MLX71121KLQ-AAA-000-RE - Melexis

MLX71121

300 to 930MHz

FSK/OOK Receiver

39010 71121 Page 1 of 29 Data Sheet

Rev. 012 Mar/15

Features

 Two RF inputs for antenna diversity, LNA cascading or differential feeding

 Integrated IF filter

 Integrated FSK and OOK demodulator

 Fully integrated PLL-based synthesizer

 Wide operating voltage

 Very low standby current consumption

 Low operating current consumption

 Average and peak detection data slicer mode

 Analog RSSI output with high dynamic range

 Noise cancellation filter

 MCU clock output

 High frequency accuracy

 32-pin QFN package

Ordering Code

Product Code Temperature Code Package Code Option Code Packing Form Code

MLX71121 K LQ AAA-000 RE

Legend:

Temperature Code: K for Temperature Range -40°C to 125°C

Package Code: LQ for QFN

Packing Form: RE for Reel

Ordering example: MLX71121KLQ-AAA-000-RE

Application Examples

 Automotive RKE

 TPMS

 Smart metering (AMR)

 Home and building automation

 Consumer remote controls

 Alarm and security systems

 Low power telemetry systems

 Garage and door openers

Pin Description

General Description

The MLX71121 is a highly-integrated single-channel/dual-band RF receiver based on a double-conversion

super-heterodyne architecture. It can receive FSK and OOK modulated signals. The IC is designed for gen-

eral purpose applications for example in the European bands at 433MHz and 868MHz or for similar applica-

tions in North America or Asia, for example at 315MHz or 915MHz.

MIXO

IFAP

IFAN

VEE

SLCSEL

DF2

VCC

MODSEL

bottom

top

MLX71121

LNAO1

LNAO2

MIXN

MIXP

VEE

LNAI2

LNAI1 RSSI

DF1

DFO

PDP

PDN

CINT

SLC

VCC

DTAO

CLKO

LNASEL

RFSEL

IFSEL

ROI

MLX71121

300 to 930MHz

FSK/OOK Receiver

39010 71121 Page 2 of 29 Data Sheet

Rev. 012 Mar/15

Table of Contents

1Theory of Operation ................................................................................................... 4

1.1General ................................................................................................................................ 4

1.2Technical Data Overview ..................................................................................................... 4

1.3Block Diagram ...................................................................................................................... 5 

1.4Operating Modes ................................................................................................................. 6

1.5LNA Selection ...................................................................................................................... 6

1.6Mixer Section ....................................................................................................................... 7

1.7IF Filter ................................................................................................................................. 7 

1.8IF Amplifier ........................................................................................................................... 7

1.9PLL Synthesizer ................................................................................................................... 7

1.10Reference Oscillator ......................................................................................................... 8

1.11Clock Output ..................................................................................................................... 8

1.12FSK Demodulator ............................................................................................................. 8

1.13Baseband Data Path ........................................................................................................ 9

1.14Data Filter ....................................................................................................................... 10

1.15Data Slicer ...................................................................................................................... 10

1.15.1Averaging Detection Mode ..................................................................................................... 11

1.15.2Peak Detection Mode ............................................................................................................. 11

1.16Data Output and Noise Cancellation Filter ..................................................................... 12

2Functional Description ............................................................................................ 14

2.1Frequency Planning ........................................................................................................... 14

2.2Calculation of Frequency Settings ..................................................................................... 15

2.3Standard Frequency Plans ................................................................................................ 16

2.4433/868MHz Frequency Diversity ...................................................................................... 16

3Pin Definitions and Descriptions ............................................................................ 17

4Technical Data .......................................................................................................... 21

4.1Absolute Maximum Ratings ............................................................................................... 21

4.2Normal Operating Conditions ............................................................................................. 21

4.3DC Characteristics ............................................................................................................. 22

4.4AC System Characteristics ................................................................................................ 23

4.5External Components ........................................................................................................ 24

5Test Circuit ............................................................................................................... 25 

MLX71121

300 to 930MHz

FSK/OOK Receiver

39010 71121 Page 3 of 29 Data Sheet

Rev. 012 Mar/15

5.1Antenna Diversity Application Circuit ................................................................................. 25

5.1.1Component List for Fig. 11 ......................................................................................................... 26

6Package Description ................................................................................................ 27

7Standard Information Regarding Manufacturability of Melexis Products with

Different Soldering Processes ................................................................................ 28

8ESD Precautions ...................................................................................................... 28

9Disclaimer ................................................................................................................. 29

10Contact Information ................................................................................................. 29

MLX71121

300 to 930MHz

FSK/OOK Receiver

39010 71121 Page 4 of 29 Data Sheet

Rev. 012 Mar/15

1 Theory of Operation

1.1 General

The MLX71121 receiver architecture is based on a double-conversion super-heterodyne approach. The two

LO signals are derived from an on-chip integer-N PLL frequency synthesizer. The PLL reference frequency

is derived from a crystal (XTAL). As the first intermediate frequency (IF1) is very high, a reasonably high

degree of image rejection is provided even without using an RF front-end filter. At applications OOKing for

very high image rejections, cost-efficient RF front-end filtering can be realized by using a SAW filter in front

of the LNA. The second mixer MIX2 is an image-reject mixer.

The receiver signal chain can be setup by one or two low noise amplifiers (LNA1, LNA2), two down-

conversion mixers (MIX1, MIX2), an on-chip IF filter (IFF) as well as an IF amplifier (IFA). By choosing the

required modulation via an FSK/OOK switch (at pin MODSEL), either the on-chip FSK demodulator (FSK

DEMOD) or the RSSI-based OOK detector is selected. A second order data filter (OA1) and a data slicer

(OA2) follow the demodulator. The data slicer threshold can be generated from the mean-value of the data

stream or by means of the positive and negative peak detectors (PKDET+/-). Some post-processing of the

data output signal can be performed by means a noise cancellation filter (NCF).

The dual LNA configuration can be used for antenna space diversity or antenna frequency diversity or to

setup an LNA cascade (to further improve the input sensitivity). Another option is to set up the two LNAs for

feeding the RF signal differentially.

A sequencer circuit (SEQ) controls the timing during start-up. This is to reduce start-up time and to minimize

power dissipation.

A clock output, which is a divide-by-8 version of the crystal oscillator signal, can be used to drive a microcon-

troller. The clock output is an open drain and gets activated only if a loading resistor is connected to positive

supply.

1.2 Technical Data Overview

 Input frequency ranges: 300 to 470MHz

 610 to

930MHz

 Power supply range: 2.1 to 5.5V

 Temperature range: -40 to +125°C

 Shutdown current: 50 nA

 Operating current: 10.0 to 11.1mA

 FSK input sensitivity: -107dBm* (433MHz)

 OOK input sensitivity: -112dBm* (433MHz)

 Internal IF: 1.8MHz with 300kHz 3dB bandwidth

 FSK deviation range: ±10kHz to ±100kHz

 Image rejection:

 65dB 1st IF (with external RF front-end filter)

 25dB 2nd IF (internal image rejection)

 Maximum data rate: 50kps RZ (bi-phase) code,

 100kps NRZ

 Spurious emission: < -54dBm

 Usable RSSI range: 45 to 55dB

 Crystal frequency: 16 to 27MHz

 MCU clock frequency: 2.0 to 3.4MHz

* at 4kbps NRZ, BER = 310-3, at LNA input pins

MLX71121

300 to 930MHz

FSK/OOK Receiver

39010 71121 Page 5 of 29 Data Sheet

Rev. 012 Mar/15

1.3 Block Diagram

Fig. 1: MLX71121 block diagram

The MLX71121 receiver IC consists of the following building blocks:

 PLL synthesizer (PLL SYNTH) to generate the first and second local oscillator signals LO1 and LO2.

The PLL SYNTH consists of a fully integrated voltage-controlled oscillator (VCO), a distributed feedback

divider chain (N1,N2), a phase-frequency detector (PFD) a charge pump (CP), a loop filter (LF) and a

crystal-based reference oscillator (RO).

 Two low-noise amplifiers (LNA1, LNA2) for high-sensitivity RF signal reception

 First mixer (MIX1) for down-conversion of the RF signal to the first IF (intermediate frequency)

 Second mixer (MIX2) with image rejection for down-conversion from the first to the second IF

 IF Filter (IFF) with a 1.8MHz center frequency and a 300kHz 3dB bandwidth

 IF amplifier (IFA) to provide a high voltage gain and an RSSI signal output

 FSK demodulator (FSK DEMOD)

 Operational amplifiers OA1 and OA2 for low-pass filtering and data slicing, respectively

 Positive (PKDET+) and negative (PKDET-) peak detectors

 Switches SW1 to select between FSK and OOK as well as SW2 to chose between averaging or peak

detection mode.

 Noise cancellation filter (NCF)

 Sequencer circuit (SEQ) and biasing (BIAS) circuit

 Clock output (DIV8)

LNAI1

LNAI2

LNASEL

VCC

MIX1

MIXN

MIXP

IFA

LO2LO1

LNA2

MIXO

LNA1

SLCSEL

ROI

CLKO

DF1

IFF

ROVCO

N2

counter

N1

counter

PFD

LF CP DIV 8

FSK

DEMOD

MODSEL

PKDET+

PKDET_

25

46

3

VEE

2

VEE

7

1

LNAO2

LNAO1

28

5

8

30

32

TEST

26

RFSEL

31

15

14

RSSI

24

IFSEL

27

13

12

VEE

11109

DF2

OA1

1617

BIAS

SEQ

ENRX

NCF

OA2

VCC

22

SLC

19

A

SK

FSK SW1

SW2

100k

100k 100k

100k

DTAO

29

CINT

23

DFO

PDP

PDN

18

20

21

MIX2

MLX71121

300 to 930MHz

FSK/OOK Receiver

39010 71121 Page 6 of 29 Data Sheet

Rev. 012 Mar/15

1.4 Operating Modes

The receiver offers two operating modes selectable by setting the corresponding logic level at pin ENRX.

ENRX Description

0 Shutdown mode

1 Receive mode

Note: ENRX is pulled down internally.

The receiver’s start-up procedure is controlled by a sequencer circuit. It performs the sequential activation of

the different building blocks. It also initiates the pre-charging of the data filter and data slicer capacitors in

order to reduce the overall start-up time and current consumption during the start-up phase.

At ENRX = 0, the receiver is in shutdown mode and draws only a few nA. The bias system and the reference

oscillator are activated after enabling the receiver by a positive edge at pin ENRX. The crystal oscillator (RO)

is turned on first. Then the crystal oscillation amplitude builds up from noise. After reaching a certain ampli-

tude level at pin ROI, the whole IC is activated and draws the full receive mode current consumption ICC. This

event is used to start the pre-charging of the external data path capacitors. Pre-charging is finished after

5504 clock cycles. After that time the data output pin DTAO output is activated.

Fig. 2: Timing diagram of start-up and shutdown behavior

1.5 LNA Selection

The receiver features two identical LNAs. Each LNA is a cascode amplifier with a voltage gain of approxi-

mately 18dB. The actual gain depends on the antenna matching network at the inputs and the LC tank net-

work between the LNA outputs and mixer input. LNA operation can be controlled by the LNASEL pin.

LNASEL Description

0 LNA1 active, LNA2 shutdown

Hi-Z LNA1 and LNA2 active

1 LNA1 shutdown, LNA2 active

Pin LNASEL is internally pulled to VCC/2 during receive mode. Therefore both LNAs are active if LNASEL is

left floating (Hi-Z state).

valid data

Hi-Z Hi-Z

ENRX

DTAO

CC

I

SDN

I

RO

I

t

onRO

t

on RX

t

SEQ

MLX71121

300 to 930MHz

FSK/OOK Receiver

39010 71121 Page 7 of 29 Data Sheet

Rev. 012 Mar/15

gain/dB

0

f

cent

f

IF2

-40

-20

B

40dB

B

3dB

1.6 Mixer Section

The mixer section consists of two mixers. Both are double-balanced mixers. The second mixer is built as an

image rejection mixer. The first mixer’s inputs (MIXP and MIXN) are functionally the same. For single-ended

drive, the unused input has to be tied to ground via a capacitor. A soft band-pass filter is placed between the

mixers.

RFSEL Description

0 Input frequency range 300 to 470MHz

1 Input frequency range 610 to 930MHz

Pin RFSEL is used to select the required RF band. The LO frequencies and the proper sidebands for image

suppression will be set accordingly.

1.7 IF Filter

The MLX71121 comprises an internal IF

filter with a -3dB bandwidth (B3dB) of

300kHz and a -40dB attenuation band-

width (B40dB) of 1.4MHz. This filter

contains three capacitively coupled bi-

quad stages that represent resonant

tanks at a filter center frequency (fcent)

of 1.8MHz

Fig. 3: IF filter tolerance scheme

1.8 IF Amplifier

After having passed the IF filter, the signal is amplified by a high-gain limiting amplifier. It consists of several

AC-coupled gain stages with a bandwidth of 400kHz to 11MHz. The overall small-signal pass-band gain is

about 80dB. A received-signal-strength indicator (RSSI) signal is generated within the IF amplifier and is

available at pin RSSI.

1.9 PLL Synthesizer

The PLL synthesizer consists of a fully integrated voltage-controlled oscillator that runs at 400MHz to

640MHz, a distributed feedback divider chain, an edge-triggered phase-frequency detector, a charge pump,

a loop filter and a crystal-based reference oscillator. The PLL is used for generating the LO signals. The LO1

is directly taken from the VCO output, and the LO2 is derived from the LO1 signal passing the N1 counter.

Another counter N2 follows N1 to provide the comparison frequency to the PFD. The overall feedback divider

ratio Ntot is 24. The values of N1 and N2 can be changed via pin RFSEL for selecting the LO1 and LO2 fre-

quencies. The table below shows the range of the LO frequencies.

RFSEL fLO1min

[MHz] fLO1max

[MHz] fLO2min

[MHz] fLO2max

[MHz] N1 N2 Ntot

0 400 640 100 160 4 6 24

1 400 640 200 320 2 12 24

MLX71121

300 to 930MHz

FSK/OOK Receiver

39010 71121 Page 8 of 29 Data Sheet

Rev. 012 Mar/15

1.10 Reference Oscillator

A Colpitts crystal oscillator with integrated functional capacitors is used as the reference oscillator (RO) of

the PLL synthesizer. The equivalent input capacitance CRO offered to the crystal at pin ROI is about 18pF.

The crystal oscillator features an amplitude control loop. This is to assure a very stable frequency over the

specified supply voltage and temperature range together with a short start-up time. A buffer amplifier with

hysteresis is between RO and PFD. Also a clock divider follows the buffer.

1.11 Clock Output

The clock output pin CKOUT is an open-drain output. For power saving reasons, the circuit is only active if

an external pull-up resistor RCL is applied to the pin. Furthermore, RCL can be used to adjust the clock

waveform. It forms an RC low-pass together with the capacitive load at the pin, the parasitics of the PCB and

the input capacitance of the external circuitry (e.g. a microcontroller).

The clock output feature is disabled if pin CKOUT is connected to ground or left open.

Fig. 4: Clock output implementation

1.12 FSK Demodulator

The integrated FSK demodulator is based on a phase-coincidence demodulator principle. An injection-locked

oscillator (ILO) is used as a frequency-dependent phase shifter. This topology features a good linearity of the

frequency-phase relationship over the entire locking range. The type of demodulator has no built-in con-

straints regarding the modulation index. It also offers a wide carrier acceptance range.

In addition, the demodulator provides an AFC loop for correcting the remaining free-running frequency error

and drift effects, and also to remove possible frequency offsets between transmitter and receiver frequen-

cies. The AFC loop features a dead band which means that the AFC loop is only closed if the demodulator

output voltage leaves the linear region of the demodulator. Most of the time, the control loop is open. This

leads to several advantages. The AFC loop bandwidth can be high and therefore the reaction time is short.

Furthermore the demodulator itself has no low-end cut-off frequency.

The FSK demodulator has a negative control slope, this means the output voltage decreases by increasing

the IF2 frequency. This guarantees an overall positive slope because the mixer section converts the receive

frequency to IF2 either with high-low or low-high side injection.

The FSK demodulator is turned off during OOK demodulation.

CLKO

DIV8

Control

logic

RO

output

RCL

C

L

VCC

MLX71121

300 to 930MHz

FSK/OOK Receiver

39010 71121 Page 9 of 29 Data Sheet

Rev. 012 Mar/15

1.13 Baseband Data Path

The baseband data path can be divided into a data filter section and a data slicer section.

Fig. 5: Block diagram of the data path

The data filter input is either connected to the OOK or to the FSK demodulation output. Pin MODSEL can be

used to set the internal switch SW1 accordingly.

MODSEL Description

0 OOK demodulation

1 FSK demodulation

For OOK demodulation, the RSSI signal of the IFA is used. During FSK demodulation, SW1 is connected to

the FSK demodulator output.

The SLCSEL pin is used to control the internal switches depending on operating and slicer mode.

Pins DF1, DF2, DFO, SLC and DTAO are left floating during shutdown mode. So they are in a high-Z state.

PKDET+

PKDET_

OA1

OA2

data filter

data slicer

DF1 DF2

DF0

Control

logic

DTAO

CINT

PDP

SLC

MODSEL

ASK

FSK SW1

100k 100k

100k

S1

100k

S2

100k

S3

S4

VCC

PDN

S5

S6

SLCSEL

switches

MLX71121

300 to 930MHz

FSK/OOK Receiver

39010 71121 Page 10 of 29 Data Sheet

Rev. 012 Mar/15

1.14 Data Filter

The data filter is formed by the operational amplifier OA1, two internal 100k resistors and two external ca-

pacitors. It is implemented as a 2nd order Sallen-Key filter. The low pass filter characteristic rejects noise at

higher frequencies and therefore leads to an increased sensitivity.

Fig. 6: Data filter

The filter’s pole locations can be set by the external capacitors CF1 and CF2. The cut-off frequency fc has to

be adjusted according to the transmission data rate R. It should be set to approximately 1.5 times the fastest

expected data rate. For a Butterworth filter characteristic, the data filter capacitors can be calculated as fol-

lows.

c

f100kπ2

1

CF1 



2

CF1

CF2 

RRZ [kbit/s] RNRZ [kbit/s] fc [kHz] CF1 [pF] CF2 [pF]

0.6 1.2 0.9 2200 1000

1.2 2.4 1.8 1200 680

1.6 3.2 2.4 1000 470

2.4 4.8 3.6 680 330

3.3 6.6 5 470 220

4.8 9.6 7.2 330 150

6.0 12 9 220 100

1.15 Data Slicer

The purpose of the data slicer is to convert the filtered data signal into a digital output. It can therefore be

considered as an analog-to-digital converter. This is done by using the operational amplifier OA2 as a com-

parator that compares the data filter output with a threshold voltage. The threshold voltage can be derived in

two different ways from the data signal.

SLCSEL Description

0 Averaging detection mode

1 Peak detection mode

OA1

data fi lter

DF1 DF2

DF0

100k 100k

CF1 CF2

MLX71121

300 to 930MHz

FSK/OOK Receiver

39010 71121 Page 11 of 29 Data Sheet

Rev. 012 Mar/15

1.15.1 Averaging Detection Mode

The simplest configuration is the averaging or RC inte-

gration method. Here an on-chip 100k resistor togeth-

er with an external slicer capacitor (CSL) are forming an

RC low-pass filter. This way the threshold voltage au-

tomatically adjusts to the mean or average value of the

analog input voltage.

To create a stable threshold voltage, the cut-off fre-

quency of the low pass has to be lower than the lowest

signal frequency.

100k

τ

CSL AVG



RZ

AVG R

1.5

τ

A long string of zeros or ones, like in NRZ codes, can

cause a drift of the threshold. That’s why a Manchester

or other DC-free coding scheme works best.

The peak detectors are disabled during averaging de-

tection mode, and the output pins PDP and PDN are

pulled to ground (S4, S6 are closed).

Fig. 7: Data path in averaging detection mode

1.15.2 Peak Detection Mode

Peak detection mode has a general advantage over

averaging detection mode because of the part attack

and slow release times. Peak detection should be used

for all non-DC-free codes like NRZ. In this configuration

the threshold is generated by using the positive and

negative peak detectors. The slicer comparator thresh-

old is set to the midpoint between the high output and

the low output of the data filter by an on-chip resistance

divider. Two external capacitors (CP1, CP2) determine

the release times for the positive and negative enve-

lope. The two on-chip resistors provide a path for the

capacitors to discharge. This allows the peak detectors

to dynamically follow peak changes of the data filter

output voltage. The attack times are very short due to

the high peak detector load currents of about 500uA.

The decay time constant mainly depends on the longest

time period without bit polarity change. This corre-

sponds to the maximum number of consecutive bits with

the same polarity (NMAX).

100k

τ

CP1/2 DECAY



NRZ

MAX

DECAY R

N

τ

Fig. 8: Data path in peak detection mode

If the receiver is in shutdown mode and peak detection mode is selected then the peak detectors are disa-

bled and the output of the positive peak detector (PDP) is connected to VEE (S4 is closed) and the output of

the negative peak detector (PDN) is connected to VCC (S5 is closed). This guarantees the correct biasing of

CP1 and CP2 during start-up.

CSL

PKDET+

PKDET_

OA2

data slicer

PDP

SLC

100k

S1

100k

S2

100k

S3

S4

Control

logic

DTAO

CINT

VCC

PDN

S5

S6

data

filter

SLCSEL

switches

VCC

CP1

CP2

PKDET+

PKDET_

OA2

data slicer

PDP

PDN

SLC

100k

S1

100k

S2

100k

S3

S4

VCC

S5

S6

Control

logic

DTAO

CINT

data

filter

SLCSEL

switches

MLX71121

300 to 930MHz

FSK/OOK Receiver

39010 71121 Page 12 of 29 Data Sheet

Rev. 012 Mar/15

1.16 Data Output and Noise Cancellation Filter

The data output pin DTAO delivers the demodulated data signal which can be further processed by a noise

cancellation filter (NCF). The NCF can be disabled if pin CINT is connected to ground. In this case the

multiplexer (MUX) connects the receiver output DTAO directly to the data slicer output.

Fig. 9: Data output and noise filter

The noise cancellation filter can suppress random pulses in the data output which are shorter than tmin.

RZNRZ RR

t66

min

6- 105.71015

1015CF3

 







The NCF can also operate as a muting circuit. So if the RF input signal is below sensitivity level (or if no RF

signal is applied) then the data output will go to a constant DC level (either HIGH or LOW). This can be

achieved by setting the bandwidth of the preceding data filter (sec 1.13) about 10 times higher than the

bandwidth of the NCF. Further the data filter cutoff frequency must be higher than the data rate, so the noise

pulses are shorter than the shortest data pulse. Otherwise, the NCF will not be able to distinguish between

noise and data pulses.

Having the NCF activated is a good means for reducing the computing power of the microcontroller that fol-

lows the receiver IC for further data processing.

In contrast to a conventional muting (or squelch) circuit, this topology does not need the RSSI signal for level

indication. The filtering process is done by means of an analogue integrator. The cut-off frequency of the

NCF is set by the external capacitor connected to pin CINT. This capacitor CF3 should be set according to

the maximum data rate. Below table provides some recommendations..

During receiver start-up a sequencer checks if pin CINT is connected to a capacitor or to ground. The maxi-

mum value of CF3 should not exceed 12nF. This defines the lowest data rate that can be processed if the

noise cancellation filter is activated.

RRZ [kbit/s] RNRZ [kbit/s] CF3[nF]

0.6 1.2 12

1.2 2.4 6.8

1.6 3.2 4.7

2.4 4.8 3.3

3.3 6.6 2.2

4.8 9.6 1.5

6.0 12 1.2

CF3

data slicer

output

CINT

NCF

noise cancel lation fil ter

MUX

DTAO

MLX71121

300 to 930MHz

FSK/OOK Receiver

39010 71121 Page 13 of 29 Data Sheet

Rev. 012 Mar/15

In shutdown mode pin DTAO is set to Hi-Z state.

MLX71121

300 to 930MHz

FSK/OOK Receiver

39010 71121 Page 14 of 29 Data Sheet

Rev. 012 Mar/15

2 Functional Description

2.1 Frequency Planning

Because of the double conversion architecture that employs two mixers and two IF signals, there are four

different combinations for injecting the LO1 and LO2 signals:

 LO1 high side and LO2 high side: receiving at fRF(high-high)

 LO1 high side and LO2 low side: receiving at fRF(high-low)

 LO1 low side and LO2 high side: receiving at fRF(low-high)

 LO1 low side and LO2 low side: receiving at fRF(low-low)

As a result, four different radio frequencies (RFs) could yield one and the same second IF (IF2). Fig. 10

shows this for the case of receiving at fRF(high-high). In the example of Fig. 10, the image signals at fRF(low-

high) and fRF(low-low) are suppressed by the bandpass characteristic provided by the RF front-end. The

bandpass shape can be achieved either with a SAW filter (featuring just a couple of MHz bandwidth), or by

the tank circuits at the LNA input and output (this typically yields 30 to 60MHz bandwidth). In any case, the

high value of the first IF (IF1) helps to suppress the image signals at fRF(low-high) and fRF(low-low).

The two remaining signals at IF1 resulting from fRF(high-high) and fRF(high-low) are entering the second mix-

er MIX2. This mixer features image rejection with so-called single-sideband (SSB) selection. This means

either the upper or lower sideband of IF1 can be selected. In the example of Fig. 10, LO2 high-side injection

has been chosen to select the IF2 signal resulting from fRF(high-high).

Fig. 10: The four receiving frequencies in a double conversion superhet receiver

It can be seen from the block diagram of Fig. 1 that there is a fixed relationship between the LO signal fre-

quencies (fLO1 , fLO2) and the reference oscillator frequency fRO.

LO21LO1 fNf  RO2LO2 fNf





The operating frequency of the internal IF filter (IFF) and FSK demodulator (FSK DEMOD) are 1.8MHz.

Therefore the second IF (IF2) is set to 1.8MHz as well.

f

LO2

f

LO2

f

LO1

f

RF

f

RF

f

RF

f

RF

MLX71121

300 to 930MHz

FSK/OOK Receiver

39010 71121 Page 15 of 29 Data Sheet

Rev. 012 Mar/15

2.2 Calculation of Frequency Settings

The receiver has two predefined receive frequency plans which can be selected by the RFSEL control pin.

Depending on the logic level of RFSEL pin the sideband selection of the second mixer and the counter set-

tings for N1 and N2 are changed accordingly.

RFSEL Injection fRFmin [MHz] fRFmax [MHz] N1 N2

0 high-low 300 470 4 6

1 low-high 610 930 2 12

The following table shows the relationships of several internal receiver frequencies for the two input frequen-

cy ranges.

fRF [MHz] fIF1 fLO1 fLO2 fRO

300 to 470

1N

fNf

1

IF21RF





1N

)f(fN

1

IF2RF1





1N

ff

1

IF2RF





1)(NN

ff

12

IF2RF





610 to 930

1N

fNf

1

IF21RF





1N

)f(fN

1

IF2RF1



1N

ff

1

IF2RF



1)(NN

ff

12

IF2RF



Given IF2 = 1.8MHz and the corresponding N1, N2 counter settings, above equations can be transferred into

the following table.

fRF [MHz] fIF1 fLO1 fLO2 fRO

300 to 470

3

7.2MHzfRF 

3

)1.8MHz4(f RF



3

1.8MHzf RF



18

1.8MHzf RF 

610 to 930

3

3.6MHzfRF 

3

)1.8MHz2(fRF



36

1.8MHzf RF 

MLX71121

300 to 930MHz

FSK/OOK Receiver

39010 71121 Page 16 of 29 Data Sheet

Rev. 012 Mar/15

2.3 Standard Frequency Plans

IF2 = 1.8MHz

RFSEL fRF [MHz] fIF1 [MHz] fLO1 [MHz] fLO2 [MHz] fRO [MHz]

0 315 107.40 422.40 105.60 17.600000

433.92 147.04 580.96 145.24 24.206667

1 868.3 288.23 580.07 290.03 24.169444

915 303.80 611.20 305.60 25.466667

2.4 433/868MHz Frequency Diversity

The receiver’s multi-band functionality can be used to operate at two different frequency bands just by

changing the logic level at pin RFSEL and without changing the crystal. This feature is applicable for com-

mon use of the 433 and 868MHz bands. Below table shows the corresponding frequency plans.

IF2 = 1.8MHz

RFSEL fRF [MHz] fIF1 [MHz] fLO1 [MHz] fLO2 [MHz] fRO [MHz]

0 433.25 146.82 580.07 145.02

24.169444

1 868.3 288.23 580.07 290.03

MLX71121

300 to 930MHz

FSK/OOK Receiver

39010 71121 Page 17 of 29 Data Sheet

Rev. 012 Mar/15

3 Pin Definitions and Descriptions

Pin No. Name I/O Type Functional Schematic Description

3 LNAO1 analog

output

LNA output 1

1 LNAI1 analog

input

LNA input 1

2 VEE ground

negative supply voltage

4 MIXP analog

input

MIX1 positive input

5 MIXN analog

input

MIX1 negative input

6 LNAO2 analog

output

LNA output 2

8 LNAI2 analog

input

LNA input 2

7 VEE ground

negative supply voltage

9 VCC supply positive supply voltage

10 MIXO analog

output

not used

pin left open

mixer 2 output

11 VEE ground negative supply voltage

12 IFAP analog

input not used

pins left open

IF amplifier positive input

13 IFAN analog

input

IF amplifier negative input

14 MODSEL

CMOS

input

modulation select input

Vbias

VEE

VCC

1

3

LNAO1

LNAI1

1k

MIXP

4

VEE VEE

VCC VCC

5

MIXN

Vbias

2k

Vbias

VEE

VCC

8

6

LNAO2

LNAI2

1k

VEE VEE

VCC VCC

14

MODSEL

400

MLX71121

300 to 930MHz

FSK/OOK Receiver

39010 71121 Page 18 of 29 Data Sheet

Rev. 012 Mar/15

Pin No. Name I/O Type Functional Schematic Description

15 SLCSEL

CMOS

input

slicer mode select input

16 DF2 analog

I/O

data filter connection 2

17 DF1 analog

I/O

data filter connection 1

18 DFO analog

output

data filter output

19 SLC analog

input

slicer reference input

20 PDP analog

output

peak detector

positive output

21 PDN analog

output

peak detector

negative output

VEE VEE

VCC VCC

15

SLCSEL

400

VCC

VEE

VCC

DF2

16

400

VEE

DF1

17

400

100k

VCC

VEE

VCC VCC

18

DFO

400

VEE

VCC

19

SLC

400 100k

100k 100k

VEE

VCC VCC

20

PDP

400

VEE

VCC

21

PDN

400

MLX71121

300 to 930MHz

FSK/OOK Receiver

39010 71121 Page 19 of 29 Data Sheet

Rev. 012 Mar/15

Pin No. Name I/O Type Functional Schematic Description

22 VCC supply positive supply voltage

23 CINT analog

input

capacitor for noise cancella-

tion filter

pin must be connected to

ground if noise cancellation

filter is not used

24 RSSI analog

output

receive signal strength

indication

25 ROI analog

input

reference oscillator input

26 TEST CMOS

input

not used

connect to ground

test pin

27 IFSEL CMOS

input

not used

connect pin to ground

IF select input

28 CLKO CMOS

output

clock output

connect pull-up resistor

to activate clock

29 DTAO CMOS

output

data output

30 ENRX CMOS

input

enable RX mode control

VEE

VCC

23

CINT

51k

VEE VEE

VCC

24

RSSI

400

25

ROI

VEE VEE

VCCVCC

16k

VEE

VCC

28

CLKO

VEE

VCC VCC

29

DTAO

220

380k

VEE VEE

VCC VCC

30

ENRX

400

MLX71121

300 to 930MHz

FSK/OOK Receiver

39010 71121 Page 20 of 29 Data Sheet

Rev. 012 Mar/15

Pin No. Name I/O Type Functional Schematic Description

31 RFSEL CMOS

input

receive frequency select

input

32 LNASEL

CMOS

input

LNA select input

VEE VEE

VCC VCC

31

RFSEL

400

VEE

VCC

32

LNASEL

400

500k 500k

MLX71121

300 to 930MHz

FSK/OOK Receiver

39010 71121 Page 21 of 29 Data Sheet

Rev. 012 Mar/15

4 Technical Data

4.1 Absolute Maximum Ratings

Operation beyond absolute maximum ratings may cause permanent damage of the device.

Parameter Symbol Condition Min Max Unit

Supply voltage VCC 0 7 V

Input voltage VIN -0.3 VCC +0.3 V

Storage temperature TSTG -55 150 °C

Junction temperature TJ 150 °C

Thermal Resistance RthJA 22 K/W

Power dissipation Pdiss 0.12 W

Electrostatic discharge VESD HBM according to MIL STD

833D, method 3015.7 ±1 kV

4.2 Normal Operating Conditions

Parameter Symbol Condition Min Max Unit

Supply voltage VCC 2.1 5.5 V

Operating temperature TA C version -10 70 C

Operating temperature TA K version - 40 125 C

Input low voltage (CMOS) VIL ENRX, SEL pins 0.3*VCC V

Input high voltage (CMOS) VIH ENRX, SEL pins 0.7*VCC V

Input frequency range fRF RFSEL=0 300 470

MHz

RFSEL=1 610 930

First IF range fIF1 RFSEL=0 100 170

MHz

RFSEL=1 200 310

LO1 range (VCO frequency) fLO1 f

LO1 = 24*fREF 400 640 MHz

LO2 range fLO2 RFSEL=0, fLO2 = fLO1 / 4 100 160 MHz

RFSEL=1, fLO2 = fLO1 / 2 200 320

XOSC frequency fREF set by the crystal 16 27 MHz

CLKO frequency fCLK f

CLK = fREF / 8 2.0 3.375 MHz

FSK deviation f ±10 ±100 kHz

Data rate OOK ROOK bi-phase code 50

kbps

NRZ 100

Data rate FSK RFSK bi-phase code 50

NRZ 100

MLX71121

300 to 930MHz

FSK/OOK Receiver

39010 71121 Page 22 of 29 Data Sheet

Rev. 012 Mar/15

4.3 DC Characteristics

all parameters under normal operating conditions, unless otherwise stated;

typical values at TA= 23 °C and VCC = 3 V, all parameters based on test circuits as shown Fig. 11

Parameter Symbol Condition Min Typ Max Unit

Operating Currents

Shutdown current ISDN ENRX=0, TA = 85°C 50 200 nA

ENRX=0, TA = 125°C 4 µA

Supply current reference

oscillator IRO ENRX=1, t < tonRO 1.5 mA

Supply current, FSK IFSK

ENRX=1, MODSEL=1

SLCSEL=0

LNASEL=0 or 1

10.2 mA

Supply current, OOK IOOK

ENRX= 1, MODSEL= 0

SLCSEL=0

LNASEL=0 or 1

9.8 mA

Digital Pin Characteristics (except of LNASEL)

Input low voltage (CMOS) VIL ENRX, SEL pins 0.3*VCC V

Input high voltage (CMOS) VIH ENRX, SEL pins 0.7*VCC V

Pull down current ENRX pin IPDEN ENRX=1 2 8 30 µA

Low level input current

ENRX pin IINLEN ENRX=0 1 µA

High level input current IINHSEL SEL pins 1 µA

Low level input current IINLSEL SEL pins 1 µA

LNASEL Pin Characteristics

Input voltage LNA1 active VLNASEL1 ENRX=1 0.1*VCC V

Input voltage LNA2 active VLNASEL2 ENRX=1 0.9*VCC V

DTAO Pin Characteristics

Output low voltage VOL DTAO pin,

ISINK = 600µA 0.3*VCC V

Output high voltage VOH DTAO pin,

ISOURCE = 600µA 0.7*VCC V

MLX71121

300 to 930MHz

FSK/OOK Receiver

39010 71121 Page 23 of 29 Data Sheet

Rev. 012 Mar/15

4.4 AC System Characteristics

all parameters under normal operating conditions, unless otherwise stated;

typical values at TA= 23 °C and VCC = 3 V, all parameters based on test circuits as shown Fig. 11

Parameter Symbol Condition Min Typ Max Unit

Receive Characteristics

Input Sensitivity 1) MODSEL RFSEL

FSK

315MHz Pmin1

1

0 -107

dBm

433MHz Pmin2 -107

868MHz Pmin3 1 -104

915MHz Pmin4 -102

OOK

315MHz Pmin5

0

0 -112

dBm

433MHz Pmin6 -112

868MHz Pmin7 1 -108

915MHz Pmin8 -105

Maximum input signal – FSK Pmax, FSK MODSEL=1

-10 dBm

Maximum input signal – OOK Pmax, OOK MODSEL=0, M>70dB -10 dBm

Spurious emission Pspur -54 dBm

Image rejection 1st IF IR1 w/o SAW filter 20 dB

Image rejection 2nd IF IR2 25 dB

LNA Parameters

Voltage gain GLNA depends on external

LC tank 18 dB

IF Filter Parameters

Center frequency fcent 1.8 MHz

3dB bandwidth B3dB 300 kHz

40dB bandwidth B40dB 1.4 MHz

IF Amplifier / RSSI

Operating frequency fIFA 0.4 11 MHz

RSSI usable range DRRSSI continuous range 45 55 dB

RSSI slope SRSSI 20 mV/dB

FSK Demodulator

Input frequency range fDEM 1.8 MHz

Carrier acceptance range ∆fDEM ±80 kHz

Demodulator sensitivity SDEM 5

mV/

kHz

1) at 4kbps NRZ, BER  310-3, peak detector data slicer, LNASEL = 0 or 1

MLX71121

300 to 930MHz

FSK/OOK Receiver

39010 71121 Page 24 of 29 Data Sheet

Rev. 012 Mar/15

Parameter Symbol Condition Min Typ Max Unit

Baseband Data Path

Data filter bandwidth BDF depending on CF1,

CF2

100 kHz

Peak detector load current IPKD 500 µA

Start-up Parameters

Reference oscillator

start-up time tonRO depending on crystal

parameters 350 650 µs

Sequencer time tSEQ 5504 / fREF 200 250 350 µs

Receiver start-up time tonRX t

onRO + tSEQ 0.6 1 ms

Frequency Stability

Frequency pulling by supply

voltage dfVCC ±3 ppm/V

4.5 External Components

Parameter Symbol Condition Min Max Unit

Crystal Parameters

Crystal frequency f0 fundamental mode, AT 16 27 MHz

Load capacitance CL 10 15 pF

Static capacitance C0 5 pF

Series resistance R1 60 

Noise Cancellation Filter

Integrator capacitor CF3 depends on data rate 12 nF

Clock Output

Pull-up resistor RCL 600



Load capacitance CL 50 pF

MLX71121

300 to 930MHz

FSK/OOK Receiver

39010 71121 Page 25 of 29 Data Sheet

Rev. 012 Mar/15

5 Test Circuit

5.1 Antenna Diversity Application Circuit

Fig. 11: Antenna diversity circuit schematic, peak detectors activated

VCC

CB0

CB2

VCC

CB3

LNASEL

RFSEL

ENRX

MLX71121

17

18

19

20

21

22

23

24

9 1011121314 1516

8

1

2

3

4

5

6

7

32L QFN 5x5

VCC

RFSEL

VEE

IFAP

IFAN

MODSEL

SLCSEL

DF2

RSSI

DFO

DF1

DTAO

SLC

PDP

VCC

PDN

MIXN

MIXP

LNAI1

CLKO

TEST

ROI

IFSEL

LNAO2

LNAO1

LNAI2

MIXO

VEE

32

30

29

28

27

25

31

26

ENRX

CINT

FSK

A

SK

output

FSK

ASK

50

C9

L3

50

C3

C4 C5

C6

L1

L2

CF1

CF2

CP1

CP2

RSSI

CB1

CX

XTAL

CRS

CLKO

CF3

RCL

MLX71121

300 to 930MHz

FSK/OOK Receiver

39010 71121 Page 26 of 29 Data Sheet

Rev. 012 Mar/15

5.1.1 Component List for Fig. 11

Part Size Value @

315 MHz Value @

433.92 MHz Value @

868.3 MHz Value @

915 MHz Tol. Description

C3 0603 100 pF 100 pF 100 pF 100 pF 5% LNA input filtering capacitor

C4 0603 4.7 pF 3.9 pF 2.2 pF 1.5 pF 5% LNA output tank capacitor

C5 0603 100 pF 100 pF 100 pF 100 pF 5% MIX1 positive input matching capacitor

C6 0603 100 pF 100 pF 100 pF 100 pF 5% MIX1 negative input matching capacitor

C9 0603 100 pF 100 pF 100 pF 100 pF 5% LNA input filtering capacitor

CB0 0805 33 nF 33 nF 33 nF 33 nF 10% decoupling capacitor

CB1 0603 330 pF 330 pF 330 pF 330 pF 10% decoupling capacitor

CB2 0603 330 pF 330 pF 330 pF 330 pF 10% decoupling capacitor

CB3 0603 330 pF 330 pF 330 pF 330 pF 10% decoupling capacitor

CF1 0603 680 pF 680 pF 680 pF 680 pF 10% data low-pass filter capacitor,

for data rate of 4 kbps NRZ

CF2 0603 330 pF 330 pF 330 pF 330 pF 10% data low-pass filter capacitor,

for data rate of 4 kbps NRZ

CF3 0603 value according to the data rate 10% optional capacitor for noise cancellation

filter

connected to ground if noise filter not used

CP1 0603 33 nF 33 nF 33 nF 33 nF 10% positive PKDET capacitor,

for data rate of 4 kbps NRZ

CP2 0603 33 nF 33 nF 33 nF 33 nF 10% negative PKDET capacitor,

for data rate of 4 kbps NRZ

CRS 0603 1 nF 1 nF 1 nF 1 nF 10% RSSI output low pass capacitor

CSL 0603 100 nF 100 nF 100 nF 100 nF 10% data slicer capacitor,

for data rate of 4 kbps NRZ

for averaging detection mode only

CX 0603 27 pF 27 pF 27 pF 27 pF 5% crystal series capacitor

L1 0603 56 nH 27 nH 0  0  5% matching inductor

L2 0603 27 nH 15 nH 3.9 nH 3.9 nH 5% LNA output tank inductor

L3 0603 56 nH 27 nH 0  0  5% matching inductor

RCL 0603 3.3 k 3.3 k 3.3 k 3.3 k 5% optional CLK output resistor,

to clock output signal generated

XTAL SMD

5x3.2

17.60000

MHz

24.206667

MHz

24.169444

MHz

25.46667

MHz fundamental-mode crystal from Telcona,

or equivalent part

20ppm cal., 30ppm temp.

Note: NIP – not in place, may be used optionally

MLX71121

300 to 930MHz

FSK/OOK Receiver

39010 71121 Page 27 of 29 Data Sheet

Rev. 012 Mar/15

6 Package Description

 The device MLX71121 is RoHS compliant.

Fig. 12: 32L QFN 5x5 Quad

all Dimension in mm

D E D2 E2 A A1 A3 L e b

min 4.75 4.75 3.00 3.00 0.80 0 0.20 0.3 0.50 0.18

max 5.25 5.25 3.25 3.25 1.00 0.05 0.5 0.30

all Dimension in inch

min 0.187 0.187 0.118 0.118 0.0315 0 0.0079 0.0118 0.0197 0.0071

max 0.207 0.207 0.128 0.128 0.0393 0.002 0.0197 0.0118

A3

A

A1

18

24 17

16

9

32

25

D

E

eb

L

D2

E2

exposed pad

The “exposed pad” is not connected to internal ground,

it should not be connected to the PCB.

MLX71121

300 to 930MHz

FSK/OOK Receiver

39010 71121 Page 28 of 29 Data Sheet

Rev. 012 Mar/15

7 Standard Information Regarding Manufacturability of Melexis

Products with Different Soldering Processes

Our products are classified and qualified regarding soldering technology, solderability and moisture sensitivi-

ty level according to following test methods:

Reflow Soldering SMD’s (Surface Mount Devices)

 IPC/JEDEC J-STD-020

Moisture/Reflow Sensitivity Classification for Nonhermetic Solid State Surface Mount Devices

(classification reflow profiles according to table 5-2)

 EIA/JEDEC JESD22-A113

Preconditioning of Nonhermetic Surface Mount Devices Prior to Reliability Testing

(reflow profiles according to table 2)

Wave Soldering SMD’s (Surface Mount Devices) and THD’s (Through Hole Devices)

 EN60749-20

Resistance of plastic- encapsulated SMD’s to combined effect of moisture and soldering heat

 EIA/JEDEC JESD22-B106 and EN60749-15

Resistance to soldering temperature for through-hole mounted devices

Iron Soldering THD’s (Through Hole Devices)

 EN60749-15

Resistance to soldering temperature for through-hole mounted devices

Solderability SMD’s (Surface Mount Devices) and THD’s (Through Hole Devices)

 EIA/JEDEC JESD22-B102 and EN60749-21

Solderability

For all soldering technologies deviating from above mentioned standard conditions (regarding peak tempera-

ture, temperature gradient, temperature profile etc) additional classification and qualification tests have to be

agreed upon with Melexis.

The application of Wave Soldering for SMD’s is allowed only after consulting Melexis regarding assurance of

adhesive strength between device and board.

Melexis recommends reviewing on our web site the General Guidelines soldering recommendation

(http://www.melexis.com/Quality_soldering.aspx) as well as trim&form recommendations

(http://www.melexis.com/Assets/Trim-and-form-recommendations-5565.aspx).

Melexis is contributing to global environmental conservation by promoting lead free solutions. For more in-

formation on qualifications of RoHS compliant products (RoHS = European directive on the Restriction Of

the use of certain Hazardous Substances) please visit the quality page on our website:

http://www.melexis.com/quality.aspx

8 ESD Precautions

Electronic semiconductor products are sensitive to Electro Static Discharge (ESD).

Always observe Electro Static Discharge control procedures whenever handling semiconductor products.

MLX71121

300 to 930MHz

FSK/OOK Receiver

39010 71121 Page 29 of 29 Data Sheet

Rev. 012 Mar/15

9 Disclaimer

Devices sold by Melexis are covered by the warranty and patent indemnification provisions appearing in its

Term of Sale. Melexis makes no warranty, express, statutory, implied, or by description regarding the infor-

mation set forth herein or regarding the freedom of the described devices from patent infringement. Melexis

reserves the right to change specifications and prices at any time and without notice. Therefore, prior to de-

signing this product into a system, it is necessary to check with Melexis for current information. This product

is intended for use in normal commercial applications. Applications requiring extended temperature range,

unusual environmental requirements, or high reliability applications, such as military, medical life-support or

life-sustaining equipment are specifically not recommended without additional processing by Melexis for

each application.

The information furnished by Melexis is believed to be correct and accurate. However, Melexis shall not be

liable to recipient or any third party for any damages, including but not limited to personal injury, property

damage, loss of profits, loss of use, interrupt of business or indirect, special incidental or consequential

damages, of any kind, in connection with or arising out of the furnishing, performance or use of the technical

data herein. No obligation or liability to recipient or any third party shall arise or flow out of Melexis’ rendering

of technical or other services.

10 Contact Information

For the latest version of this document, go to our website at

www.melexis.com

Or for additional information contact Melexis Direct:

Europe, Africa, Asia: America:

Phone: +32 1367 0495 Phone: +1 248 306 5400

E-mail:

sales_europe@melexis.com

E-mail:

sales_usa@melexis.com

ISO/TS 16949 and ISO14001 Certified