

fREFOSCMHz

Note 8:

Series resistance of the resonator (ceramic resonator or crystal) should be minimized to the extent possible. In cases where the resonatorseries 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 Hint35 for crystal recommendations.

March 20035MICRF002/RF022

Typical Characteristics

Supply Current

vs. Frequency

CURRENT (mA)

Supply Currentvs. Temperature

CURRENT (mA)

250

300

350

400

450

500

FREQUENCY (MHz)

TEMPERATURE (°C)

MICRF002/RF0226March 2003

Functional Diagram

CTH

Figure 1. MICRF002 Block Diagram

Applications Information and FunctionalDescription

Refer to figure 1 “MICRF002 Block Diagram”. Identified in theblock diagram are the four sections of the IC: UHFDownconverter, OOK Demodulator, Reference and Control,and Wakeup. Also shown in the figure are two capacitors(CTH, CAGC) and one timing component, usually a crystal orceramic resonator. With the exception of a supply decouplingcapacitor, and antenna impedance matching network, theseare the only external components needed by the MICRF002to assemble a complete UHF receiver.

For optimal performance is highly recommended that theMICRF002 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 usercan control the operating mode and selectable features of theIC. These inputs are CMOS compatible, and are internallypulled-up. IF Bandpass Filter Roll-off response of the IF Filteris 5th order, while the demodulator data filter exhibits a 2ndorder response.

Step 1: Selecting The Operating Mode

Fixed-Mode Operation

For applications where the transmit frequency is accuratelyset (that is, applications where a SAW or crystal-basedtransmitter is used) the MICRF002 may be configured as astandard superheterodyne receiver (fixed mode). In fixed-mode operation the RF bandwidth is narrower making thereceiver less susceptible to interfering signals. Fixed mode isselected by connecting SWEN to ground.Sweep-Mode Operation

When used in conjunction with low-cost L-C transmitters theMICRF002 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 ratesgreater than the data rate. This technique effectively in-creases the RF bandwidth of the MICRF002, allowing thedevice to operate in applications where significant transmit-ter-receiver frequency misalignment may exist. The transmitfrequency may vary up to ±0.5% over initial tolerance, aging,and temperature. In sweep-mode a band approximately1.5% around the nominal transmit frequency is captured. Thetransmitter may drift up to ±0.5% without the need to retunethe receiver and without impacting system performance.The swept-LO technique does not affect the IF bandwidth,therefore noise performance is not degraded relative to fixedmode. The IF bandwidth is 430kHz whether the device isoperating in fixed or sweep-mode.

Due to limitations imposed by the LO sweeping process, theupper limit on data rate in sweep mode is approximately5.0kbps.

Similar performance is not currently available with crystal-based superheterodyne receivers which can operate onlywith SAW- or crystal-based transmitters.

Design Steps

The following steps are the basic design steps for using theMICRF002 receiver:

1). Select the operating mode (sweep or fixed)2). Select the reference oscillator3). Select the CTH capacitor4). Select the CAGC capacitor

5). Select the demodulator filter bandwidth

March 20037MICRF002/RF022

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

where there is a strong interferer in the swept RF band. Thisis because the process indiscriminately includes all signalswithin the sweep range. An MICRF002 may be used in placeof a superregenerative receiver in most applications.

Frequency fT is in MHz. Connect a crystal of frequency fT toREFOSC on the MICRF002. Four-decimal-place accuracyon the frequency is generally adequate. The following tableidentifies fT for some common transmit frequencies when theMICRF002 is operated in fixed mode.

TransmitFrequency

fTX315MHz390MHz418MHz433.92MHz

ReferenceOscillator

Frequency

fT

4.8970MHz6.0630MHz6.4983MHz6.7458MHz

Step 2: Selecting The ReferenceOscillator

All timing and tuning operations on the MICRF002 are de-rived from the internal Colpitts reference oscillator. Timingand tuning is controlled through the REFOSC pin in one ofthree ways:

1. Connect a ceramic resonator2. Connect a crystal

3. Drive this pin with an external timing signal

The specific reference frequency required is related to thesystem transmit frequency and to the operating mode of thereceiver as set by the SWEN pin.

Crystal or Ceramic Resonator Selection

If operating in fixed-mode, a crystal is recommended. Insweep-mode either a crystal or ceramic resonator may beused. When a crystal of ceramic resonator is used theminimum voltage is 300mVPP. If using an externally appliedsignal it should be AC-coupled and limited to the operatingrange of 0.1VPP to 1.5VPP.

Selecting Reference Oscillator Frequency fT(Fixed Mode)

As with any superheterodyne receiver, the mixing betweenthe internal LO (local oscillator) frequency fLO and the incom-ing transmit frequency fTX ideally must equal the IF centerfrequency. Equation 1 may be used to compute the appropri-ate fLO for a given fTX:(1)

Table 2.Oscillator Values For Typical Transmit Frequencies

(high-side mixing)Selecting REFOSC Frequency fT(Sweep Mode)

Selection of the reference oscillator frequency fT in sweepmode is much simpler than in fixed mode due to the LOsweeping 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

In SWEEP mode a reference oscillator with frequency accu-rate to two-decimal-places is generally adequate. A crystalmay be used and may be necessary in some cases if thetransmit frequency is particularly imprecise.

TransmitFrequency

fTX315MHz390MHz418MHz433.92MHz

ReferenceOscillator

Frequency

fT

4.88MHz6.05MHz6.48MHz6.73MHz

fT=

fLO

fLO=fTX

f

±0.86TX 315

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 imagefrequency above the frequency of interest and low-sidemixing results in a frequency below.

After choosing one of the two acceptable values of fLO, useEquation 2 to compute the reference oscillator frequency fT:(2)

ffT=64.5

Table 3.Recommended Reference Oscillator ValuesMICRF002/RF0228March 2003

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 theexternal 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 valuesrange from 5ms to 50ms. Optimization of the value of CTH isrequired to maximize range.Selecting Capacitor CTH

The first step in the process is selection of a data-slicing-leveltime constant. This selection is strongly dependent on sys-tem issues including system decode response time and datacode structure (that is, existence of data preamble, etc.). Thisissue is covered in more detail in Application Note 22.

The effective resistance of RSC is listed in the electricalcharacteristics table as 145k at 315MHz, this value scaleslinearly with frequency. Source impedance of the CTH pin atother frequencies is given by equation (4), where fT is in MHz:(4)

Selecting CAGC Capacitor in Continuous Mode

A CAGC capacitor in the range of 0.47µF to 4.7µF is typicallyrecommended. The value of the CAGC should be selected tominimize the ripple on the AGC control voltage by using asufficiently large capacitor. However if the capacitor is toolarge the AGC may react too slowly to incoming signals. AGCsettling time from a completely discharged (zero-volt) state isgiven approximately by Equation 6:(6)

t=1.333CAGC 0.44

RSC=145k

4.8970fT

τ of 5x the bit-rate is recommended. Assuming that a slicinglevel time constant τ has been established, capacitor CTHmay be computed using equation(5)

CTH=

τRSC

where:

CAGC is in µF, and t is in seconds.

Selecting CAGC Capacitor in Duty-Cycle Mode

Voltage droop across the CAGC capacitor during shutdownshould be replenished as quickly as possible after the IC isenabled. As mentioned above, the MICRF002 boosts thepush-pull current by a factor of 45 immediately after start-up.This fixed time period is based on the reference oscillatorfrequency fT. The time is 10.9ms for fT = 6.00MHz, and variesinversely with fT. The value of CAGC capacitor and theduration of the shutdown time period should be selected suchthat the droop can be replenished within this 10ms period.Polarity of the droop is unknown, meaning the AGC voltagecould droop up or down. Worst-case from a recovery stand-point is downward droop, since the AGC pull-up current is1/10th magnitude of the pulldown current. The downwarddroop is replenished according to the Equation 7:(7)

ICAGC

A standard ±20% X7R ceramic capacitor is generally suffi-cient. Refer to Application Hint 42 for CTH and CAGC selectionexamples.

=

V t

Step 4: Selecting The CAGC Capacitor

The signal path has AGC (automatic gain control) to increaseinput dynamic range. The attack time constant of the AGC isset externally by the value of the CAGC capacitor connectedto the CAGC pin of the device. To maximize system range, itis 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 ofat least 0.47µF are recommended.

The AGC control voltage is carefully managed on-chip toallow duty-cycle operation of the MICRF002. When thedevice 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 capacitorleakage 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 andpull 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 timeto restore the correct AGC voltage. The current is boosted bya factor of 45.

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 4.7µFCAGC, then the allowable droop is about 144mV. Using thesame equation with 200nA worst case pin leakage andassuming 1µA of capacitor leakage in the same direction, themaximum allowable t (shutdown time) is about 0.56s fordroop 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 timeconstant). Generally the design value of 10:1 is adequate forthe vast majority of applications. If adjustment is required theconstant may be varied by adding a resistor in parallel with theCAGC capacitor. The value of the resistor must be determinedon a case by case basis.

Step 5: Selecting The Demod FilterBandwidth

The inputs SEL0 and SEL1 control the demodulator filterbandwidth in four binary steps (625Hz to 5000Hz in sweep,1250Hz to 10000Hz in fixed mode), see Table 1. Bandwidthmust be selected according to the application. The demodu-lator bandwidth should be set according to equation 8.9

MICRF002/RF022

March 2003

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

It should be noted that the values indicated in table 1 arenominal values. The filter bandwidth scales linearly withfrequency so the exact value will depend on the operatingfrequency. Refer to the “Electrical Characteristics” for theexact filter bandwidthat a chosen frequency.

SEL01010

SEL11100

DemodulatorBandwidthSweepMode5000Hz2500Hz1250Hz625Hz

FIXEDMode10000Hz5000Hz2500Hz1250Hz

Table 1. Nominal Demodulator Filter Bandwidth vs.

SEL0, SEL1 and Operating Mode

MICRF002/RF02210March 2003

Additional Applications Information

n addition to the basic operation of the MICRF002 the

following enhancements can be made. IAntenna Impedance Matching

As shown in table 4 the antenna pin input impedance isfrequency dependant.

The ANT pin can be matched to 50 Ohms with an L-typecircuit. That is, a shunt inductor from the RF input to groundand another in series from the RF input to the antenna pin.Inductor values may be different from table depending onPCB material, PCB thickness, ground configuration, and howlong the traces are in the layout. Values shown were charac-terized for a 0.031 thickness, FR4 board, solid ground planeon bottom layer, and very short traces. MuRata and Coilcraftwire wound 0603 or 0805 surface mount inductors weretested, however any wire wound inductor with high SRF (selfresonance frequency) should do the job.Shutdown Function

Duty-cycled operation of the MICRF002 (often referred to aspolling) is achieved by turning the MICRF002 on and off viathe SHUT pin. The shutdown function is controlled by a logicstate applied to the SHUT pin. When VSHUT is high, thedevice goes into low-power standby mode. This pin is pulledhigh internally, it must be externally pulled low to enable thereceiver.

Frequency(MHz)

300305310315320325330335340345350355360365370375380385390395400405410

ZIN()Z1112–j16612–j16512–j16313–j16212–j16012–j15712-j15512–j15211-j15011–j14811–j14511–j14311–j14111–j13910–13710–j13510–j13310–j13110–j13010–j12810–j12610–j12410–j12210–j12010–j11810–j11710–j11510–j1148–j112

S110.803–j0.5290.800–j0.5300.796–j0.5360.791–j0.5360.789–j0.5430.782–j0.5500.778–j0.5560.770–j0.5640.767–j0.5720.762–j0.5780.753–j0.5860.748–j0.5920.742–j0.5970.735–j0.6030.732–j0.6120.725–j0.6190.718–j0.6250.711–j0.6310.707–j0.6340.700–j0.6410.692–j0.6470.684–j0.6530.675–j0.6600.667–j0.6670.658–j0.6730.653–j0.6770.643–j0.6840.638–j0.6870.635–j0.704

LS

HUNT(nH)

151515151512121215151212101012121010101010101010101010108.2

LSERIES(nH)

7272727268686868565656565656474747474343433939393636333333

415420

425430435440

j100

Table 4. Input Impedance Versus Frequency

50

∞

–j25j100

March 200311MICRF002/RF022

Power Supply Bypass Capacitors

VDDBB and VDDRF should be connected together directly atthe IC pins. Supply bypass capacitors are stronglyrecommended. They should be connected to VDDBB andVDDRF and should have the shortest possible lead lengths.For best performance, connect VSSRF to VSSBB at thepower supply only (that is, keep VSSBB currents from flowingthrough the VSSRF return path).

Increasing Selectivity With an Optional BandPassFilter

For applications located in high ambient noise environments,a fixed value band-pass network may be connected betweenthe 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 andnecessary overload protection.Data Squelching

During quiet periods (no signal) the data output (DO pin)transitions randomly with noise. Most decoders candescriminate between this random noise and actual data butfor some system it does present a problem. There are threepossible approaches to reducing this output noise:1). Analog squelch to raise the demodulator threshold

2). Digital squelch to disable the output when data is notpresent

3). Output filter to filter the (high frequency) noise glitches onthe data output pin.

The simplest solution is add analog squelch by introducing asmall offset, or squelch voltage, on the CTH pin so that noisedoes not trigger the internal comparator. Usually 20mV to30mV is sufficient, and may be achieved by connecting aseveral-megohm resistor from the CTH pin to either VSS orVDD, depending on the desired offset polarity. Since theMICRF002 has receiver AGC noise at the internal compara-tor input is always the same, set by the AGC. The squelchoffset requirement does not change as the local noise strengthchanges from installation to installation. Introducing squelchwill reduce sensitivity and also reduce range. Only introducean amount of offset sufficient to quiet the output. Typicalsquelch resistor values range from 6.8M to 10M .Wake-Up Function

The WAKEB output signal can be used to reduce systempower consumption by enabling the rest of a system when anRF signal is present. The WAKEB is an output logic signalwhich goes active low when the IC detects a constant RFcarrier. The wake-up function is unavailable when the IC is inshutdown mode.

To activate the Wake-Up function, a received constant RFcarrier must be present for 128 counts or the internal systemclock. The internal system clock is derived from the referenceoscillator and is 1/256 the reference oscillator frequency. Forexample:

fT = 6.4MHz

fS = fT/256 = 25kHzPS = 1/fS = 0.04ms

128 counts x 0.04ms = 5.12msMICRF002/RF022

12

where:

fT = reference oscillator frequencyfS = system clock frequencyPS = system clock period

The Wake-Up counter will reset immediately after a detectedRF carrier drops. The duration of the Wake-Up signal outputis then determined by the required wake up time plus anadditional RF carrier on time interval to create a wake uppulse output.

WAKEB Output Pulse Time = TWAKE + Additional RFCarrier On Time

For designers who wish to use the wakeup function whilesquelching the output, a positive squelching offset voltagemust be used. This simply requires that the squelch resistorbe connected to a voltage more positive than the quiescentvoltage on the CTH pin so that the data output is low inabsence of a transmission.

I/O Pin Interface Circuitry

Interface circuitry for the various I/O pins of the MICRF002are diagrammed in Figures 1 through 6. The ESD protectiondiodes at all input and output pins are not shown.

CTH Pin

Figure 2.CTH Pin

Figure 2 illustrates the CTH-pin interface circuit. The CTH pinis driven from a P-channel MOSFET source-follower withapproximately 10µA of bias. Transmission gates TG1 andTG2 isolate the 6.9pF capacitor. Internal control signalsPHI1/PHI2 are related in a manner such that the impedanceacross the transmission gates looks like a “resistance” ofapproximately 100k . The dc potential at the CTH pin isapproximately 1.6V

March 2003

CAGC Pin

REFOSC Pin

Figure 5.REFOSC Pin

The REFOSC input circuit is shown in Figure 5. Input imped-ance is high (200k ). This is a Colpitts oscillator with internal30pF capacitors. This input is intended to work with standardceramic resonators connected from this pin to the VSSBBpin, although a crystal may be used when greater frequencyaccuracy is required. The nominal dc bias voltage on this pinis 1.4V.

SEL0, SEL1, SWEN, and SHUT Pins

Figure 3.CAGC Pin

Figure 3 illustrates the CAGC pin interface circuit. The AGCcontrol voltage is developed as an integrated current into acapacitor CAGC. The attack current is nominally 15µA, whilethe 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 thevoltage at CAGC decreases. Modification of the attack/decayratio is possible by adding resistance from the CAGC pin toeither VDDBB or VSSBB, as desired.

Both the push and pull current sources are disabled duringshutdown, which maintains the voltage across CAGC, andimproves recovery time in duty-cycled applications. To fur-ther improve duty-cycle recovery, both push and pull currentsare increased by 45 times for approximately 10ms afterrelease of the SHUT pin. This allows rapid recovery of anyvoltage droop on CAGC while in shutdown.

DO and WAKEB Pins

DO

SHUT

SEL0,SEL1,SWEN

to InternalCircuits

Figure 6a.SEL0, SEL1, SWEN

Figure 6b.SHUT

Control input circuitry is shown in Figures 6a and 6b. Thestandard input is a logic inverter constructed with minimumgeometry MOSFETs (Q2, Q3). P-channel MOSFET Q1 is alarge 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 typically1M .

Figure 4.DO and WAKEB Pins

The output stage for DO (digital output) and WAKEB (wakeupoutput) is shown in Figure 4. The output is a 10µA push and10µA pull switched-current stage. This output stage is ca-pable of driving CMOS loads. An external buffer-driver isrecommended for driving high-capacitance loads.

March 200313MICRF002/RF022

Applications Example

315MHz Receiver/Decoder Application

Figure 7a illustrates a typical application for the MICRF002UHF Receiver IC. This receiver operates continuously (notduty cycled) in sweep mode, and features 6-bit addressdecoding 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 wouldalso change if the optional input filter is used. Changes fromthe 1kb/s data rate may require a change in the value of R1.A bill of materials accompanies the schematic.

+5VInput

8.2pF

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

ItemU1U2CR1D1R1R2C1C3C2C4

VishayVishayVishayVishayVishay

PartNumberMICRF002HT-12DCSA6.00MGSSF-LX100LID

Manufacturer

MicrelHoltekMurataLumex

DescriptionUHFreceiverlogicdecoder

6.00MHzceramicresonator

redLED68k1/4W5%1k1/4W5%

4.7µFdippedtantalumcapacitor4.7µFdippedtantalumcapacitor2.2µFdippedtantalumcapacitor8.2pFCOGceramiccapacitor

Figure 7b.Bill of Material

VendorVishayHoltekLumexMurata

Telephone(203)268-6261(408)894-9046(800)278-5666(800)241-6574

FAX—(408)894-0838(847)359-8904(770)436-3030

Figure ponent Vendors

MICRF002/RF02214March 2003

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 boardmaterial were to be substituted, impedance matching andcharacterization data stated in this document may not bevalid. The gerber files for this board can be downloaded fromthe Micrel website at .

PCB Component Side Layout

PCB Silk Screen

PCB Solder Side Layout

.OSC.+5VGND

March 200315MICRF002/RF022

Package Information

16-Pin SOP (M)

8-Pin SOP (M)

MICREL, INC.1849 FORTUNE DRIVESAN JOSE, CA95131USA

TEL + 1 (408) 944-0800 FAX + 1 (408) 944-0970 WEB

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 canreasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical implant intothe 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’suse or sale of Micrel Products for use in life support appliances, devices or systems is at Purchaser’s own risk and Purchaser agrees to fully indemnify

Micrel for any damages resulting from such use or sale.

© 2003 Micrel, Incorporated.

MICRF002/RF02216March 2003

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