Holtek BC2401 Instruction Manual

BC2401 Application Guidelines

AN0435EV1.00 1/ 8December 11, 2016

BC2401 Application Guidelines

D/N: AN0435E

Introduction

Holtek’s BC2401 is an RF receiver which supports OOK demodulation in the 315MHz and

433.92MHz frequency bands. The device includes fully integrated super regeneration

signal reception technology to achieve the best performance/cost ratio. For product

development convenience, the BC2401 can detect received signals by reading the pin

state directly. The BC2401 can operates with a simple OOK modulation RF transmitter to

develop wireless products, such as wireless transmission controls for home appliances,

computer peripherals and radio controlled toys to name but a few.

As mentioned above, the BC2401 is an RF receiver. Product design engineers, when

using such products for the first time, are often faced with some difficult problems during

product design. Holtek has prepared solutions including some frequently asked questions

based on their past experience to help engineers to quickly understand the RF receiver

operation to overcome these initial problems. This application note will show how to use

the BC2401 using specific examples.

Functional Description

The BC2401 is a super regeneration architecture RF receiver which contains a front-end

receiver and a digital demodulator. The architecture is shown as follows.

LNA

VCO

Quench

Signal

generator

Digit

Demodulator

HIRC

RFIN

L1 L2

DOUT

VDDRF

VSSRF

VDD VSS

The reception signal frequency can be setup by external reactive components connected

to L1 and L2. The internal oscillator will operate continuously after power-on to provide

frequency for the demodulator. When the signal frequency has been setup by the

components on L1 and L2, the relevant output signal will be generated on the DOUT pin

once the device is powered on.

BC2401 Application Guidelines

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The above figure shows the general design architecture of the BC2401. An antenna, a

matching circuit, a BC2401 device and a decoder IC are all that is necessary to

implement a high frequency signal receiver function.

Feature

The BC2401 contains the following features:

Supports RF OOK ASK demodulation

Operating voltage: 4.0V~5.5V

Operating bandwidth: 300MHz~450MHz

Symbol rate: 5Kbps

High sensitivity: -100dBm@5V / 0.1%BER / 315MHz / 433MHz

Operating current consumption less than 4mA

Integrated LNA and super regeneration oscillator

Small package type: 8-pin SOP

Application Circuits

Note: Special attention should be paid to three parts in the circuit. The first part is the

antenna part labeled with ANT1, the second part is the high frequency input matching

circuit which includes C5 and L2 while the third part is the LC Tank circuit which contains

L1, C6 and L3. More detail information will be introduced in the following sections.

Decoder IC BC2401 AntennaData Out Match Circuit

BC2401 Application Guidelines

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Bill of Materials:

Symbol Description

Value

Unit Vendor Part Number

315MHz

433MHz

BC2401

—

Pcs

Holtek

BC2401

Resistor

Walsin

WR06X102JRR

Capacitor

10μ

muRata

GRM188B30J106ME47#

Capacitor

0.1μ

muRata

GRM188R71H104KA93#

Capacitor

0.1μ

muRata

GRM188R71H104KA93#

Capacitor

3.5p

muRata

GQM1875C2ExRxCB12#

Capacitor

5.5p

muRata

GQM1875C2ExRxCB12#

Inductor

39n

ACX

HI0603-1B39N_H_

Inductor

39n

27n

ACX

HI0603-1BxxN_H_

Adjustable inductor

3.5

GANG SONG

MD-0507U-3.5T-S-BR

LC Tank Selection Guides

The BC2401 reception frequency is setup by inductors and capacitor connected between

Pins 7 and Pin 6, as shown below.

The relationship between the inductor, capacitor and the frequency setup is shown as

follows.

)( C

Frequency

Users should initially decide upon their desired reception frequency before choosing the

component values. After determining the frequency, then choose the actual value of

either the inductor or the capacitor, after which the other component values can be

calculated using the following equations:

Condition 1: If the frequency and capacitance have been determined:

3)2(

Condition 2: If the frequency and inductance have been determined:

6)2(

OSC2

OSC1

C 6

L 3

L 1

BC2401 Application Guidelines

AN0435EV1.00 4/ 8December 11, 2016

It is recommended that low tolerance inductor and capacitor should be used to effectively

improve the reception sensitivity. Recommended values for the different frequency bands

are shown in the following table.

315MHz

433MHz

39nH

5.5pF

3pF

3.5T

Note: The adjustable inductor L3 should be finely tuned.

RF Input Matching Circuit Guides

To receive the radio signals, as well as requiring an antenna, an impedance matching

circuit is also required as shown in the following figure. Good impedance matching can

reduce noise thus improving reception sensitivity. A network analyzer will normally be

required to adjust the impedance matching. The selected capacitor and inductor should

have high Q values for improved reception sensitivity.

The recommended values for the different frequency bands for the PCB Layout are listed

in the following table.

315MHz

433MHz

3.5pF

2pF

39nH

27nH

Note: If the PCB layout is changed, the impedance matching circuit should be adjusted

accordingly.

Antenna

C 5

L 2

R F IN

BC2401 Application Guidelines

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Antenna Selection Guides

Users can select a dipole or patch antennas with a 50ΩSMA interface as shown in the

following diagram.

Or use a λ/4-long copper wire, single conductor or stranded wire, shown as follows.

Attention should be paid to the considerations in the next section for laying out an

antenna directly on the circuit board.

PCB Layout Note

Component Placement Rules

The first consideration should be RF signal path. The RF-related components placement

and the PADs between these components should be placed as close as possible to the

device to minimise the wire length.

Enough space must be reserved for the extra width of the VCC and GND traces.

Routing

As right angle routing tracks accumulate charges more readily and may affect PCB

stability it is better to use 45 degree bevel or arc angles as far as possible when routing.

The distance between two traces should not be less than 6 mils.

The distance between a trace and through holes should not be less than 6 mils.

The distance between two adjacent through holes should not be less than 6 mils.

The width of the VCC and GND main traces should not be less than 12mils.

Power lines should be connected to a bypass capacitor located near the IC power pins.

BC2401 Application Guidelines

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Antenna

The bottom layer beneath the RF antenna components should not have poured copper

traces to avoid adversely affecting the RF performance.

The RF matching components should have poured copper traces to increase stability.

With the exception of RF matched components, other components should not be located

near the antenna to reduce interference on the RF circuits.

PCB Layout Example

Top View

Bottom View

BC2401 Application Guidelines

AN0435EV1.00 7/ 8December 11, 2016

Conclusion

This application note has introduced how to use the Holtek BC2401 device, a super

regeneration high frequency receiver, in which a matching circuit is required to be

connected to the high frequency input pin, RFIN, and how an adjustable inductor is

adjusted according to the desired frequency band.

Version and Modification Information

Date Author Issue

2016.07.7 何信智(Ho,Walers) First Version

Reference Files

Reference file: BC2401 Datasheet.

For more information, refer to the Holtek official website http://www.holtek.com.tw/home.

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BC2401 Application Guidelines

AN0435EV1.00 8/ 8December 11, 2016

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