MICRF213
3.3V, QwikRadio® 315MHz Receiver
General Description
Features
®
The MICRF213 is a general purpose, 3.3V QwikRadio
receiver that operates at 315MHz with a typical
sensitivity of -110dBm.
The MICRF213 functions as a super-heterodyne
receiver for OOK and ASK modulation up to 7.2kbps.
The down-conversion mixer also provides image
rejection. All post-detection data filtering is provided on
the MICRF213. Any one of four filter bandwidths may be
selected externally by the user using binary steps (from
1.18kHz to 9.44kHz, Manchester Encoded). The user
need only configure the device with a set of easily
determined values, based upon data rate, code
modulation format, and desired duty-cycle operation.
Datasheets and support documentation are available on
Micrel’s website at: www.micrel.com.
•
•
•
•
•
•
•
•
-2
Up to –110dBm sensitivity, 1kbps and BER 10
Image rejection mixer
Frequency from 300MHz to 350MHz
Low current consumption: 3.9mA @ 315MHz,
continuous on data rates to 7.2kbps (Manchester
Encoded)
Analog RSSI output
No IF filter required
Excellent selectivity and noise rejection
Low external part count
Typical Application
315MHz, 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 19, 2015
Revision 2.0
Micrel, Inc.
MICRF213
Ordering Information
Part Number
Temperature Range
Package
–40°C to +105°C
16-Pin QSOP
MICRF213AYQS
Pin Configuration
RO1
1
16 RO2
GNDRF
2
15 NC
ANT
3
14 RSSI
GNDRF
4
13 CAGC
VDD
5
12 CTH
SQ
6
11 SEL1
SEL0
7
10 DO
SHDN
8
9 GND
16-Pin QSOP (QS)
(Top View)
Pin Description
16-Pin
QSOP
Pin
Name
1
RO1
2
GNDRF
3
ANT
4
GNDRF
5
VDD
6
SQ
7
SEL0
Logic control input with active internal pull-up. Used in conjunction with SEL1 to control the demodulator low
pass filter bandwidth. (See filter table for SEL0 and SEL1 in application section)
8
SHDN
Shutdown logic control input. Active internal pull-up.
9
GND
Negative supply connection for all chip functions except RF input.
10
DO
11
SEL1
Logic control input with active internal pull-up. Used in conjunction with SEL0 to control the demodulator low
pass filter bandwidth. (See filter table for SEL0 and SEL1 in application subsection)
12
CTH
Demodulation threshold voltage integration capacitor connection. Tie an external capacitor across CTH pin
and GND to set the settling time for the demodulation data slicing level. Values above 1nF are
recommended and should be optimized for data rate and data profile.
13
CAGC
AGC filter capacitor connection. CAGC capacitor, normally greater than 0.47uF, is connected from this pin to
GND
14
RSSI
Received signal strength indication output. Output is from a buffer with 200 ohms typical output impedance.
15
NC
16
RO2
August 19, 2015
Pin Function
Reference resonator input connection to Colpitts oscillator stage. May also be driven by external reference
signal of 1.5V p-p amplitude maximum.
Negative supply connection associated with ANT RF input.
RF signal input from antenna. Internally AC-coupled. It is recommended that a matching network with an
inductor-to-RF ground is 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.
Demodulated data output.
Not Connected (Connect to Ground)
Reference resonator input connection to Colpitts oscillator stage, 7pF, in parallel with low resistance MOS
switch-to-GND, during normal operation. Driven by startup excitation circuit during the internal startup control
sequence.
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Micrel, Inc.
MICRF213
Absolute Maximum Ratings(1)
Operating Ratings(2)
Supply Voltage (VDD) .................................................+5V
Input Voltage ............................................................. +5V
Junction Temperature ......................................... +150ºC
Lead Temperature (soldering, 10sec.) .................. 260°C
Storage Temperature (TS) .....................-65°C to +150°C
Maximum Receiver Input Power ........................+10dBm
(3)
ESD Rating .................................................. 3KV HBM
Supply voltage (VDD) .............................+3.0V to +3.6V
Ambient Temperature (TA) ............... –40°C to +105°C
Input Voltage (VIN) ...................................... 3.6V (Max)
Maximum Input RF Power .............................. –20dBm
Electrical Characteristics(4)
Specifications apply for 3.0V < VDD < 3.6V, VSS = 0V, CAGC = 4.7µF, CTH = 0.47µF, fRX = 315MHz unless otherwise noted.
Bold values indicate –40°C TA +105°C. 900bps data rate (Manchester encoded), reference oscillator frequency = 9.81563MHz.
Symbol
Parameter
Condition
Min
IDD
Operating Supply Current
Continuous Operation, fRX = 315MHz
ISHUT
Shut down Current
Typ
Max
Units
3.9
mA
0.33
µA
RF/IF Section
Image Rejection
st
20
dB
0.86
MHz
-110
dBm
fRX = 315MHz
235
kHz
fRX = 315MHz
32.5 – j235
Ω
1 IF Center Frequency
fRX = 315MHz
Receiver Sensitivity @
1kbps
fRX = 315MHz (matched to 50Ω) BER=10
IF Bandwidth
Antenna Input
Impedance
Receive Modulation Duty
Cycle
AGC Attack / Decay
Ratio
AGC pin leakage current
AGC Dynamic Range
Note 5
-2
20
tATTACK / tDECAY
80
%
0.1
TA = 25ºC
TA = +105ºC
RFIN @ -50dBm
RFIN @ -110dBm
±2
±800
1.13
1.70
nA
nA
V
V
9.81563
MHz
300
kΩ
Reference Oscillator
Reference Oscillator
Frequency
Reference Oscillator
Input Impedance
Reference Oscillator
Input Range
Reference Oscillator
Source Current
fRX = 315MHz
Crystal Load Cap = 10pF
0.2
V(REFOSC) = 0V
1.5
3.5
Vp-p
µA
Notes:
1.
Exceeding the absolute maximum rating may damage the device.
2.
The device is not guaranteed to function outside of its operating rating.
3.
Device is ESD sensitive. Use appropriate ESD precautions. Exceeding the absolute maximum rating may damage the device.
4.
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) at a data rate of 1kbps.
5.
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 is
Ton/(Ton+Toff) = 50%; without preamble, duty cycle is Ton/(Ton+ Toff + Tquiet) = 50msec/(200msec)=25%. Ton is the (Average number of
1’s/burst) x bit time, and Toff = Tburst -Ton.)
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Micrel, Inc.
MICRF213
Electrical Characteristics(4)
Specifications apply for 3.0V < VDD < 3.6V, VSS = 0V, CAGC = 4.7µF, CTH = 0.47µF, fRX = 315MHz unless otherwise noted.
Bold values indicate –40°C TA +105°C. 900bps data rate (Manchester encoded), reference oscillator frequency = 9.81563MHz.
Symbol
Parameter
Condition
Min
Typ
Max
Units
Demodulator
CTH Source Impedance
CTH Leakage Current
Demodulator Filter
Bandwidth @ 315MHz
(Programmable, see
application section)
FREFOSC = 9.81563MHz
165
kΩ
TA = 25ºC
TA = +105ºC
SEL0=0, SEL1=0
±2
±800
1180
nA
nA
SEL0=1, SEL1=0
2360
SEL0=0, SEL1=1
4720
SEL0=1, SEL1=1
9400
Hz
Digital / Control Functions
DO pin output current
As output
source @ 0.8Vdd
sink @ 0.2Vdd
260
600
µA
2
µsec
V
Output rise and fall times
CI = 15pF, pin DO, 10-90%
RSSI DC Output Voltage
Range
-110dBm
0.4
-50dBm
1.9
V
RSSI response slope
-110dBm to -50dBm
25
mV/dB
400
µA
200
Ω
0.3
Sec
RSSI
RSSI Output Current
RSSI Output Impedance
RSSI Response Time
August 19, 2015
±15
50% data duty cycle, input power to Antenna = 20dBm
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Micrel, Inc.
MICRF213
Typical Characteristics
Sensitivity Graphs
4.5
DC Current
vs. Frequency
0
Selectivity
vs. Frequency Response
-10
-20
-30
4.0
-40
-50
-60
3.5
-70
-80
3.0
280
-106
Sesitivity
vs. BER
1.8
300
320
340
FREQUENCY (MHz)
360
-90
304
308 312 316 320 324
FREQUENCY (MHz)
AGC Voltage
vs. Input Power
1.7
-108
-110
1.6
1.5
1.4
-112
-114
1.3
1.2
1.1
-116
1.00E-04 1.00E-03 1.00E-02 1.00E-01
BER
August 19, 2015
1
-150
-100
-50
INPUT POWER (dBm)
5
0
Revision 2.0
Micrel, Inc.
MICRF213
Functional Diagram
CAGC
AGC
IMAGE
REJECT
FILTER
ANT
RF
Amp
IF
Amp
Mixer
VDD
–f
f
Control Logic
Mixer
fLO
VSS
SEL
SEL
SQUELCH
SHDN
RSSI
Detector
RSSI
OOK
Demodulator
Programmable
Low Pass Filter
IF
Amp
i
DO
DO
Synthesizer
Control
Logic
Control Logic
Reference and Control
Slicing
Level
CTH
Reference
Oscillator
RO1
RO2
Crystal
Figure 1. Simplified Block Diagram
is set to 32 times the crystal reference frequency via a
phase-locked loop synthesizer with a fully integrated
loop filter.
Functional Description
Figure 1 shows the basic structure of the MICRF213. It
is made of three sub-blocks: Image Rejection UHF
Down-converter, the OOK Demodulator, and Reference
and Control Logics. Outside the device, the MICRF213
requires only three components to operate; two
capacitors (CTH, and CAGC) and the reference
frequency device, usually a quartz crystal. An additional
five components may be used to improve performance.
These are: power supply decoupling capacitor, two
components for the matching network and two
components for the pre-selector band pass filter.
Image Reject Filter and Band-Pass Filter
The IF ports of the mixer produce quadrature down
converted IF signals. These IF signals are low-pass
filtered. This removes higher frequency products prior to
the image reject filter where they are combined to reject
the image frequencies. The IF signal then passes
through a third order band pass filter. The IF center
frequency is 0.86MHz. The IF BW is 235KHz @
315MHz, this will vary with RF operating frequency. The
IF BW can be calculated via direct scaling:
Receiver Operation
Operating Freq (MHz)
315
BW IF = BW IF@315MHz ×
LNA
The RF input signal is AC-coupled into the gate circuit of
the grounded source LNA input stage. The LNA is a
Cascoded NMOS.
These filters are fully integrated inside the MICRF213.
After filtering, four active gain controlled amplifier stages
enhance the IF signal to proper level for demodulation.
Mixers and Synthesizer
The LO ports of the Mixers are driven by quadrature
local oscillator outputs from the synthesizer block. The
local oscillator signal from the synthesizer is placed on
the low side of the desired RF signal. This allows
suppression of the image frequency at twice the IF
frequency below the wanted signal. The local oscillator
August 19, 2015
OOK Demodulator
The demodulator section is comprised of detector,
programmable low pass filter, slicer, and AGC
comparator.
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Micrel, Inc.
MICRF213
Detector and Programmable Low-Pass Filter
The demodulation starts with the detector removing the
carrier from the IF signal. Post detection, the signal
becomes base band information. The programmable
low-pass filter further enhances the base band
information. There are four programmable low-pass filter
BW settings: 1180Hz, 2360Hz, 4270Hz, 9400Hz for
315MHz operation. Low pass filter BW will vary with RF
Operating Frequency. Filter BW values can be easily
calculated by direct scaling. See the equation below for
the filter BW calculation:
1.5µA current is then sourced into the external CAGC
capacitor. When the output signal is greater than
750mV, a 15µA current sink discharges the CAGC
capacitor. The voltage, developed on the CAGC
capacitor, acts to adjust the gain of the mixer and the IF
amplifier to compensate for RF input signal level
variation.
Reference Control
There are two components in the Reference Control
sub-block: 1) Reference Oscillator and, 2) Control Logic
through parallel Inputs: SEL0, SEL1, SHDN.
Operating Freq (MHz)
BW Operating Freq = BW @315MHz ×
315
Reference Oscillator
VBIAS
It is very important to choose filter setting that best fits
the intended data rate as this will minimize data
distortion.
Demod BW is set at 9700Hz @ 315MHz as default
(assuming both SEL0 and SEL1 pins are floating). The
low pass filter can be hardware set by external pins
SEL0 and SEL1.
SEL0
0
1
0
1
SEL1
0
0
1
1
M1
gm
RO1
1
C0
Demod BW (@ 315MHz)
1180Hz
2360Hz
4270Hz
9400Hz
- default
Startup
Circuit
CC1
IBIAS
CC2
M2
M3
RO2
C1
Table 1. Demodulation BW Selection
M4
Slicer, Slicing Level and Squelch
The signal, prior to slicer, is still linear demodulated AM.
Data slicer converts this signal into digital “1”s and “0”s
by comparing with the threshold voltage built up on the
CTH capacitor. This threshold is determined by
detecting the positive and negative peaks of the data
signal and storing the mean value. Slicing threshold
default is 50%. After the slicer, the signal becomes
digital OOK data.
During long periods of “0”s or no data period at all,
threshold voltage on the CTH capacitor may be very
low. Large random noise spikes during this time may
cause erroneous “1”s at DO pin. Squelch pin when pull
down low will suppress these errors.
Normally on
Figure 2. Reference Oscillator Circuit
The reference oscillator in the MICRF213 (reference
Figure 2) uses a basic Colpitts crystal oscillator
configuration with a MOS transconductor to provide
negative resistance. All capacitors shown in the figure
are integrated inside MICRF213. R01 and R02 are
external pins of MICRF213. The user only need connect
the reference oscillation crystal.
Reference oscillator crystal frequency can be calculated
thus as:
FREFOSC = FRF/(32 + 1.1/12)
For 315MHz, FREFOSC = 9.81563 MHz.
To operate the MICRF213 with minimum offset, crystal
frequencies should be specified with 10pF loading
capacitance.
AGC Comparator
The AGC comparator monitors the signal amplitude
from the output of the programmable low-pass filter.
When the output signal is less than 750mV threshold,
August 19, 2015
R2
R1
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Micrel, Inc.
MICRF213
Application Information
Figure 3. QR213HE1 Application Example, 315MHz
The MICRF213 can be fully tested by using one of the
many evaluation boards designed by Micrel and
intended for use with this device. As an entry level,
the QR213HE1 (reference Figure 3) offers a good
start for most applications. It has a helical PCB
antenna with its matching network, a band-pass-filter
front-end as a pre-selector filter, matching network
and the minimum components required to make the
device work. The minimum components are a crystal,
Cagc, and Cth capacitors. By removing the matching
network of the helical PCB antenna (C9 and L3), a
whip antenna (ANT2) or a RF connector (J2) can be
used instead. Figure 3 shows the entire schematic for
315MHz. Other frequencies can be used and the
values needed are listed in the tables below.
Capacitor C9 and inductor L3 are the passive
elements for the helical PCB matching network. It is
recommended that a tight tolerance be used for these
devices; such as 2% for the inductor and 0.1pF for the
capacitor. PCB variations may require different values
and optimization. Table 2 shows the matching
elements for the device frequency range. For
additional information, reference the: Small PCB
Antennas for Micrel RF Products application note.
Freq (MHz)
303.825
315
345
C9 (pF)
1.2
1.2
1.2
C9 and place the whip antenna in the hole provided in
the PCB. Also, a RF signal can be injected there.
L1 and C8 form the pass-band-filter front-end. Its
purpose is to attenuate undesired outside band noise
which reduces the receiver performance. It is
calculated by the parallel resonance equation
f = 1/(2*PI*(SQRT(L1*C8)). Table 3 shows the most
used frequency values.
Freq (MHz)
303.825
315
345
L1 (nH)
39
39
39
Table 3. Band-Pass-Filter Front-End Values
There is no need for the band-pass-filter front-end for
applications where it is proven the outside band noise
does not cause a problem. The MICRF213 has image
reject mixers which improve significantly the selectivity
and rejection of outside band noise.
Capacitor C3 and inductor L2 form the L-shape
matching network. The capacitor provides additional
attenuation for low frequency outside band noise and
the inductor provides additional ESD protection for the
antenna pin. Two ways can be used to find these
values, which are matched close to 50Ω. One method
is done by calculating the values using the equations
below and another by using a Smith chart. The latter
is made easier by using software that plots the values
of the components C8 and L1, like WinSmith by Noble
Publishing.
To calculate the matching values, one needs to know
L3 (nH)
82
75
62
Table 2. Matching Values for the Helical PCB Antenna
To use another antenna, such as the whip kind, remove
August 19, 2015
C8 (pF)
6.8
6.8
5.6
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Micrel, Inc.
MICRF213
the input impedance of the device. Table 4 shows the
input impedance of the MICRF213 and the suggested
matching values used for the most frequencies.
Please keep in mind that these suggested values may
be different if the layout is not exactly the same as the
one depicted here.
Freq (MHz)
303.825
315
345
C3 (pF)
1.8
1.8
1.8
L2 (nH)
72
68
56
Second, we plot the shunt inductor (68nH) and the
series capacitor (1.8pF) for the desired input
impedance (Figure 5). We can see the matching
leading to the center of the Smith Chart or close to
50Ω.
Z device (Ω)
34.6– j245.1
32.5 – j235
25.3 – j214
Table 4. Matching Values for the
Most Used Frequencies
For the frequency of 315MHz, the input impedance is
Z = 32.5 – j235Ω, then the matching components are
calculated by:
Equivalent parallel = B = 1/Z = 0.577 + j4.175
msiemens
Rp = 1 / Re (B);
Xp = 1 / Im (B)
Rp = 1.733 kΩ;
Xp = 239.5 Ω
Q = SQRT (Rp/50 + 1)
Q = 5.972
Xm = Rp / Q
Xm = 290.21 Ω
Resonance Method For L-shape Matching Network
Lc = Xp / (2.Pi.f);
Lp = Xm / (2.Pi.f)
L2 = (Lc.Lp) / (Lc + Lp);
C3 = 1 / (2.Pi.f.Xm)
L2 = 66.3nH
C3 = 1.74pF
Doing the same calculation example with the Smith
Chart, it would appear as follows,
First, we plot the input impedance of the device,
(Z = 32.5 – j235)Ω @ 315MHz.(Figure 4).
Figure 5. Plotting the Shunt Inductor
and Series Capacitor
Crystal Y1 or Y1A (SMT or leaded respectively) is the
reference clock for all the device internal circuits.
Desired crystal characteristics are: 10pF load
capacitance, 30ppm, ESR < 50Ω and a -40ºC to
+105ºC temperature range. Table 5 shows the crystal
frequencies and one of Micrel’s approved crystal
manufactures (www.hib.com.br).
The oscillator of the MICRF213 is a Colpitts type. It is
very sensitive to stray capacitance loads. Thus, very
good care must be taken when laying out the printed
circuit board. Avoid long traces and ground plane on
Figure 4. Device’s Input Impedance, Z = 32.5 – j235 Ω
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MICRF213
the top layer close to the REFOSC pins RO1 and
RO2. When care is not taken in the layout, and
crystals from other vendors are used, the oscillator
may take longer times to start as well as the time to
good data in the DO pin to show up. In some cases, if
the stray capacitance is too high (>20pF), the
oscillator may not start at all.
The crystal frequency is calculated by REFOSC = RF
Carrier/(32+(1.1/12)). The local oscillator is low side
injection (32 × 9.81563MHz = 314.1MHz), that is, its
frequency is below the RF carrier frequency and the
image frequency is below the LO frequency. Refer to
Figure 6. The product of the incoming RF signal and
local oscillator signal will yield the IF frequency, which
will then be demodulated by the detector of the
device.
Image
Frequency
according to Table 6. For example, if the pulse period
is 140µsec, 50% duty cycle, then the pulse width will
be 70µsec (PW = (140 µsec * 50%) / 100). So, a
bandwidth of 9.286kHz would be necessary (0.65 /
70µsec). However, if this data stream had a pulse
period with a 20% duty cycle, then the bandwidth
required would be 23.2kHz (0.65 / 28µsec), which
exceeds the maximum bandwidth of the demodulator
circuit. If one tries to exceed the maximum bandwidth,
the pulse would appear stretched or wider.
Desired
Signal
SEL0
JP1
SEL1
JP2
Demod.
BW
(hertz)
Shortest
Pulse
(usec)
Maximum
baud rate for
50% Duty
Cycle (hertz)
Short
Short
Open
Short
Short
Open
Open
Open
1180
2360
4720
9400
551
275
138
69
908
1815
3631
7230
Table 6. JP1 and JP2 Setting, 315MHz
Capacitors C6 and C4, Cth and Cagc capacitors
respectively, provide the time base reference for the
data pattern received. These capacitors are selected
according to data profile, pulse duty cycle, dead time
between two received data packets and if the data
pattern has or not a preamble. See Figure 7 for an
example of a data profile.
Other frequencies will have different demodulator
bandwidth limits, which are derived from the reference
oscillator frequency. Table 7 and Table 8, below,
show the limits for the other two most used
frequencies.
f (MHz)
fLO
Figure 6. Low Side Injection Local Oscillator
REFOSC
(MHz)
9.467411
9.81563
10.75045
Carrier
(MHz)
303.825
315
345.0
HIB Part Number
SA-9.467411-F-10-H-30-30-X
SA-9.815630-F-10-H-30-30-X
SA-10.750450-F-10-H-30-30-X
Table 5. Crystal Frequency and Vendor Part Number
JP1 and JP2 are the bandwidth selection for the
demodulator bandwidth. To set it correctly, it is
necessary to know the shortest pulse width of the
encoded data sent in the transmitter. Reference the
example of the data profile, in the Figure 7, below:
SEL0
JP1
SEL1
JP2
Demod.
BW
(hertz)
Shortest
Pulse
(usec)
Short
Open
Short
Open
Short
Short
Open
Open
1140
2280
4550
9100
570
285
143
71
PW1 PW2
Maximum
baud rate for
50% Duty
Cycle (hertz)
8770
1754
3500
7000
Table 7. JP1 and JP2 Setting, 303.825MHz
Preamble
Header
1
2
3
4
5
6
7
8
9
10
t1
t2
SEL0
JP1
SEL1
JP2
Demod.
BW
(hertz)
Shortest
Pulse
(usec)
Short
Open
Short
Open
Short
Short
Open
Open
1290
2580
5170
10340
504
252
126
63
PW2 = Narrowest pulse width
t1 & t2 = data period
Figure 7. Example of a Data Profile
PW2 is shorter than PW1, so PW2 should be used for
the demodulator bandwidth calculation. The
calculation is found by 0.65/shortest pulse width. After
this value is found, the setting should be done
August 19, 2015
Maximum
baud rate for
50% Duty
Cycle (Hertz)
992
1985
3977
7954
Table 8. JP1 and JP2 Setting, 345.0MHz
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Micrel, Inc.
MICRF213
For best results, the values should always be
optimized for the data pattern used. As the baud rate
increases, the capacitor values decrease. Table 9
shows suggested values for Manchester Encoded
data at 50% duty cycle.
SEL0
JP1
SEL1
JP2
Short
Open
Short
Open
Short
Short
Open
Open
Demod.
BW
(hertz)
1400
2800
5300
9700
Cth
Cagc
100nF
47nF
22nF
10nF
4.7uF
2.2uF
1uF
0.47uF
DO Pin
Table 9. Suggested Cth and Cagc Values
JP3 is a jumper used to configure the digital squelch
function. When it is high, there is no squelch applied
to the digital circuits and the DO (data out) pin yields a
hash signal. When the pin is low, the DO pin activity is
considerably reduced. It will have more or less than
shown in the figure below depending upon the outside
band noise. The penalty for using squelch is a delay in
obtaining a good signal in the DO pin. That is, it takes
longer for the data to show up. The delay is
dependent upon many factors such as RF signal
intensity, data profile, data rate, Cth and Cagc
capacitor values, and outside band noise. See Figure
8 and 9.
Figure 9. Data Out Pin with Squelch (SQ = 0)
DO Pin
Figure 8. Data Out Pin with No Squelch (SQ = 1)
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Other components used include: C5, which is a
decoupling capacitor for the Vdd line; R4 reserved for
future use and not needed for the evaluation board;
R3 for the shutdown pin (SHDN = 0, device is
operation), which can be removed if that pin is
connected to a microcontroller or an external switch;
and R1 and R2 which form a voltage divider for the
AGC pin. One can force a voltage in this AGC pin to
purposely decrease the device sensitivity. Special
care is needed when doing this operation, as an
external control of the AGC voltage may vary from lot
to lot and may not work the same in several devices.
Three other pins need to be discussed as well. They
are the DO, RSSI, and shut down pins. The DO pin
has a driving capability of 0.4mA. This is good enough
for most of the logic families ICs in the market today.
The RSSI pin provides a transfer function of the RF
signal intensity vs. voltage. It is very useful to
determine the signal to noise ratio of the RF link,
crude range estimate from the transmitter source and
AM demodulation, which requires a low Cagc
capacitor value.
The shut down pin (SHDN) is useful to save energy.
Making its level close to Vdd (SHDN = 1), the device
is then not in operation. Its DC current consumption is
less than 1µA (do not forget to remove R3). When
toggling from high to low, there will be a time required
for the device to come to steady state mode, and a
time for data to show up in the DO pin. This time will
be dependent upon many things such as temperature,
crystal used, and if the there is an external oscillator
with faster startup time. Crystal vendors suggest that
the data will show up in the DO pin around 1msec
time, and 2msec over the temperature range of the
device. See Figure 10.
Revision 2.0
Micrel, Inc.
MICRF213
3.3V
MICRF2XX
10 ohm
(Vdd) pin
MICRF2XX
Bias
control &
POR
4.7uF
2.2uF
Test Mode
Circuits
Change the SHDN
pin and Vdd pin
connections to
Test Bus
(SHDN) pin
(SHDN) pin
100K
This device turns on,
preventing POR from setting
operating modes correctly
To prevent the erroneous startup, a simple RC
network is recommended. The 10Ω resistor and the
4.7µF capacitor provide a delay of about 200µs
between the VDD and SHDN during the power up,
thus ensuring the part to enter to shutdown stage
before the part is actually turned on. The 2.2µF
capacitor bootstraps the voltage on SHDN, ensuring
that SHDN voltage leads the supply voltage on Vdd
during the power up. This gives the POR circuit time
to set internal register bits. The SHDN pin can be
brought low to turn the chip on once the initialization is
completed. The 2.2µF and 100kΩ network form a RC
delay of about 200ms before the SHDN pin is brought
to low again. The 100kΩ resistor discharges the
SHDN pin to turn the chip on.
Figure 10. Time-to-Good Data After Shut Down Cycle,
Room Temperature
Important Note
A few customers have reported that some MICRF213
receivers do not start up correctly. When the issue
occurs, DO either chatters or stays at low voltage
level. An unusual operating current is observed and
the part cannot receive or demodulate data even
when a strong OOK signal is present.
Micrel has confirmed that this is the symptom of
incorrect power on reset (POR) of internal register
bits. The MICRF213 is designed to start up in
shutdown mode (SHDN pin must be in logic high
during Vdd ramp up). When the SHDN pin is tied to
GND, and if the supply is ramped up slowly, a “test
bus pull down” circuit may be activated. Once the
chip enters this mode, the POR does not have the
chance to set register bits (and hence operating
modes) correctly. The test bus pull down acts on the
SHDN pin, and can be illustrated as the following
diagram.
Vdd pin
SHDN pin
The suggestion provided above will generally
serve to prevent the startup issue from happening
to the MICRF213 series ASK receiver. However,
exact values of the RC network depend on the
ramp rate of the supply voltage, and should be
determined on a case-by-case basis.
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Revision 2.0
Micrel, Inc.
MICRF213
PCB Considerations and Layout
Figures 11 to 16 show some of the printed circuit
layers for the QR211HE1 board. The MICRF213
shares the exact same board with different component
values. Use the Gerber files provided (downloadable
from Micrel Website: www.micrel.com) which have the
remaining layers needed to fabricate this board. When
copying or making one’s own boards, be sure and
make the traces as short as possible. Long traces
alter the matching network and the values suggested
are no longer valid. Suggested Matching Values may
vary due to PCB variations. A PCB trace 100 mills
(2.5mm) long has about 1.1nH of inductance.
Optimization should always be done with exhaustive
range tests. Make individual ground connections to
the ground plane with a via for each ground
connection. Do not share vias with ground
connections. Each ground connection = 1 via or more
vias. Ground plane must be solid and possibly without
interruptions. Avoid ground plane on top next to the
matching elements. It normally adds additional stray
capacitance which changes the matching. Do not use
phenolic material, only FR4 or better materials.
Phenolic material is conductive above 200MHz. The
RF path should be as straight as possible avoiding
loops and unnecessary turns. Separate ground and
Vdd lines from other circuits (microcontroller, etc).
Known sources of noise should be laid out as far as
possible from the RF circuits. Avoid thick traces, the
higher the frequency, the thinner the trace should be
in order to minimize losses in the RF path.
Figure 11. QR211/213HE1 Top Layer
Figure 12. QR211/213HE1 Bottom Layer, Mirror Image
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Revision 2.0
Micrel, Inc.
MICRF213
Figure 13. QR211/213HE1 Top Silkscreen Layer
Figure 14. QR211/213HE1 Bottom Silkscreen Layer, Mirror Image
Figure 15. QR211/213HE1 Dimensions
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Revision 2.0
Micrel, Inc.
MICRF213
QR213HE1 Bill of Materials, 315MHz
Item
Part Number
Manufacturer
Description
ANT1
ANT2
(1)
C3
MuRata
C4
Murata
(1)
Murata
(1)
Murata
(1)
C8
Murata
(1)
C9
Murata
(1)
(2)
C5
C6
JP1,JP
2
1
1
(2)
0.1µF, 0402/0603
1
(2)
0.47µF, 0402/0603
1
6.8pF, 0402/0603
1
1.2pF, 0402/0603
1
short, 0402, 0Ω resistor
2
open, 0402, not placed
1
(np) not placed
1
JP3
J2
J3
L2
L3
Coilcraft
(3)
Coilcraft
(3)
/ Murata
(1)
/ Murata
(1)
/ Murata
(1)
R1,R2
(2)
R3
Y1
Vishay
HCM49
(5)
HIB
(5)
Y1A
HC49
HIB
U1
MICRF213AYQS
Micrel Inc.
(6)
1
230mm 20 AWG, rigid wire
4.7µF, 0603/0805
/ Vishay
(3)
(np)50Ω Ant
1.8pF, 0402/0603
/ Vishay
Coilcraft
1
(2)
/ Vishay
Vishay
L1
Qty.
Helical PCB Antenna Pattern
CON6
1
/ ACT1
(4)
39nH 5%, 0402/0603
1
/ ACT1
(4)
68nH 5%, 0402/0603
1
/ ACT1
(4)
75nH 2%, 0402/0603
1
(np) 0402, not placed
2
100kΩ, 0402
1
(np)9.81563MHz Crystal
1
9.81563MHz Crystal
1
®
3.3V, QwikRadio 315MHz Receiver
1
Notes:
1. Murata: www.murata.com
2. Vishay: www.vishay.com
3. Coilcraft: www.coilcraft.com
4. ACT1: www.act1.com
5. HIB: www.hib.com.br
6. Micrel, Inc.: www.micrel.com
August 19, 2015
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Revision 2.0
Micrel, Inc.
MICRF213
Package Information and Recommended Land Pattern(1)
16-Pin QSOP (QS)
Note:
1. Package information is correct as of the publication date. For updates and most current information, go to www.micrel.com.
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Revision 2.0
Micrel, Inc.
MICRF213
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
Micrel, Inc. is a leading global manufacturer of IC solutions for the worldwide high performance linear and power, LAN, and timing &
communications markets. The Company’s products include advanced mixed-signal, analog & power semiconductors; high-performance
communication, clock management, MEMs-based clock oscillators & crystal-less clock generators, Ethernet switches, and physical layer transceiver ICs.
Company customers include leading manufacturers of enterprise, consumer, industrial, mobile, telecommunications, automotive, and computer
products. Corporation headquarters and state-of-the-art wafer fabrication facilities are located in San Jose, CA, with regional sales and support
offices and advanced technology design centers situated throughout the Americas, Europe, and Asia. Additionally, the Company maintains an
extensive network of distributors and reps worldwide.
Micrel makes no representations or warranties with respect to the accuracy or completeness of the information furnished in this datasheet. This
information is not intended as a warranty and Micrel does not assume responsibility for its use. Micrel reserves the right to change circuitry,
specifications and descriptions at any time without notice. No license, whether express, implied, arising by estoppel or otherwise, to any
intellectual property rights is granted by this document. Except as provided in Micrel’s terms and conditions of sale for such products, Micrel
assumes no liability whatsoever, and Micrel disclaims any express or implied warranty relating to the sale and/or use of Micrel products including
liability or warranties relating to fitness for a particular purpose, merchantability, or infringement of any patent, copyright, or other intellectual
property right.
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.
© 2007 Micrel, Incorporated.
August 19, 2015
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Revision 2.0