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.
®
Features
•
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Complete receiver on a chip
-2
-109dBm sensitivity, 1kbps, and BER 10
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
Typical Application
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
Micrel Inc.
MICRF221
Ordering Information
Part Number
MICRF221AYQS
Temperature Range
–40° to +105°C
Package
16-Pin QSOP
Pin Configuration
16-Pin QSOP (QS)
Pin Description
16-Pin
QSOP
1
2
3
4
5
6
7
8
9
10
Pin
Name
RO1
GNDRF
ANT
GNDRF
VDD
SQ
SEL0
SHDN
GND
DO
Pin Function
Reference Oscillator (input): Reference resonator input connection to pierce oscillator stage. May also be
driven by external reference signal of 1.5V p-p amplitude maximum. 7pF to GND during normal operation.
Negative supply connection associated with ANT RF input.
Antenna (input): RF signal input from antenna. Internally AC coupled. It is recommended a matching network
with an inductor-to-RF ground be used to improve ESD protection.
Negative supply connection associated with ANT RF input.
Positive supply connection for all chip functions.
Squelch control logic input with an active internal pull-up (3uA typical) pulls the logic-input HIGH when the
device is enabled. This feature is not recommended in MICRF221 and this pin should remain floating.
Select (input): Logic control input with active 3μA (8μA max) internal pull-up when not in shutdown or SLEEP
mode. It does not need to be defined in SLEEP mode. Used in conjunction with SEL1 to control D3 bandwidth
LSB when serial interface contains default setting.
Shutdown logic control input. Active internal pull-up.
Negative supply connection for all chip functions except for RF input.
Demodulated data (output): May be blanked until bit checking test is acceptable. A current limited CMOS
output during normal operation this pin is also used as a CMOS Schmitt input for serial interface data. A 25kΩ
pull-down is present when device is in shutdown and sleep modes.
Select (input): Logic control input with active 3μA (8μA max) internal pull-up when not in shutdown or SLEEP
mode. It does not need to be defined in SLEEP mode. Used in conjunction with SEL0, to control D4
bandwidth MSB, when serial interface contains default setting.
Demodulation threshold voltage integration capacitor. Capacitor-to-GND sets the settling time for the
demodulation data slicing level. Values above 1nF are recommended and should be optimized for data rate
and data profile.
AGC filter capacitor. A capacitor, normally greater than 0.47μF, is connected from this pin-to-GND
Received signal strength indication (output): Output is from a switched capacitor integrating op amp with
220Ω typical output impedance.
Serial interface input clock. CMOS Schmitt input. A 25kΩ pull-down is present when device is in shutdown
mode.
Reference resonator connection. 7pF to GND during normal operation.
11
SEL1
12
13
14
15
16
CTH
CAGC
RSSI
SCLK
RO2
August 12, 2015
2
Revision 2.0
Micrel Inc.
MICRF221
Absolute Maximum Ratings
(1)
Supply Voltage (VDD) ................................................ +5V
Input Voltage. ............................................................. +5V
Junction Temperature ........................................... +150ºC
Lead Temperature (soldering, 10sec.) .................... 300°C
Storage Temperature (Ts) ......................–65ºC to +150°C
Maximum Receiver Input Power ......................... +10dBm
(3)
EDS Rating ..................................................... 2kV HBM
Operating Ratings
(2)
Supply voltage (VDD) ............................ +3.0V to +3.6V
Ambient Temperature (T
A
) ................. –40°C to +105°C
Input Voltage (Vin) ................................................. 3.6V
Maximum Input RF Power ................................ –20dBm
(6)
Receive Modulation Duty Cycle .................... 20~80%
Electrical Characteristics
Specifications apply for V
DD
= 3.3V, V
SS
= 0V, C
AGC
= 4.7µF, C
TH
= 0.1µF, f
RX
= 850MHz to 950MHz unless otherwise noted.
Bold
values indicate –40°C - T
A
- 105°C.
Symbol
Iss
Ishut
Parameter
MICRF221 Operating
Supply Current
Shutdown Current
Condition
Continuous Operation, f
RX
= 868MHz
Continuous Operation, f
RX
= 915MHz
Min
Typ
9.0
mA
9.5
50
nA
Max
Units
RF/IF Section
Symbol
Parameter
Image Rejection
1 IF Center Frequency
f
RX
= 915MHz
Receiver Sensitivity @
(4)
1kbps
f
RX
= 868MHz (matched to 50Ω)
f
RX
= 915MHz (matched to 50Ω)
f
RX
= 868MHz
IF Bandwidth
f
RX
= 915MHz
f
RX
= 868MHz
Antenna Input Impedance
f
RX
= 915MHz
Receive Modulation Duty
Cycle
Spurious Reverse
(5)
Isolation
AGC Attack / Decay Ratio
AGC Pin Leakage Current
T
A
= +105ºC
Note 6
ANT pin, RSC = 50 Ω
t
ATTACK
/ t
DECAY
T
A
= 25ºC
20
-78
0.1
+/-2
nA
+/-800
st
Condition
Min
Typ
20
Max
Units
dB
MHz
f
RX
= 868MHz
1.219
1.285
-109
dBm
-109
360
kHz
380
9.4 – j72
9 – j67
80
%
dBm
Ω
August 12, 2015
3
Revision 2.0
Micrel Inc.
MICRF221
Electrical Characteristics (Continued)
Reference Oscillator
Symbol
Parameter
Reference Oscillator
Frequency
Reference Oscillator Input
Impedance
Time to Data
Reference Oscillator Input
Range
Reference Oscillator
Source Current
Condition
f
RX
= 868MHz
f
RX
= 915MHz
RO1 Pin
From Shutdown
With External Drive
RO1 Pin, V(REFOSC) = 0V
0.5
380
Min
Typ
13.54856
MHz
14.27643
1500
1
1.5
kΩ
ms
Vp-p
µA
Max
Units
Auto-polling Operation
Symbol
Parameter
(7)
Condition
Min
10
Typ
Max
1300
Units
ms
µA
Tsleep Programming
Range
Isleep
(8)
SLEEP Current
2ms on, 1.3s off
15
Demodulator
Symbol
Parameter
CTH Source Impedance
CTH Leakage Current
T
A
= +105ºC
Demodulator Filter
Bandwidth @ 915MHz
Programmable, see application section
1712
Condition
Frefosc = 14.27643MHz
T
A
= 25ºC
Min
Typ
100
+/-2
nA
+/-800
13000
Hz
Max
Units
kΩ
Digital / Control Functions
Symbol
Parameter
Input High Voltage
Input Low Voltage
Output Voltage High
Output Voltage Low
DO Pin Output Current
As output, sink @ 0.2 V
DD
Output Rise and Fall
Times
CI = 15 pF, pin DO, 10-90%
Condition
Pins SCLK, DO (as input), SHDN
Pins SCLK, DO (as input), SHDN
DO
DO
As output, source @ 0.8 V
DD
260
µA
600
2
µs
0.8Vdd
0.2Vdd
Min
0.8Vdd
0.2Vdd
Typ
Max
Units
V
V
V
V
August 12, 2015
4
Revision 2.0
Micrel Inc.
MICRF221
Electrical Characteristics (Continued)
RSSI
Symbol
Parameter
RSSI DC Output Voltage
Range
RSSI Response Slope
RSSI Output Impedance
-109dBm to -40dBm
Condition
Min
Typ
0.2 to 2.0
26
220
Max
Units
V
mV/dB
Ω
Notes:
1.
2.
3.
4.
5.
6.
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 C
TH
, 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
isT
ON
/(T
ON
+ T
OFF
)= 50%; without preamble, duty cycle is T
ON
/(T
ON
+ T
OFF
+ T
QUIET
) = 50ms/200ms = 25%. T
ON
is the number of 1’s during
the burst time × bit time T
OFF
= T
BURST
– T
ON
.
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.
7.
8.
August 12, 2015
5
Revision 2.0
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