MICRF011 QwikRadiotm Receiver/Data Demodulator Preliminary Information General Description The MICRF011, an enhanced version of the MICRF001, is a single chip OOK (ON-OFF Keyed) Receiver IC for remote wireless applications, employing Micrel’s latest QwikRadiotm technology. This device is a true “antenna-in, data-out” monolithic device. All RF and IF tuning is accomplished automatically within the IC, which eliminates manual tuning and reduces production costs. Receiver functions are completely integrated. The result is a highly reliable yet extremely low cost solution for high volume wireless applications. Because the MICRF011 is a true single-chip radio receiver, it is extremely easy to apply, minimizing design and production costs, and improving time to market. The MICRF011 is a functional and pin equivalent upgrade to the MICRF001, providing improved range, lower power consumption, and higher data rate support when in FIXED mode. The MICRF011 provides two fundamental modes of operation, FIXED and SWP. In FIXED mode, the device functions like a conventional superheterodyne receiver, with an (internal) local oscillator fixed at a single frequency based on an external reference crystal or clock. As with any conventional superheterodyne receiver, the transmit frequency must be accurately controlled, generally with a crystal or SAW (Surface Acoustic Wave) resonator. In SWP mode, the MICRF011 sweeps the (internal) local oscillator at rates greater than the baseband data rate. This effectively “broadens” the RF bandwidth of the receiver to a value equivalent to conventional super-regenerative receivers. Thus the MICRF011 can operate with less expensive LC transmitters without additional components or tuning, even though the receiver topology is still superheterodyne. In this mode the reference crystal can be replaced with a less expensive ± 0.5% ceramic resonator. All post-detection (demodulator) data filtering is provided on the MICRF011, so no external filters need to be designed. Any one of four filter bandwidths may be selected externally by the user. Bandwidths range in binary steps, from 0.625kHz to 5kHz (SWP mode) or 1.25kHz to 10kHz (FIXED mode). The user only needs to program the appropriate filter selection based on data rate and code modulation format. Features • • • • • • • • • • • Complete UHF receiver on a monolithic chip Frequency range 300 to 440 MHz Typical range over 200 meters with monopole antenna Data rates to 2.5kbps (SWP), 10kbps (FIXED) Automatic tuning, no manual adjustment No Filters or Inductors required Low Operating Supply Current—2.4 mA at 315MHz Fully pin compatible with MICRF001 Very low RF re-radiation at the antenna Direct CMOS logic interface to standard decoder and microprocessor ICs Extremely low external part count Applications • • • Garage Door/Gate Openers Security Systems Remote Fan/Light Control IMPORTANT: Items in bold type represent changes from the MICRF001 specification. Differences between the MICRF001 and -011 are identified in table 2, together with design considerations for using the -011 in present MICRF001 designs. Typical Operating Circuit 385.5 MHz, 1200 bps OOK RECEIVER Micrel Inc. • 1849 Fortune Drive San Jose, Ca 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 944-0970 • http://www.micrel.com MICRF011 QwikRadio tm Micrel Ordering Information Part Number MICRF011BN MICRF011BM Temperature Range -40°C to +85°C -40°C to +85°C Package 14-Pin DIP 14-Pin SOIC Pin Configuration (DIP and SOIC) Pin Description Pin Number Pin Name 1 2/3 SEL0 VSSRF 4 ANT 5 VDDRF 6 VDDBB 7 CTH 8 9/10 DO VSSBB 11 CAGC 12 13 SEL1 REFOSC 14 SWEN December 1998b Pin Function Programs desired Demodulator Filter Bandwidth. This pin in internally pulled-up to VDD. See Table 1. This pin is the ground return for the RF section of the IC. The bypass capacitor connected from VDDRF to VSSRF should have the shortest possible lead length. For best performance, connect VSSRF to VSSBB at the power supply only (i.e., keep VSSBB currents from flowing through VSSRF return path). This is the receive RF input, internally ac-coupled. Connect this pin to the receive antenna. Input impedance is high (FET gate) with approximately 2pF of shunt (parasitic) capacitance. 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 selectivity and input overload protection. (See “Application Note 22, MICRF001 Theory of Operation”.) This pin is the positive supply input for the RF section of the IC. VDDBB and VDDRF should be connected directly at the IC pins. Connect a low ESL, low ESR decoupling capacitor from this pin to VSSRF, as short as possible. This pin is the positive supply input for the baseband section of the IC. VDDBB and VDDRF should be connected directly at the IC pins. This capacitor extracts the (DC) average value from the demodulated waveform, which becomes the reference for the internal data slicing comparator. Treat this as a low-pass RC filter with source impedance of 118kohms (for REFOSC frequency ft=4.90MHz). Note that variation in source resistance with filter selection no longer exists, as it does for the MICRF001. (See “Application Note 22, MICRF001 Theory of Operation”, section 6.4). A standard ± 20% X7R ceramic capacitor is generally sufficient. Output data pin. CMOS level compatible. This is the ground return for the baseband section of the IC. The bypass and output capacitors connected to VSSBB should have the shortest possible lead lengths. For best performance, connect VSSRF to VSSBB at the power supply only (i.e., keep VSSBB currents from flowing through VSSRF return path). Integrating capacitor for on-chip receive AGC (Automatic Gain Control). The Decay/Attack time-constant (TC) ratio is nominally set as 10:1. Use of 0.47µF or greater is strongly recommended for best range performance. See “Application Note 22, MICRF001 Theory of Operation” for further information. Programs desired Demodulator Filter Bandwidth. This pin in internally pulled-up to VDD. See Table 1. This is the timing reference for on-chip tuning and alignment. Connect either a ceramic resonator or crystal (mode dependent) between this pin and VSSBB, or drive the input with an AC coupled 0.5Vpp input clock. Use ceramic resonators without integral capacitors. Note that if operated in FIXED mode, a crystal must be used; however in SWP mode, one may use either a crystal or ceramic resonator. See “Application Note 22, MICRF001 Theory of Operation” for details on frequency selection and accuracy. This logic pin controls the operating mode of the MICRF011. When SWEN = HIGH, the MICRF011 is in SWP mode. This is the normal (default) mode of the device. When SWEN = LOW, the device operates as a conventional single-conversion superheterodyne receiver. (See “Application Note 22, MICRF001 Theory of Operation” for details.) This pin is internally pulled-up to VDD. 2 MICRF011 MICRF011 QwikRadio SEL0 SEL1 1 0 1 0 tm Micrel Demodulator Bandwidth (Hz) SWP Mode 5000 2500 1250 625 1 1 0 0 FIXED Mode 10000 5000 2500 1250 Table 1 Nominal Demodulator (Baseband) Filter Bandwidth vs. SEL0, SEL1 and Mode No . 1. Design Change Local Oscillator sweep range reduced 2X. Affects SWP mode only. 2. Local Oscillator sweep rate reduced 2X. Affects SWP mode only. 3. IF Center Frequency reduced 2X. Affects both modes SWP and FIXED. IF Bandwidth reduced 2X. Affects both modes SWP and FIXED. FIXED mode Demod Filter cutoff frequencies increased 2X. Affects FIXED mode only. CTH Pin Impedance 118kΩ @ ft=4.90 MHz [see Note 4]. Affects both modes SWP and FIXED. 4. 5. 6. Retrofit Design Action Reconsider Tx/Rx Frequency Alignment Error Budget, per App. Note 22. If alignment tolerances cannot be met, consider: (1) tighten ceramic resonator tolerance, (2) replace ceramic resonator with crystal, or (3) not to upgrade to -011 Impacts SWP mode maximum data rate. If data rate constraint cannot be met, consider (1) reduce system data rate by 2X, or (2) not to upgrade to -011 Factor this change into Tx/Rx Frequency Alignment Error Budget. FIXED mode users of -001 must change crystal frequency. Factor this change into Tx/Rx Frequency Alignment Error Budget. For FIXED mode only, choose next lower filter frequency (via control pins SEL0/1), to maintain same range performance Recompute appropriate value of CTH capacitor, and change value on PCB Table 2 MICRF001/011 Change List and Design Retrofit Guidelines December 1998b 3 MICRF011 MICRF011 QwikRadio tm Micrel ABSOLUTE MAXIMUM RATINGS Operating Ratings Supply Voltage (VDDRF, VDDBB).................................+7V Voltage on any I/O Pin.........................VSS-0.3 to VDD+0.3 Junction Temperature..............................................+150°C Storage Temperature Range.....................-65°C to + 150°C Lead Temperature (soldering, 10 seconds).............+ 260°C Supply Voltage (VDDRF, VDDBB)..................4.75V to 5.5V Ambient Operating Temperature (TA)..........-40°C to +85°C Package Thermal Resistance θJA (14 Pin DIP)........90°C/W Package Thermal Resistance θJA (14 Pin SOIC)...120°C/W This device is ESD sensitive: Meets Class 1ESD test requirements (Human body Model, HBM), in accordance with MIL-STD-883C, Method 3015. Do not operate or store near strong electrostatic fields. Use appropriate ESD precautions. Electrical Characteristics Unless otherwise stated, these specifications apply for Ta=-40°C to 85°C, 4.75<VDD<5.5V. All voltages are with respect to Ground; Positive currents flow into device pins. CAGC = 4.7µF, CTH = .047µF, VDDRF= VDDBB = VDD. REFOSC frequency =4.90MHz. Note: Items in bold represent changes from the MICRF001 specification. Parameter Test Conditions Power Supply Operating Current RF/IF Section Receiver Sensitivity IF Center Frequency IF 3dB Bandwidth RF Input Range Receive Modulation Duty-Cycle Maximum Receiver Input Spurious Reverse Isolation AGC Attack / Decay ratio Local Oscillator Stabilization Time Demod Section CTH Source Impedance CTH Source Impedance Variation Demod Filter Bandwidth Demod Filter Bandwidth Digital Section REFOSC Input Impedance Input Pullup Current Input High Voltage Input Low Voltage Output Current Output High Voltage Output Low Voltage Output Tr, Tf Note 1: Note 2: Note 3: MIN Note 1, 3 Note 4 Note 3, 4 TYP MAX UNITS 2.4 mA -103 0.86 0.43 dBm MHz MHz MHz % dBm µVrms 300 20 440 80 -20 30 0.1 2.5 Rsc = 50Ω ANT pin, Rsc = 50Ω Note 2 T(Attack) / T(Decay) To 1% of Final Value Note 5 msec Ω % Hz Hz 118k -15 SEL0 = SEL1 = SWEN = VDD, Note 4, 6 SEL0 = SEL1 = VDD, SWEN = VSS Note 4, 6 SEL0, SEL1, SWEN = VSS SEL0, SEL1, SWEN SEL0, SEL1, SWEN DO pin, Push-Pull DO pin, Iout = -1µA DO pin, Iout = +1µA DO pin, Cload= 15pF +15 4160 8320 200k 8 0.8VDD 0.2VDD 10 0.9VDD 0.1VDD 10 Ω µA V V µA V V µsec Sensitivity is defined as the average signal level measured at the input necessary to achieve 10e-2 Bit Error Rate (BER). The input signal is defined as a return-to-zero (RZ) waveform with 50% average duty cycle (e.g., Manchester Encoded Data) at a data rate of 300bps. The RF input is assumed to be matched into 50Ω. Spurious reverse isolation represents the spurious components which appear on the RF input (ANT) pin measured into 50Ω with an input RF matching network. Sensitivity, a commonly specified Receiver parameter, provides an indication of the Receiver’s input referred noise, generally input thermal noise. However, it is possible for a more sensitive receiver to exhibit range performance no better than that of a less sensitive receiver, if the “ether” noise is appreciably higher than the thermal noise. “Ether” noise refers to other interfering “noise” sources, such as FM radio stations, pagers, etc. A better indicator of receiver range performance is usually given by its Selectivity, often stated as Intermediate Frequency (IF) or Radio Frequency (RF) bandwidth, depending on receiver topology. Selectivity is a measure of the rejection by the receiver of “ether” noise. More selective receivers will almost invariably provide better range. Only when the receiver selectivity is so high that most of the noise on the receiver input is actually thermal will the receiver demonstrate sensitivity-limited performance. December 1998b 4 MICRF011 MICRF011 Note 4: Note 5: Note 6: QwikRadio tm Micrel Parameter scales linearly with REFOSC frequency ft. For any REFOSC frequency other than 4.90MHz, compute new parameter value as the ratio [(REFOSC FREQ (in MHz) / 4.90] * [Parameter Value @ 4.90MHz]. Example: For REFOSC Freq. ft = 6.00MHz, [Parameter Value @ 6.00MHz] = (6.00 / 4.90) *[Parameter Value @ 4.90MHz]. Parameter scales inversely with REFOSC frequency ft. For any REFOSC frequency other than 4.90MHz, compute new parameter value as the ratio [4.90 / (REFOSC FREQ (in MHz)] * [Parameter Value @ 4.90MHz]. Example: For REFOSC Freq. ft = 6.00MHz, [Parameter Value @ 6.00MHz] = (4.90 / 6.00) * [Parameter Value @ 4.90MHz]. Demod filter bandwidths are related in a binary manner, so any of the (lower) nominal filter values may be derived simply by dividing this parameter value by 2, 4, or 8 as desired. Typical Performance Characteristics MICRF011 IDD vs Frequency (Temperature=25°°C, VDD=5.0V, SWP Mode) 6.10 5.60 5.10 IDD(mA) 4.60 4.10 3.60 3.10 2.60 2.10 1.60 250 275 300 325 350 375 400 425 450 475 500 Frequency (MHz) MICRF011 IDD vs Temperature (Frequency=315MHz, VDD=5.0V, SWP Mode) 3.30 3.10 2.90 IDD(mA) 2.70 2.50 2.30 2.10 1.90 -40 -20 0 20 40 60 85 Temperature (C) December 1998b 5 MICRF011 MICRF011 QwikRadio tm Micrel MICRF011 Block Diagram December 1998b 66 MICRF011 MICRF011 QwikRadio Functional Description Please refer to “MICRF011 Block Diagram”. Identified in the figure are the three principal functional blocks of the IC, namely (1) UHF Downconverter, (2) OOK Demodulator, and (3) Reference and Control. Also shown in the figure are two capacitors (CTH, CAGC) and one timing component (CR), usually a ceramic resonator. With the exception of a supply decoupling capacitor, these are all the external components needed with the MICRF011 to construct a complete UHF receiver. Three control inputs are shown in the block diagram, SEL0, SEL1 and SWEN. Through these logic inputs the user can control the operating mode and programmable functions of the IC. These inputs are CMOS compatible, and are pulled-up on the IC. Input SWEN selects the operating mode of the IC (FIXED mode or SWP mode). When low, the IC is in FIXED mode, and functions as a conventional superheterodyne receiver. When SWEN is high, the IC is in SWP mode. In this mode, while the topology is still superheterodyne, the local oscillator (LO) is deterministically swept over a range of frequencies at rates greater than the data rate. When coupled with a peak-detecting demodulator, this technique effectively increases the RF bandwidth of the MICRF011, so the device can operate in applications where significant Transmitter/Receiver frequency misalignment may exist. [Note: The swept LO technique does not affect the IF bandwidth, so noise performance is not impacted relative to FIXED mode. In other words, the IF bandwidth is the same (500kHz) whether the device is in FIXED or SWP mode.] Due to limitations imposed by the LO sweeping process, the upper limit on data rate in SWP mode is approximately 2.5kbps. Data rates beyond 10kbps are possible in FIXED mode however. Examples of SWP mode operation include applications which utilize low-cost LC-based transmitters, whose transmit frequency may vary up to ± 0.5% over initial tolerance, aging, and temperature. In this (patent-pending) mode, the LO frequency is varied in a prescribed fashion which results in downconversion of all signals in a band approximately 1.5% around the transmit frequency. So the Transmitter may drift up to ± 0.5% without the need to retune the Receiver, and without impacting system performance. Such performance is not achieved with currently available crystalbased superheterodyne receivers, which can operate only with SAW or crystal based transmitters. [Note: In SWP mode only, a range penalty will occur in installations where there exists a competing signal of sufficient strength in this small frequency band of 1.5% around the transmit frequency. This results from the fact that sweeping the LO indiscriminately “sweeps” all signals within the sweep range down into the IF band. This same penalty also exists with super-regenerative type receivers, as their RF bandwidth is also generally 1.5%. So any application for a super-regenerative receiver is also an application for the MICRF011 in SWP mode.] For applications where the transmit frequency is accurately set for other reasons (e.g., applications where a SAW December 1998b 77 tm Micrel transmitter is used for its mechanical stability), the user may choose to configure the MICRF011 as a standard superheterodyne receiver (FIXED mode), mitigating the aforementioned problem of a competing close-in signal. This can be accomplished by tying SWEN to ground. Doing so forces the on-chip LO frequency to a fixed value. In FIXED mode, the ceramic resonator would be replaced with a crystal. Generally, however, the MICRF011 can be operated in SWP mode, using a ceramic resonator, with either LC or CRYSTAL/SAW based transmitters, without any significant range difference. The inputs SEL0 and SEL1 control the Demodulator filter bandwidth in four binary steps (625Hz-5000Hz in SWP, 1250Hz-10000Hz in FIXED mode), and the user must select the bandwidth appropriate to his needs. th Rolloff response of the IF Filter is 5 order, while the nd demodulator data filter exhibits a 2 order response. Multiplication factor between the REFOSC frequency ft and the internal Local Oscillator (LO) is 64.5X for FIXED mode, and 64.25X for SWP mode (i.e., for ft = 6.00MHz in FIXED mode, LO frequency = 6.00MHz * 64.5 = 387MHz). Slicing Level and the CTH Capacitor Extraction of the DC value of the demodulated signal for purposes of logic-level data slicing is accomplished by external capacitor CTH and the on-chip switched-cap “resistor” RSC, indicated in the block diagram. The effective resistance of RSC is 118kohms. The value of capacitor CTH is easily calculated, once the slicing level time-constant is chosen. Values vary somewhat with decoder type, data pattern, and data rate, but typical Slicing Level time constants range 5-50msec. Optimization of the CTH value is required to maximize range, as discussed in “Application Note 22, MICRF001 Theory of Operation”, section 6.4. During quiet periods (i.e., no signal transmissions) the Data Output (DO pin) transitions randomly based on noise. This may present problems for some decoders. The most common solution is to introduce a small offset (“Squelch”) on the CTH pin so that noise does not trigger the internal comparator. Usually 20-30mV is sufficient, and may be introduced by connecting a several-Megohm resistor from the CTH pin to either VSS or VDD, depending on the desired offset polarity. Since the MICRF011 is an AGC’d receiver, noise at the internal comparator input is always the same, set by the AGC. So the squelch offset requirement does not change as the local “ether” noise changes from installation to installation. Note that introducing squelch will reduce range modestly, so only introduce an amount sufficient to “quiet” the output. AGC Function and the CAGC Capacitor The signal path has automatic gain control (AGC) to increase input dynamic range. An external capacitor, CAGC, must be connected to the CAGC pin of the device. The ratio of decay-to-attack time-constant is fixed at 10:1 (i.e., the attack time constant is 1/10th the decay time constant), and this ratio cannot be changed by the user. However, the attack time constant is selectable by the user through the value of capacitor CAGC. MICRF011 MICRF011 QwikRadio [By adding resistance from the CAGC pin to VDDBB or VSSBB in parallel with the CAGC capacitor, the ratio of decay-to-attack time-constant may be varied, although the value of such adjustments must be studied on a perapplication basis. Generally the design value of 10:1 is adequate for the vast majority of applications.] See “Application Note 22”. Transmit Freq. ftx (MHz) (1) connect a ceramic resonator, or (2) connect a crystal, or (3) drive this pin with an external timing signal. REFOSC Freq. ft (MHz) 315 418 433.92 2. All timing and tuning operations on the MICRF011 are derived from the REFOSC function. This function is a single-pin Colpitts-type oscillator. The user may handle this pin in one of three possible ways: Micrel Here ft is in MHz. Connect a crystal of frequency ft to the REFOSC pin of the MICRF011. 4 decimal-place accuracy on the frequency is generally adequate. The following table identifies ft for some common Transmit frequencies when the MICRF011 is operated in FIXED mode. To maximize system range, it is important to keep the AGC control voltage ripple low, preferably under 10mVpp once the control voltage has attained its quiescent value. For this reason capacitor values ≥ 0.47uF are recommended. Reference Oscillator (REFOSC) and External Timing Element tm 4.8970 6.4983 6.7458 Selecting REFOSC Frequency ft (SWP Mode) Selection of REFOSC frequency ft in SWP mode is much simpler than in FIXED mode, due to the LO sweeping process. Further, accuracy requirements of the frequency reference component are significantly relaxed. In SWP mode, ft is given by equation (3): ft = ftx / 64.25. The third approach is attractive for further lowering system cost if an accurate reference signal exists elsewhere in the system (e.g., a reference clock from a crystal or ceramic resonator-based microprocessor). An externally applied signal should be AC-coupled, and resistively-divided down (or otherwise limited) to approximately 0.5Vpp. The specific reference frequency required is related to the system transmit frequency, and the operating mode of the device as set by the SWEN control pin. See “Application Note 22, MICRF001 Theory of Operation” for a discussion of frequency selection and accuracy requirements. MICRF011 Frequency and Capacitor Selection (3) Connect a ceramic resonator of frequency ft to the REFOSC pin of the MICRF011. 2-decimal place accuracy is generally adequate. (A crystal may also be used if desired, but may be necessary to reduce the Rx frequency ambiguity if the Tx frequency ambiguity is excessive. See Application Note 22 for further details.) 3. Selecting Capacitor CTH First step in the process is selection of a Data Slicing Level timeconstant. This selection is strongly dependent on system issues, like system decode response time and data code structure (e.g., existence of data preamble, etc.). This issue is too broad to discuss here, and the interested reader should consult the Application Note 22. Selection of the REFOSC frequency ft, Slicing Level (CTH) capacitor, and AGC capacitor are briefly summarized in this section. Please see Application Note 22 for complete details. Source impedance of the CTH pin is given by equation (4), where ft is in MHz: 1. Selecting REFOSC Frequency ft (FIXED Mode) Assuming that a Slicing Level Timeconstant TC has been established, capacitor CTH may be computed using equation (5): As with any superheterodyne receiver, the difference between the (internal) Local Oscillator (LO) frequency flo and the incoming Transmit frequency ftx must ideally equal the IF Center frequency. Equation (1) may be used to compute the appropriate flo for a given ftx: flo = ftx ± 1.064 * (ftx / 390) Rsc = 118kΩ * (4.90 / ft). CTH = TC / Rsc. (4) (5) (1) where 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”, and there is generally no preference of one over the other. After choosing one of the two acceptable values of flo, use equation (2) to compute the REFOSC frequency ft: ft = flo / 64.5. December 1998b (2) 88 MICRF011 MICRF011 QwikRadio 3. Selecting CAGC Capacitor tm Micrel Selection of CAGC is dictated by minimizing the ripple on the AGC control voltage, by using a sufficiently large capacitor. It is Micrel’s experience that CAGC should be in the vicinity of 0.47µF to 4.7µF. Large capacitor values should be carefully considered, as this determines the time required for the AGC control voltage to settle from a completely discharged condition. AGC settling time from a completely discharged (0-volt) state is given approximately by equation (6): capacitor CAGC. The attack current is nominally 15µA, while the decay current is a 1/10th scaling of this, approximately 1.5µA. Signal gain of the RF/IF strip inside the IC diminishes as the voltage on CAGC decreases. By simply adding a capacitor to CAGC pin, the attack/decay time constant ratio is fixed at 1:10. Further discussion on setting the attack time constant is found in “Application Note 22, MICRF001 Theory of Operation”, section 6.5. Modification of the attack/decay ratio is possible by adding resistance from CAGC pin either to VDDBB or VSSBB, as desired. ∆T = (1.333 * CAGC) – 0.44 4. DO Pin (6) where CAGC is in microfarads, and ∆T is in seconds. I/O Pin Interface Circuitry Interface circuitry for the various I/O pins of the MICRF011 is shown in Figures 1 through 6. Specific information regarding each of these circuits is discussed in the following sub-paragraphs. Not shown are ESD protection diodes which are applied to all input and output pins. 1. ANT Pin The ANT pin is internally AC-coupled via a 3pF capacitor, to The output stage for the Data Comparator (DO pin) is shown in Figure 4. The output is a 10µA push-10µA pull, switched current stage. Such an output stage is capable of driving CMOS-type loads. An external buffer-driver is recommended for driving high capacitance loads. 5. REFOSC Pin The REFOSC input circuit is shown in Figure 5. Input impedance is quite 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 VSSBB, although a crystal may be used instead, where greater frequency accuracy is required. The resonators should not contain integral capacitors, since these capacitors are contained inside the IC. Externally applied signals should be AC-coupled, amplitude limited to approximately 0.5Vpp. The nominal DC bias voltage on this pin is 1.4V. 6. Control Inputs (SEL0, SEL1, SWEN) Figure 1 ANT Pin an RF N-channel MOSFET, as shown in Figure 1. Impedance on this pin to VSS is quite high at low frequencies, and decreases as frequency increases. In the UHF frequency range, the device input can be modeled as 6.3kΩ in parallel with 2pF (pin capacitance) shunt to VSSRF. Control input circuitry is shown in Figure 6. 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. 2. CTH Pin Figure 2 illustrates the CTH pin interface circuit. CTH pin is driven from a P-channel MOSFET source-follower biased with approximately 10µA of bias current. 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 118kΩ. The DC potential on the CTH pin is approximately 1.6V. 3. CAGC Pin Figure 3 illustrates the CAGC pin interface circuit. The AGC control voltage is developed as an integrated current into a December 1998b 99 MICRF011 MICRF011 QwikRadio tm Figure 3 CAGC Pin Figure 2 CTH Pin Figure 4 DO Pin December 1998b Micrel Figure 6 SEL0, SEL1, SWEN Figure 5 REFOSC Pin 1010 MICRF011 MICRF011 QwikRadio tm Micrel Typical Application The Figure below illustrates a typical application for the MICRF011 UHF Receiver IC. Operation in this example is at 385.5MHz, and may be customized by selection of the appropriate reference frequency (CR1), and adjustment of the antenna length. The value of C4 would also change, if the optional input filter is used. Changes from the 1kbps data rate may require a change in the value of R1. The Bill of Materials is shown in the accompanying chart. Typical MICRF011 Application 385.5 MHz Operating Frequency 1kbps Operation 6-Bit Address Decode Bill of Materials Item U1 U2 CR1 D1 R1 R2 C1 C3 C2 C4 Part Number MICRF011 HT-12D CSA6.00MG SSF-LX100LID Manufacturer Micrel Holtek Murata Lumex Bourns Bourns Panasonic Panasonic Panasonic Panasonic Description UHF Receiver Logic decoder 6.00MHz Cer. Res. RED LED 68k, 1/4W ,5% 1k,1/4W, 5% 4.7µF, Dip Tant. Cap 0.47µF, Dip Tant. Cap 2.2µF, Dip Tant. Cap 8.2pF, COG Cer. Cap Vendor Bourns Holtek Lumex Murata Panasonic Telephone (909) 781-5500 (408) 894-9046 (800) 278-5666 (800) 241-6574 (201) 348-7000 Fax (909) 781-5273 (408) 894-0838 (847) 359-8904 (770) 436-3030 (201) 348-8164 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 This information is believed to be accurate and reliable, however no responsibility is assumed by Micrel for its use nor for any infringement of patents or other rights of third parties resulting from its use. No license is granted by implication or otherwise under any patent or patent right of Micrel Inc. This is preliminary information and a final specification has not been completed. Before making any final design determination, consult with Micrel for final specifications. ©1998 Micrel Incorporated December 1998b 11 MICRF011