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, Figure 1, 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 1.25 kHz to 10 kHz. 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.
Features
•
•
•
•
•
•
•
•
•
•
•
•
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Complete Receiver on a Chip
-109dBm sensitivity, 1 kbps and BER 10E-02
Image Rejection Mixer
850 MHz to 950 MHz frequency range
Low Power, 9mA @ 868 MHz, 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
Ordering Information
Part Number
MICRF221AYQS
Temperature Range
–40° to +105°C
Package
16-Pin QSOP
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
October 2008
M9999-100108
(408) 955-1690
Micrel Inc.
MICRF221
Pin Configuration
RO1
GNDRF
ANT
GNDRF
Vdd
SQ
SEL0
SHDN
1
2
3
4
5
6
7
8
16 RO2
15 SCLK
14 RSSI
13 CAGC
12 CTH
11 SEL1
10 DO
9 GND
Figure 2. MICRF221AYQS Pin Configuration
Pin Description
16-Pin
QSOP
1
Pin
Name
RO1
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 when not shut down. Low to reverse level set
by serial interface bit D17. Low enables squelch for default SIF register.
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.
2
3
4
5
6
7
GNDRF
ANT
GNDRF
Vdd
SQ
SEL0
8
9
10
SHDN
GND
DO
11
SEL1
12
CTH
13
14
15
16
CAGC
RSSI
SCLK
RO2
October 2008
2
M9999-100108
(408) 955-1690
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
EDS Rating
(3)
.....................................................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
Receive Modulation Duty Cycle
(6)
.................... 20~80%
Electrical Characteristics
Specifications apply for V
DD
=3.3V, V
SS
= 0V, C
AGC
= 4.7uF, C
TH
= 0.1uF, f
RX
= 850 MHz to 950 MHz unless otherwise noted.
Bold
values indicate –40°C - T
A
- 105°C.
Symbol
Iss
Parameter
MICRF221 Operating
Supply Current
Shut down Current
Condition
Continuous Operation, f
RX
= 868 MHz
Continuous Operation, f
RX
= 915 MHz
Min
Typ
9.0
9.5
50
Max
Units
mA
nA
Ishut
RF/IF Section
Symbol
Parameter
Image Rejection
1
st
IF Center Frequency
Condition
Min
Typ
20
Max
Units
dB
MHz
f
RX
= 868 MHz
f
RX
= 915 MHz
1.219
1.285
-109
-109
360
380
9.4 – j72
9 – j67
20
-78
0.1
+/-2
+/-800
80
Receiver Sensitivity @
1kbps
(4)
IF Bandwidth
f
RX
= 868 MHz (matched to 50Ω)
f
RX
= 915 MHz (matched to 50Ω)
f
RX
= 868 MHz
f
RX
= 915 MHz
dBm
kHz
Antenna Input
Impedance
Receive Modulation Duty
Cycle
Spurious Reverse
Isolation
(5)
AGC Attack / Decay
Ratio
AGC pin leakage current
f
RX
= 868 MHz
f
RX
= 915 MHz
Note 6
ANT pin, RSC = 50
Ω
t
ATTACK
/ t
DECAY
T
A
= 25ºC
T
A
= +105ºC
Ω
%
dBm
nA
October 2008
3
M9999-100108
(408) 955-1690
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
= 868 MHz
f
RX
= 915 MHz
RO1 Pin
From Shut Down
With External Drive
RO1 Pin, V(REFOSC) = 0V
Min
Typ
13.54856
14.27643
1500
1
Max
Units
MHz
kΩ
msec
1.5
Vp-p
µA
0.5
380
Autopolling Operation
(7)
Symbol
Parameter
Tsleep Programming
Range
Condition
Min
10
Typ
Max
1300
Units
msec
µA
Isleep
(8)
SLEEP Current
2msec on, 1.3 sec Off
15
Demodulator
Symbol
Parameter
CTH Source Impedance
CTH Leakage Current
Condition
Frefosc = 14.27643MHz
T
A
= 25ºC
T
A
= +105ºC
Min
Typ
100
+/-2
+/-800
Max
Units
kΩ
nA
Demodulator Filter
Bandwidth @ 915MHz
Digital / Control Functions
Programmable, see application section
1712
13000
Hz
Symbol
Parameter
Input High Voltage
Input Low Voltage
Output Voltage High
Output Voltage Low
DO pin output current
Condition
Pins SCLK, DO (As input), SHDN
Pins SCLK, DO (As input), SHDN
DO
DO
As output, source @ 0.8 V
DD
As output, sink @ 0.2 V
DD
Min
0.8Vdd
Typ
Max
Units
V
0.2Vdd
0.8Vdd
0.2Vdd
260
600
2
V
V
V
µA
µsec
Output rise and fall times
CI = 15 pF, pin DO, 10-90%
October 2008
4
M9999-100108
(408) 955-1690
Micrel Inc.
MICRF221
Electrical Characteristics (continued)
RSSI
Symbol
Parameter
RSSI DC Output Voltage
Range
RSSI response slope
RSSI Output Impedance
Condition
Min
Typ
0.2 to 2.0
Max
Units
V
mV/dB
Ω
-109 dBm to -40 dBm
26
220
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 50Ohms 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
) = 50msec/200msec = 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.
October 2008
5
M9999-100108
(408) 955-1690
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