Micrel MICRF022YM-FS12 300-440mhz qwikradioâ® ask receiver Datasheet

MICRF002/RF022
300-440MHz QwikRadio® ASK Receiver
General Description
The MICRF002 is a single chip ASK/OOK (ON-OFF
Keyed) RF receiver IC. This device is a true “antenna-in to
QwikRadio®
data-out” monolithic device. All RF and IF tuning is
accomplished automatically within the IC which eliminates
Features
manual tuning and reduces production costs. The result is
• 300MHz to 440MHz frequency range
a highly reliable yet low cost solution.
• Data-rate up to 10kbps (fixed-mode)
The MICRF002 is a fully featured part in 16-pin packaging,
the MICRF022 is the same part packaged in 8-pin
• Low Power Consumption
packaging with a reduced feature set (see “Ordering
• 2.2mA fully operational (315MHz)
Information” for more information).
• 0.9µA in shutdown
The MICRF002 is an enhanced version of the MICRF001
• 220µA in polled operation (10:1 duty-cycle)
and MICRF011. The MICRF002 provides two additional
• Wake-up output flag to enable decoders and
functions over the MICRF001/011, (1) a Shutdown pin,
microprocessors
which may be used to turn the device off for duty-cycled
• Very low RF re-radiation at the antenna
operation, and (2) a “Wake-up” output, which provides an
output flag indicating when an RF signal is present. These
• Highly integrated with extremely low external part count
features make the MICRF002 ideal for low and ultra-low
power applications, such as RKE and remote controls.
Applications
All IF filtering and post-detection (demodulator) data
filtering is provided within the MICRF002, so no external
• Automotive remote keyless entry (RKE)
filters are necessary. One of four demodulator filter
• Remote controls
bandwidths may be selected externally by the user.
• Remote fan and light control
The MICRF002 offer two modes of operation; fixed-mode
• Garage door and gate openers
(FIX) and sweep-mode (SWP). In fixed-mode the
MICRF002 functions as a conventional superhet receiver.
In sweep-mode the MICRF002 employs a patented
sweeping function to sweep a wider RF spectrum. Fixedmode provides better selectivity and sensitivity
performance and sweep-mode enables the MICRF002 to
be used with low cost, imprecise transmitters.
Data sheets and support documentation can be found on
Micrel’s web site at: www.micrel.com.
_________________________________________________________________________________________________________
Ordering Information
Part Number
Demodulator
Bandwidth
Operating Mode
Shutdown
WAKEB
Output Flag
Package
Lead Finish
MICRF002YM
User Programmable
Fixed or Sweep
Yes
Yes
16-Pin SOIC
Pb-Free
MICRF022YM-SW48
5000Hz
Sweep
No
Yes
8-Pin SOIC
Pb-Free
MICRF022YM-FS12
1250Hz
Fixed
Yes
No
8-Pin SOIC
Pb-Free
MICRF022YM-FS24
2500Hz
Fixed
Yes
No
8-Pin SOIC
Pb-Free
MICRF022YM-FS48
5000Hz
Fixed
Yes
No
8-Pin SOIC
Pb-Free
QwikRadio is a registered trademark of Micrel, Inc. The QwikRadio ICs were developed under a partnership agreement with AIT of Orlando, FL.
Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
July 2008
M9999-070808
Micrel, Inc.
MICRF002/RF022
Typical Application
1/4 Wave Monopole
MICRF002
SEL0
SEL0
VSSRF
10pF
SWEN
REFOSC
VSSRF
68nH
+5V
SEL1
ANT
VDDRF
VDDBB
CAGC
WAKEB 4.7µF
SHUT
CTH
15nH
0.047µF
4.8970MHz
DO
NC
VSSBB
Data
Output
315MHz 800bps On-Off Keyed Receiver
Pin Configuration
16 SWEN
SEL0 1
VSSRF 2
15 REFOSC
VSSRF 3
14 SEL1
ANT 4
13 CAGC
VDDRF 5
12 WAKEB
VDDBB 6
11 SHUT
CTH 7
VSSRF 1
ANT 2
7 CAGC
VDDRF 3
10 DO
NC 8
8 REFOSC
6 SHUT/WAKEB
CTH 4
9 VSSBB
16-Pin SOIC (M)
5 DO
8-Pin SOIC (M)
8-Pin Options
The standard 16-pin package allows complete control of
all configurable features. Some reduced function 8-pin
versions are also available, see “Ordering Information”
on page 1.
For high-volume applications additional customized 8-pin
devices can be produced. SWEN, SEL0 and SEL1 pins
are internally bonded to reduce the pin count; pin 6 may
be configured as either SHUT or WAKEB
SEL0
SEL1
1
Demodulator Bandwidth
Sweep-Mode
Fixed-Mode
1
5000Hz
10000Hz
0
1
2500Hz
5000Hz
1
0
1250Hz
2500Hz
0
0
625Hz
1250Hz
Table 1. Nominal Demodulator Filter Bandwidth vs.
SEL0, SEL1 and Operating Mode
July 2008
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MICRF002/RF022
Pin Description
Pin Number
SOIC-16
Pin Number
SOIC-8
Pin Name
1
–
SEL0
2, 3
1
VSSRF
4
2
ANT
5
3
VDDRF
RF Power Supply: Positive supply input for the RF section of the IC.
6
–
VDDBB
Base-Band Power Supply: Positive supply input for the baseband section
(digital section) of the IC.
7
4
CTH
8
–
NC
9
–
VSSBB
10
5
DO
11
6
SHUT
12
–
WAKEB
13
7
CAGC
Automatic Gain Control (Analog I/O): Connect an external capacitor to set the
attack/decay rate of the on-chip automatic gain control.
14
–
SEL1
Bandwidth Selection Bit 1 (Digital Input): Used in conjunction with SEL0 to set
the desired demodulator filter bandwidth. See Table 1. Internally pulled-up to
VDDRF.
15
8
REFOSC
16
–
SWEN
July 2008
Pin Name
Bandwidth Selection Bit 0 (Digital Input): Used in conjunction with SEL1 to set
the desired demodulator filter bandwidth. See Table 1. Internally pulled-up to
VDDRF.
RF Power Supply: Ground return to the RF section power supply.
Antenna (Analog Input): For optimal performance the ANT pin should be
impedance matched to the antenna. See “Applications Information” for
information on input impedance and matching techniques.
Data Slicing Threshold Capacitor (Analog I/O): Capacitor connected to this
pin extracts the dc average value from the demodulated waveform which
becomes the reference for the internal data slicing comparator.
Not internally connected
Base-Band Power Supply: Ground return to the baseband section power
supply.
Data Output (Digital Output)
Shutdown (Digital Input): Shutdown-mode logic-level control input. Pull low to
enable the receiver. Internally pulled-up to VDDRF.
Wakeup (Digital Output): Active-low output that indicates detection of an
incoming RF signal.
Reference Oscillator: Timing reference, sets the RF receive frequency.
Sweep-Mode Enable (Digital Input): Sweep- or Fixed-mode operation control
input. SWEN high= sweep mode; SWEN low = conventional superheterodyne
receiver. Internally pulled-up to VDDRF.
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MICRF002/RF022
Absolute Maximum Ratings(1)
Operating Ratings(2)
Supply Voltage (VDDRF, VDDBB)........................................+7V
Input/Output Voltage (VI/O). ....................VSS–0.3 to VDD+0.3
Junction Temperature (TJ) ....................................... +150°C
Storage Temperature (Ts) ........................... –65°C to 150°C
Lead Temperature (soldering, 10 sec.)...................... 260°C
ESD Rating(3)
Supply Voltage (VDDRF, VDDBB).................... +4.75V to +5.5V
RF Frequency Range.............................. 300MHz to 440Hz
Data Duty-Cycle ................................................20% to 80%
Reference Oscillator Input Range.............. 0.1VPP to 1.5VPP
Ambient Temperature (TA) .......................... –40°C to +85°C
Electrical Characteristics(4)
VDDRF = VDDBB = VDD where +4.75V ≤ VDD ≤ 5.5V, VSS = 0V; CAGC = 4.7µF, CTH = 100nF; SEL0 = SEL1 = VSS; fixed mode
(SWEN = VSS); fREFOSC = 4.8970MHz (equivalent to fRF = 315MHz); data-rate = 1kbps (Manchester encoded). TA = 25°C,
bold values indicate –40°C ≤ TA ≤ +85°C; current flow into device pins is positive; unless noted.
Symbol
Parameter
Condition
Typ
Max
Units
IOP
Operating Current
continuous operation, fRF = 315MHz
2.2
3.2
mA
polled with 10:1 duty cycle, fRF = 315MHz
220
µA
continuous operation, fRF = 433.92MHz
3.5
mA
ISTBY
Standby Current
Min
polled with 10:1 duty cycle, fRF = 433.92MHz
350
µA
VSHUT = VDD
0.9
µA
fRF = 315MHz
–97
dBm
fRF = 433.92MHz
–95
dBm
RF Section, IF Section
Receiver Sensitivity (Note 4)
fIF
IF Center Frequency
Note 6
0.86
MHz
fBW
IF Bandwidth
Note 6
0.43
MHz
Maximum Receiver Input
RSC = 50Ω
–20
dBm
Spurious Reverse Isolation
ANT pin, RSC = 50Ω, Note 5
30
µVRMS
AGC Attack to Decay Ratio
tATTACK ÷ tDECAY
0.1
AGC Leakage Current
TA = +85°C
±100
nA
Note 8
290
kΩ
5.2
µA
Reference Oscillator
ZREFOSC
Reference Oscillator Input
Impedance
Reference Oscillator Source
Current
Demodulator
ZCTH
CTH Source Impedance
Note 7
145
kΩ
IZCTH(leak)
CTH Leakage Current
TA = +85°C
±100
nA
Demodulator Filter Bandwidth
Sweep Mode
(SWEN = VDD or OPEN)
Note 6
VSEL0 = VDD. VSEL1 = VDD
V SEL0 = VSS. V SEL1 = VDD
V SEL0 = VDD. V SEL1 = VSS
V SEL0 = VSS. V SEL1 = VSS
4000
2000
1000
500
Hz
Hz
Hz
Hz
Demodulator Filter Bandwidth
Fixed Mode
(SWEN = VSS)
Note 6
VSEL0 = VDD. VSEL1 = VDD
V SEL0 = VSS. V SEL1 = VDD
V SEL0 = VDD. V SEL1 = VSS
V SEL0 = VSS. V SEL1 = VSS
8000
4000
2000
1000
Hz
Hz
Hz
Hz
July 2008
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Micrel, Inc.
Symbol
MICRF002/RF022
Parameter
Condition
Min
Typ
Max
Units
0.8
VDD
Digital/Control Section
VIN(high)
Input-High Voltage
SEL0, SEL1, SWEN
VIN(low)
Input-Low Voltage
SEL0, SEL1, SWEN
IOUT
Output Current
DO, WAKEB pins, push-pull
VOUT(high)
Output High Voltage
DO, WAKEB pins, IOUT = –1µA
VOUT(low)
Output Low Voltage
DO, WAKEB pins, IOUT = +1µA
tR, tF
Output Rise and Fall Times
DO, WAKEB pins, CLOAD = 15pF
VDD
0.2
10
µA
VDD
0.9
0.1
10
VDD
µs
Notes:
1. Exceeding the absolute maximum rating may damage the device.
2. The device is not guaranteed to function outside its operating rating.
3. Devices are ESD sensitive, use appropriate ESD precautions. Meets class 1 ESD test requirements, (human body model HBM), in accordance with
MIL-STD-883C, method 3015. Do not operate or store near strong electrostatic fields.
4. Sensitivity is defined as the average signal level measured at the input necessary to achieve 10-2 BER (bit error rate). The RF input is assumed to be
matched to 50Ω.
5. Spurious reverse isolation represents the spurious components which appear on the RF input pin (ANT) measured into 50Ω with an input RF
matching network.
6. Parameter scales linearly with reference oscillator frequency fT. For any reference oscillator frequency other than 4.8970MHz, compute new
parameter value as the ratio:.
f
REFOSC
MHz
4.8970MHz
× (parameter value at 4.8970MHz)
7. Parameter scales inversely with reference oscillator frequency fT. For any reference oscillator frequency other than 4.8970MHz, compute new
parameter value as the ratio:
4.8970MHz
f
REFOSC
MHz
× (parameter value at 4.8970MHz)
8. Series resistance of the resonator (ceramic resonator or crystal) should be minimized to the extent possible. In cases where the resonator series
resistance is too great, the oscillator may oscillate at a diminished peak-to-peak level, or may fail to oscillate entirely. Micrel recommends that series
resistances for ceramic resonators and crystals not exceed 50Ohms and 100Ω respectively. Refer to Application Hint 35 for crystal
recommendations.
July 2008
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Micrel, Inc.
MICRF002/RF022
Typical Characteristics
Supply Current
vs. Frequency
3.5
TA = 25°C
VDD = 5V
CURRENT (mA)
CURRENT (mA)
6.0
Supply Current
vs. Temperature
4.5
3.0
1.5
250
Sweep Mode,
Continuous Operation
300
350
400
450
FREQUENCY (MHz)
July 2008
500
3.0
f = 315MHz
VDD = 5V
2.5
2.0
Sweep Mode,
Continuous Operation
1.5
-40 -20
0
20
40
60
80 100
TEMPERATURE (°C)
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Micrel, Inc.
MICRF002/RF022
Functional Diagram
CAGC
AGC
Control
CAGC
2nd Order
Programmable
Low-Pass Filter
5th Order
Band-Pass Filter
ANT
RF
Amp
f RX
fIF
fLO
IF
Amp
IF
Amp
Peak
Detector
430kHz
SwitchedCapacitor
Resistor
RSC
Comparator
VDD
VSS
DO
CTH
Synthesizer
UHF Downconverter
OOK Demodulator
CTH
SEL0
SEL1
SWEN
Control
Logic
Resettable
Counter
WAKEB
SHUT
fT
REFOSC
Cystal
or
Ceramic
MICRF002
Resonator
Reference
Oscillator
Reference and Control
Wakeup
Figure 1. MICRF002 Block Diagram
Application Information and Functional
Description
Design Steps
The following steps are the basic design steps for using the
MICRF002 receiver:
1. Select the operating mode (sweep or fixed)
2. Select the reference oscillator
3. Select the CTH capacitor
4. Select the CAGC capacitor
5. Select the demodulator filter bandwidth
Refer to Figure 1 “MICRF002 Block Diagram”. Identified in
the block diagram are the four sections of the IC: UHF
Downconverter, OOK Demodulator, Reference and
Control, and Wakeup. Also shown in the figure are two
capacitors (CTH, CAGC) and one timing component,
usually a crystal or ceramic resonator. With the exception
of a supply decoupling capacitor, and antenna impedance
matching network, these are the only external components
needed by the MICRF002 to assemble a complete UHF
receiver.
For optimal performance is highly recommended that the
MICRF002 is impedance matched to the antenna, the
matching network will add an additional two or three
components.
Four control inputs are shown in the block diagram: SEL0,
SEL1, SWEN, and SHUT. Using these logic inputs, the
user can control the operating mode and selectable
features of the IC. These inputs are CMOS compatible, and
are internally pulled-up. IF Bandpass Filter Roll-off
response of the IF Filter is 5th order, while the demodulator
data filter exhibits a 2nd order response.
July 2008
Step 1: Selecting the Operating Mode
Fixed-Mode Operation
For applications where the transmit frequency is accurately
set (that is, applications where a SAW or crystal-based
transmitter is used) the MICRF002 may be configured as a
standard superheterodyne receiver (fixed mode). In fixedmode operation the RF bandwidth is narrower making the
receiver less susceptible to interfering signals. Fixed mode
is selected by connecting SWEN to ground.
Sweep-Mode Operation
When used in conjunction with low-cost L-C transmitters
the MICRF002 should be configured in sweep-mode. In
sweep-mode, while the topology is still superheterodyne,
the LO (local oscillator) is swept over a range of
frequencies at rates greater than the data rate. This
technique effectively increases the RF bandwidth of the
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M9999-070808
Micrel, Inc.
MICRF002/RF022
MICRF002, allowing the device to operate in applications
where
significant
transmitter-receiver
frequency
misalignment may exist. The transmit frequency may vary
up to ±0.5% over initial tolerance, aging, and temperature.
In sweep-mode a band approximately 1.5% around the
nominal transmit frequency is captured. The transmitter
may drift up to ±0.5% without the need to retune the
receiver and without impacting system performance.
The swept-LO technique does not affect the IF bandwidth,
therefore noise performance is not degraded relative to
fixed-mode. The IF bandwidth is 430kHz whether the
device is operating in fixed- or sweep-mode. Due to
limitations imposed by the LO sweeping process, the upper
limit on data rate in sweep mode is approximately 5.0kbps.
Similar performance is not currently available with
crystalbased superheterodyne receivers which can operate
only with SAW- or crystal-based transmitters. In sweepmode, a range reduction will occur in installations where
there is a strong interferer in the swept RF band. This is
because the process indiscriminately includes all signals
within the sweep range. An MICRF002 may be used in
place of a superregenerative receiver in most applications.
the appropriate fLO for a given fTX:
(1)
Frequencies fTX and fLO are in MHz. Note that two values of
fLO exist for any given fTX, distinguished as “high-side
mixing” and “low-side mixing”. High-side mixing results in
an image frequency above the frequency of interest and
low-side mixing results in a frequency below.
After choosing one of the two acceptable values of fLO, use
Equation 2 to compute the reference oscillator frequency fT:
(2)
fT =
fLO
64.5
Frequency fT is in MHz. Connect a crystal of frequency fT to
REFOSC on the MICRF002. Four-decimal-place accuracy
on the frequency is generally adequate. The following table
identifies fT for some common transmit frequencies when
the MICRF002 is operated in fixed mode.
Step 2: Selecting the Reference Oscillator
All timing and tuning operations on the MICRF002 are
derived from the internal Colpitts reference oscillator.
Timing and tuning is controlled through the REFOSC pin in
one of three ways:
1. Connect a ceramic resonator
2. Connect a crystal
3. Drive this pin with an external timing signal
The specific reference frequency required is related to the
system transmit frequency and to the operating mode of
the receiver as set by the SWEN pin.
Transmit Frequency fTX
Reference Oscillator
Frequency fT
315MHz
4.8970MHz
390MHz
6.0630MHz
418MHz
6.4983MHz
433.92MHz
6.7458MHz
Table 2. Fixed-Mode Recommended Reference Oscillator
Values for Typical Transmit Frequencies
(high-side mixing)
Selecting REFOSC Frequency fT (Sweep-Mode)
Selection of the reference oscillator frequency fT in sweepmode is much simpler than in fixed mode due to the LO
sweeping process. Also, accuracy requirements of the
frequency reference component are significantly relaxed.
In sweep-mode, fT is given by Equation 3:
Crystal or Ceramic Resonator Selection
Do not use resonators with integral capacitors since
capacitors are included in the IC, also care should be taken
to ensure low ESR capacitors are selected. Application Hint
34 and Application Hint 35 provide additional information
and recommended sources for crystals and resonators.
If operating in fixed-mode, a crystal is recommended. In
sweep-mode either a crystal or ceramic resonator may be
used. When a crystal of ceramic resonator is used the
minimum voltage is 300mVPP. If using an externally applied
signal it should be AC-coupled and limited to the operating
range of 0.1VPP to 1.5VPP.
(3)
fT =
fLO
64.25
In sweep-mode a reference oscillator with frequency
accurate to two-decimal-places is generally adequate. A
crystal may be used and may be necessary in some cases
if the transmit frequency is particularly imprecise.
Selecting Reference Oscillator Frequency fT (FixedMode)
As with any superheterodyne receiver, the mixing
between the internal LO (local oscillator) frequency fLO and
the incoming transmit frequency fTX ideally must equal the
IF center frequency. Equation 1 may be used to compute
July 2008
f ⎞
⎛
fLO = f TX ± ⎜⎜ 0.86 TX ⎟⎟
315 ⎠
⎝
Transmit Frequency fTX
Reference Oscillator
Frequency fT
315MHz
4.88MHz
390MHz
6.05MHz
418MHz
6.48MHz
433.92MHz
6.73MHz
Table 3. Sweep-Mode Recommended Reference Oscillator
Values for Typical Transmit Frequencies
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Micrel, Inc.
MICRF002/RF022
To further enhance duty-cycled operation, the AGC push
and pull currents are boosted for approximately 10ms
immediately after the device is taken out of shutdown. This
compensates for AGC capacitor voltage droop and reduces
the time to restore the correct AGC voltage. The current is
boosted by a factor of 45.
Step 3: Selecting the CTH Capacitor
Extraction of the dc value of the demodulated signal
for purposes of logic-level data slicing is accomplished
using the external threshold capacitor CTH and the onchip switched capacitor “resistor” RSC, shown in the
block diagram.
Slicing level time constant values vary somewhat with
decoder type, data pattern, and data rate, but typically
values range from 5ms to 50ms. Optimization of the
value of CTH is required to maximize range.
Selecting CAGC Capacitor in Continuous Mode
A CAGC capacitor in the range of 0.47µF to 4.7µF is typically
recommended. The value of the CAGC should be selected to
minimize the ripple on the AGC control voltage by using a
sufficiently large capacitor. However if the capacitor is too
large the AGC may react too slowly to incoming signals.
AGC settling time from a completely discharged (zero-volt)
state is given approximately by Equation 6:
Selecting Capacitor CTH
The first step in the process is selection of a data-slicinglevel time constant. This selection is strongly dependent on
system issues including system decode response time and
data code structure (that is, existence of data preamble,
etc.). This issue is covered in more detail in Application
Note 22.
The effective resistance of RSC is listed in the electrical
characteristics table as 145kΩ at 315MHz, this value scales
linearly with frequency. Source impedance of the CTH pin at
other frequencies is given by Equation 4, where fT is in
MHz:
(4)
R SC = 145kΩ
(6)
where:
CAGC sin in µF, and ∆t is in seconds.
Selecting CAGC Capacitor in Duty-Cycle Mode
Voltage droop across the CAGC capacitor during shutdown
should be replenished as quickly as possible after the IC is
enabled. As mentioned above, the MICRF002 boosts the
push-pull current by a factor of 45 immediately after startup. This fixed time period is based on the reference
oscillator frequency fT. The time is 10.9ms for fT = 6.00MHz,
and varies inversely with fT. The value of CAGC capacitor
and the duration of the shutdown time period should be
selected such that the droop can be replenished within this
10ms period.
Polarity of the droop is unknown, meaning the AGC voltage
could droop up or down. Worst-case from a recovery
standpoint is downward droop, since the AGC pull-up
current is 1/10th magnitude of the pulldown current. The
downward droop is replenished according to the Equation
7:
4.8970
fT
τ of 5x the bit-rate is recommended. Assuming that a slicing
level time constant τ has been established, capacitor CTH
may be computed using Equation 5:
(5)
C TH =
τ
R SC
A standard ±20% X7R ceramic capacitor is generally
sufficient. Refer to Application Hint 42 for CTH and CAGC
selection examples.
Step 4: Selecting the CAGC Capacitor
The signal path has AGC (automatic gain control) to
increase input dynamic range. The attack time constant of
the AGC is set externally by the value of the CAGC capacitor
connected to the CAGC pin of the device. To maximize
system range, it is important to keep the AGC control
voltage ripple low, preferably under 10mVPP once the
control voltage has attained its quiescent value. For this
reason capacitor values of at least 0.47µF are
recommended.
The AGC control voltage is carefully managed on-chip to
allow duty-cycle operation of the MICRF002. When the
device is placed into shutdown mode (SHUT pin pulled
high), the AGC capacitor floats to retain the voltage. When
operation is resumed, only the voltage droop due to
capacitor leakage must be replenished. A relatively lowleakage capacitor is recommended when the devices are
used in dutycycled operation.
July 2008
∆t = 1.333C AGC − 0.44
(7)
I
∆V
=
C AGC
∆t
where:
I = AGC pullup current for the initial 10ms (67.5µA)
CAGC = AGC capacitor value
∆t = droop recovery time
∆V = droop voltage
For example, if user desires ∆t = 10ms and chooses a
4.7µF CAGC, then the allowable droop is about 144mV.
Using the same equation with 200nA worst case pin
leakage and assuming 1µA of capacitor leakage in the
same direction, the maximum allowable ∆t (shutdown time)
is about 0.56s for droop recovery in 10ms.
The ratio of decay-to-attack time-constant is fixed at 10:1
(that is, the attack time constant is 1/10th of the decay time
constant). Generally the design value of 10:1 is adequate
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MICRF002/RF022
for the vast majority of applications. If adjustment is
required the constant may be varied by adding a resistor in
parallel with the CAGC capacitor. The value of the resistor
must be determined on a case by case basis.
Demoulator bandwidth =
(8)
0.65
Shortest pulse − width
It should be noted that the values indicated in Table 1 are
nominal values. The filter bandwidth scales linearly with
frequency so the exact value will depend on the operating
frequency. Refer to the “Electrical Characteristics” for the
exact filter bandwidth at a chosen frequency.
Step 5: Selecting The Demod Filter Bandwidth
The inputs SEL0 and SEL1 control the demodulator filter
bandwidth in four binary steps (625Hz to 5000Hz in sweep,
1250Hz to 10000Hz in fixed-mode), see Table 3.
Bandwidth must be selected according to the application.
The demodulator bandwidth should be set according to
Equation 8:
SEL0
SEL1
1
Demodulator Bandwidth
Sweep-Mode
Fixed-Mode
1
5000Hz
10000Hz
0
1
2500Hz
5000Hz
1
0
1250Hz
2500Hz
0
0
625Hz
1250Hz
Table 1. Nominal Demodulator Filter Bandwidth vs.
SEL0, SEL1 and Operating Mode
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MICRF002/RF022
Additional Applications Information
In addition to the basic operation of the MICRF002 the
following enhancements can be made. In particular it is
strongly recommended that the antenna impedance is
matched to the input of the IC.
Antenna Impedance Matching
As shown in Table 4 the antenna pin input impedance is
frequency dependant. The ANT pin can be matched to 50Ω
with an L-type circuit. That is, a shunt inductor from the RF
input to ground and another in series from the RF input to
the antenna pin.
Inductor values may be different from table depending on
PCB material, PCB thickness, ground configuration, and
how long the traces are in the layout. Values shown were
characterized for a 0.031 thickness, FR4 board, solid
ground plane on bottom layer, and very short traces.
MuRata and Coilcraft wire wound 0603 or 0805 surface
mount inductors were tested, however any wire wound
inductor with high SRF (self resonance frequency) should
do the job.
Shutdown Function
Duty-cycled operation of the MICRF002 (often referred to
as polling) is achieved by turning the MICRF002 on and off
via the SHUT pin. The shutdown function is controlled by a
logic state applied to the SHUT pin. When VSHUT is high,
the device goes into low-power standby mode. This pin is
pulled high internally, it must be externally pulled low to
enable the receiver.
LSERIES
LSHUNT
Frequency
(MHz)
ZIN
Z11
S11
LSHUNT(nH)
LSERIES(nH)
300
12-j166
0.803-j0.529
15
72
305
12-j165
0.800-j0.530
15
72
310
12-j163
0.796-j0.536
15
72
315
13-j162
0.791-j0.536
15
72
320
12-j160
0.789-j0.543
15
68
325
12-j157
0.782-j0.550
12
68
330
12-j155
0.778-j0.556
12
68
335
12-j152
0.770-j0.564
12
68
340
11-j150
0.767-j0.572
15
56
345
11-j148
0.762-j0.578
15
56
350
11-j145
0.753-j0.586
12
56
355
11-j143
0.748-j0.592
12
56
360
11-j141
0.742-j0.597
10
56
365
11-j139
0.735-j0.603
10
56
370
10-j137
0.732-j0.612
12
47
375
10-j135
0.725-j0.619
12
47
380
10-j133
0.718-j0.625
10
47
385
10-j131
0.711-j0.631
10
47
390
10-j130
0.707-j0.634
10
43
395
10-j128
0.700-j0.641
10
43
400
10-j126
0.692-j0.647
10
43
405
10-j124
0.684-j0.653
10
39
410
10-j122
0.675-j0.660
10
39
415
10-j120
0.667-j0.667
10
39
420
10-j118
0.658-j0.673
10
36
425
10-j117
0.653-j0.677
10
36
430
10-j115
0.643-j0.684
10
33
435
10-j114
0.638-j0.687
10
33
440
8-j112
0.635-j0.704
8.2
33
Table 4. Input Impedance vs. Frequency
j100
j25
–j25
July 2008
∞
50
0
–j100
11
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Micrel, Inc.
MICRF002/RF022
reference oscillator and is 1/256 the reference oscillator
frequency. For example:
fT = 6.4MHz
fS = fT/256 = 25kHz
PS = 1/fS = 0.04ms
128 counts x 0.04ms = 5.12ms
where:
fT = reference oscillator frequency
fS = system clock frequency
PS = system clock period
The Wake-Up counter will reset immediately after a
detected RF carrier drops. The duration of the Wake-Up
signal output is then determined by the required wake up
time plus an additional RF carrier on time interval to create
a wake up pulse output.
WAKEB Output Pulse Time = TWAKE + Additional
RF Carrier On Time
For designers who wish to use the wakeup function while
squelching the output, a positive squelching offset voltage
must be used. This simply requires that the squelch resistor
be connected to a voltage more positive than the quiescent
voltage on the CTH pin so that the data output is low in
absence of a transmission.
Power Supply Bypass Capacitors
VDDBB and VDDRF should be connected together directly at
the IC pins. Supply bypass capacitors are strongly
recommended. They should be connected to VDDBB and
VDDRF and should have the shortest possible lead lengths.
For best performance, connect VSSRF to VSSBB at the power
supply only (that is, keep VSSBB currents from flowing
through the VSSRF return path).
Increasing Selectivity with an Optional BandPass
Filter
For applications located in high ambient noise
environments, a fixed value band-pass network may be
connected between the ANT pin and VSSRF to provide
additional receive selectivity and input overload protection.
A minimum input configuration is included in Figure 7 it
provides some filtering and necessary overload protection.
Data Squelching
During quiet periods (no signal) the data output (DO pin)
transitions randomly with noise. Most decoders can
discriminate between this random noise and actual data but
for some system it does present a problem. There are three
possible approaches to reducing this output noise:
1. Analog squelch to raise the demodulator threshold
2. Digital squelch to disable the output when data is
not present
3. Output filter to filter the (high frequency) noise
glitches on the data output pin.
The simplest solution is add analog squelch by introducing
a small offset, or squelch voltage, on the CTH pin so that
noise does not trigger the internal comparator. Usually
20mV to 30mV is sufficient, and may be achieved by
connecting a several-megohm resistor from the CTH pin to
either VSS or VDD, depending on the desired offset polarity.
Since the MICRF002 has receiver AGC noise at the
internal comparator input is always the same, set by the
AGC. The squelch offset requirement does not change as
the local noise strength changes from installation to
installation. Introducing squelch will reduce sensitivity and
also reduce range. Only introduce an amount of offset
sufficient to quiet the output. Typical squelch resistor values
range from 6.8MΩ to 10MΩ.
I/O Pin Interface Circuitry
Interface circuitry for the various I/O pins of the MICRF002
are diagrammed in Figures 1 through 6. The ESD
protection diodes at all input and output pins are not shown.
CTH Pin
VDDBB
PHI1B
CTH
VSSBB
PHI2
VSSBB
PHI1
Figure 2. CTH Pin
Figure 2 illustrates the CTH pin interface circuit. The CTH pin
is driven from a P-channel MOSFET source-follower with
approximately 10µA of bias. Transmission gates TG1 and
TG2 isolate the 6.9pF capacitor. Internal control signals
PHI1/PHI2 are related in a manner such that the
impedance across the transmission gates looks like a
“resistance” of approximately 100kΩ. The dc potential at
the CTH pin is approximately 1.6V
Wake-Up Function
The WAKEB output signal can be used to reduce system
power consumption by enabling the rest of a system when
an RF signal is present. The WAKEB is an output logic
signal which goes active low when the IC detects a
constant RF carrier. The wake-up function is unavailable
when the IC is in shutdown mode.
To activate the Wake-Up function, a received constant RF
carrier must be present for 128 counts or the internal
system clock. The internal system clock is derived from the
July 2008
PHI2B
Demodulator
Signal
2.85Vdc
12
M9999-070808
Micrel, Inc.
MICRF002/RF022
driver is recommended for driving high-capacitance loads.
CAGC Pin
VDDBB
REFOSC Pin
VDDBB
Active
Bias
67.5µA
1.5µA
Comparator
200k
REFOSC
250
30pF
CAGC
30pF
30µA
VSSBB
Timout
VSSBB
675µA
15µA
Figure 5. REFOSC Pin
The REFOSC input circuit is shown in Figure 5. Input
impedance is high (200kΩ). This is a Colpitts oscillator with
internal 30pF capacitors. This input is intended to work with
standard ceramic resonators connected from this pin to the
VSSBB pin, although a crystal may be used when greater
frequency accuracy is required. The nominal dc bias
voltage on this pin is 1.4V.
VSSBB
Figure 3. CAGC Pin
Figure 3 illustrates the CAGC pin interface circuit. The AGC
control voltage is developed as an integrated current into a
capacitor CAGC. The attack current is nominally 15µA, while
the decay current is a 1/10th scaling of this, nominally
1.5µA, making the attack/decay time constant ratio a fixed
10:1. Signal gain of the RF/IF strip inside the IC diminishes
as the voltage at CAGC decreases. Modification of the
attack/decay ratio is possible by adding resistance from the
CAGC pin to either VDDBB or VSSBB, as desired.
Both the push and pull current sources are disabled during
shutdown, which maintains the voltage across CAGC, and
improves recovery time in duty-cycled applications. To
further improve duty-cycle recovery, both push and pull
currents are increased by 45 times for approximately 10ms
after release of the SHUT pin. This allows rapid recovery of
any voltage droop on CAGC while in shutdown.
SEL0, SEL1, SWEN, and SHUT Pins
VDDBB
Q1
Q2
VSSBB
SHUT
to Internal
Circuits
Q4
SEL0,
SEL1,
SWEN
Q3
VSSBB
Figure 6a. SEL0, SEL1, SWEN Pins
DO and WAKEB Pins
VDDBB
VDDBB
10µA
Q1
Comparator
Q2
to Internal
Circuits
VSSBB
DO
SHUT
Q3
VSSBB
10µA
Figure 6b. SHUT Pin
VSSBB
Control input circuitry is shown in Figures 6a and 6b. The
standard input is a logic inverter constructed with minimum
geometry MOSFETs (Q2, Q3). P-channel MOSFET Q1 is
a large channel length device which functions essentially
as a “weak” pullup to VDDBB. Typical pull-up current is 5µA,
leading to an impedance to the VDDBB supply of typically
1MΩ.
Figure 4. DO and WAKEB Pins
The output stage for DO (digital output) and WAKEB
(wakeup output) is shown in Figure 4. The output is a 10µA
push and 10µA pull switched-current stage. This output
stage is capable of driving CMOS loads. An external bufferJuly 2008
13
M9999-070808
Micrel, Inc.
MICRF002/RF022
Operation in this example is at 315MHz, and may be
customized by selection of the appropriate frequency
reference (Y1), and adjustment of the antenna length. The
value of C4 would also change if the optional input filter is
used. Changes from the 1kb/s data rate may require a
change in the value of R1. A bill of materials accompanies
the schematic.
Applications Example
315MHz Receiver/Decoder Application
Figure 7 illustrates a typical application for the MICRF002
UHF Receiver IC. This receiver operates continuously (not
duty cycled) in sweep mode, and features 6-bit address
decoding and two output code bits.
0.4λ monopole
antenna (11.6in)
+5V
Supply
Input
U1 MICRF002
C4
Optional Filter
8.2pF, 16.6nH
pcb foil inductor
1in of 30mil trace
L1
C1
4.7µF
C2
2.2µF
SEL0
SEL0
VSSRF
SWEN
REFOSC
VSSRF
ANT
VDDRF
VDDBB
SEL1
CAGC
WAKEB
SHUT
CTH
NC
DO
VSSBB
4.8970MHz
Y1
6-bit
address U2 HT-12D
A0
VDD
A1
VT
A2
A3
A4
A5
4.7µF
A6
A7
VSS
RF Baseband
(Analog) (Digital)
Ground Ground
OSC1
OSC2
DIN
D11
D10
D9
D8
R2
1k
R1
68k
Code Bit 0
Code Bit 1
Figure 7. 315MHz, 1kbps On-Off Keyed Recwiver/Decoder
Bill of Materials
Item
Part Number
C1
Qty.
4.7µF, Dipped Tantalum Capacitor
1
(1)
2.2µF, Dipped Tantalum Capacitor
1
(1)
4.7µF, Dipped Tantalum Capacitor
1
(1)
8.2pF, COG Ceramic Capacitor
1
(2)
6.00MHz, Ceramic Resonator
1
(3)
RED LED
1
Vishay
C3
Vishay
C4
D1
Description
(1)
Vishay
C2
CR1
Manufacturer
Vishay
CSA6.00MG
SSF-LX100LID
Murata
Lumex
R1
U1
U2
68k, 1/4W, 5%
1
1k, 1/4W, 5%
1
300-440MHz QwikRadio® ASK Receiver
1
Logic Decoder
1
(1)
R2
Vishay
MICRF002
HT-12D
Micrel, Inc.(4)
Holtek
(5)
Notes:
1. Vishay Tel: (203) 268-6261
2. Murata Tel: (800) 241-6574, Fx: (770) 436-3030
3. Lumex Tel: (800) 278-5666, Fx: (847) 359-8904
5. Micrel, Inc.: (408) 944-0800
5. Holtek Tel: (408) 894-9046, Fx: (408) 894-0838
July 2008
14
M9999-070808
Micrel, Inc.
MICRF002/RF022
PCB Layout Information
The MICRF002 evaluation board was designed and
characterized using two sided 0.031 inch thick FR4
material with 1 ounce copper clad. If another type of printed
circuit board material were to be substituted, impedance
matching and characterization data stated in this document
may not be valid. The gerber files for this board can be
downloaded from the Micrel website at www.micrel.com.
PCB Component Side Layout
PCB Silk Screen
PCB Solder Side Layout
J2
C5
REF.OSC.
GND
(Not Placed)
MICRF002
JP1
J1
RF INPUT
Z1
Z3
Z2
SEL0
2
3
4
ANT
5
VDDRF
6
VDDBB
SHUT
11
7
CTH
DO
10
VSSBB
9
Z4
R1
8
SWEN
16
VSSRF
REFOSC
15
VSSRF
SEL1
14
CAGC
13
WAKEB
12
NC
JP3
Y1
6.7458MHz
JP2
C4(CAGC)
4.7µF
J5
SHUT
GND
DO
GND
Squelch
Resistor
(Not Placed)
J3
+5V
GND
R2
10k
J4
C1
4.7µF
July 2008
1
C2
0.1µF
C3(CTH)
0.047µF
15
M9999-070808
Micrel, Inc.
MICRF002/RF022
Package Information
16-Pin SOIC (M)
8-Pin SOIC (M)
July 2008
16
M9999-070808
Micrel, Inc.
MICRF002/RF022
MICREL, INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA
TEL +1 (408) 944-0800 FAX +1 (408) 474-1000 WEB http://www.micrel.com
The information furnished by Micrel in this data sheet is believed to be accurate and reliable. However, no responsibility is assumed by Micrel for its
use. Micrel reserves the right to change circuitry and specifications at any time without notification to the customer.
Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product
can reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical implant
into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user. A
Purchaser’s use or sale of Micrel Products for use in life support appliances, devices or systems is a Purchaser’s own risk and Purchaser agrees to fully
indemnify Micrel for any damages resulting from such use or sale.
© 2003 Micrel, Incorporated.
July 2008
17
M9999-070808
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