ZXLD1615
ADJUSTABLE DC-DC BOOST CONVERTER WITH INTERNAL SWITCH INTSOT23-5
DESCRIPTION
The ZXLD1615 is a PFM inductive boost converterdesigned to provide output voltages of up to 28Vfrom a 2.5V to 5.5V input supply.
The ZXLD1615 includes the output switch and peakcurrent sense resistor, and can provide up to 10mAoutput current at maximum output voltage. Highercurrent is available at lower output voltages.Quiescent current is typically 60A and a shutdownfunction is provided to reduce this current to lessthan 100nA in the 'off' state.
Nominal output voltage can be set up to a maximumof 28V by two external resistors and can be adjustedto lower values by a PWM control signal applied tothe 'Enable' pin. Depending upon the controlfrequency, the PWM signal will provide either
continuous (low ripple) or gated control. The PWMfilter components are contained within the chip.Minimum output voltage is determined by the inputsupply.
The device is assembled in a low profile TSOT23-5pin package.
ADVANCED FEATURES
•Internal 30V NDMOS switch
•True analog output voltage control via PWM
with internal filter
APPLICATIONS
•LCD and OLED bias•Cellular / mobile phones•Digital cameras•PDAs•LCD modules
•Varactor and PIN diode bias•Palmtop computers
FEATURES
•Low profile TSOT23-5 pin package•Internal PWM filter for adjustable output•High efficiency (85% typ)
•Wide input voltage range: 2.5V to 5.5V•Up to 250mA output current at 5V•Low quiescent current: (60A typ)•100nA maximum shutdown current•Up to 1MHz switching frequency•Low external component count
TYPICAL APPLICATION CIRCUIT
PINOUT
TOP VIEW
ISSUE 3 - AUGUST 2004
1
SEMICONDUCTORS元器件交易网www.cecb2b.com
ZXLD1615
ABSOLUTE MAXIMUM RATINGS
(Voltages to GND unless otherwise stated)Input voltage (VIN)7VLX output voltage (VLX)Switch output current (ILX)Power dissipation (PD)Operating temperature (TOP)Storage temperature (TST)Junction temperature (TjMAX)
30V500mA
300mW-40 to 85°C-55 to 150°C125°C
ELECTRICAL CHARACTERISTICS:(Test conditions: VIN=VEN=3V, TAMB=25°C unless otherwise stated(1))
SymbolVINIINParameterInputvoltageSupplycurrentQuiescentShutdownVFBfLXTOFFTON(2)ILXpkRLXILX(leak)VENHVENLIENLIENHFBpincontrolvoltageOperatingfrequencyLXoutput‘OFF’timeLXoutput‘ON’timeSwitchpeakcurrentlimitSwitch'On'resistanceSwitchleakagecurrentVLX=20V1.5L=10H,VOUT=28V,5mAload3201.751VIN0.4-100112020100L=10H,VOUT=28V,5mAload350VEN=VIN,ILX=0,OutputnotswitchingVEN=0V0.98600500560<101001001.07µAnAVkHznsµsmA⍀µAVVnAAµs%ConditionsMin2.5TypMax5.5UnitsVENpinhighlevelInputvoltageDeviceactiveENpinlowlevelInputvoltageENpinlowlevelinputcurrentDeviceinshutdownVEN=0VENpinhighlevelinputcurrentVEN=VINVENswitchedfromhightolow10kHz 2Nominal ‘on’ time (TONnom)is defined by the input voltage (VIN), coil inductance (L) and peak current (ILXpkdc) according to the expression:TONnom= {ILX(pkdc)x L/VIN}+200ns 3This is the time for which the device remains active after the EN pin has been asserted low. This delay is necessary to allow the output to bemaintained during dc PWM mode operation. 4The maximum PWM signal frequency during this mode of operation should be kept as low as possible to minimize errors due to the turn-offdelay ISSUE 3 - AUGUST 2004 SEMICONDUCTORS2 元器件交易网www.cecb2b.com ZXLD1615 PIN DESCRIPTION PinNo.123NameLXGNDFBDescriptionOutputofNDMOSswitchGround(0V)FeedbackpinforvoltagecontrolloopNominalvoltage1.025V4ENEnableinput(activehightoturnondevice)AlsousedtoadjustoutputcurrentbyPWMsignal.ConnecttoVinforpermanentoperation.5VINInputvoltage(2.5Vto5.5V).Decouplewithcapacitorclosetodevice.BLOCK DIAGRAM ISSUE 3 - AUGUST 2004 3 SEMICONDUCTORS元器件交易网www.cecb2b.com ZXLD1615 Device Description The device is a PFM flyback dc-dc boost converter,working in discontinuous mode. With reference to the chip block diagram and typicalapplication circuit, the operation of the device is asfollows: Control loop When 'EN' is high, the control circuits become activeand the low side of the coil (L1) is switched to groundvia NDMOS transistor (MN). The current in L1 isallowed to build up to an internally defined level(nominally 320mA) before MN is turned off. Theenergy stored in L1 is then transferred to the outputcapacitor (C2) via schottky diode (D1). The outputvoltage is sensed at pin 'FB' by external resistors R1and R2 and compared to a reference voltage VREF(1.025V nominal). A comparator senses when theoutput voltage is above that set by the reference andits output is used to control the 'off' time of theoutput switch. The control loop is self-oscillating,producing pulses of up to 5s maximum duration(switch 'on'), at a frequency that varies in proportionto the output current. The feedback loop maintains avoltage of VREFat the FB pin and therefore defines amaximum output voltage equal to VREF*(R1+R2)/R1.The minimum 'off' time of the output switch is fixedat 0.5s nominal, to allow time for the coil's energyto be dissipated before the switch is turned on again.This maintains stable and efficient operation indiscontinuous mode. Filtered PWM operation The input of an internal low pass filter is switched toVREFwhen the EN pin is high and switched to groundwhen the EN pin is low. The output of this filterdrives the comparator within the control loop. Acontinuous high state on EN therefore provides afiltered voltage of value Vref to the comparator.However, by varying the duty cycle of the EN signalat a suitably high frequency (f>10kHz), the controlloop will see a voltage, that has an average valueequal to the duty cycle multiplied by VREF. This provides a means of adjusting the output voltage to alower value. It also allows the device to be bothturned on and adjusted with a single signal at the‘EN’ pin. The output during this mode of operationwill be a dc voltage equal to VREF*(R1+R2)/R1x dutycycle. GatedPWM operation The internal circuitry of the ZXLD1615 is turned offwhen no signal is present on the 'EN' pin for morethan 120s (nominal). A low frequency signal appliedto the EN pin will therefore gate the device 'on' and'off' at the gating frequency and the duty cycle of thissignal can be varied to provide an average outputequal to VREF*(R1+R2)/R1 x duty cycle. For bestaccuracy, the gating frequency should be made aslow as possible (e.g. below 1kHz), such that the turnoff delay of the chip is only a small proportion of thegating period Further details of setting output current are given inthe application notes. ISSUE 3 - AUGUST 2004 SEMICONDUCTORS4 元器件交易网www.cecb2b.com ZXLD1615 TYPICAL CHARACTERISTICSISSUE 3 - AUGUST 2004 5 SEMICONDUCTORS元器件交易网www.cecb2b.com ZXLD1615 TYPICAL PERFORMANCE GRAPHS (For typical applications circuit at 22H Murata LQH32CN series, TA=25 °C unless otherwise stated) ISSUE 3 - AUGUST 2004 SEMICONDUCTORS6 元器件交易网www.cecb2b.com ZXLD1615 APPLICATIONS Setting output voltage The ZXLD1615 has an adjustable output voltage allowing the end user maximum flexibility. To set theoutput voltage a potential divider network is needed(see R1 and R2 in typical applications circuit). The output voltage is determined by the equation: R2⎞⎛⎟VOUT=VFB⎜1+⎝R1⎠where VFB = 1.025V. The following table gives suggested values forvarious output voltages.RequiredR1outputvoltage5V12V18V21V25V28V270K⍀91K⍀60K⍀51K⍀43K⍀39K⍀R21M⍀1M⍀1M⍀1M⍀1M⍀1M⍀1) PWM output voltage adjustment (analogue mode)During this mode of operation the device operation iscontinuous, providing a low ripple output voltage(VOUT) directly proportional to the duty cycle (D) ofthe logic signal applied to the EN pin according to therelationship:VOUT= D x VOUT(nom) Square wave signals applied to the EN pin, forexample, will turn the device on and produce anominal regulated output of 13.5V. The ZXLD1615 contains a timing circuit that switchesthe device on a few microseconds after the application of a rising edge to EN and turns it backoff again nominally 120µs after the falling edge ofEN. For continuous PWM mode operation, thefrequency of the control signal must therefore bemaintained above 10kHz at all times, to prevent theinternal delay circuit from timing out and switchingthe device into standby mode. The maximum frequency applied to EN should be limited to 100kHzto minimize errors due to internal switching delays2) PWM output voltage adjustment (gated mode)This method of adjustment can be used in applications where the output ripple is less importantthan the supply current. The method of adjustment isthe same as in 1) above, however, during this modeof operation, the device is gated on and off, providing an average output voltage (VOUT) directlyproportional to the duty cycle (D) of the logic signalapplied to the EN pin according to the relationship:VOUT(AVG)= D x VOUT(nom) The ripple on this voltage will be determined by thesize of the output capacitor. The output voltage can be adjusted all the way downto the input voltage by either method of PWMcontrol, but for best results, the duty cycle range should be kept within the specified range. Lower dutycycles will result in increased output ripple and non-linearity in the relationship between duty cycleand output voltage. If a greater control range is required, the nominal output can be reduced by theuse of external resistors before the PWM signal isapplied. Minimizing output voltage ripple For applications requiring lower output ripple it maybe necessary to add a small ceramic capacitor inparallel with R2. A value of 4.7pF is suitable for mostoutput ranges. Output voltage can be adjusted from VIN+ VFto themaximum output voltage rating of the internalswitch, 30V. Once the nominal output voltage has been set, it canbe adjusted to a lower value by applying a pulse width modulated (PWM) control signal to the EN pin.PWM adjustment permits the device to be turned onand the output voltage set by a single logic signalapplied to the EN pin. No external resistors arerequired and the amplitude of the control signal isnot critical, providing it conforms to the limitsdefined in the electrical characteristics. ISSUE 3 - AUGUST 2004 7 SEMICONDUCTORS元器件交易网www.cecb2b.com ZXLD1615 Capacitor selection A ceramic capacitor grounded close to the GND pinof the package is recommended at the output of thedevice. Surface mount types offer the bestperformance due to their lower inductance. A minimum value of 0.22F is advised, although highervalues will lower switching frequency and improveefficiency especially at lower load currents. A highervalue will also minimize ripple when using the deviceto provide an adjustable dc output current. A good quality, low ESR capacitor should also beused for input decoupling, as the ESR of thiscapacitor is effectively in series with the sourceimpedance and lowers overall efficiency. Thiscapacitor has to supply the relatively high peakcurrent to the coil and smooth the current ripple onthe input supply. A minimum value of 4.7F is acceptable if the input source is close to the device,but higher values will improve performance at lowerinput voltages, when the source impedance is high.The input capacitor should be mounted as close aspossible to the IC. For maximum stability over temperature, capacitorswith X7R dielectric are recommended, as these havea much smaller temperature coefficient than othertypes. A table of recommended manufacturers is providedbelow: ManufacturerMurataTaiyoYudenKemetAVXWebsitewww.murata.comwww.t-yuden.comwww.kement.comwww.avxcorp.comInductor selection The choice of inductor will depend on available board space as well as required performance. Smallvalue inductors have the advantage of smaller physical size and may offer lower series resistanceand higher saturation current compared to largervalues. A disadvantage of lower inductor values isthat they result in higher frequency switching, whichin turn causes reduced efficiency due to switchlosses. Higher inductor values can provide betterperformance at lower supply voltages. However, ifthe inductance is too high, the output power will belimited by the internal oscillator, which will preventthe coil current from reaching its peak value. Thiscondition will arise whenever the ramp time (ILX(peak)x L/VIN) exceeds the nominal 5s maximum 'on' timelimit for the LX output.PartNo.L(H)CMD4D11-100MCDO1608-103LQH31CN100LB2012Y100MR10101010DCR()0.4570.161.30.5ISAT(A)0.51.10.230.1Sumidawww.sumida.comCoilcraftwww.coilcraft.comMuratawww.murata.comTaiyoYudenwww.t-yuden.comRecommended inductor values for the ZXLD1615 arein the range 6.8H to 22H. The inductor should bemounted as close to the device as possible with lowresistance connections to the LX and VINpins. Suitable coils for use with the ZXLD1615 are shownin the table below: ManufacturerISSUE 3 - AUGUST 2004 SEMICONDUCTORS8 元器件交易网www.cecb2b.com ZXLD1615 Diode selection The rectifier diode (D1) should be a fast low capacitance schottky diode with low reverse leakageat the working voltage. It should also have a peakcurrent rating above the peak coil current and a continuous current rating higher than the maximumoutput load current. The table below gives some typical characteristics fordiodes that can be used with the ZXLD1615:DiodeZHCS400ZHCS500VF@100mA(mV)300300IFSM(mA)10001000Ic(mA)400500IRat30V(A)1515PackageSOD323SOT23Layout considerations PCB tracks should be kept as short as possible tominimize ground bounce, and the ground pin of thedevice should be soldered directly to the groundplane. It is particularly important to mount the coiland the input/output capacitors close to the device tominimize parasitic resistance and inductance, whichwill degrade efficiency. The FB pin is a high impedance input, so PCB track lengths to this shouldalso be kept as short as possible to reduce noise pickup. Excess capacitance from the FB pin to groundshould be avoided. ISSUE 3 - AUGUST 2004 9 SEMICONDUCTORS元器件交易网www.cecb2b.com ZXLD1615 REFERENCE DESIGNSGeneral Boost Converter VIN=2.5V to 5.5V, VOUTup to 28V See page 7 in datasheet for R1 and R2 values for various output voltages. 1 Cell Li-Ion to 3.3V Sepic Converter ISSUE 3 - AUGUST 2004 SEMICONDUCTORS10 元器件交易网www.cecb2b.com ZXLD1615 1 Cell Li-Ion to 5V Sepic Converter Triple Output Boost Converter for LCD or OLED Bias Note:For all manufacturers listing please refer to application section on page 7 of this datasheet. ISSUE 3 - AUGUST 2004 11 SEMICONDUCTORS元器件交易网www.cecb2b.com ZXLD1615 PACKAGE OUTLINEPACKAGE DIMENSIONS MillimetersDIMMIN.AA1A2bcDEE1ee1LL2Q-0.010.840.300.12MAX.1.000.100.900.450.20MIN.-0.00030.03300.01180.0047MAX.0.03930.00390.03540.01770.0078Inches2.90BSC2.80BSC1.60BSC0.95BSC1.90BSC0.300.500.114BSC0.110BSC0.062BSC0.037BSC0.074BSC0.01180.01960.25BSC4°12°0.010BSC4°12°ORDERING INFORMATIONDEVICEZXLD1615ET5DEVICEDESCRIPTIONTEMPERATURERANGEPARTMARK615TAPINGOPTIONSTA,TCBoostconverterinSOT23-5-40°Cto+85°CTA reels 3,000 devices, TC reels 10,000 devices ©ZetexSemiconductors plc 2004 Europe ZetexGmbH Streitfeldstraße19D-81673 MünchenGermany Telefon: (49) 45 49 49 0Fax: (49) 45 49 49 49europe.sales@zetex.comAmericas ZetexInc 700 Veterans Memorial HwyHauppauge, NY 11788USA Telephone: (1) 631 360 2222Fax: (1) 631 360 8222usa.sales@zetex.comAsia Pacific Zetex(Asia) Ltd 3701-04MetroplazaTower 1HingFongRoad, KwaiFongHong Kong Telephone: (852) 26100 611Fax: (852) 24250 494asia.sales@zetex.comCorporate HeadquartersZetexSemiconductors plc Lansdowne Road,ChaddertonOldham, OL9 9TYUnited Kingdom Telephone (44) 161 622 4444Fax: (44) 161 622 4446hq@zetex.comThese offices are supported by agents and distributors in major countries world-wide. Thispublicationisissuedtoprovideoutlineinformationonlywhich(unlessagreedbytheCompanyinwriting)maynotbeused,appliedorreproducedforanypurposeorformpartofanyorderorcontractorberegardedasarepresentationrelatingtotheproductsorservicesconcerned.TheCompanyreserves the right to alter without notice the specification, design, price or conditions of supply of any product or service.Forthelatestproductinformation,logontowww.zetex.comISSUE 3 - AUGUST 2004 SEMICONDUCTORS12
因篇幅问题不能全部显示，请点此查看更多更全内容
Copyright © 2019- 99spj.com 版权所有 湘ICP备2022005869号-5
违法及侵权请联系：TEL:199 18 7713 E-MAIL:2724546146@qq.com
本站由北京市万商天勤律师事务所王兴未律师提供法律服务