MICRF211AYQS RF Receiver

Technical Specifications of MICRF211AYQS

Datasheet	MICRF211AYQS datasheet
Category	RF/IF and RFID
Family	RF Receivers
Manufacturer	Microchip Technology
Series	–
Packaging	Tube
Part Status	Not For New Designs
Frequency	380MHz ~ 450MHz
Sensitivity	-110dBm
Data Rate (Max)	10 kbps
Modulation or Protocol	ASK, OOK
Applications	ISM, Garage Door Openers, RKE
Current – Receiving	6mA
Data Interface	PCB, Surface Mount
Memory Size	–
Antenna Connector	PCB, Surface Mount
Features	No IF Filter Required
Voltage – Supply	3 V ~ 3.6 V
Operating Temperature	-40°C ~ 105°C
Package / Case	16-SSOP (0.154″, 3.90mm Width)
Supplier Device Package	16-QSOP

MICRF211AYQS General Description

The MICRF211 is a general-purpose, 3V QwikRadio Receiver that runs at 433.92MHz and has a typical sensitivity of –110dBm. Its specifications are as follows: The MICRF211 is a super-heterodyne receiver that can handle OOK and ASK modulation at up to 10kbps. In addition, picture rejection can be accomplished with the down-conversion mixer. Onboard the MICRF211 is a data filtering system that processes all post-detection information. The user can make an external selection in binary steps ranging from 1.25 kHz to 10 kHz to select any of the four possible filter bandwidths. The user needs to set up the device with easily calculated parameters. These values are based on the data rate, code modulation type, and desired duty-cycle operation.

MICRF211AYQS Features

• Sensitivity of -110dBm, 1kbps, and BER 10-2.
• mixer for image rejection.
• Between 380 and 450 MHz in frequency.
• Low power, continuous on data rates up to 10kbps, 6.0mA @ 433.92MHz (Manchester Encoded).
• The analogue output of RSSI.
• No IF filter is necessary.
• Excellent noise rejection and selectivity.
• Low number of exterior parts.

Functional Description

The MICRF211’s fundamental construction can be understood by referring to the Simplified Block Diagram provided above. the OOK Demodulator, Image Rejection UHF Down-converter, and Reference and Control Logics are the three sub-blocks that compose it. Only three components are necessary for the MICRF211 to function when it is placed outside the device.

These are two capacitors, CAGC  and CTH, and the reference frequency device, typically a quartz crystal. To get a higher level of performance, it is possible to use an additional five components. These include a decoupling capacitor for the power supply, two components for the matching network, and two for the pre-selector bandpass filter.

Receiver Operation

● LNA

The grounded source LNA input stage’s gate circuit receives the signal from the RF input stage using AC coupling. A cascaded version of the NMOS is the LNA.

● Mixers and Synthesizer

The outputs of the local quadrature oscillator from the synthesizer block drive the LO ports on the Mixers. The signal from the synthesizer’s local oscillator is positioned on the low side of the intended RF signal. This places it in a position where it can suppress the image frequency at a frequency that is twice as low as the wanted signal’s IF frequency. Using a phase-locked loop synthesizer with a fully integrated loop filter, the local oscillator is tuned to a frequency 32 times that of the crystal reference frequency.

● OOK Demodulator

The components that make up the demodulator portion are the detector, a programmable low-pass filter, a slicer, and an analog gain comparator.

● Slicer, Slicing Level and Squelch

The signal is still linearly demodulated AM before it reaches the slicer. This signal is then converted into digital “1s” and “0s” by the data slicer, which compares it with the threshold voltage built up on the CTH capacitor. The mean value is stored and used to set this threshold when the positive and negative peaks of the data signal have been identified and located. The default value for the slicing threshold is 50%. Once the slicer is done with it, the signal becomes digital OOK data. The threshold voltage on the CTH capacitor may be extremely low when there are extended stretches of “0”s or when there is no data. Large bursts of random noise at this time could result in an incorrect reading of “1” at the DO pin. These mistakes will be suppressed when the squelch pin is pulled down to its lowest position.

● AGC Comparator

The signal amplitude produced by the programmable low-pass filter is fed into the AGC comparator so that it can be monitored. A current of 1.5-microampere amperes is supplied into the external CAGC capacitor whenever the output signal is lower than the thresh-hold of 750 millivolts. A current sink of 15 microamperes will discharge the CAGC capacitor whenever the output signal exceeds 750 millivolts. The voltage created on the CAGC capacitor is used to modify the gain of the mixer and the IF amplifier. This is done to account for variations in the level of the RF input signal.

Application Information

One of the several evaluation boards that Micrel has built specifically for this device, the MICRF211, allows for comprehensive testing of the device. The QR211HE1, which can be seen on the right, is an excellent starting point for most applications. It has a helical PCB antenna along with its matching network. This band-pass-filter front-end acts as a pre-selector filter, a matching network, and the bare minimum components necessary for the device to function: crystal, Cage, and Cth capacitors.

These components are what make the device work. A whip antenna (ANT2) or an RF connector (J2) can be used as an alternative to the helical PCB antenna (C9 and L3) if the matching network is removed from the helical PCB antenna. Its whole schematic may be seen in the figure above, which depicts the 433.92MHz frequency. Alternate frequencies may be utilized, and the necessary values are provided in the following tables. The passive components of the spiral PCB matching network are the capacitor C9 and the inductor L3, respectively. Inductors should have a 2% tolerance and capacitors 0.1pF. Various PCB modifications could call for different values and different levels of optimization.

Conclusion

Attention: There have been reports from many consumers that their MICRF211 receivers need to power on properly. DO either start chatting or maintains a low voltage state when the problem occurs. An abnormal operating current is seen, and the component fails to receive or demodulate data even with a robust OOK signal. According to Micrel, this indicates a faulty power-on reset (POR) of internal register bits. The MICRF211 may be powered up while on standby. It is possible to activate a “test bus pull down” circuit by connecting the SHDN pin to GND and gradually increasing the supply voltage. The POR cannot accurately set register bits (and thus operating modes) after the chip enters this mode.

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