Micrel MICRF009BM Qwikradio low-power uhf receiver Datasheet

MICRF009
QwikRadio® Low-Power UHF Receiver
Insert as inline graphic
General Description
QwikRadio®
The MICRF009 is a single chip, ASK/OOK (ON-OFF
Keyed) RF receiver IC. It provides the same function but
with performance enhancements over earlier QwikRadio®
receivers. Two key improvements are: higher sensitivity
(typically 6dB higher than the MICRF002) and faster
recovery from shutdown (typically 1ms). Just like all other
members of the QwikRadio® family, the MICRF009
achieves low power operation, a very high level of
integration, and it is particularly easy to use.
All post-detection (demodulator) data filtering is provided
on the MICRF009, so no external baseband filters are
required. One of two filter bandwidths may be selected
externally by the user. The user only needs to program the
appropriate filter selection based on the data rate and code
modulation format.
The MICRF009 offer two modes of operation; fixed-mode
(FIX) and sweep-mode (SWP). In fixed-mode the
MICRF009 functions as a conventional superheterodyne
receiver. In sweep-mode the MICRF009 employs a
patented sweeping function to sweep a wider RF spectrum.
Fixed-mode provides better selectivity and sensitivity
performance while sweep mode enables the MICRF009 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.
Features
•
•
•
•
•
•
•
•
•
•
High sensitivity (–104dBm)
Fast recovery from shutdown (1ms)
300MHz to 440MHz frequency range
Data-rate up to 2.0kbps (fixed-mode, Manchester encoding)
Low power consumption
– 2.9mA fully operational (315MHz)
– 0.15µA in shutdown
– 290µA in polled mode (10:1 duty-cycle)
Shutdown input
Automatic tuning, no manual adjustment
Very low RF re-radiation at the antenna
Highly integrated with extremely low external part count
1ms time to good data
Applications
•
•
•
•
Automotive remote keyless entry (RKE)
Long range RF identification
Remote fan and light control
Garage door and gate openers
Ordering Information
Part Number
Demodulator Bandwidth
Operating Mode
Shutdown
Package
MICRF009BM
User Programmable
Fixed or Sweep
Yes
16-pin SOIC
Typical Application
315Mhz 1200Bps On-Off Keyed Receiver
Fixed Mode
Power, Connect and Protect is a trademark of Micrel, Inc.
QwikRadio is a registered trademark of Micrel, Inc. The QwikRadio Ics were developed under a partnership agreement with AIT of Orlando, Florida.
Micrel, Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax +1 (408) 474-1000 • http://www.micrel.com
January 18, 2005
M9999-011805
(408) 955-1690
Micrel
MICRF009
Pin Configuration
Demodulator Bandwidth
Sweep-Mode
Fixed-Mode
1
1250Hz
2500Hz
0
625Hz
1250Hz
Table 1. Nominal Demodulator Filter Bandwidth vs. SEL0,
Operating Mode at 433.92 MHz
SEL0
Note:
SEL0 must connect to VDD = 1 or VSS = 0. Do not float SEL0
Standard 16-Pin SOIC (M)
Pin Description
Pin Number
Pin Name
1
SEL0
2, 3
VSSRF
4
ANT
5
VDDRF
RF [Analog] Supply (Input): Positive supply input for the RF section of the IC. VDDBB and VDDRF
should be connected together directly at the IC pins.
6
VDDBB
Baseband [Digital] Supply (Input): Positive supply input for the baseband section of the IC. VDDBB and
VDDRF should be connected together at the IC pins.
7
CTH
[Data Slicing] Threshold Capacitor (External Component): Capacitor extracts the DC average value
from the demodulated waveform, which becomes the reference for the internal data slicing comparator.
See “Applications Information” for selection.
8
NC
9
VSSBB
10
DO
11
SHUT
Shutdown (Input): Shutdown-mode logic-level control input. Pull low to enable the receiver. This input
has an internal pulled-up to VDDRF.
12
CAGC
AGC Capacitor (External Component): Integrating capacitor for on-chip AGC (automatic gain control).
See “Applications Information” for capacitor selection.
13
SEL1
Bandwidth Selection Bit 1 (Input): Must tie to ground. Reserved for future use.
14
REFOSC2
Reference Oscillator (External Component or Input): Timing reference for on-chip tuning and
alignment.
15
REFOSC1
Reference Oscillator (External Component or Input): Timing reference for on-chip tuning and
alignment.
16
SWEN
January 18, 2005
Pin Function
Bandwidth Selection Bit 0 (Input): Configure to set the desired demodulator filter bandwidth. See Table
1. 0 = VSS, 1 = VDD, don not float SEL0
RF [Analog] Return (Input): Ground return to the RF section power supply. See “Applications
Information” for bypass capacitor details.
Antenna (Input): See “Applications Information” for information on input impedance. For optimal
performance the antenna impedance should be matched to the antenna pin impedance.
No connect.
Baseband [Digital] Return (Input): Ground return to the baseband section power supply. See
“Applications Information” for bypass capacitor and layout details.
Digital Output (Output): CMOS level compatible data output signal.
Sweep-Mode Enable (Input): Sweep- or fixed-mode operation control input. When SWEN is high, the
MICRF009 is in sweep mode; when SWEN is low, the receiver operates as a conventional singleconversion superheterodyne receiver. This pin is internally pulled-up to VDDRF.
2
M9999-011805
(408) 955-1690
Micrel
MICRF009
Absolute Maximum Ratings(1)
Operating Ratings(2)
Supply Voltage (VDDRF, VDDBB)................................... +7V
Input/Output Voltage (VI/O) ................ VSS–0.3 to VDD+0.3
Max. Input Power .................................................. +20dBm
Junction Temperature (TJ) ..................................... +150°C
Storage Temperature Range (TS)........... –65°C to +150°C
Lead Temperature (soldering, 10 sec.).................. +260°C
ESD Rating ............................................................. Note 3
Supply Voltage (VDDRF, VDDBB) ...............+4.75V to +5.5V
Max. Input Power ...................................................... 0dBm
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 = 0.022µF; SEL0 = VDD; SEL1 = VSS; fixed mode
(SWEN = VSS); fREFOSC = 9.794MHz (equivalent to fRF = 315MHz); datarate = 600bps (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
IOP
Operating Current
ISTBY
Standby Current
Min
Typ
Max
Units
continuous operation, fRF = 315MHz
2.9
4.5
mA
Polled with 10:1 duty cycle, fRF = 315MHz
290
µA
µA
Continuous operation, fRF = 433.92MHz
4.7
Polled with 10:1 duty cycle, fRF = 433.92MHz
470
VSHUT = 0.8VDD
0.15
fRF = 315MHz
–102
dBm
7.5
µA
0.5
µA
RF Section, IF Section
Receiver Sensitivity(4)
fRF = 433.92MHz
–104
dBm
fIF
IF Center Frequency
Note 5
0.86
MHz
fBW
IF 3dB Bandwidth
Note 5
0.68
MHz
30
µVrms
(6)
Spurious Reverse Isolation
ANT pin, RSC = 50Ω
AGC Attack to Decay Ratio
tATTACK ÷ tDECAY
AGC Leakage Current
TA = +85°
±100
nA
Reference Oscillator
Input Impedance
Note 7
290
kΩ
Reference Oscillator Source
Note 8
5.0
µA
145
kΩ
0.1
Reference Oscillator
ZREFOSC
Demodulator
ZCTH
CTH Source Impedance
Note 9
IZCTH(leak)
CTH Leakage Current
TA = +85°C
±100
nA
Demodulator Filter
Bandwidth Sweep Mode
(SWEN = VDD or OPEN)(5)
VSEL0 = VDD
VSEL0 = VSS
1000
500
Hz
Hz
Demodulator Filter Bandwidth
Fixed Mode (SWEN = VSS)(5)
VSEL0 = VDD
VSEL0 = VSS
2000
1000
Hz
Hz
January 18, 2005
3
M9999-011805
(408) 955-1690
Micrel
Symbol
MICRF009
Parameter
Condition
Min
Typ
Max
U
Digital/Control Section
VIH
Input High Voltage
SEL0, SEL1, SWEN
VIL
Input Low Voltage
SEL0, SEL1, SWEN
IOUT
Output Current
DO pin, push-pull
VOH
Output High Voltage
DO pin, IOUT = –30µA
VOL
Output Low Voltage
DO pin, IOUT = +30µA
tR, tF
Output Rise and Fall Time
DO pin, CLOAD = 15pF
VDD
0.8
VDD
0.2
45
µA
VDD
0.9
VDD
0.1
4
µs
Notes:
1. Exceeding absolute maximum ratings may damage the device.
2. The device is not guaranteed to function outside its operating ratings.
3. Devices are ESD sensitive, use appropriate ESD precautions. The device 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. Parameter scales linearly with reference oscillator frequency fT. For any reference oscillator frequency other than 9.794MHz, compute new
parameter value as the ratio:
fREFOSC MHZ
× (parameter value at 9.79MHz )
9.794MHz
6. Spurious reverse isolation represents the spurious components, which appear on the RF input pin (ANT) measured into 50Ω with an input RF
matching network.
7. 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 50Ω and 100Ω, respectively.
8. Crystal load capacitor is 10pF. See Figure 5 in “REFOSC” section for reference oscillator operation.
9. Parameter scales inversely with reference oscillator frequency fT. For any reference oscillator frequency other than 9.794MHz, compute new
parameter value as the ratio:
9.794MHz
× (parameter value at 9.794MHz)
fREFOSCMHZ
January 18, 2005
4
M9999-011805
(408) 955-1690
Micrel
MICRF009
Typical Characteristics
Supply Current
vs. Frequency
3.5
6.0
CURRENT (mA)
CURRENT (mA)
TA = 25°C
VDD = 5V
4.5
3.0
Sweep Mode,
Continuous Operation
1.5
250
300
350
400
450
FREQUENCY (MHz)
January 18, 2005
Supply Current
vs. Temperature
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)
5
M9999-011805
(408) 955-1690
Micrel
MICRF009
Functional Diagram
Figure 1. MICRF009 Block Diagram
Application Information and Function
Description
Design Steps
The following steps are the basic design steps for using the
MICRF009 receiver:
1. Select the operating mode (sweep or fixed)
2. Select the reference oscillator
3. Select the demodulator filter bandwidth
4. Select the CTH capacitor
5. Select the CAGC capacitor
Refer to “MICRF009 Block Diagram.” Identified in the block
diagram are the three sections of the IC: 1) UHF
Downconverter, 2) OOK Demodulator, 3) Reference and
Control. Also shown in the figure are two capacitors (CTH,
CAGC) and one timing component, which is 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 MICRF009 to assemble a complete UHF receiver.
For optimal performance it is highly recommended that the
MICRF009 is impedance-matched to the antenna. The
matching network will add 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. The IF Bandpass Filter Roll-off
response of the IF Filter is 5th order, while the demodulator
data filter exhibits a 2nd order response.
January 18, 2005
Step 1: Selecting The Operating Mode
Fixed-Mode Operation
For applications where the transmit frequency is set
accurately (that is, applications where a SAW or crystalbased transmitter is used), the MICRF009 may be
configured as a standard superheterodyne receiver (fixedmode). In fixed-mode 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 LC transmitters,
the MICRF009 should be configured in sweep-mode. In
sweep-mode, while the topology is still superheterodynes,
the local oscillator (LO) is swept over a range of
frequencies at rates greater than the data rate. This
technique effectively increases the RF bandwidth of the
6
M9999-011805
(408) 955-1690
Micrel
MICRF009
between the internal LO (local oscillator) frequency fLO and
the incoming transmit frequency fTX, should equal the IF
center frequency. Equation 1 may be used to compute the
appropriate fLO for a given fTX:
MICRF009, 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 680kHz 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 1250Hz.
Similar performance is not currently available with crystalbased superheterodyne receivers, which can operate only
with SAW- or crystal-based transmitters.
In sweep-mode, a range reduction will occur in installation
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 MICRF009 may be
used in place of a super-regenerative receiver in most
applications.
⎛
f ⎞
fLO = fTX ± ⎜0.86 TX ⎟
315 ⎠
⎝
(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. There is
generally no preference of one over the other.
After choosing one of the two acceptable values of fLO, use
Equation 2 to compute the reference oscillator frequency
fT:
fT = 2 ×
(2)
Frequency fT is in MHz. Connect a crystal of frequency fT
to REFOSC on the MICRF009. Four-decimal-place
accuracy on the frequency is generally adequate. The
following table identifies fT for some common transmit
frequencies when the MICRF009 is operated in fixedmode.
Step 2: Selecting The Reference Oscillator
All timing and tuning operations on the MICRF009 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
9.7941MHz
390MHz
12.1260MHz
418MHz
12.9966MHz
433.92MHz
13.4916MHz
Table 1. 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 sweep
mode 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 crystals are selected. Contact Micrel RF
Applications for suggested suppliers and part numbers.
If operating in fixed-mode, a crystal is recommended. In
sweep-mode either a crystal or ceramic resonator may be
used. When a crystal or 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.
fT = 2 ×
fTX
64.25
(3)
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
(Fixed-Mode)
As with any superheterodynes receiver, the difference
January 18, 2005
fLO
64.5
Transmit Frequency (fTX)
7
Reference Oscillator
Frequency (fT)
M9999-011805
(408) 955-1690
Micrel
MICRF009
315MHz
9.81MHz
390MHz
12.140MHz
418MHz
13.01MHz
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 MICRF009. When the
device is placed into shutdown mode (SHUT pin is 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 duty-cycled operation.
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.
433.92MHz
13.51MHz
Table 2. Sweep-Mode Recommended Reference Oscillator
Values For Typical Transmit Frequencies
Step 3: Selecting 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 on-chip
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.This issue is covered in
more detail in “Application Note 22.” 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. Caution! 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:
∆t = 1.333 × CAGC − 0.44
(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 also 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:
R SC = 145Ω
9.7940
fT
where:
CAGC is 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 MICRF009 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. The worst-case from a recovery
standpoint is downward droop, since the AGC pull-up
current is 1/10th magnitude of the pull-down current. The
downward droop is replenished according to the Equation
7:
(4)
τ of 5x the bit-rate is recommended. The effective
resistance of RSC is listed in the electrical characteristics
table as 145kΩ at 315MHz, this value scales inversely with
frequency. Source impedance of the CTH pin at other
frequencies is given by equation (5), where fT is in MHz:
C TH =
τ
R SC
(5)
A standard ±20% X7R ceramic capacitor is generally
sufficient. Refer to “Application Hint 42” for CTH and CAGC
selection examples.
Step 4: Selecting CAGC Capacitor
I
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
January 18, 2005
CAGC
=
∆V
∆t
(7)
where:
I = AGC pull-up current for the initial 10ms (67.5µA)
8
M9999-011805
(408) 955-1690
Micrel
MICRF009
CAGC = AGC capacitor value
The ratio of decay-to-attack time-constant is fixed at 1:10
(that is, the attack time constant is 10 times of the decay
time constant). Generally the design value of 1:10 is
adequate for the vast majority of applications. If adjustment
is required, adding a resistor in parallel of the CAGC
capacitor may vary the ratio. The value of the resistor must
be determined on a case-by-case basis.
∆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, the 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.
January 18, 2005
9
M9999-011805
(408) 955-1690
Micrel
MICRF009
pin so that noise does not trigger the internal comparator.
Usually 20mV to 30mV is sufficient, and may be achieved
by connecting a several-meg-ohm resistor from the CTH
pin to either VSSBB or VDDBB, depending on the desired
offset polarity. Since MICRF009’s 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 10MΩ to 6.8MΩ for low to high squelch
strength.
Step 5: Selecting The Demodulator Filter
Bandwidth
The input SEL0 controls the demodulator filter bandwidth in
two binary steps, (625Hz to 1250Hz in sweep, 1250Hz to
2500Hz in fixed mode), see Table 3. Bandwidth must be
selected according to the application. The demodulator
bandwidth should be set according to equation 8. SEL1
tied to VSS by default.
Demodulator Bandwidth =
0.65
(8)
shortest pulse - width
It should be noted that the values indicated in Table 1 are
the 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.
SEL0
1
I/O Pin Interface Circuitry
Interface circuitry for the various I/O pins of the MICRF009
are diagrammed in Figures 2 through 8. The ESD
protection diodes at all input and output pins are not
shown.
Demodulator Bandwidth
Sweep Mode
Fixed Mode
1250Hz
2500Hz
CTH Pin
0
625Hz
1250Hz
Table 3. Nominal Demodulator Filter Bandwidth
vs. SEL0 and Operating Mode at 433.92MHz
Power Supply Bypass Capacitors
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, VDDBB to
VDDRF at the power supply only (that is, keep base-band
currents from flowing through the RF return path).
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 145kΩ. The DC potential at
the CTH pin is approximately 1.6V
Increasing Selectivity with 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 receiver selectivity and input overload protection.
A minimum input configuration is included in Figure 9. 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.
For some systems, it does present a problem. There are
three possible approaches to reduce 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 to add analog squelch by
introducing a small offset, or squelch voltage, on the CTH
January 18, 2005
CAGC Pin
Figure 3. CAGC Pin
10
M9999-011805
(408) 955-1690
Micrel
MICRF009
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
7µA, while the decay current is a 10 times scaling of this,
approximately 85µA. Signal gain of the RF/IF strip inside
the IC diminishes as the voltage on CAGC decreases. By
simply adding a capacitor to CAGC pin, the attack/decay
time constant ratio is fixed at 10:1. 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 2 times for approximately 10ms
after release of the SHUT pin. This allows rapid recovery of
any voltage droop on CAGC while in shutdown.
Figure 5. REFOSC Pin
SEL0, SEL1, SWEN, and SHUT Pins
DO Pin
The output stage for the digital output (DO) is shown in
Figure 4. The output is a 45µA push and 45µA pull
switched-current stage. This output stage is capable of
driving CMOS loads. An external buffer-driver is
recommended for driving high capacitance loads.
Figure 6a. SEL0/SEL1/SWEN Pins
Figure 6b. SHUT Pin
Control input circuitry is shown in Figure 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” pull-up to VDDBB. Typical pull-up current is
5µA, leading to an impedance to the VDDBB supply of
typically 1MΩ.
Figure 4. DO Pin
REFOSC1 and REFOSC2 Pin
The REFOSC input circuit is shown in Figure 5. Input
impedance is quite high (200kΩ). This is a Colpitts
oscillator, with internal 10pF capacitors. This input is
intended to work with standard crystal resonators,
connected from this pin to REFOSC2.
This REFOSC2 pin appears as a low resistance path to
VSS during normal operation and is an input to a buffer
amplifier used during the initial start up phase to ensure
rapid build up of crystal oscillations.
The resonators should not contain integral capacitors,
since these capacitors are contained inside the IC.
Externally applied signals should be AC-coupled,
amplitude limited to approximately 0.5VPP. The nominal
DC bias voltage on this pin is 1.4V
January 18, 2005
11
M9999-011805
(408) 955-1690
Micrel
MICRF009
Additional Applications Information
Frequency
(Mhz)
In addition to the basic operation of the MICRF009, 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 Figure 7, and Table 4, the antenna pin input
impedance is frequency dependent.
The ANT pin can be matched to 50Ω with an L-type circuit
as shown in Figure 3. That is, a shunt inductor from the
antenna input to ground and another in series from the
antenna input to the ANT pin.
Inductor values may be different from Table 4, 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 MICRF009 (often referred to
as polling) is achieved by turning the MICRF009 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, and it must be externally pulled low
to enable the receiver.
j100
j25
–j25
Z11, ohms
C3, pF
L2, nH
300
0.944,-36.65
14.45-j150
2.2
47
305
0.940,-37.499
14.84-j145
2.2
47
310
0.942,-37.579
14.28-j145
2.2
47
315
0.945, -37.66
13.48-j145
2.2
47
320
0.943,-38.237
13.58-j143
2
47
325
0.942, -38.814
13.43-j140
1.8
47
330
0.94, -39.39
13.5-j138
1.8
47
335
0.938, -39.967
13.59-j136
1.8
43
340
0.937, -40.544
13.44-j134
1.8
43
345
0.935, -41.12
13.51-j132
1.8
43
350
0.933, -41.697
13.57-j130
2
39
355
0.931, -42.274
13.62-j123
2.2
36
360
0.93, 42.85
13.48-j126
2.2
36
365
0.928, -43.427
13.52-j124
2
36
370
0.926, -44.004
13.57-j122
1.8
36
375
0.925, -44.581
13.42-j120
2.2
33
380
0.923, -45.157
13.46-j118
2
33
385
0.921, -45.734
13.49-j117
1.8
33
390
0.92, -46.311
13.35-j115
1.8
33
395
0.917, -46.729
13.6-j114
1.8
33
400
0.914, -47.148
13.89-j113
2
30
405
0.912, -47.566
14.00-j112
1.8
30
410
0.909, -47.985
14.25-j110
1.8
30
415
0.907, -48.403
14.34-j109
2.2
27
420
0.906, -48.797
14.28-j108
2
27
425
0.909, -49.152
13.63-j107
2
27
430
0.911, -49.507
13.15-j107
1.8
27
435
0.911, -49.925
12.94-j106
1.8
27
440
0.904, -50.571
13.66-j104
Table 4
1.8
27
∞
50
0
S11
Mag, angle
–j100
Figure 7
January 18, 2005
12
M9999-011805
(408) 955-1690
Micrel
MICRF009
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 1kbps data rate may require a
change in the value of R1. A bill of materials accompanies
the schematic.
Application Example
315MHz Receiver/Decoder Application
Figure 8 illustrates a typical application for the MICRF009
UHF Receiver IC. This receiver operates continuously (not
duty cycled) in sweep mode, and features 6-bit address
decoding and two output code bits.
Figure 8. 315Mhz, 1.2kbps On-Off Keyed Receiver with Decoder
Sweep Mode
Bill of Materials
Item
Part Number
C1, C5
C2
Manufacturer
Description
Vishay(1)
4.7µF ceramic or tantalum capacitor
2
(1)
0.1µF ceramic or tantalum capacitor
1
(1)
2.2µF ceramic or tantalum capacitor
1
(1)
8.2pF COG ceramic capacitor
1
9.81 ceramic resonator
1
Vishay
C3
Vishay
C4
Vishay
Y1
See Crystal App. Note
(2)
Qty
D1
SSF-LX100LID
Lumex
Red LED
1
L1
0603CS-47NX_BC
Coil Craft(5)
47nH Inductor
1
68k, 1/4W, 5%
1
R1
(1)
R2
U1
MICRF009
U2
HT-12D
Vishay
1k, 1/4W, 5%
1
Micrel(3)
UHF receiver
1
(4)
Logic decoder
1
Holtek
Notes:
1.
Vishay tel: 203-268-6261
2.
Lumex tel: 800-278-5666
3.
Micrel Semiconductor tel: 408-944-0800
4.
Holtek tel: 408-894-9046
5.
Coil Craft tel: 847-639-2361
January 18, 2005
13
M9999-011805
(408) 955-1690
Micrel
MICRF009
printed circuit board material were to be substituted,
impedance matching and characterization data stated in
this document may not be valid. The Bill of Materials and
gerber files for this board can be downloaded from the
Micrel website at www.micrel.com.
PCB Layout Information
The MICRF009 evaluation board was designed and
characterized using two sided 0.031 inch thick FR4
material with 1 ounce copper clad. If another type of
PCB Solder Side Layout
PCB Component Layout
PCB Silk Screen
PCB for QR009HPF
January 18, 2005
14
M9999-011805
(408) 955-1690
Micrel
MICRF009
Figure 9. 433.92MHz, 1200bps, High Pass Filter Input
January 18, 2005
15
M9999-011805
(408) 955-1690
Micrel
MICRF009
Package Information
16-Pin SOIC (M)
MICREL, INC. 1849 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.
© 2005 Micrel, Incorporated.
January 18, 2005
16
M9999-011805
(408) 955-1690
Similar pages