RF Monolithics, Inc.

Phone: (972) 233-2903

Fax: (972) 387-8148

E-mail: info@rfm.com

Page 1 of 10

RFM Europe

Phone: 44 1963 251383

Fax: 44 1963 251510

http://www.rfm.com

RX6501-062905

Designed for Short-Range Wireless Control Applications

Supports RF Data Transmission Rates Up to 19.2 kbps

3 V, Low Current Operation plus Sleep Mode

Stable, Easy to Use, Low External Parts Count

Complies with Directive 2002/95/EC (RoHS)

The RX6501 hybrid receiver is ideal for short-range wireless control applications where robust operation,
small size, low power consumption and low cost are required. The RX6501 employs RFM's amplifier-se-
quenced hybrid (ASH) architecture to achieve this unique blend of characteristics. All critical RF functions are
contained in the hybrid, simplifying and speeding design-in. The RX6501 is sensitive and stable. A wide dy-
namic range log detector provides robust performance in the presence of on-channel interference or noise.
Two stages of SAW filtering provide excellent receiver out-of-band rejection. The RX6501 generates virtually
no RF emissions, facilitating compliance with ETSI I-ETS 300 220 and similar regulations.

Rating

Value

Units

Power Supply and All Input/Output Pins

-0.3 to +4.0

Non-Operating Case Temperature

-50 to +100

°C

Soldering Temperature (10 seconds / 5 cycles max.)

260

°C

868.35 MHz

Hybrid

Receiver

RX6501

SM-20H Case

Electrical Characteristics

Characteristic

Sym

Notes

Minimum

Typical

Maximum

Units

Operating Frequency

868.15

868.55

MHz

Modulation Types

OOK & ASK

Data Rate

19.2

kbps

Receiver Performance, High Sensitivity Mode

Sensitivity, 1.2 kbps, 10-3 BER, AM Test Method

-107.5

dBm

Sensitivity, 1.2 kbps, 10-3 BER, Pulse Test Method

-101.5

dBm

Current, 1.2 kbps (R

= 330 K)

2.9

Sensitivity, 2.4 kbps, 10-3 BER, AM Test Method

-106

dBm

Sensitivity, 2.4 kbps, 10-3 BER, Pulse Test Method

-100

dBm

Current, 2.4 kbps (R

= 330 K)

3.0

Sensitivity, 19.2 kbps, 10-3 BER, AM Test Method

-97

dBm

Sensitivity, 19.2 kbps, 10-3 BER, Pulse Test Method

-91

dBm

Current, 19.2 kbps

3.1

Receiver Performance, Low Current Mode

Sensitivity, 1.2 kbps, 10-3 BER, AM Test Method

-104

dBm

Sensitivity, 1.2 kbps, 10-3 BER, Pulse Test Method

-98

dBm

Current, 1.2 kbps (R

= 2000 K)

1.65

RF Monolithics, Inc.

Phone: (972) 233-2903

Fax: (972) 387-8148

E-mail: info@rfm.com Page 2 of 10

RFM Europe

Phone: 44 1963 251383

Fax: 44 1963 251510

http://www.rfm.com

RX6501-062905

Electrical Characteristics (typical values given for 3.0 Vdc power supply, 25 °C)

Characteristic

Sym

Notes

Minimum

Typical

Maximum

Units

Receiver Out-of-Band Rejection, ±5% fo

±5%

Receiver Ultimate Rejection

ULT

100

Sleep Mode Current

0.7

µA

Power Supply Voltage Range

2.2

3.7

Vdc

Power Supply Voltage Ripple

P-P

Ambient Operating Temperature

-40

°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 methods. See Ap-
pendix 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. Sensitivity
data and receiver current are given at 1.2 kbps for both high sensitivity operation (R

= 330 K) and low current operation (R

= 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.

Dimension

Inches

Min

Nom

Max

Min

Nom

Max

9.881

10.033

10.135

.389

.395

.400

6.731

6.858

6.985

.265

.270

.275

1.778

1.930

2.032

.070

.076

.080

1.651

1.778

1.905

.065

.070

.075

0.381

0.508

0.635

.015

.020

.025

0.889

1.016

1.143

.035

.040

.045

3.175

3.302

3.429

.125

.130

.135

1.397

1.524

1.651

.055

.060

.065

SM-20H Package Drawing

ASH Transceiver Pin Out

RFIO

LPFADJ

RREF

THLD2

AGCCAP

PKDET

BBOUT

CMPIN

RXDATA

TXMOD

THLD1

PRATE

PWIDTH

GND1

VCC1

GND2

VCC2

GND3

CNTRL0

CNTRL1

RF Monolithics, Inc.

Phone: (972) 233-2903

Fax: (972) 387-8148

E-mail: info@rfm.com Page 3 of 10

RFM Europe

Phone: 44 1963 251383

Fax: 44 1963 251510

http://www.rfm.com

RX6501-062905

Data Output

TOP VIEW

GND

CNT

RL0

CNT

RL1

WIDTH

RATE

THLD

RREF

GND2

DATA

LPF
ADJ

CMP

OUT

DET

RF
A1

VCC

RFIO

GND1

+ 3

VDC

ASH Receiver Application Circuit

OOK Configuration

+ 3

VDC

TH1

REF

LPF

BBO

DCB

ESD

RFB1

R/S

LPF

BBO

Item

Symbol

OOK

ASK

Units

Notes

Nominal NRZ Data Rate

NOM

1.2

2.4

19.2

kbps

see page 1& 2

Minimum Signal Pulse

MIN

833.33

416.67

52.08

µs

single bit

Maximum Signal Pulse

MAX

3333.33

1666.68

208.32

µs

4 bits of same value

BBOUT Capacitor

BBO

0.2

0.1

0.015

µF

±10% ceramic

BBOUT Resistor

BBO

±5%

LPFAUX Capacitor

LPF

0.01

0.0047

µF

±5%

LPFADJ Resistor

LPF

330

300

100

±5%

RREF Resistor

REF

100

±1%

THLD1 Resistor

TH1

±1%, typical values

PRATE Resistor

330

±5%

PWIDTH Resistor

270 to GND

±5%

DC Bypass Capacitor

DCB

4.7

µF

tantalum

RF Bypass Capacitor 1

RFB1

±5% NPO

Antenna Tuning Inductor

50 ohm antenna

Shunt Tuning/ESD Inductor

ESD

100

50 ohm antenna

Receiver Set-Up, 3.0 Vdc, -40 to +85 °C

CAUTION: Electrostatic Device. Observe precautions when handling.

RF Monolithics, Inc.

Phone: (972) 233-2903

Fax: (972) 387-8148

E-mail: info@rfm.com Page 4 of 10

RFM Europe

Phone: 44 1963 251383

Fax: 44 1963 251510

http://www.rfm.com

RX6501-062905

ASH Receiver Block Diagram & Timing Cycle

Antenna

Pulse

Generator

SAW

Delay Line

SAW Filter

RFA1

RFA2

Data
Out

Detector &

Low-Pass

Filter

RF Data Pulse

RFA1 Out

RF Input

Delay Line
Out

PW2

PW1

PRI

PRC

Figure 1

ASH Receiver Theory of Operation

Introduction

RFM's RX6500 series amplifier-sequenced hybrid (ASH) receivers are
specifically designed for short-range wireless control and data communica-
tion applications. The receivers provide robust operation, very small size,
low power consumption and low implementation cost. All critical RF func-
tions 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 regu-
lations.

Amplifier-Sequenced Receiver Operation

The ASH receiver's unique feature set is made possible by its system ar-
chitecture. 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 decoupling provisions. Stability is achieved
by distributing the total RF gain over

time. This is in contrast to a superhet-

erodyne receiver, which achieves stability by distributing total RF gain over
multiple frequencies.

Figure 1 shows the basic block diagram and timing cycle for an amplifier-
sequenced receiver. Note that the bias to RF amplifiers RFA1 and RFA2
are independently controlled by a pulse generator, and that the two ampli-
fiers are coupled by a surface acoustic wave (SAW) delay line, which has
a typical delay of 0.5 µs.

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 µs. 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 µs,
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 signal pulse from RFA1 somewhat. As shown in the timing di-
agram, 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 receiver ultimate rejection.

Amplifier-sequenced receiver operation has several interesting character-
istics that can be exploited in system design. The RF amplifiers in an am-
plifier-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 consumption. 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

(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 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.

RF Monolithics, Inc.

Phone: (972) 233-2903

Fax: (972) 387-8148

E-mail: info@rfm.com Page 5 of 10

RFM Europe

Phone: 44 1963 251383

Fax: 44 1963 251510

http://www.rfm.com

RX6501-062905

Figure 2

RX6500 Series ASH Receiver Block Diagram

Figure 2 is the general block diagram of the RX6500 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 impedance 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 compo-
nents. For some impedances, two inductors and a capacitor will be re-
quired. 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 µs.

The second amplifier, RFA2, provides 51 dB of gain below saturation. 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 pro-
vide a logarithmic response. This is added to the output of the full-wave de-
tector to produce an overall detector response that is square law for low
signal levels, and transitions into a log response for high signal levels. This
combination provides excellent threshold sensitivity and more than 70 dB
of detector dynamic range. In combination with the 30 dB of AGC range in
RFA1, more than 100 dB of receiver dynamic range is achieved.

The detector output drives a gyrator filter. The filter provides a three-pole,
0.05 degree equiripple low-pass response with excellent group delay flat-
ness 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 resistor.

The filter is followed by a base-band amplifier which boosts the detected
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 de-
tected signal is riding on a 1.1 Vdc level that varies somewhat with supply
voltage, temperature, etc. BBOUT is coupled to the CMPIN pin or to an ex-
ternal 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 great-
ly reduced by increasing the threshold level, but at the expense of sensitiv-
ity. The best 3 dB bandwidth for the low-pass filter is also affected by the
threshold level setting of DS1. The bandwidth must be increased as the
threshold is increased to minimize data pulse-width variations with signal
amplitude.

RX6501 ASH Receiver Block Diagram

RFA1

RFA2

SAW

Delay Line

SAW

CR Filter

Log

Antenna

RFIO

ESD
Choke

Detector

Low-Pass

Filter

Pulse Generator

& RF Amp Bias

LPFADJ

PRATE

PWIDTH

RXDATA

CN TRL1

CN TRL0

REF

THLD1

Bias Control

Power
Down
Control

Threshold

Control

BBOUT

DS1

Ref

Thld

BBO

LPF

TH1

VCC1: Pin 2
VCC2: Pin 16
GND1: Pin 1
GND2: Pin 10
GND3: Pin 19
NC: Pin 8
RREF: Pin 11
CMPIN: Pin 6
NC: Pin 4
NC: Pin 12

RFA1

11 RREF

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