1
Rating
Value
Units
Power Supply and All Input/Output Pins
-0.3 to +4.0
V
Non-Operating Case Temperature
-50 to +100
o
C
Soldering Temperature (10 seconds)
250
o
C
Absolute Maximum Ratings
Electrical Characteristics (typical values given for 3.0 Vdc power supply, 25
o
C)
Characteristic
Sym
Notes
Minimum
Typical
Maximum
Units
Operating Frequency
f
O
433.72
434.12
MHz
Modulation Type
OOK/ASK
Data Rate
19.2
kbps
Receiver Performance, High Sensitivity Mode
Sensitivity, 1.2 kbps, 10-3 BER, AM Test Method
1
-110.5
dBm
Sensitivity, 1.2 kbps, 10-3 BER, Pulse Test Method
1
-104.5
dBm
Current, 1.2 kbps (R
PR
= 330 K)
2
2.9
mA
Sensitivity, 2.4 kbps, 10-3 BER, AM Test Method
1
-109
dBm
Sensitivity, 2.4 kbps, 10-3 BER, Pulse Test Method
1
-103
dBm
Current, 2.4 kbps (R
PR
= 330 K)
2
3.0
mA
Sensitivity, 19.2 kbps, 10-3 BER, AM Test Method
1
-105
dBm
Sensitivity, 19.2 kbps, 10-3 BER, Pulse Test Method
1
-99
dBm
Current, 19.2 kbps
3.1
mA
Receiver Performance, Low Current Mode
Sensitivity, 1.2 kbps, 10-3 BER, AM Test Method
1
-104
dBm
Sensitivity, 1.2 kbps, 10-3 BER, Pulse Test Method
1
-98
dBm
Current, 1.2 kbps (R
PR
= 2000 K)
2
1.65
mA
RX5500
433.92 MHz
Hybrid
Receiver
Designed for Short-Range Wireless Control Applications
3 V, Low Current Operation plus Sleep Mode
Characterized for Automotive Applications
High EMI Rejection Capability
The RX5500 hybrid receiver is ideal for short-range wireless control applications where robust
operation, small size, low power consumption and low cost are required. The RX5500 employs
RFM's amplifier-sequenced hybrid (ASH) architecture to achieve this unique blend of character-
istics. All critical RF functions are contained in the hybrid, simplifying and speeding design-in.
The RX5500 is sensitive and stable. A wide dynamic range log detector provides robust perfor-
mance in the presence of on-channel interference or noise. Two stages of SAW filtering provide
excellent receiver out-of-band rejection. The RX5500 generates virtually no RF emissions, facili-
tating compliance with ETSI I-ETS 300 220 and similar regulations.
2
Electrical Characteristics (typical values given for 3.0 Vdc power supply, 25
o
C)
Characteristic
Sym
Notes
Minimum
Typical
Maximum
Units
Receiver Out-of-Band Rejection, 5% f
O
R
5%
3
80
dB
Receiver Ultimate Rejection
R
ULT
3
100
dB
Sleep Mode Current
I
S
0.7
A
Power Supply Voltage Range
V
CC
2.2
3.7
Vdc
Power Supply Voltage Ripple
10
mV
P-P
Ambient Operating Temperature
T
A
-40
85
o
C
Notes:
1. Typical sensitivity data is based on a 10
-3
bit error rate (BER), using DC-balanced data. There are two test methods commonly used to
measure OOK/ASK receiver sensitivity, the "100% AM" test method and the "Pulse" test method. Sensitivity data is given for both test meth-
ods. See Appendix 3.8 in the ASH Transceiver Designer's Guide for the details of each test method, and for sensitivity curves for a 2.2 to
3.7 V supply voltage range at five operating temperatures. The application/test circuit and component values are shown on the next page and
in the Designer's Guide.
2. At low data rates it is possible to adjust the ASH pulse generator to trade-off some receiver sensitivity for lower operating current. Sensitiv-
ity data and receiver current are given at 1.2 kbps for both high sensitivity operation (R
PR
= 330 K) and low current operation (R
PR
= 2000 K).
3. Data is given with the ASH radio matched to a 50 ohm load. Matching component values are given on the next page.
4. See Table 1 on Page 8 for additional information on ASH radio event timing.
S M - 2 0 L P a c k a g e D r a w i n g
0 . 0 8 "
( 2 . 0 3 )
0 . 1 2 5 "
( 3 . 2 0 )
0 . 0 2 "
( 0 . 5 1 )
0 . 0 4 "
( 1 . 0 2 )
0 . 1 3 "
( 3 . 3 0 )
0 . 4 3 "
( 1 0 . 9 )
0 . 3 8 "
( 9 . 6 5 )
0 . 0 7 5 "
( 1 . 9 0 )
3
4
5
6
7
9
1 1
1 2
1 3
1 4
1 5
1 6
1 7
1 9
A S H T r a n s c e i v e r P i n O u t
R F I O
8
2
1 0
2 0
1
1 8
L P F A D J
R R E F
T H L D 2
A G C C A P
P K D E T
B B O U T
C M P I N
R X D A T A
T X M O D
T H L D 1
P R A T E
P W I D T H
G N D 1
V C C 1
G N D 2
V C C 2
G N D 3
C N T R L 0
C N T R L 1
Item
Symbol
OOK
OOK
OOK
Units
Notes
Nominal NRZ Data Rate
DR
NOM
1.2
2.4
19.2
kbps
see pages 1 & 2
Minimum Signal Pulse
SP
MIN
833.33
416.67
52.08
s
single bit
Maximum Signal Pulse
SP
MAX
3333.33
1666.68
208.32
s
4 bits of
same value
BBOUT Capacitor
C
BBO
0.2
0.1
0.015
F
10% ceramic
BBOUT Resistor
R
BBO
12
12
0
K
5%
LPFAUX Capacitor
C
LPF
0.01
0.0047
-
F
5%
LPFADJ Resistor
R
LPF
330
300
100
K
5%
RREF Resistor
R
REF
100
100
100
K
1%
THLD1 Resistor
R
TH1
0
0
0
K
1%, typical values
PRATE Resistor
R
PR
330
330
330
K
5%
PWIDTH Resistor
R
PW
270 to GND
270 to GND
270 to GND
K
5%
DC Bypass Capacitor
C
DCB
4.7
4.7
4.7
F
tantalum
RF Bypass Capacitor 1
C
RFB1
100
100
100
pF
5% NPO
Antenna Tuning Inductor
L
AT
56
56
56
nH
50 ohm antenna
Shunt Tuning/ESD Inductor
L
ESD
220
220
220
nH
50 ohm antenna
3
Receiver Set-Up, 3.0 Vdc, -40 to +85
0
C
CAUTION: Electrostatic Sensitive Device. Observe precautions when handling.
D a t a O u t p u t
T O P V I E W
G N D
3
C N T
R L 0
C N T
R L 1
P
W I D T H
P
R A T E
T H L D
1
N C
R R E F
G N D 2
N C
R X
D A T A
L P F
A D J
C M P
I N
B B
O U T
P K
D E T
R F
A 1
V C C
1
V C C
2
R F I O
G N D 1
+ 3
V D C
A S H R e c e i v e r A p p l i c a t i o n C i r c u i t
O O K C o n f i g u r a t i o n
1
2 0
2
3
4
5
6
7
8
9
1 0
1 1
1 2
1 3
1 4
1 5
1 6
1 7
1 8
1 9
+ 3
V D C
R
P W
R
P R
R
T H 1
R
R E F
R
L P F
C
B B O
C
D C B
L
A T
L
E S D
C
R F B 1
+
R / S
C
L P F
R
B B O
4
ASH Receiver Theory of Operation
Introduction
RFM's RX5500 amplifier-sequenced hybrid (ASH) receivers are
specifically designed for short-range wireless control and data com-
munication applications. The receivers provide robust operation,
very small size, low power consumption and low implementation
cost. All critical RF functions are contained in the hybrid, simplifying
and speeding design-in. The ASH receiver can be readily configured
to support a wide range of data rates and protocol requirements.
The receiver features virtually no RF emissions, making it easy to
certify to short-range (unlicensed) radio regulations.
Amplifier-Sequenced Receiver Operation
The ASH receiver's unique feature set is made possible by its sys-
tem architecture. The heart of the receiver is the amplifier-
sequenced receiver section, which provides more than 100 dB of
stable RF and detector gain without any special shielding or de-
coupling provisions. Stability is achieved by distributing the total RF
gain over time. This is in contrast to a superheterodyne receiver,
which achieves stability by distributing total RF gain over multiple
frequencies.
Figure 1 shows the basic block diagram and timing cycle for an am-
plifier-sequenced receiver. Note that the bias to RF amplifiers RFA1
and RFA2 are independently controlled by a pulse generator, and
that the two amplifiers are coupled by a surface acoustic wave
(SAW) delay line, which has a typical delay of 0.5 s.
An incoming RF signal is first filtered by a narrow-band SAW filter,
and is then applied to RFA1. The pulse generator turns RFA1 ON
for 0.5 s. The amplified signal from RFA1 emerges from the SAW
delay line at the input to RFA2. RFA1 is now switched OFF and
RFA2 is switched ON for 0.55 s, amplifying the RF signal further.
The ON time for RFA2 is usually set at 1.1 times the ON time for
RFA1, as the filtering effect of the SAW delay line stretches the sig-
nal pulse from RFA1 somewhat. As shown in the timing diagram,
RFA1 and RFA2 are never on at the same time, assuring excellent
receiver stability. Note that the narrow-band SAW filter eliminates
sampling sideband responses outside of the receiver passband, and
the SAW filter and delay line act together to provide very high re-
ceiver ultimate rejection.
Amplifier-sequenced receiver operation has several interesting char-
acteristics that can be exploited in system design. The RF amplifiers
in an amplifier-sequenced receiver can be turned on and off almost
instantly, allowing for very quick power-down (sleep) and wake-up
times. Also, both RF amplifiers can be off between ON sequences
to trade-off receiver noise figure for lower average current consump-
tion. The effect on noise figure can be modeled as if RFA1 is on
continuously, with an attenuator placed in front of it with a loss
equivalent to 10*log
10
(RFA1 duty factor), where the duty factor is the
average amount of time RFA1 is ON (up to 50%). Since an
amplifier-sequenced receiver is inherently a sampling receiver, the
overall cycle time between the start of one RFA1 ON sequence and
A S H R e c e i v e r B l o c k D i a g r a m & T i m i n g C y c l e
A n t e n n a
P u l s e
G e n e r a t o r
S A W
D e l a y L i n e
S A W F i l t e r
R F A 1
R F A 2
D a t a
O u t
D e t e c t o r &
L o w - P a s s
F i l t e r
R F D a t a P u l s e
P 1
P 2
R F A 1 O u t
R F I n p u t
P 1
D e l a y L i n e
O u t
P 2
t
P W 2
t
P W 1
t
P R I
t
P R C
Figure 1
5
the start of the next RFA1 ON sequence should be set to sample
the narrowest RF data pulse at least 10 times. Otherwise, significant
edge jitter will be added to the detected data pulse.
RX5500 Series ASH Receiver Block Diagram
Figure 2 is the general block diagram of the RX5500 series ASH
receiver. Please refer to Figure 2 for the following discussions.
Antenna Port
The only external RF components needed for the receiver are the
antenna and its matching components. Antennas presenting an im-
pedance in the range of 35 to 72 ohms resistive can be satisfactorily
matched to the RFIO pin with a series matching coil and a shunt
matching/ESD protection coil. Other antenna impedances can be
matched using two or three components. For some impedances,
two inductors and a capacitor will be required. A DC path from RFIO
to ground is required for ESD protection.
Receiver Chain
The output of the SAW filter drives amplifier RFA1. The output of
RFA1 drives the SAW delay line, which has a nominal delay of 0.5
s.
The second amplifier, RFA2, provides 51 dB of gain below satura-
tion. The output of RFA2 drives a full-wave detector with 19 dB of
threshold gain. The onset of saturation in each section of RFA2 is
detected and summed to provide a logarithmic response. This is
added to the output of the full-wave detector to produce an overall
detector response that is square law for low signal levels, and tran-
sitions into a log response for high signal levels. This combination
provides excellent threshold sensitivity and more than 70 dB of
The detector output drives a gyrator filter. The filter provides a
three-pole, 0.05 degree equiripple low-pass response with excellent
group delay flatness and minimal pulse ringing. The 3 dB bandwidth
of the filter can be set from 4.5 kHz to 1.8 MHz with an external re-
sistor.
The filter is followed by a base-band amplifier which boosts the de-
tected signal to the BBOUT pin. When the receiver RF amplifiers
are operating at a 50%-50% duty cycle, the BBOUT signal changes
about 10 mV/dB, with a peak-to-peak signal level of up to 685 mV.
For lower duty cycles, the mV/dB slope and peak-to-peak signal
level are proportionately less. The detected signal is riding on a
1.1 Vdc level that varies somewhat with supply voltage, tempera-
ture, etc. BBOUT is coupled to the CMPIN pin or to an external data
recovery process (DSP, etc.) by a series capacitor. The correct
value of the series capacitor depends on data rate, data run length,
and other factors as discussed in the ASH Transceiver Designer's
Guide.
When the receiver is placed in the power-down (sleep) mode, the
output impedance of BBOUT becomes very high. This feature helps
preserve the charge on the coupling capacitor to minimize data
slicer stabilization time when the receiver switches out of the sleep
mode.
Data Slicers
The CMPIN pin drives data slicer DS1, which convert the analog
signal from BBOUT back into a digital stream. Data slicer DS1 is a
capacitively-coupled comparator with provisions for an adjustable
threshold. The threshold, or squelch, offsets the comparator's slicing
level from 0 to 90 mV, and is set with a resistor between the RREF
and THLD1 pins. This threshold allows a trade-off between receiver
sensitivity and output noise density in the no-signal condition. For
best sensitivity, the threshold is set to 0. In this case, noise is output
continuously when no signal is present. This, in turn, requires the
circuit being driven by the RXDATA pin to be able to process noise
(and signals) continuously.
This can be a problem if RXDATA is driving a circuit that must
"sleep" when data is not present to conserve power, or when it its
necessary to minimize false interrupts to a multitasking processor.
In this case, noise can be greatly reduced by increasing the thresh-
old level, but at the expense of sensitivity. The best 3 dB bandwidth
R X 5 5 0 0 S e r i e s A S H R e c e i v e r B l o c k D i a g r a m
R F A 1
R F A 2
S A W
D e l a y L i n e
S A W
C R F i l t e r
L o g
A n t e n n a
R F I O
E S D
C h o k e
D e t e c t o r
L o w - P a s s
F i l t e r
B B
P u l s e G e n e r a t o r
& R F A m p B i a s
L P F A D J
P R A T E
P W I D T H
R X D A T A
C N T R L 1
C N T R L 0
R
R E F
T H L D 1
B i a s C o n t r o l
P o w e r
D o w n
C o n t r o l
T h r e s h o l d
C o n t r o l
B B O U T
D S 1
R e f
T h l d
C
B B O
R
L P F
R
P R
R
P W
R
T H 1
2 0
1 7
1 8
1 4
1 5
9
5
6
1 3
V C C 1 : P i n 2
V C C 2 : P i n 1 6
G N D 1 : P i n 1
G N D 2 : P i n 1 0
G N D 3 : P i n 1 9
N C : P i n 8
R R E F : P i n 1 1
C M P I N : P i n 6
N C : P i n 4
N C : P i n 1 2
R F A 1
3
7
1 1 R R E F
Figure 2
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