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PDF MICRF221 Data sheet ( Hoja de datos )
| Número de pieza | MICRF221 | |
| Descripción | 850 MHz to 950 MHz Receiver | |
| Fabricantes | Micrel Semiconductor | |
| Logotipo |  |
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MICRF221
3.3V, QwikRadio® 850 MHz to 950 MHz
Receiver
General Description
The MICRF221 is a third generation QwikRadio®
receiver, offering all the benefits of Micrel's earlier
QwikRadio® products with significant improvements,
including: enhanced sensitivity, automatic duty-cycle
feature and RSSI output.
The MICRF221 is a super-heterodyne receiver,
designed for OOK and ASK modulation. The down-
conversion mixer also provides image rejection.
The MICRF221 receiver provides a SLEEP Mode for
duty-cycle operation and an enhanced, customer
programmable "WAKE" function. These features are
further combined into a wholly integrated "self-polling"
scheme that is ideal for low and ultra-low power
applications, such as RKE and RFID
All post-detection data filtering is provided on the
MICRF221 receiver. Any one of four filter bandwidths
may be selected externally by the user in binary steps,
from 1.25kHz to 10kHz. The user needs only to program
the device with a set of easily determined values based
on data rate, code modulation format, and desired duty-
cycle operation.
Datasheets and support documentation are available on
Micrel’s website at: www.micrel.com.
Typical Application
Features
• Complete receiver on a chip
• -109dBm sensitivity, 1kbps, and BER 10-2
• Image rejection mixer
• 850MHz to 950MHz frequency range
• Low power, 9mA @ 868MHz, continuous on
• Data rates to 10kbps (Manchester Encoded)
• Auto polling (sleep mode, current < 0.1 mA)
• Analog RSSI output
• Programmable “low sensitivity” mode
• No IF filter required
• Excellent selectivity and noise rejection
• Low external part count
• Additional functions programmed through serial
interface
Figure 1: MICRF221 Receiver 915.0 MHz, 1kHz Baud Rate Example
QwikRadio is a registered trademark of Micrel, Inc.
Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
August 12, 2015
Revision 2.0
1 page  
Micrel Inc.
MICRF221
Electrical Characteristics (Continued)
RSSI
Symbol
Parameter
Condition
RSSI DC Output Voltage
Range
RSSI Response Slope
-109dBm to -40dBm
RSSI Output Impedance
Min Typ Max Units
0.2 to 2.0
V
26 mV/dB
220 Ω
Notes:
1.
2.
3.
4.
5.
6.
7.
8.
Exceeding the absolute maximum rating may damage the device.
The device is not guaranteed to function outside its operating rating.
Device is ESD sensitive. Use appropriate ESD precautions. Exceeding the absolute maximum rating may damage the device.
Sensitivity is defined as the average signal level measured at the input necessary to achieve 10-2 BER (bit error rate). The input signal is
defined as a return-to-zero (RZ) waveform with 50% average duty cycle (Manchester encoded).
Spurious reverse isolation represents the spurious component which appears on the RF input pin (ANT), measured into 50Ω with an input
RF matching network.
When data burst does not contain preamble, duty cycle is defined as total duty cycle, including any “quiet” time between data bursts. When
data bursts contain preamble sufficient to charge the slice level on capacitor CTH, then duty cycle is the effective duty cycle of the burst
alone. [For example, 100msec burst with 50% duty cycle, and 100msec “quiet” time between bursts). If burst includes preamble, duty cycle
isTON/(TON + TOFF)= 50%; without preamble, duty cycle is TON/(TON + TOFF + TQUIET) = 50ms/200ms = 25%. TON is the number of 1’s during
the burst time × bit time TOFF = TBURST – TON.
Auto-polling refers to power-cycling mode of operation where characteristics of the received signal are used to determine the likelihood of
an incoming data signal at the beginning of the Ton period. If there is no signal detected within a period programmable by the user, the
user can program the number of bits: 0,2,4,8 that must be good for device to wake up. The time will depend on the data rate. If two bad
bits are detected this will cause device to revert to SLEEP. If no bits are detected device will revert to SLEEP in 5ms, 10ms, or 20ms
depending on selected demodulator bandwidth. Otherwise, the device remains “On” until commanded into SLEEP by an external source
e.g., decoder or microprocessor. This technique minimizes the average Ton time. Refer to Serial Interface and Applications sub-sections
for further details.
Average SLEEP mode current depends on the SLEEP time programmed and the SLEEP oscillator variation which is ~+/-20% independent
of ref osc.
August 12, 2015
5 Revision 2.0
5 Page 
Micrel Inc.
Operation
Trigger pulses are generated from internal D0 edges
and compare with programmable window generated
from the reference clock frequency. If time between
data edges falls within the window data pulse width is
bad. Detected stable bits are counted. Wakeup will
occur allowing data to output if sufficient data bits are
detected. Two bad pulses or lack of pulse cause
device to go to sleep for sleep timer duration.
Serial Interface
Control Register Individual Truth Tables:
D0 D1 D2 MODE: Desense
0 X X No Desense - default
1 0 0 Not recommended for use
1 1 0 Not recommended for use
1 0 1 Not recommended for use
1 1 1 Not recommended for use
D3
D4
MODE:
Demod Bandwidth (at 915MHz)
0 0 1625Hz
1 0 3250Hz
0 1 6500Hz
1 1 13000Hz - default
D5 D6 MODE
1 0 Slice Level 30%
0 1 Slice Level 40%
1 1 Slice Level 50% - default
0 0 Slice Level 60%
D7 D8 MODE: Bit Check Setting
0 0 Bitcheck 0 bits - default
1 0 Bitcheck 2 bits
0 1 Bitcheck 4 bits
1 1 Bitcheck 8 bits
D9
D10
D11
MODE:
Bitcheck Window Times
MICRF221
(915MHz)
0 0 0 67µs, 136µs, 270µs, 541µs
1 0 0 64µs, 126µs, 252µs, 505µs
0 1 0 59µs, 118µs, 234µs, 469µs
1 1 0 54µs, 108µs, 216µs, 434µs
0 0 1 49µs, 100µs, 198µs, 397µs
1 0 1 45µs, 90µs, 180µs, 361µs
0 1 1 41µs, 82µs, 163µs, 325µs
1 1 1 36µs, 72µs, 144µs, 289µs
D12
D13
D14
MODE:
Sleep Time
0 0 0 10ms
1 0 0 20ms
0 1 0 40ms
1 1 0 80ms
0 0 1 160ms
1 0 1 320ms
0 1 1 640ms
1 1 1 1280ms
D15 MODE: Auto Poll
0 Awake – does not poll - default
1 Auto-polls with Sleep periods
D16 MODE: Demod BW Select
0 Normal Demod BW’s - default
1 Fast Demod BW’s
D17
0 Squelch circuit off - default
1 Should not be used
D18 MODE
Sleep polling watchdog active - default
0
Watchdog time for D3, D4, BW setting:
11 01 10
00
5ms 5ms 10ms 20ms
1
Sleep polling watchdog disabled - unlimited
poll period
D19 MODE
0 RSSI offset 0mV - default
1 RSSI offset +200mV
August 12, 2015
11 Revision 2.0
11 Page | ||
| Páginas | Total 26 Páginas | |
| PDF Descargar | [ Datasheet MICRF221.PDF ] | |
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