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PDF MICRF230 Data sheet ( Hoja de datos )
| Número de pieza | MICRF230 | |
| Descripción | 400MHz to 450MHz ASK/OOK Receiver | |
| Fabricantes | Micrel Semiconductor | |
| Logotipo |  |
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MICRF230
400MHz to 450MHz ASK/OOK Receiver
with RSSI and Squelch
General Description
The MICRF230 is a 400MHz to 450MHz super-
heterodyne, image-reject, RF receiver with automatic gain
control, ASK/OOK demodulator, analog RSSI output, and
integrated squelch features. It only requires a crystal and a
minimum number of external components to implement.
The MICRF230 is ideal for low-cost, low-power, RKE,
TPMS, and remote actuation applications.
The MICRF230 achieves −112dBm sensitivity at a bit rate
of 1kbps with 1% BER. Four demodulator filter bandwidths
are selectable using SEL0 and SEL1 from 1625Hz to
13kHz at 433.92MHz, allowing the device to support bit
rates up to 20kbps. The device operates from a supply
voltage of 3.5V to 5.5V and typically consumes 6.0mA at
433.92MHz. The MICRF230 has a shutdown mode that
reduces current to 0.5µA. The squelch feature decreases
the activity on the data output pin until valid bits are
detected while maintaining overall receiver sensitivity.
Datasheets and support documentation are available on
Micrel’s web site at: www.micrel.com.
Features
• −112dBm sensitivity at 1kbps with 1% BER
• Supports bit rates up to 20kbps at 433.92MHz
• 25dB image-reject mixer
• No IF filter required
• 60dB analog RSSI output range
• 3.5V to 5.5V supply voltage range
• 6.0mA supply current at 434MHz
• 0.5μA supply current in shutdown mode
• 16-pin 4.9mm × 6.0mm QSOP package
• −40°C to +105°C temperature range
• 2kV HBM ESD rating
Applications
• Automotive remote keyless entry (RKE)
• Long range RFID
• Remote fan and light control
• Garage door and gate openers
• Remote metering
• Low data rate unidirectional wireless data links
Typical Application
MICRF230 Typical Application Circuit for 433.92MHz
Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
April 15, 2015
Revision 2.0
1 page  
Micrel, Inc.
MICRF230
Electrical Characteristics (Continued)
VDD = 5.0V, VEN = 5V, SQ = Open, CAGC = 4.7µF, CCTH = 0.1µF, unless otherwise noted. Bold values indicate –40°C ≤ TA ≤ +105°C.
Symbol Parameter
Condition
Min.
Typ.
Max. Units
Reference Oscillator
fRF Reference Oscillator Frequency fRF = 433.92MHz
Reference Buffer Input Impedance
RO1 when driven externally
13.52313
1.6
MHz
kΩ
Reference Oscillator Bias Voltage
RO2
1.15 V
Reference Oscillator Input Range
External input, AC couple to RO1
0.2
1.5 VP-P
Reference Oscillator Source Current VRO1 = 0V
300 µA
Demodulator
CTH Source Impedance(5)
fREF = 13.52313MHz
120 KΩ
CTH Leakage Current In CTH
Hold Mode
Digital / Control Functions
TA = +25ºC
TA = +105ºC
1
10
nA
DO Pin Output Current
Output Rise Time
Output Fall Time
As output source at 0.8VDD
As output sink at 0.2VDD
15pF load on DO pin, transition
time between 0.1VDD and 0.9VDD
300
680
µA
600
ns
200
Input High Voltage
EN, SQ
0.8VDD
V
RSSI(6)
Input Low Voltage
Output Voltage High
Output Voltage Low
EN, SQ
DO
DO
0.8VDD
0.2VDD
0.2VDD
V
V
V
VRSSI
RSSI DC Output Voltage Range
−110dBm RF input level
−50dBm RF input level
0.4
V
2.06
RSSI Output Current
5kΩ load to GND,
−50dBm RF input level
400 µA
RSSI Output Impedance
200 Ω
RSSI Response Time
SEL0:SEL1 = 00, RF input power
stepped from no input to −50dBm
9
ms
RF Leakage
LO Leakage for 433.92MHz
432.68064MHz
(fXAL = 13.52127MHz)
-106
dBm
Notes:
5. CTH source impedance is inversely proportional to the reference frequency. In production test, the typical source impedance value is verified with
12MHz reference frequency.
6. RSSI exhibit variation through manufacturing process, it is recommended that the reading is calibrated by software in system MCU when it is being
used.
April 15, 2015
5
Revision 2.0
5 Page 
Micrel, Inc.
MICRF230
ASK/OOK Demodulator
The demodulator section is comprised of detector,
programmable low pass filter, slicer, and AGC
comparator.
Detector and Programmable Low-Pass Filter
The demodulation starts with the detector removing the
carrier from the IF signal. Post detection, the signal
becomes baseband information. The low-pass filter
further enhances the baseband signal.
There are four selectable low-pass filter BW settings:
1625Hz, 3250Hz, 6500Hz and 13000Hz for 433.92MHz
operation. The low-pass filter BW is directly proportional
to the crystal reference frequency, and RF Operating
Frequency. Filter BW values can be easily calculated by
direct scaling. Equation 5 illustrates filter Demod BW
calculation:
×BWOperating Freq = BW@433.92MHz Operating Freqruency (MHz)
433.92
Eq. 5
It is very important to select a suitable low-pass filter BW
setting for the required data rate to minimize bit error
rate. Use the sensitivity curves that show BER vs. bit
rates for different SEL0:SEL1 settings as a guide.
This low-pass filter with −3dB corner frequency
bandwidth can be configured by setting the registers as in
Table 1 for 433.92MHz.
Table 1. Low-Pass Filter Bandwidth Selection @ 434MHz RF
Input
SEL1
0
0
1
1
SEL0
0
1
0
1
Low-Pass
Filter BW
1625Hz
3250Hz
6500Hz
13000Hz
Maximum
Encoded Bit Rate
2.5KBps
5KBps
10KBps
20KBps
Bit rate refers to the encoded bit rate. Encoded bit rate is
1/(shortest pulse duration) that appears at DO:
Figure 3. Transmitted Bit Rate through the air
Slicer and CTH
The signal before the slicer, labeled “Audio Signal” in
Figure 1, is still a baseband analog signal. The data slicer
converts the analog signal into ones and zeros based on
50% of the slicing threshold voltage built up in the CTH
capacitor. After the slicer, the signal is demodulated OOK
digital data. When there is only thermal noise at ANT pin,
the voltage level on CTH pin is about 650mV. This
voltage starts to drop when there is RF signal present.
When the RF signal level is greater than −100dBm, the
voltage is about 400mV.
The capacitor value from the CTH pin to GND is not
critical to the sensitivity of MICRF230. However, it should
be large enough to provide a stable slicing level for the
comparator. The0.1μF value used in the evaluation board
is good for all bit rates from 500bps to 20kbps.
CTH Hold Mode
If the internal demodulated signal (DO in Figure 1) is at
logic LOW for more than approximately 4ms, the chip
automatically enters CTH hold mode, which holds the
voltage on CTH pin constant even without a RF input
signal. This is useful in a transmission gap, or “dead
time”, used in many encoding schemes. When the signal
reappears, CTH voltage does not need to resettle. This
improves the time to output with no pulse width distortion,
or time to good data (TTGD).
AGC Loop
The AGC comparator monitors the signal amplitude from
the output of the programmable low-pass filter. The AGC
loop in the chip regulates the signal from the output point
to be at a constant level when the input RF signal is
within the AGC loop dynamic range (about −115dBm to
−40dBm).
When the chip first turns on, the fast charge feature
charges the AGC node up with 120µA typical current.
When the voltage on AGC increases, the gains of the
mixer and IF amplifier go up, increasing the amplitude of
the audio signal (as labeled in Figure 1), even with only
thermal noise at the LNA input. The fast-charge current is
disabled when the audio signal crosses the slicing
threshold, causing DO’ to go high, for the first time.
When an RF signal is applied, a fast-attack period
ensues when 600µA current discharges the AGC node to
reduce the gain to a proper level. Once the loop reaches
equilibrium, the fast attack current is disabled, leaving
only 15µA to discharge AGC or 1.5µA to charge AGC.
The fast attack current is enabled only when the RF
signal increases faster than the ability of the AGC loop to
track it.
The ability of the chip to track to a signal that decreased
in strength becomes much slower, since only 1.5μA is
available to charge the AGC to increase the gain. When
designing a transmitter that communicates with the
April 15, 2015
11
Revision 2.0
11 Page | ||
| Páginas | Total 20 Páginas | |
| PDF Descargar | [ Datasheet MICRF230.PDF ] | |
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