MICRF219A
300MHz to 450MHz ASK/OOK Receiver with
Auto-Poll, and RSSI
General Description
Features
The MICRF219A is a 300MHz to 450MHz superheterodyne, image-reject, RF receiver with automatic gain
control, ASK/OOK demodulator, and analog RSSI output.
It only requires a crystal and a minimum number of
external components to implement. The MICRF219A is
ideal for low-cost, low-power, RKE, TPMS, and remote
actuation applications.
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The MICRF219A achieves −110dBm sensitivity at a bit
rate of 1kbps with 0.1% BER. Four demodulator filter
bandwidths are selectable in binary steps from 1625Hz to
13kHz at 433.92MHz, allowing the device to support bit
rates up to 20kbps. The device operates from a supply
voltage of 3.0V to 3.6V, and typically consumes 4.3mA of
supply current at 315MHz and 6.0mA at 433.92MHz. A
shutdown mode reduces supply current to 0.1μA typical.
Datasheets and support documentation can be found on
Micrel’s website at: www.micrel.com.
–110dBm sensitivity at 1kbps with 0.1% BER
Auto-polling mode with bit checking
Supports bit rates up to 20kbps at 433.92MHz
25dB image-reject mixer
No IF filter required
60dB analog RSSI output range
3.0V to 3.6V supply voltage range
4.3mA supply current at 315MHz
6.0mA supply current at 434MHz
13μA supply current in sleep mode
0.1μA supply current in shutdown mode
16-pin QSOP package (4.9mm x 6.0mm)
−40°C to +105°C temperature range
3kV HBM ESD Rating
_________________________________________________________________________________________________________________________
Typical Application
MICRF219A Typical Application Circuit (433.92MHz, 1kbps)
Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
August 12, 2015
Revision 3.0
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Micrel, Inc.
MICRF219A
Ordering Information
Part Number
MICRF219AAYQS
Temperature Range
Package
–40°C to +105°C
16-Pin QSOP
Pin Configuration
MICRF219AAYQS
Pin Description
Pin
Number
Pin
Name
1
RO1
2
GNDRF
3
ANT
4
GNDRF
5
VDD
6
SQ
Squelch Control Logic-Level Input. An internal pull-up (5μA typical) pulls the logic-input HIGH when the
device is enabled. This feature is not recommended in MICRF219A and this pin should remain floating.
7
SEL0
Tie this pin to VDD to ensure robust register programming. Use register bits D[4:3] to set demodulation
bandwidth.
8
SHDN
Shutdown Control Logic-Level Input. A logic-level LOW enables the device. A logic-level HIGH places the
device in low-power shutdown mode. An internal pull-up (5μA typical) pulls the logic input HIGH. To ensure
that the part starts up correctly, connect a 1μF capacitor from VDD to SHDN, and a 50kΩ resistor from
SHDN pin to GND. After the supply voltage settles, apply a HIGH logic level voltage to SHDN to turn the
part off, then a LOW logic level voltage to turn the part on before programming or operating the device.
9
GND
10
DO
11
SEL1
August 12, 2015
Pin Function
Reference resonator connection to the Pierce oscillator. May also be driven by external reference signal of
200mVp-p to 1.5V p-p amplitude maximum. Internal capacitance of 7pF to GND during normal operation.
Ground connection for ANT RF input. Connect to PCB ground plane.
Antenna Input: RF Signal Input from Antenna. Internally AC coupled. It is recommended to use a matching
network with an inductor to RF ground to improve ESD protection.
Ground connection for ANT RF input. Connect to PCB ground plane.
Positive supply connection for all chip functions. Bypass with 0.1μF capacitor located as close to the VDD
pin as possible.
Ground connection for all chip functions except for RF input. Connect to PCB ground plane.
Data Output. Demodulated data output. A current limited CMOS output during normal operation, 25kΩ pulldown is present when device is in shutdown.
Tie this pin to VDD to ensure robust register programming. Use register bits D[4:3] to set demodulation
bandwidth.
2
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MICRF219A
Pin Description (Continued)
Pin
Number
Pin
Name
12
CTH
13
CAGC
AGC Filter Capacitor. Connect a capacitor from this pin to GND. Refer to the AGC Loop and CAGC
section for information on the capacitor value.
14
RSSI
Received Signal Strength Indicator. The voltage on this pin is an inversed amplified version of the voltage
on CAGC. Output is from a switched capacitor integrating op amp with 250Ω typical output impedance.
15
SCLK
Programming clock input.
16
RO2
Reference resonator connection to the Pierce oscillator. Internal capacitance of 7pF to GND during normal
operation.
August 12, 2015
Pin Function
Demodulation Threshold Voltage Integration Capacitor. Connect a 0.1μF capacitor from CTH pin to GND
to provide a stable slicing threshold.
3
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MICRF219A
Absolute Maximum Ratings(1)
Operating Ratings(2)
Supply Voltage (VDD) ...................................................... +5V
SQ, SEL0, SEL1, SCLK,
SHDN DC Voltage. ........................ −0.3V to VDD + 0.3V
ANT DC Voltage ............................................ -0.3V to +0.3V
Junction Temperature .............................................. +150°C
Lead Temperature (soldering, 10sec.) ..................... +300°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
Maximum Input RF Power........................................... 0dBm
Receive Modulation Duty Cycle ........................ 20% to 80%
Frequency Range ................................. 300MHz to 450MHz
Electrical Characteristics(4)
VDD = 3.3V, VSHDN = 0V, SQ = open, CCAGC = 4.7µF, CCTH = 0.1µF, unless otherwise noted. Bold values indicate
–40°C ≤ TA ≤ 105°C. “Bit rate” refers to the encoded bit rate throughout this datasheet (see Note 4).
Parameter
Condition
Min.
Typ.
Max.
Units
Continuous Operation, fRF = 315MHz
4.3
Continuous Operation, fRF = 433.92MHz
6.0
Sleep Current
Only sleep clock is on
13
µA
Shutdown Current
VSHDN = VDD
0.1
µA
Operating Supply Current
mA
Receiver
−112.5
433.92MHz, D[4:3] = 00, BER = 1%
Conducted Receiver Sensitivity @
1kbps (Note 5)
−110
433.92MHz, D[4:3] = 00, BER = 0.1%
−110
315MHz, D[4:3] = 01, BER = 0.1%
Image Rejection
IF Center Frequency (fIF)
−3dB IF Bandwidth
CAGC Voltage Range
dBm
−112.5
315MHz, D[4:3] = 01, BER = 1%
fIMAGE = fRF – 2fIF
25
fRF = 315MHz
0.85
fRF = 433.92MHz
1.18
fRF = 315MHz
235
fRF = 433.92MHz
330
−40dBm RF input level
1.15
−100dBm RF input level
1.55
dB
MHz
kHz
V
Reference Oscillator
Reference Oscillator Frequency
fRF = 315MHz
9.81713
fRF = 433.92MHz
13.52313
MHz
Reference Buffer Input Impedance
RO1 when driven externally
1.6
kΩ
Reference Oscillator Bias Voltage
RO2
1.15
V
Reference Oscillator Input Range
External input, AC couple to RO1
Reference Oscillator Source Current
VRO1 = 0V
August 12, 2015
0.2
1.5
300
4
VP-P
µA
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MICRF219A
Electrical Characteristics(4) (Continued)
VDD = 3.3V, VSHDN = 0V, SQ = open, CCAGC = 4.7µF, CCTH = 0.1µF, unless otherwise noted. Bold values indicate
–40°C ≤ TA ≤ 105°C. “Bit rate” refers to the encoded bit rate throughout this datasheet (see Note 4).
Parameter
Condition
Min.
Typ.
Max.
Units
Demodulator
fREF = 9.81713MHz
165
fREF = 13.52313MHz
120
TA = +25ºC
TA = +105ºC
1
10
nA
As output source @ 0.8VDD
As output sink @ 0.2VDD
300
680
µA
600
Output Fall Time
15pF load on DO pin, transition time between
0.1VDD and 0.9VDD
Input High Voltage
SHDN, SQ
Input Low Voltage
SHDN, SQ
Output Voltage High
DO
Output Voltage Low
DO
CTH Source Impedance, Note 6
CTH Leakage Current In CTH Hold
Mode
kΩ
Digital / Control Functions
DO Pin Output Current
Output Rise Time
ns
200
0.8VDD
V
0.2VDD
0.8VDD
V
V
0.2VDD
V
RSSI
RSSI DC Output Voltage Range
RSSI Output Current
−110dBm RF input level
0.5
−50dBm RF input level
2.0
5kΩ load to GND, −50dBm RF input level
400
µA
250
Ω
10
ms
RSSI Output Impedance
RSSI Response Time
D[4:3] = 00, RF input power stepped from no
input to −50dBm
V
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.
Encoded bit rate is 1/(shortest pulse duration) that appears at MICRF219A DO pin:
5.
In an ON/OFF keyed (OOK) signal, the signal level goes between a “mark” level (when the RF signal is ON) and a “space” level (when the RF
signal is OFF). Sensitivity is defined as the input signal level when “ON” necessary to achieve a specified BER (bit error rate). BER measured with
the built-in BERT function in Agilent E4432B using PN9 sequence. Sensitivity measurement values are obtained using an input matching network
corresponding to 315MHz or 433.92MHz.
6.
CTH source impedance is inversely proportional to the reference frequency. In production test, the typical source impedance value is verified with
12MHz reference frequency.
August 12, 2015
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MICRF219A
Typical Characteristics
VDD = 3.3V, TA = +25°C, BER measured with PN9 sequence, unless otherwise noted.
Current vs. Receiver Frequency
Current vs. Supply Voltage
fRF = 433.92MHz
6.5
Current vs. Supply Voltage
fRF = 315MHz
7.5
5.0
+105ºC
6.0
+105ºC
5.0
4.5
4.0
6.5
+25ºC
6.0
5.5
+25ºC
4.0
-40ºC
4.5
300
325
350
375
400
425
450
3.5
3.0
3.1
RECEIVER FREQUENCY (MHz)
CAGC Voltage vs. Input Power
2.0
3.2
3.3
3.4
3.5
3.6
3.0
3.1
3.2
3.3
3.4
3.5
3.6
-111
-110
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
RSSI vs. Input Power
BER vs. Input Power
D[4:3] = 00
2.5
1.8
10
2.0
+105ºC
1.6
-40ºC
1.4
+25ºC
433.92MHz
-40ºC
BER (%)
RSSI VOLTAGE (V)
CAGC VOLTAGE (V)
4.5
-40ºC
5.0
3.5
CURRENT (mA)
5.5
CURRENT (mA)
CURRENT (mA)
7.0
1.5
+25ºC
1.0
+105ºC
1.2
0.5
1.0
-125
0.0
-125
315MHz
1
`
PN9 SEQUENCE @ 1kbps
-75
-50
-25
0
-100
Sensitivity at 1% BER
D[4:3] = 00
-98
SENSITIVITY (dBm)
SENSITIVITY (dBm)
-102
-104
315MHz
-108
433.92MHz
-110
-50
-25
0
-112
-98
-102
-100
-104
315MHz
-108
433.92MHz
-110
2
4
6
8
BIT RATE (kbps)
August 12, 2015
10
12
-112
-102
-104
315MHz
-106
433.92MHz
-108
-110
-114
-116
-113
Sensitivity at 1% BER
D[4:3] = 10
-100
-106
-114
INPUT POWER (dBm)
-112
-114
0
-115
Sensitivity at 1% BER
D[4:3] = 01
-100
-106
-75
INPUT POWER (dBm)
INPUT POWER (dBm)
SENSITIVITY (dBm)
-100
0.1
-116
-112
0
3
6
9
12
BIT RATE (kbps)
6
15
18
21
0
10
20
30
40
BIT RATE (kbps)
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MICRF219A
Typical Characteristics (Continued)
VDD = 3.3V, TA = +25°C, BER measured with PN9 sequence, unless otherwise noted.
Sensitivity at 1% BER
D[4:3] = 11
Bandpass Filter Attenuation
fXTAL = 13.52313MHz
-98
-102
-104
315MHz
-106
433.92MHz
-108
-110
0
10
20
30
40
0
0
-1
-1
-2
-3
-4
-5
-6
-7
-8
-3
-4
-5
-6
-7
-8
-9
-10
-10
-11
433.6
50
-2
-9
433.8
434.0
434.2
-11
314.8
314.9
315.0
315.1
315.2
INPUT FREQUENCY (MHz)
INPUT FREQUENCY (MHz)
BIT RATE (kbps)
Sensitivity for 1% BER vs.
Frequency, fXTAL = 9.81713MHz
Sensitivity for 1% BER vs.
Frequency, fXTAL = 13.52313MHz
-40
-50
-50
SENSITIVITY (dBm)
-40
-60
-70
-80
-90
-100
-60
-70
-80
-90
-100
-110
-110
-120
419
ATTENTUATION (dB)
ATTENTUATION (dB)
SENSITIVITY (dBm)
1
1
-100
SENSITIVITY (dBm)
Bandpass Filter Attenuation
fXTAL = 9.81713MHz
424
429
434
439
444
INPUT FREQUENCY (MHz)
August 12, 2015
449
-120
304
309
314
319
324
INPUT FREQUENCY (MHz)
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MICRF219A
Functional Diagram
Figure 1. Simplified Block Diagram
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MICRF219A
Functional Description
Therefore, the reference frequency fREF needed for a
given desired RF frequency (fRF) is approximately:
The simplified block diagram (Figure 1) illustrates the
basic structure of the MICRF219A receiver. It is made up
of four sub-blocks:
•
•
•
•
UHF Down-Converter
ASK/OOK Demodulator
Reference and Control logic
Auto-poll circuitry
fREF = fRF / (32 +
87
)
1000
Eq. 3
Outside the device, the MICRF219A receiver requires
just a few components to operate: a capacitor from
CAGC to GND, a capacitor from CTH to GND, a
reference crystal resonator with associated loading
capacitors, LNA input matching components, and a
power-supply decoupling capacitor.
Receiver Operation
UHF Downconverter
The UHF down-converter has six sub-blocks: LNA,
mixers, synthesizer, image reject filter, band pass filter
and IF amplifier.
Figure 2. Low-Side Injection Local Oscillator
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 to remove higher frequency products prior to the
image reject filter where they are combined to reject the
image frequency. The IF signal then passes through a
third order band pass filter. The IF bandwidth is 330kHz
@ 433.92MHz, and will scale with RF operating
frequency according to:
LNA
The RF input signal is AC-coupled into the gate of the
LNA input device. The LNA configuration is a cascoded
common source NMOS amplifier. The amplified RF
signal is then fed to the RF ports of two double balanced
mixers.
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 (Figure 2). The
product of the incoming RF signal and local oscillator
signal will yield the IF frequency, which will be
demodulated by the detector of the device. The image
reject mixer suppresses the image frequency which is
below the wanted signal by 2x the IF frequency. The
local oscillator frequency (fLO) is set to 32x the crystal
reference frequency (fREF) via a phase-locked loop
synthesizer with a fully-integrated loop filter:
fLO = 32 x fREF
Operating Freq (MHz)
BW IF = BW IF@433.92 MHz ×
433.92
Eq. 4
These filters are fully integrated inside the MICRF219A.
After filtering, four active gain controlled amplifier stages
enhance the IF signal to its proper level for
demodulation.
ASK/OOK Demodulator
The demodulator section is comprised of detector,
programmable low pass filter, slicer, and AGC
comparator.
Eq. 1
MICRF219A uses an IF frequency scheme that scales
the IF frequency (fIF) with fREF according to:
fIF = fREF x
August 12, 2015
87
1000
Eq. 2
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MICRF219A
Detector and Programmable Low-Pass Filter
The demodulation starts with the detector removing the
carrier from the IF signal. Post detection, the signal
becomes baseband information. The low-pass filter
further enhances the baseband signal. There are four
selectable low-pass filter BW settings: 1625Hz, 3250Hz,
6500Hz, and 13000Hz for 433.92MHz operation. The
low-pass filter BW is directly proportional to the crystal
reference frequency, and hence RF Operating
Frequency. Filter BW values can be easily calculated by
direct scaling. Equation 5 illustrates filter Demod BW
calculation:
Slicer and CTH
The signal prior to the slicer, labeled “Audio Signal” in
Figure 1, is still baseband analog signal. The data slicer
converts the analog signal into ones and zeros based on
50% of the slicing threshold voltage built up in the CTH
capacitor. After the slicer, the signal is demodulated
OOK digital data. When there is only thermal noise at
ANT pin, the voltage level on CTH pin is about 650mV.
This voltage starts to drop when there is RF signal
present. When the RF signal level is greater than
−100dBm, the voltage is about 400mV.
The value of the capacitor from CTH pin to GND is not
critical to the sensitivity of MICRF219A, although it
should be large enough to provide a stable slicing level
for the comparator. The value used in the evaluation
board of 0.1μF is good for all bit rates from 500bps to
20kbps.
Operating Freq (MHz)
BW Operating Freq = BW @433.92MHz ×
433.92
Eq. 5
CTH Hold Mode
If the internal demodulated signal (DO’ in Figure 1) is at
logic LOW for more than about 4msec, the chip
automatically enters CTH hold mode, which holds the
voltage on CTH pin constant even without RF input
signal. This is useful in a transmission gap, or
“deadtime”, used in many encoding schemes. When the
signal reappears, CTH voltage does not need to resettle, improving the time to output with no pulse width
distortion, or time to good data (TTGD).
It is very important to select a suitable low-pass filter BW
setting for the required data rate to minimize bit error
rate. Use the operating curves that show BER vs. bit
rates for different D[4:3] settings as a guide.
This low-pass filter −3dB corner, or the demodulation
BW, is set at 13000Hz @ 433.92MHz as default
(assuming both SEL0 and SEL1 pins are connected to
VDD). The low-pass filter can be set by changing register
bits D[4:3]. Table 2 demonstrates the scaling for
315MHz RF frequency:
D[4]
D[3]
Low-Pass
Filter BW
Maximum
Encoded Bit Rate
0
0
1625Hz
2.5kbps
0
1
3250Hz
5kbps
1
0
6500Hz
10kbps
1
1
13000Hz
20kbps
AGC Loop and CAGC
The AGC comparator monitors the signal amplitude from
the output of the programmable low-pass filter. The AGC
loop in the chip regulates the signal at this point to be at
a constant level when the input RF signal is within the
AGC loop dynamic range (about −115dBm to −40dBm).
When the chip first turns on, the fast charge feature
charges the CAGC node up with 120µA typical current.
When the voltage on CAGC increases, the gains of the
mixer and IF amplifier go up, increasing the amplitude of
the audio signal (as labeled in Figure 1), even with only
thermal noise at the LNA input. The fast-charge current
is disabled when the audio signal crosses the slicing
threshold, causing DO’ to go high, for the first time.
When an RF signal is applied, a fast attack period
ensues, when 600µA current discharges the CAGC
node to reduce the gain to a proper level. Once the loop
reaches equilibrium, the fast attack current is disabled,
leaving only 15µA to discharge CAGC or 1.5µA to
charge CAGC. The fast attack current is enabled only
when the RF signal increases faster than the ability of
the AGC loop to track it.
Table 1. Low-Pass Filter Selection @ 434MHz RF input
D[4]
D[3]
Low-Pass
Filter BW
Maximum
Encoded Bit Rate
0
0
1170Hz
1.8kbps
0
1
2350Hz
3.6kbps
1
0
4700Hz
7.2kbps
1
1
9400Hz
14.4kbps
Table 2. Low-Pass Filter Selection @ 315MHz RF input
August 12, 2015
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MICRF219A
The ability of the chip to track to a signal that
DECREASED in strength is much slower, since only
1.5μA is available to charge CAGC to increase the gain.
When designing a transmitter that communicates with
the MICRF219A, ensure that the power level remains
constant throughout the transmit burst.
The value of CAGC impacts the time to good data
(TTGD), which is defined as the time when signal is first
applied, to when the pulse width at DO is within 10% of
the steady state value. The optimal value of CAGC
depends on the setting of the D4 and D3 bits. A smaller
CAGC value does NOT always result in a shorter TTGD.
This is due to the loop dynamics, the fast discharge
current being 600µA, and the charge current being only
1.5µA. For example, if D4 = D3 = 0, the low pass filter
bandwidth is set to a minimum and CAGC capacitance is
too small, TTGD will be longer than if CAGC capacitance
is properly chosen. This is because when RF signal first
appears, the fast discharge period will reduce VCAGC very
fast, lowering the gain of the mixer and IF amplifier. But
since the low pass filter bandwidth is low, it takes too
long for the AGC comparator to see a reduced level of
the audio signal, so it can not stop the discharge current.
This causes an undershoot in CAGC voltage and a
corresponding overshoot in RSSI voltage. Once CAGC
undershoots, it takes a long time for it to charge back up
because the current available is only 1.5µA.
Table 3 lists the recommended minimum CAGC values
for different D[4:3] settings to insure that the voltage on
CAGC does not undershoot. The recommendation also
takes into account the behavior in auto-polling. If CAGC
is too small, the chip can have a tendency to false wake
up (DO releases even when there is no input signal).
D4
D3
CAGC value
0
0
4.7μF
0
1
2.2μF
1
0
1μF
1
1
1μF
the fast discharge current on CAGC, and the loop is too
slow to stop this fast discharge current in time. Since the
voltage on CAGC is too low, the audio signal level is
lower than the slicing threshold (voltage on CTH), and
DO pin is low. Once the fast discharge current stops,
only the small 1.5µA charge current is available in
settling the AGC loop to the correct level, causing the
recovery from CAGC undershoot/RSSI overshoot
condition to be slow. As a result, TTGD is about 9.1ms.
Figure 3. RSSI Overshoot and Slow TTGD (9.1ms)
Figure 4 shows the behavior with a larger capacitor on
CAGC pin (2.2μF), D[4:3] = 01. In this case, VCAGC does
not undershoot (RSSI does not overshoot), and TTGD is
relatively short at 1ms.
Table 3. Minimum Suggested CAGC Values
Figure 3 illustrates what occurs if CAGC capacitance is
too small for a given D[4:3] setting. Here, D[4:3] = 01,
the capacitance on CAGC pin is 0.47μF, and the RF
input level is stepped from no signal to −100dBm. RSSI
voltage is shown instead of CAGC voltage because
RSSI is a buffered version of CAGC (with an inversion
and amplification). Probing CAGC directly can affect the
loop dynamics through resistive loading from a scope
probe, especially in the state where only 1.5μA is
available, whereas probing RSSI does not. When RF
signal is first applied, RSSI voltage overshoots due to
August 12, 2015
Figure 4. Proper TTGD (1ms) with Sufficient CAGC
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MICRF219A
Reference Oscillator
The reference oscillator in the MICRF219A (Figure 5)
uses a basic Pierce crystal oscillator configuration with
MOS transconductor. Though the MICRF219A has builtin load capacitors for the crystal oscillator, the external
load capacitors are still required for tuning it to the right
frequency. RO1 and RO2 are external pins of the
MICRF219A to connect the crystal to the reference
oscillator.
Auto-Polling
The MICRF219A can be programmed into an autopolling mode by setting register bit D[15] to 1, where it
monitors if there is a valid incoming RF signal while
holding DO low. In this mode, the chip goes between
sleep state and polling state. In sleep state, only a low
power sleep clock is on, resulting in very low current
consumption of 13μA typical. The sleep time is
programmable from 10ms to 1.28s. In a polling state,
every block in the MICRF219A is on, and the chip looks
for signal with bit durations greater than a userprogrammed value. This operation is subsequently
called “bit checking” in this datasheet. A “valid bit” is a
mark or space with duration that is longer than the bit
check window. A “bad bit” is a mark or space with
duration that is shorter than the bit check window. The
user can set different bit check window time to suit a
particular signal by programming register bits D[11:9] as
listed in the register programming section. The number
of consecutive valid bits before releasing DO and exiting
polling mode can also be set by register bits D[8:7].
Figure 5. Reference Oscillator Circuit
Reference oscillator crystal frequency can be calculated
using Equation 3. For example, if fRF = 433.92MHz, fREF
= 13.52313MHz. Table 4 lists the values of reference
frequencies at different popular RF frequencies. To
operate the MICRF219A with minimum offset, use
proper loading capacitance recommended by the crystal
manufacturer.
RF Input Frequency (MHz)
Reference Frequency (MHz)
315.0
9.81713*
390.0
12.15446
418.0
13.02708
433.92
13.52313*
Figure 6. One Bad Bit Followed by Two Valid Bits
During the bit checking operation, DO is held low while
the bit checker examines the pulse widths at the node
labeled DO’ in Figure 1. If there is no signal present and
DO’ randomly chatters, the MICRF219A returns to sleep
after seeing 4 consecutive bad bits.
Note that since DO’ randomly chatters with no signal
present, the amount of time it takes for 4 consecutive
bad bits to happen is random. Therefore, the duration of
polling time is random without signal.
If enough consecutive valid bits are found, DO is
released and the MICRF219A stays on in the continuous
receive mode. Once the chip is in continuous receive
mode, it will not go back to sleep automatically when RF
signal is removed. The register bits must be
programmed again to put the MICRF219A back into
auto-polling mode.
*Empirically derived, slightly different from Equation 3.
Table 4. Reference Frequency Examples
August 12, 2015
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MICRF219A
Serial Interface Register Programming
There are twenty register bits in MICRF219A. The
functions are described in the following tables.
D19
D18
D11
Always set this bit to 0
Always set this bit to 1
SQ
Pin
0
D17
D10
D9
Set Bit-Check Window Time
(433.92 MHz, time in μs)
D4=1
D4=1
D4=0
D4=0
D3=1
D3=0
D3=1
D3=0
0
0
0
71
143
285
570
0
0
1
67
133
266
532
0
1
0
62
124
247
494
0
1
1
57
114
228
457
1
0
0
52
105
209
419
1
0
1
48
95
190
381
0
Not recommended
1
1
0
43
86
172
343
0
1
Squelch Circuit Disabled
1
1
1
38
76
152
305
1
0
Squelch Circuit Disabled (default)
1
1
Not recommended
D16
Always set this bit to 0
D15
Default value of D[11:9] = 111.
Set number of consecutive valid
bits before releasing DO
D8
D7
Auto-Poll Enable
0
0
0 bit - default
0
Awake – does not poll - default
0
1
4
1
Auto-polls with sleep periods
1
0
8
1
1
16
D14
0
D13
0
D12
0
D6
D5
Set slice level
0
0
1
20ms
0
1
Slice Level 30%
0
1
0
40ms Default
1
0
Slice Level 40%
0
1
1
80ms
1
1
Slice Level 50%
1
0
0
160ms
0
0
Slice Level 60%
1
0
1
320ms
1
1
0
640ms
D4
D3
1
1
1
1280ms
0
0
1625Hz
D11
D10
D9
0
0
0
0
0
0
Set Sleep Time
10ms
0
1
3250Hz
1
0
6500Hz
(315 MHz, time in μs)
1
1
13000Hz
D0
0
1
1
1
1
D1
X
0
1
0
1
D4=1
D4=0
D4=0
D3=1
D3=0
D3=1
D3=0
98
196
393
785
1
92
183
367
733
1
0
85
170
341
681
0
1
1
79
157
314
629
1
0
0
72
144
288
577
1
0
1
66
131
262
525
1
1
0
59
118
236
473
1
1
1
53
105
210
420
August 12, 2015
Demod Bandwidth (at 433.92MHz)
Set Bit-Check Window Time
D4=1
13
- default
D2
X
0
0
1
1
- default
default
Not recomended
Not recomended
Not recomended
Not recomended
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MICRF219A
Programming the device is accomplished by the use of
pins DO and SCLK. Normally, DO (Pin 10) is outputting
data and needs to switch to an input pin made by the
start sequence, as shown at Figure 7.
High at the SCLK pin tri-states the DO pin, enabling the
external drive into the DO pin with an initial low level.
The start sequence is completed by taking SCLK low,
then high while DO is low, followed by taking DO high,
then low while SCLK is high. The serial interface is
initialized and ready to receive the programming data.
Bits are serially programmed starting with the most
significant bit (MSB = D19) if all bits are being
programmed until the least significant bit (LSB =D0) For
instance, if only the bits D0, D1, and D2 are being
programmed, then these are the only bits that need to be
programmed with the start sequence, D2, D1, D0, plus
the stop sequence. Or, if only the bit D17 is needed,
then the sequence must be from start sequence, D17
through D0 plus the stop sequence, making sure the
other bits (besides D17) are programmed as needed. It
is recommended that all parallel input pins (SEL0, SEL1,
and SQ) be kept high when using the serial interface.
After the programming bits are finished, a stop sequence
(as shown in Figure 8) is required to end the mode and
re-establish the DO pin as an output again. To do so, the
SCLK pin is kept high while the DO pin changes from
low to high, then low again, followed by the SCLK pin
made low. Timing of the programming bits are not
critical, but should be kept as shown below:
SCLK frequency should be greater than 5kHz to avoid
automatic reset from internal circuitry.
T1 < 0.1 us, Time from SCLK to convert DO to
input pin
T6 > 0.1 us, SCLK high time
T7 > 0.1 us, SCLK low time
T2, T3, T4, T5, T8, T9, T10 > 0.1 us
Figure 7. Serial Interface Start Sequence
Figure 8. Serial Interface Stop Sequence
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MICRF219A
Serial Interface Register Loading Examples
See Figures 9 to 11. (Channel 1 is the DO pin, and
channel 2 is the SCLK pin).
Figure 11. D[19:18] = 11, D[17:0] = All 0s
Figure 9. All Bits D19 through D0 = 0
Figure 10. All Bits D19 through D0 = 1
August 12, 2015
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MICRF219A
Auto-Poll Programming Example
RF frequency 433.92MHz, bit rate 1kbps, bit width 1ms.
D[19] = 0, AGC fast attack enabled
D[18] = 1, watchdog timer is OFF
D[17] = 0,
D[16] = 0
D[15] = 1, device is placed in autopoll
D[14:12] = 100, sleep time 160ms
D[11:9] = 011, bit check window time 457μs with D[4:3]
= 00
D[8:7] = 10, number of consecutive valid bits is 8
D[6:5] = 11, slice level 50%
D[4:3] = 00, demodulator bandwidth = 1.625kHz
D[2:0] = 000
Figure 12. Auto-Poll Example
From MSB to LSB, see Table 5:
D19
D18
D17
D16
D15
D14
D13
D12
0
D11
1
D10
0
D9
0
D8
1
D7
1
D6
0
D5
0
0
D4
1
D3
1
D2
1
D1
0
D0
1
1
0
0
0
0
0
As noted in the Absolute Maximum Ratings section, the
voltage on SCLK can go up to VDD + 0.3V without
causing damage. But applying VDD + 0.3V to SCLK can
put the part in an unknown test mode. If this accidently
happens, cycle the power supply to restore the part to
normal operation.
Table 5. Auto-Poll example bit sequence.
August 12, 2015
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MICRF219A
Application Information
Initial Startup
When supply voltage is initially applied, it should rise
monotonically from 0V to 3.3V to ensure proper startup
of the crystal oscillator and the PLL. It should not have
multiple bounces across 2.6V, which is the threshold of
the undervoltage lockout (UVLO) circuit inside
MICRF219A. The SHDN pin needs to have 50kΩ
resistor to GND and a coupling capacitor to VDD as
shown in the evaluation board schematic to ensure that
the part starts up in shutdown mode first. Then the micro
controller can bring the SHDN pin voltage down to turn
the part on.
Figure 14. Sufficient Preamble Length
Antenna and RF Port Connections
The evaluation board offers two options of injecting the
RF input signal: through a PCB antenna or through a
50Ω SMA connector. The SMA connection allows for
conductive testing, or an external antenna.
Length of Preamble
When using MICRF219A in auto-polling mode, the
preamble of the corresponding transmitter should be
long enough to guarantee that the MICRF219A becomes
fully awake during the preamble portion of the burst.
This way the entire data portion will be received. A good
rule of thumb to use is:
Low-Noise Amplifier Input Matching
Capacitor C3 and inductor L2 form the “L” shape input
matching network to the SMA connector. The capacitor
cancels out the inductive portion of the net impedance
after the shunt inductor, and provides additional
attenuation for low-frequency outside band noise. The
inductor is chosen to over resonate the net capacitance
at the pin, leaving a net-positive reactance and
increasing the real part of the impedance. It also
provides additional ESD protection for the antenna pin.
The input impedance of the device is listed in Table 6 to
aid calculation of matching values. Note that the net
impedance at the pin is easily affected by component
pads parasitic due to the high input impedance of the
device. The numbers in Table 6 does NOT include trace
and component pad parasitic capacitance, which total
about 0.75pF on the evaluation board.
The matching components to the PCB antenna (L3 and
C9) were empirically derived for best over-the-air
reception range.
Preamble length = 1.2 x sleep time + length of
valid bits sequence
The factor of 1.2 is to accommodate sleep time variation
due to process shift.
Figure 13 shows an example of insufficient length
preamble. MICRF219A starts checking bits during the
data portion of the burst, so by the time it becomes fully
awake and releases DO, part of the data portion is lost.
In Figure 14, the preamble length is sufficient. The chip
wakes up during the preamble and is ready for the data
portion.
Z Device (Ω)
315
23 − j290
390
14 – j230
418
17 – j216
433.92
12 – j209
Table 6. Input Impedance for the Most Used frequencies
Figure 13. Preamble Length Too Short
August 12, 2015
Frequency (MHz)
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MICRF219A
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.
Crystal Selection
The crystal resonator provides a reference clock for all
the device internal circuits. Crystal tolerance needs to
be chosen such that the down-converted signal is
always inside the IF bandwidth of MICRF219A. From
this consideration, the tolerance should be ±50ppm on
both the transmitter and the MICRF219A side. The ESR
should be less than 300Ω, and the temperature range of
the crystal should match the range required by the
application. With the Abracon crystal listed in the Bill of
Materials, a typical MICRF219A crystal oscillator still
starts up at +105ºC with additional 400Ω series
resistance.
The oscillator of the MICRF219A is a Pierce-type
oscillator. Good care must be taken when laying out the
printed circuit board. Avoid long traces and place the
ground plane on the top layer close to the REFOSC pins
RO1 and RO2. When care is not taken in the layout, and
the crystals used are not verified, the oscillator may not
start or takes longer to start. Time-to-good-data will be
longer as well.
VDD pin
Important Note
A few customers have reported that some MICRF219A
receiver 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.
SHDN pin
Micrel has confirmed that this is the symptom of
incorrect power on reset (POR) of internal register bits.
The MICRF219A 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 in the
following diagram.
The suggestion provided above will generally serve
to prevent the startup issue from happening to the
MICRF219A 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.
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
August 12, 2015
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MICRF219A
PCB Considerations and Layout
The MICRF219A evaluation board is a good starting
point for prototyping of most applications. The Gerber
files are downloadable from the Micrel website and
contain the remaining layers needed to fabricate this
board. When copying or making one’s own boards,
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 mils (2.5mm) long
has about 1.1nH inductance. Optimization should always
be done with range tests. Make sure the individual
ground connection has a dedicated via rather then
sharing a few of ground points by a single via. Sharing
ground via will increase the ground path inductance.
Ground plane should be solid and with no sudden
interruptions. Avoid using ground plane on top layer next
to the matching elements. It normally adds additional
stray capacitance which changes the matching. Do not
use Phenolic materials as they are conductive above
200MHz. Typically, FR4 or better materials are
recommended. The RF path should be as straight as
possible to avoid loops and unnecessary turns.
Separate ground and VDD lines from other digital or
switching power circuits (such microcontroller, etc).
Known sources of noise should be laid out as far as
possible from the RF circuits. Avoid unnecessary wide
traces which would add more distribution capacitance
(between top trace to bottom GND plane) and alter the
RF parameters.
August 12, 2015
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MICRF219A
PCB Recommended Layout Considerations
MICRF219A Evaluation Board Assembly
MICRF219A Evaluation Board Top Layer
MICRF219A Evaluation Board Bottom Layer
August 12, 2015
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MICRF219A
MICRF219A Evaluation Board Schematic
August 12, 2015
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MICRF219A
Bill of Materials − MICRF219A Evaluation Board: 433.92MHz
Item
Part Number
Manufacturer
Description
Qty.
Murata
(1)
1.2pF ±0.25pF, 0603 capacitor
1
Murata
(1)
4.7μF ±10%, 0805 capacitor
1
GRM188R71E104K
Murata
(1)
0.1μF ±10%, 0603 capacitor
2
NP
0
C9
GQM1885C2A1R5C
Murata
(1)
1.5pF ±0.25pF, 0603 capacitor
1
C10, C11
GRM1885C1H100J
Murata
(1)
10pF ±5%, 0603 capacitor
2
Murata
(1)
1μF ±10%, 0603 capacitor
1
NP, SMA, Edge Conn.
0
AMPMODU Breakaway Headers 40 P(6pos)
R/A HEADER GOLD
1
C3
C4
C5, C6
GQM1885C2A1R2C
GRM219R60J475K
C7
C12
GRM188R61A105K
J2
(2)
J3
571-41031480
Mouser
L2
LQG18HN39NJ00
Murata
(1)
39nH ±5%, 0603 multi layer ceramic inductor
1
Murata
(1)
33nH ±5%, 0603 multi layer ceramic inductor
1
(3)
50kΩ ±5%, 0402 resistor
1
(3)
100kΩ ±5%, 0402 resistor
1
L3
R3
R4
R5, R6
LQG18HN33NJ00
CRCW040250KFKEA
CRCW0402100KFKEA
CRCW04020000Z
Vishay
Vishay
(3)
Vishay
R7, R8, R9
Y1
ABLS-13.52313MHz-10J4Y
Y2
DSX321GK-13.52313MHz
U1
MICRF219AAYQS
Abracon
(4)
(5)
KDS
(6)
Micrel, Inc.
0Ω ±5%,, 0402 resistor
2
NP
0
13.52313MHz, HC49/US
1
NP, (13.52313MHz, −40°C to +105°C), DSX321GK
0
300MHz to 450MHz ASK/OOK Receiver with Auto-Poll,
and RSSI
1
Notes:
1. Murata: www.murata.com.
2. Mouser: www.mouser.com.
3. Vishay Tel: www.vishay.com.
4. Abracon: www.abracon.com.
5. KDS: www.kds.info/index_en.htm.
6. Micrel, Inc.: www.micrel.com.
August 12, 2015
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MICRF219A
Bill of Materials − MICRF219A Evaluation Board: 315MHz
Item
C3
C4
C5, C6
Part Number
Manufacturer
C10, C11
C12
1.5pF ±0.25pF, 0603 Capacitor
1
Murata
(7)
4.7μF ±10%, 0805 Capacitor
1
GRM188R71E104K
Murata
(7)
0.1μF ±10%, 0603 Capacitor
2
NP
0
GQM1885C2A1R2C
Murata
(7)
1.2pF ±0.25pF, 0603 Capacitor
1
Murata
(7)
10pF ±5%, 0603 Capacitor
2
Murata
(7)
1μF ±10%, 0603 Capacitor
1
NP, SMA, Edge Conn.
0
(8)
AMPMODU Breakaway Headers 40 P(6pos) R/A HEADER
GOLD
1
(7)
68nH ±5%, 0603 Multi Layer Ceramic Inductor
2
(9)
50kΩ ±5%, 0402 Resistor
1
(9)
100kΩ ±5%, 0402 Resistor
1
(9)
0Ω ±5%,, 0402 Resistor
2
GRM21BR60J475K
GRM1885C1H100J
GRM188R61A105K
J2
J3
571-41031480
Mouser
L2, L3
LQG18HN68NJ00
Murata
R3
R4
R5, R6
Qty.
Murata
GQM1885C2A1R5C
C7
C9
Description
(7)
CRCW040250KFKEA
CRCW0402100KFKEA
CRCW04020000Z
Vishay
Vishay
Vishay
R7, R8, R9
Y1
ABLS-9.81713MHz-10J4Y
Abracon
Y2
DSX321GK-9.81713MHz
KDS
U1
MICRF219AAYQS
(10)
(11)
(12)
Micrel, Inc.
NP
0
9.81713MHz, HC49/US
1
NP, (9.81713MHz, −40°C to +105°C), DSX321GK
0
300MHz to 450MHz ASK/OOK Receiver with Auto-Poll,
and RSSI
1
Notes:
7. Murata: www.murata.com.
8. Mouser: www.mouser.com.
9. Vishay Tel: www.vishay.com.
10. Abracon: www.abracon.com.
11. KDS: www.kds.info/index_en.htm.
12. Micrel, Inc.: www.micrel.com.
August 12, 2015
23
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Micrel, Inc.
MICRF219A
Package Information and Recommended Land Pattern(13)
QSOP16 Package (AQS16)
Note:
13. Package information is correct as of the publication date. For updates and most current information, go to www.micrel.com.
August 12, 2015
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Micrel, Inc.
MICRF219A
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.
© 2011 Micrel, Incorporated.
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