Zetex - AN36 - ZXBM200x series of variable speed 2-phase ...NTC Thermistor The ZXBM200x series are...

ZXBM200x SERIES OF VARIABLE SPEED 2-PHASE

FAN MOTOR CONTROLLER

PURPOSE

This Applications document is intended to aidusers in their development of the controllerelectronics for fan and blower motors usingthe ZXBM200x series of variable speed,2-phase, DC brushless motor controllers.

The document will not discuss mechanicaldetails of motor design including suchaspects as the position of commutation inrelationship to windings etc, for which it isassumed the user already has priorknowledge.

ZXBM200x DESCRIPTION

The ZXBM200x is a series of 2-phase, DCbrushless motor pre-drivers with variablespeed control suitable for fan and blowermotors. A full description is to be found in thedevice Datasheet available by logging on towww.zetex.com/zxbm.

There are three variants available for thecontroller and all are identical in every aspectexcept the Lock and FG output functions onPin 6. The output on the ZXBM2003 isrotational frequency FG, on the ZXBM2002the pin indicates when the controller in theLock state whilst in the ZXBM2001 the outputis a combination of both the Lock and FGsignals.

For the purpose of aiding clarity in thisdocument the device Block Diagram andPinout Diagram.

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Applications Note AN36Issue 1 - JULY 2002

Block Diagram

The Pinning is shown for the ZXBM2001 as this is the variant

discussed and illustrated in this document. Applications for

the ZXBM2002 and ZXBM2003 will be identical with the only

difference being the function of Pin 6 as discussed above.

Pinout Diagram

APPLICATION REQUIREMENTS

Introduction

A typical electronics application circuit for a2-phase, DC brushless motor will consist of,but not be restricted to, three main buildingblocks. First will be the controller itselfcontaining the functions as described in thedatasheet. Attached to this will be a Halldevice as a means of monitoring andcontrolling the commutation of the motorand finally there will be the power driverdevices used to switch the two Phasewindings.

On top of these three building blocks will beother items such as the Speed Controlstimulus circuit, e.g. a thermistor. Furtherfunctions may be required dependant uponapplication, perhaps as a means of ‘valueadding’ to the overall final product. Someideas of this nature will also be discussed in alater section.

The first part of the Applications Note,however, discusses the various interfaceaspects of the external componentrequirements to the ZXBM200x series. To aidclarity in this first section any circuits givenwill show only the areas of interest to thatsection of discussion. This is followed by asection of practical examples that will includecircuits in their entirety.

The Hall Sensor

Two types of Hall sensor can be used inconjunction with the ZXBM200x controllers,those having an unbuffered output stage,sometimes known as a ‘naked’ Hall, andthose with a buffered output. Figures 1 and 2show the two respective types and theirconnection to the ZXBM2001.

The unbuffered type have a differential lowlevel signal output with the shape of thissignal being a direct representation of themagnetic field from the permanent magnetRotor. These sensors are connected to theZXBM using the differential inputs H+ and H-on Pins 2 and 3 respectively. See Figure 1 forconnection details. R1 in Figure 1 should bechosen to suit the Hall sensor type and isprovided to bias to the Hall device.

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Applications Note AN36Issue1 - JULY 2002

Figure 1Connection of unbuffered (naked) Hall

Figure 2Connection of buffered Hall

The buffered type of Hall sensor should be ofthe latching or bipolar type. These have aninternal amplifier and thus provide a largeamplitude square wave output. This signal issingle ended and is applied into Pin 3, H+, asshown in Figure 2. On some buffered Hallsensors the output is of the Open Collectortype and will therefore require a pull-upresistor (R1 in Figure 2) to attain the full signalamplitude. The H- pin will require to be held ata voltage approximately half the Hall outputswing. The potential divider R2 and R3 inFigure 2 is provided for this.

Speed Control

Applied power, motor eff iciency andmechanical loading determine maximummotor speed, the controller allows full speedadjustment by modifying the applied poweronly.

Speed control is attained through an integralPulse Width Modulation (PWM) circuit withinthe ZXBM200x series. The PWM signalcontrols the speed by switching therespective active Phase output at a muchhigher frequency, typically 25kHz, comparedwith the commutation1 frequency. The PWMis used to control the percentage of time theoutput driver is turned on for. This PWMcircuit is controlled through two pins, Pin 6,the CPWM pin, and Pin 4, the SPD input. TheCPWM pin has a capacitor attached of 150pF toproduce a 1V p-p 25kHz triangular waveform.The circuit has also been used quitesuccessfully with 100pF to produce a PWMfrequency of 34kHz. The motor speed isdetermined by the voltage at the SPD pin.

There are two methods for controlling theZXBM200x using the SPD pin. The first is thedirect control of the SPD pin by a voltage froman external voltage source or systemcontroller. The second method is to use athermistor as a temperature sensor so as theZXBM200x is in a feedback loop to control thefan speed against the temperatureconditions. A third method of control isavailable by applying a PWM signal from anexternal source. All these will be discussed inmore detail in the following sections.

Voltage control of the SPD pin

Voltage control is achieved by applying avoltage of between 1 volt and 2 volts to theSPD pin. A voltage of 1 volt on this pin willensure the drivers are switched on for 100%of the PWM duty cycle i.e. the motor will runat full speed.

Progressively increasing the SPD voltage to 2volts will reduce the percentage of PWM dutycycle drive to the Phase windings to reducethe motor speed. With a SPD voltage of 2volts the outputs will be switched off all thetime i.e. no drive will be present.

In reality a 2-phase DC brushless motor willhave a minimum practical rotational speedbelow which the motor will not run. This isvery much dependant upon the power, sizeand mechanics of the motor concerned butcould well mean that anything less than 40%PWM drive, represented by a SPD voltage of1.6V, is impractical.

The ability of starting the motor under suchlow speed condit ions also has to beconsidered as in most cases a motor willrotate at a far lower power input than isneeded to start it. Further discussion will begiven on this subject later.

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Note:1 Commutation is the process of alternate (phase)switching at the speed of rotation.

NTC Thermistor

The ZXBM200x series are designed to beused in conjunction with an NTC typethermistor with a value of 100k� at 25�C. Thethermistor is connected directly between theSPD pin and Ground. The thermistor caneither be local i.e. part of the Fan or Bloweritself and positioned where it can easilydetect the air temperature, or it can be remoteto the device, perhaps positioned on amotherboard or in an air duct.

An NTC thermistor has a non-l inearcharacteristic whereby there is a largerchange in resistance between 25�C and 30�Cthan there is between 55�C and 60�C. SeeFigure 3. However from Ohms Law when tworesistors are in parallel and one changes in alinear fashion it will produce a resultantnon-linear resistance characteristic but withthe opposite curve to that of the thermistor.See Figure 4. Now when these two effects areput together the resultant characteristic seenin Figure 3 is achieved.

The SPD pin on the ZXBM200x seriescontains an internal resistor network of19.5k� to an internal 2V rail and 52. 5k� toGround. The purpose of this is to set thespeed range for a 100k� NTC thermistor andto help cancel out the thermistor ’snon-linearity against temperature.

The manner in which the non-linearity isremoved can be seen in Figure 14 where theSPD voltage is linear with any slight non-linearity in the speed response more likelydue to other motor characteristics.

It is also possible to use the ZXBM200x seriesin conjunction with other lower values of NTCthermistor, for example one with a value of10k� at 25�C. In this case an external resistivedivider as shown in Figure 5 below is used toset the control speed range. The ratio of R1and R2 in this figure should be chosen to givethe desired speed range against temperature.With careful selection of the R1 and R2, it ispossible for a linear response within ±1% tobe achievable.

If needed R1 and R2 can also be added whenusing a 100k� thermistor in order to adjustthe speed range to match the particularthermistor’s characteristics.

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Figure 3

Figure 4

One problem with using an external potentialdivider (R1 & R2 in Figure 5) is that the motorbecomes susceptible to supply voltagechanges. Say the supply voltage falls,normally the speed would drop due to lessvoltage across the windings, however as thepotential divider is across the supply, as thevoltage falls so the voltage at the SPD pin willfall. As a lower SPD voltage represents ahigher speed so a lowering of the supplytherefore causes the fan to speed up. Toovercome this it is probably best to use aZener regulated supply to the ZXBM200x.

The following Table 1 gives an indication ofthe values required for R1 and R2 againstdifferent thermistor values. It should benoted that these are only for guidance as thefinal value will depend upon the thermistorand motor characteristics and so will needfine adjustment by experimentation. If theZXBM200x device is to be run from a Zenerregulated supply to control the speed versessupply voltage variation so R1 and R2 willneed allowances made for the voltage valueof Zener chosen.

As the Bipolar drivers have a slower turn-offcharacteristics when driven from theZXCB200x series slightly different values ofR2 are required over those for MOSFETs.

When driving the SPD pin from a signal orthermistor remote from the fan or controllerthere may be a need to provide noiseprotection at the SPD pin. In order to maintaina smooth speed control characteristic thiswill take the form of a capacitor of between100nF and 1�F connected between the SPDand Gnd pins somewhere close to the device.This should suffice for most purposes andcan be determined for each particularapplication.

A capacitor on this pin also has an effect onthe start-up characteristic of the motor as thecharging of the capacitor will lag behind therise of the supply voltage. As a low voltage onthe SPD pin represents a higher speed theeffect at start-up, if the SPD value is not set forfull speed, will be for the motor speed toincrease past its allotted point before settlingback to that required. Whilst for the capacitorvalues stated above this effect may not benoticeable, for values greater than 1�F it canbe used to advantage. In situations where themotor will be regularly started at a speedlower than its practical start value it can helpto get motors started, in effect giving themotor a ‘kick’ to start it.

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ThermistorValue

SupplyVoltage

MOSFET Bipolar

R1 R2 R1 R2

4.7k�

5V 3.3k� 2.2k� 3.3k� 1.5k�

12V 6.8k� 1.2k� 6.8k� 1.0k�

24V 15k� 1.3k� 15k� 1.0k�

10k�

5V 5.6k� 3.3k� 5.6k� 2.4k�

12V 13k� 2.2k� 13k� 1.8k�

24V 36k� 3.3k� 33k� 2.2k�

47k�

5V 24k� 12k� 22k� 8.6k�

12V 56k� 9.1k� 56k� 7.5k�

24V 130k� 10k� 130k� 8.6k�

100k�

5V * * * *

12V * * * *

24V * * * *

Table 1

* Note: Not normally required - dependent uponthermistor and speed range needed.

Figure 5showing resistive divider used with <100k� thermistors

External PWM

The ZXBM200x series are also capable ofbeing driven from an externally derived PWMsignal. This is particularly useful where thedevice is to be used with existing systemcontrollers that provide such an output.

The PWM control waveform can be in theform of a digital signal. The main criteriabeing that it should have a low level of lessthan 1V and a high level greater than 2V (butnot exceeding 5V). A conventional 3.3V or 5Vbased TTL or CMOS signal is ideal The signalis applied to Pin 8, the CPWM pin, with Pin 4,the SPD pin, being left open circuit. A lowlevel on the CPWM pin represents the windingdrive Off period and a high level the Onperiod.

Figure 6 il lustrates an external inputwaveform on the CPWM pin together with theresulting drive at one of the phase windings.There is some delay through the ZXBM200xdevice that ensures the drive reaches 100%PWM slightly before the input reaches 100%duty cycle.

Fixed speed applications

For applications where the speed controlfunction is not required the device can be setto run at full speed by simply holding the SPDpin at a voltage below 1V. The best way to dothis is by attaching a 10k� resistor to Ground.A direct link to Ground can cause the SPD pinand its associated circuit not to function asrequired.

Winding Drive

The driving of the two phases of the motor isachieved using a pair of external powertransistors driven from Pin 10 and Pin 9, Ph1and Ph2 respectively, of the ZXBM200xcontroller. These transistors can be either ofthe Bipolar or MOSFET type. Bothmethodologies are similar and incorporateclamping to restrict the level of windingavalanche to be within the capabilities of thetransistors chosen. Each Transistor type willbe discussed in detail together with theirrespective merits and limitations.

Bipolar Power Transistors

Bipolar devices at one time were theuniversal power driving method, however,with MOSFETs becoming more readilyavailable bipolar use has diminished. In thecase of the ZXBM200x series it has beenfound that bipolar devices are very suited tothe lower power, lower current end of theapplications range.

Figures 7 and 8 illustrate a bipolar driveroutput stage with two methods of clamping.

In both Figures 7 and 8, R1 and R2 provide thebase drive to the Output transistors Q1 andQ2. The value of these resistors should bechosen to provide sufficient current tomaintain a good saturation voltage of thedriver transistors but not to exceed the Ph1and Ph2 drive capabilities of the ZXBM200xunder worst case conditions.

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Figure 6

The ZXBM200x series have a Darlingtonemitter follower output stage and thereforerely upon an external method of turning thedrivers off. R3 and R4 provide that function. Itshould be borne in mind that R3 and R4 willdetract from the base current drive providedby R1 and R2 so the final choice of values willbe a balance of the two requirements, turn-offand base drive.

Another consideration of the output stage isthat of protecting the bipolar drivers from theeffects of the back emf when switching thewindings. This takes the form of a voltage‘fly-back’ of several times the supply voltageand so some form of clamping is required toprevent this voltage from over-stressing thedriver devices.

Two forms of clamping can berecommended, that in Figure 7 shows astraightforward Zener diode placed acrossthe collector to emitter of Q1 and Q2. This willabsorb any voltage spikes appearing at thecollector. This arrangement also has theeffect of protecting Q1 and Q2 against anynegative going voltages appearing as a resultof the switching. The disadvantage is that thesize of the Zener needs to be sufficient toabsorb all the energy from the voltage spike.

Figure 8 provides and alternative method ofclamping whereby the Zener diodes areconnected between the collector and base ofQ1 and Q2 to form an active clampingarrangement. Any voltages seen at thecollector will provide base current to thedrivers to turn them back on. This has theeffect of limiting the voltage excursion at thecollector and the power is thus absorbed inthe larger output devices.

The disadvantage of this active clampingscheme is the need to protect for negativevoltage excursions of the power transistorcollector. The need for this is twofold, the firstbeing to limit the negative voltage inducednoise and the second to avoid exceeding theemitter-base breakdown voltage of the powertransistors. To prevent this the diodes D1 andD2 are included as protection to restrict thenegative excursion of the Q1 and Q2collectors.

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Figure 8Bipolar Output Drive Stage Using Active Clamping

Figure 7Bipolar Output Drive Stage

MOSFET Power Transistors

Power MOSFET devices are becomingincreasingly popular and as regard theZXBM200x provide a very good method ofdriving the motor phase windings. Figures 9and 10 illustrate the methodology of thedriver circuit.

The components in Figures 9 & 10 have a verysimilar topography to that of the Bipolar drivewith again two variants, one with the directZener clamping and the second having activeclamping.

The main difference arising in the activeclamping circuit in Figure 10 is the need for adiode in series with the active clamp Zenerdiode. This prevents the Zener being forwardbiased and thus detracting from the gatedrive when the MOSFET is turned on. In theactive clamp circuit there is also no need forany drain to source negative voltageprotection as this will be achieved by theinherent body diode of the MOSFET.

When using MOSFET devices i t is acompromise between the Voltage rating andthe RDS(on) of the MOSFET with a highervoltage rating producing a higher RDS(on).The aim therefore should always be to use thelowest voltage rating to suit the applicationas this will give the lowest full-speed RDS(on)related dissipation. The disadvantage is thatthere will be a slightly higher dissipationwhen using active clamping as this will beworking harder to maintain a lower voltagewhen the fan is running at near to full speed.

The latest generation of N channel trenchMOSFETS from Zetex provide suitablesolutions with the ZXMN6A11G and theZXMN10A11G, 60V and 100V devicesrespectively, having been used in theapplications described.

Reverse Supply protection

An increasingly common requirement formodern systems is for components andmodules to have a degree of reverse supplyprotection. This is particularly so forAutomotive applications. To achieve this asupply blocking diode is required in the Fanelectronics.

For the best performance from theZXBM200x device it is best to provideseparate diodes for the device and thewinding supplies. This is illustrated in the fullapplications circuit in Figure 17. The mainreason for this is that having blocked thereverse path to the power supply for theswitching currents, high voltages can beexperienced at the winding high end. Thisenergy manifests itself as excessive voltagesand these are required to be kept away fromthe device supply.

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Figure 9MOSFET Output Drive Stage

Figure 10MOSFET Output Drive Stage Using Active Clamping.

Another hazard with the excessive voltagesfrom the blocking diodes is that it can causethis energy to be dissipated within the Zenerclamping arrangement. As this energy wouldnormally have been returned to the supply forreuse it seems appropriate to attempt to savethe energy for reuse within the fan itself. Thisis achieved with the Capacitor C5 in Figure 17.

Care needs to be taken with the selection ofthe capacitor type and value for eachapplication. For multilayer chip capacitors itwill be a cost verses value issue and forelectrolytic capacitors a size verses valueissue. In both cases the voltage tolerance ofthe chosen part needs careful considerationas the capacitor needs to reliably withstandthe peak voltages.

When used, the capacitor gives considerableeff ic iency improvements with notedreductions in supply current and driverdevice temperature. Figure 11 shows thewinding supply at the winding common pointand shows the voltage being clamped by thedriver active clamping. Figure 12 shows theeffects of adding a 4.7�F multilayer ceramiccapacitor (C5 in Figure 17).

APPLICATION CIRCUIT EXAMPLES

In this section are shown complete circuitexamples developed using the ZXBM2001together with the type of fan it was developedfor. Examples are given for a variety ofapplications with the intention that thesecircuits will form the starting point for a usersfuture development in conjunction with theguidelines given in the previous section.

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Figure 11Winding Supply

Figure 12Winding Supply with 4.7�F Capacitor

6V supply with ‘naked’ hall andbipolar drive

The first example in Figure 13 is for a 6V axialfan driver. The design uses an unbufferedHall sensor and bipolar drive transistors. TheZetex FMMT619 transistor will furnish outputpowers up to 2W with the SOT23 package,however, in excess of this the SOT89 package(FCX619) might be more suitable if drivertemperature is excessive. Measurements ofthe fan speed verses the thermistortemperature is shown in the accompanyinggraph in Figure 14.

12V Supply with buffered Hall andMOSFET drivers

This second example in Figure 15 shows acomplete circuit using MOSFET drivers and a12V supply. It also makes use of the morecommon buffered Hall sensor. The outputdevices are the Zetex ZXMN6A11G MOSFETswhich are rated at 60V so the clamping isachieved with 56V Zeners. Avalancheproblems are averted by not attempting toturn the MOSFETs off too quickly and 1k� forR3 and R4 meets those aims. It should besuitable for powers up to 20W. The speedresponse is shown in Figure 16.

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Figure 136V Axial Fan using bipolar drive.

Figure 14.

Figure 1512V motor with MOSFET drive.

Figure 16.

12V Supply with Reverse SupplyProtection

This following circuit in Figure 17 is similar tothat in Figure 15 except that it has the reversepolarity protection feature added. This isachieved with D3 providing protection to theZXBM2001 and D4 providing protection tothe motor windings. C5 is also added tosmooth out the excessive supply disturbanceas discussed in previous sections.

Another point of note with this circuit is thatthe PWM frequency was set to run at 34kHz bymaking C1 the more readily available 100pFvalue. Running at this higher frequency hasnot been seen to be a problem with MOSFETswhere the on and off switching is clean andthus gives minimal switching losses.

24V Supply with Reverse SupplyProtection

The final circuit example in Figure 18 is usedto illustrate the supply provision for a 24 Vapplication. Again MOSFETs are used withreverse supply protection incorporated. TheZXBM2001 takes its supply from the sameprotection diode as the windings, however,because C4 is large and the supply to theZXBM2001 regulated by ZD3 and C3 thesupply commutation ripple is not a problem.

The higher voltage, 100V, ZetexZXMN10N11G MOSFETs are used with 75VZener active clamping.

The circuit in Figure 18 has also been used fora motor design with an input supply of 48V. Inthis case higher voltage rating componentswere selected to withstand the higherwinding avalanche voltages.

USEFUL APPLICATION IDEAS

Failsafe dual fan systems

In high reliability systems there is a need toensure the cooling scheme is also reliable.This is often achieved by the use of 2 fans thatwill ensure there is still a degree of coolingshould one fan fail. An improvement to this isto run each of the two fans at half speed and inthe event of a failure of one fan to speed upthe remaining fan to full speed. Figure 19illustrates such a system where two fansusing the ZXBM2001 are connected together.

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Figure 1712V Supply with Reverse Supply Protection.

Figure 1824V motor with Reverse Polarity Protection.

In Figure 19 the SPD pin on both fans isarranged such that they run at half speed, orperhaps a little faster with R6 and R3.Consider Fan A, R1 and C1 integrate out theFG frequency pulses such that Q1 is alwayskept off . I f a lock condit ion is thenencountered with the fan the Lock/FG pin willgo permanently high and switch on Q1. Thisin turn will send a signal to Fan B such that itwill switch R2 to ground. With the value of R2chosen such that the SPD voltage of Fan B is<1V it will ensure Fan B is set to full speed tocompensate to the now stopped Fan A.

Conversely R4, C4, Q2 and R5 will ensure thatif Fan B stops Fan A will be set to full speed.

By careful selection of the values of R1/C1 andR4/C4 it is possible to only partially take outthe FG speed pulses. This will make one fanspeed up should the other slow downsufficiently but not actually stop. To removethe need for C1 and C4 the ZXBM2002 variantwith the Lock only output can be used so theFG pulses do not need to be removed.

SPD Voltage Conversion

There may be situations where the SDP inputcontrol voltage range will be incompatiblewith the application requirements perhapsbecause the motor is to be controlled from analready defined and different voltage source.Figure 20 provides a simple voltage rangeconversion for a control signal where a highervoltage represents a higher speed.

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Figure 19Failsafe dual fan system.

Figure 20SPD control voltage level conversion.

Biplolar driver active switch off

The problems of base turn off when drivingbipolar devices has been mentionedpreviously. Figure 21 is an active turn offcircuit that can be added to each phase drivetransistor of the circuits shown in Figures 7 or8. The transistor Q3A and Q3B can of themulti-pack type and forms a simple doubleinverter function to actively discharge thebase charge of Q1.

Removal of Speed Variation withSupply Voltage

It has already been discussed that when usinga 10k� NTC thermistor and an externalpotential divider an increase in supplyvoltage results in a slower speed. It istherefore possible when using a 10k� NTCthermistor to remove supply voltagevariation by feeding a percentage of thesupply voltage change into the SPD pin.

To do this the circuit in Figure 22 is used. Inthis circuit a Zener diode is used to partlyremove supply voltage variation. A Zenervoltage half that of the supply voltage shouldsuffice. R1 and R2 should be small in relationto R3 and R4 and provides a partly regulatedvoltage that in turn is used for the potentialdivider for the Thermistor network. A raisingof the supply voltage would normally put ahigher voltage across the windings and soincrease the speed. This is now countered bythe fact that a small percentage of the supplyincrease appears at the R1/R2 junction. Thispercentage increase also appears at theR3/R4 junction - the SPD pin. An increase inthe control voltage on the SPD causes alowering of the PWM drive and thus a lowerspeed. Careful manipulation of the R1/R2 andR3/R4 ratios will enable constant speed to beattained over a wide supply voltage range butst i l l a l lowing speed variat ion withtemperature.

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Figure 21Active switch-off circuit for bipolar dirver devices

Figure 22Constant Speed versus Supply Voltage

LAYOUT CONSIDERATIONS

Whilst it is understandable that the circuitlayout is likely to be severely compromised inthe restricted environment of small 2-Phasebrushless Fan and Blowers a number ofpoints are worth mentioning.

The capacitors for CLCK and CPWM (C1 and C2respectively in all the Figures) need to bepositioned as close to the device as possiblewith the latter being the more important. Thedecoupling capacitor (C3 in all the Figures)also needs to be as close to the device aspossible.

As much area as possible should be kept ascopper for the tracks associated with theoutput stage and ground rail with thetechnique of laying out the gaps rather thanlaying out the tracks being preferred.Allotting as much copper to the tab of thewinding driver transistors is beneficial whenusing surface mount packages as they relyupon the copper of the PCB to dissipate asmuch of the heat as possible with the PCBitself in effect becoming the heatsink.

The power rails to the device and to thewindings should be kept separate wherepossible. Where the power comes onto thePCB it should go in one direction to thewindings and in the other direction to thecontroller and its associated components, ineffect to form a star connection.

APPLICATIONS ASSISTANCE

Zetex Applications Engineers have a wealthof experience in using the ZXBM200n seriesof variable speed, 2-phase, DC brushlessmotor controllers and are always available tohelp with customer applications. Should helpbe sought please contact your nearest Zetexoffice for assistance.

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Applications Note AN36Issue 1 - JULY 2002

Europe

Zetex plcFields New RoadChaddertonOldham, OL9 8NPUnited KingdomTelephone (44) 161 622 4422Fax: (44) 161 622 [email protected]

Zetex GmbHStreitfeldstraße 19D-81673 München

GermanyTelefon: (49) 89 45 49 49 0Fax: (49) 89 45 49 49 [email protected]

Americas

Zetex Inc700 Veterans Memorial HwyHauppauge, NY11788

USATelephone: (631) 360 2222Fax: (631) 360 [email protected]

Asia Pacific

Zetex (Asia) Ltd3701-04 Metroplaza, Tower 1Hing Fong RoadKwai FongHong KongTelephone: (852) 26100 611Fax: (852) 24250 [email protected]

These offices are supported by agents and distributors in major countries world-wide.

This publication is issued to provide outline information only which (unless agreed by the Company in writing) may not be used,applied or reproduced for any purpose or form part of any order or contract or be regarded as a representation relating to theproducts or services concerned. The Company reserves the right to alter without notice the specification, design, price orconditions of supply of any product or service.

For the latest product information, log on to www.zetex.com

© Zetex plc 2002

Zetex - AN36 - ZXBM200x series of variable speed 2-phase ...NTC Thermistor The ZXBM200x series are...

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