Home

ANALOG DEVICES ADP1109A handbook

1. Inductor Selection In a step up or boost converter Figure 1 the inductor must store enough power to make up the difference between the input voltage and the output voltage T he inductor power is calculated from the equation P Vor V o Vin min X Lour 1 where V y is the diode forward voltage 70 5 V for a 1N 5818 Schottky Energy is only stored in the inductor whilethe ADP1109A switch is ON so the energy stored in the inductor on each switching cycle must be must be equal to or greater than PL fo SC in order for the ADP 11094 to regulate the output voltage W hen the internal power switch turns ON current flow in the inductor increases at the rate of where L is in H enrys and R is the sum of the switch equivalent resistance typically 0 8 at 25 and the dc resistance of the inductor In most applications the voltage drop across the switch is small compared to Vi so a simpler equation can be used 2 Rt _ Vin l el R 1 3 4 Replacing t in the above equation with the ON time of the ADP1109A 5 5 us typical will define the peak current for a given inductor value and input voltage At this point the induc tor energy can be calculated as follows E 5L x peak 5 As previously mentioned E must be greater than P fosc so that the ADP 1109A can deliver the necessary power to the load For best efficiency peak current should be limited to 1A or less Higher sw
2. loop stability without requiring external components for fre quency compensation A shutdown feature permits the oscillator to be shut off H old ing SHUTDOWN low will disable the oscillator and the ADP1109A s quiescent current will remain 460 uA T he output voltage of the ADP1109A is set with two external resistors T hree fixed voltage models are also available the ADP1109A 3 3 43 3 V ADP1109A 5 5 V and ADP1109A 12 12 V The fixed voltage models are identical to the ADP1109A except that laser trimmed voltage setting resistors are included on the chip On the fixed voltage models of the AD P1109A simply connect the SENSE pin Pin 8 directly to the output voltage COMPONENT SELECTION General Notes on Inductor Selection When the ADP1109A internal power switch turns on current begins to flow in the inductor Energy is stored in the inductor core while the switch is on and this stored energy is then trans ferred to the load when the switch turns off T o specify an inductor for the AD P1109A the proper values of inductance saturation current and dc resistance must be deter mined T his process is not difficult and specific equations are provided in this data sheet In general terms however the induc tance value must be low enough to store the required amount of energy when both input voltage and switch ON time areat a minimum but high enough that the inductor will not saturate when both Viy and switch ON time are a
3. 0LC AVX TPS SERIES Figure 2 2 V Powered Flash Memory VPP Generator 10 MBRS130T3 SHUTDOWN COILTRONICS CTX10 1 SUMIDA CD54 100LC AVX TPS SERIES Figure 3 2V to 5 V Converter SHUTDOWN COILTRONICS CTX33 2 SUMIDA CD54 330LC AVX TPS SERIES Figure 4 5 V to 12 V Converter With Shutdown to 0 V at Output 33pH MBRS130T3 Sw ADP1109A 7 SHUTDOWN GND GND SHUTDOWN COILTRONICS CTX33 2 SUMIDA CD54 330LC AVX TPS SERIES Figure 5 3V to 9 V Converter REV 0 1109 OSCILLATOR FREQUENCY kHz 170 150 50 40 0 25 70 85 TEMPERATURE C Figure 6 Oscillator Frequency vs Temperature 5 V VcE saT Vin AND Igy 0 65A TEMPERATURE C Figure 9 Switch Saturation Voltage vs Temperature OUTPUT VOLTAGE V 0 0 25 70 85 TEMPERATURE C Figure 12 12 V Output Voltage vs Temperature REV 0 DUTY CYCLE Figure 7 Duty Cycle vs Temperature SWITCH ON TIME psec QUIESCENT CURRENT pA 68 65 62 TEMPERATURE C 6 0 5 5 40 0 25 70 85 TEMPERATURE C Figure 10 Switch On Time vs Temperature 600 500 400 300 200 2 4 6 8 10 12 14 16 INPUT VOLTAGE Volts Figure 13 Quiescent Current vs In
4. 25 718A 1109 fv fS ANALOG DEVICES Micropower Low Cost Fixed 3 3 V 5 V 12 Vand Adjustable DC to DC Converter ADP1109A FEATURES Operates at Supply Voltages 2 V to 9 V Fixed 3 3 V 5 V 12 V and Adjustable Output Minimum External Components Required Ground Current 460 pA Oscillator Frequency 120 kHz Logic Shutdown 8 Lead DIP and SO 8 Packages APPLICATIONS Cellular Telephones Single Cell to 5 V Converters Laptop and Palmtop Computers Pagers Cameras Battery Backup Supplies Portable Instruments Laser Diode Drivers Hand Held Inventory Computers GENERAL DESCRIPTION The ADP1109A is a versatile step up switching regulator T he device requires only minimal external components to operate as a complete switching regulator TheADP1109A 5 can deliver 100 mA at 5 V from a3 V input and the ADP1109A 12 can deliver 60 mA at 12 V from a 5 V input T he device also features a logic controlled shutdown capability that when a logic low is applied will shut down the oscillator T he 120 kH z operating frequency allows for the use of small surface mount components T he gated oscillator capability eliminates the need for frequency compensation REV 0 Information furnished by Analog Devices is believed to be accurate and reliable However no responsibility is assumed by Analog Devices for its use nor for any infringements of patents or other rights of third parties which may result from its use No license
5. H Vin 2 0 V SHUTDOWN PIN LOW Vit 0 8 V SHUTDOWN PIN INPUT CURRENT Vsuurpowu 4V liu 10 uA SHUTDOWN PIN INPUT CURRENT Vsuurpowu 0 lu 20 uA NOTES All limits at temperature extremes are guaranteed via correlation using standard quality control methods Specifications subject to change without notice ABSOLUTE MAXIMUM RATINGS Supply Voltage Vous 0 4 V to 20V SW Pin Voltage 0 4 V to 50V Shutdown Pin Voltage 6 0 V Switch Current 12A M aximum Power Dissipation 300 mW Operating Temperature Range 0 to 70 C Storage Temperature Range 65 C to 150 C Lead T emperature Soldering 10sec 300 C T his is a stress rating only operation beyond these limits can cause the device to be permanently damaged a2 REV 0 1109 PIN FUNCTION DESCRIPTIONS Pin Mnemonic Function 1 Vin Input Supply Voltage 2 NC No Connection 3 SW Collector N ode of Power T ransistor 4 PGND Power Ground 5 GND Ground 6 NC No Connection 7 SHUTDOWN When logic low is applied to this pin 8 FB SEN SE oscillator is shut down On the ADP1109A Adjustable this pin goes directly to the comparator input On the AD P1109A 3 3 ADP1109A 5 and AD P1109A 12 this pin is connected through the internal resistor that sets the output voltage ORDERING GUIDE Outpu
6. ent must not exceed the maximum switch current of 1 2 A If the calculated peak current is greater than 1 2 A either the input voltage must be increased or the load current decreased Output Voltage Selection T he output voltage is fed back to the AD P11094 via resistors R1 and R2 Figure 5 When the voltage at the comparator s inverting input falls below 1 25 V the oscillator turns on and the output voltage begins to rise T he output voltage is therefore set by the formula R2 V 125V 1 OUT 5V x Rd Resistors R1 and R2 are provided internally on fixed voltage versions of the ADP 11094 In this case a complete dc dc con verter requires only four external components REV 0 Capacitor Selection For optimum performance the AD P 1109A s output capacitor must be carefully selected C hoosing an inappropriate capacitor can result in low efficiency and or high output ripple Ordinary aluminum electrolytic capacitors are inexpensive but often have poor Equivalent Series Resistance ESR and quiva lent Series Inductance ESL Low ESR aluminum capacitors specifically designed for switch mode converter applications are also available and these are a better choice than general purpose devices E ven better performance can be achieved with tantalum capacitors although their cost is higher Very low values of ESR can be achieved by using OS CON capacitors Sanyo C orpora tion San Diego CA T hese devices are fairly
7. is granted by implication or otherwise under any patent or patent rights of Analog Devices FUNCTIONAL BLOCK DIAGRAM Vin SENSE O ADP11094A 3 3 R1 152 ADP1109A 5 R1 83kQ ADP1109A 12 R1 29KQ COMPARATOR 120kHz OSCILLATOR PGND ADP1109A GND SHUTDOWN PGND TYPICAL APPLICATION L1 33uH D1 Flash Memory VPP Generator One Technology Way P O Box 9106 Norwood MA 02062 9106 U S A Tel 781 329 4700 World Wide Web Site http www analog com Fax 781 326 8703 Analog Devices Inc 1997 1 1094 SP EC Fl CATI ONS 0 C lt 70 C Vy 3 V unless otherwise noted Parameter Conditions Min Max Units QUIESCENT CURRENT Switch Off I 460 580 pA INPUT VOLTAGE Vin 2 9 V COMPARATOR TRIP POINT VOLTAGE 1 20 1 25 1 30 V COMPARATOR HYSTERESIS ADP1109A 8 12 5 mV OUTPUT VOLTAGE ADP1109A 3 3 2V lt Viy lt 3 Vout 3 13 3 30 3 47 V ADP1109A 5 2V lt Vins5V 4 75 5 00 5 25 V ADP1109A 12 2V lt Vins9V 11 45 12 00 12 55 V OUTPUT VOLTAGE RIPPLE ADP1109A 3 3 15 35 mV ADP1109A 5 25 50 mV ADP1109A 12 60 120 mV OSCILLATOR FREQUENCY fosc 95 120 155 kHz DUTY CYCLE Full Load DC 57 67 77 SWITCH ON TIME ton 3 8 5 6 7 4 us SWITCH SATURATION VOLTAGE 500 mA VcesAT ADP1109A 3 3 Vin 23V 0 4 0 8 V ADP1109A 5 Vin 23V 0 4 0 8 V ADP1109A 12 Vi 23V 0 4 0 8 V SWITCH LEAKAGE CURRENT Vow 29V TA 25 1 10 SHUTDOWN PIN HIG
8. itch currents will reduce efficiency because of increased saturation voltage in the switch H igh peak current also increases output ripple As a general rule keep peak current as low as possible to minimize losses in the switch inductor and diode REV 0 1109 In practice the inductor value is easily selected using the equa tions above For example consider a supply that will generate 12 V at 120 mA from a 5 V source T he inductor power re quired is from Equation 1 121 0 5V 5V x 120mA 900 mW On each switching cycle the inductor must supply P 900mW fosc 120kHz The required inductor power is fairly low in this example so the peak current can also be low Assuming a peak current of 600 mA as a starting point Equation 4 can be rearranged to recommend an inductor value 7 5uJ pa Ni p aN 600 mA 5 5 us 45 8 pH Substituting a standard inductor value of 33 uH with 0 2 Q dc resistance will produce a peak switch current of 10 Q 5 5 us sperem Je i Oncethe peak current is known the inductor energy can be calculated from Equation 5 E 5 33 x 768 mA 9 7 pJ T he inductor energy of 9 7 uJ is greater than the P fosc re quirement of 7 5 yJ so the 33 uH inductor will work in this application By substituting other inductor values into the same equations the optimum inductor value can be selected When selecting an inductor the peak curr
9. put Voltage 18 20 SATURATION VOLTAGE V QUIESCENT CURRENT pA 01 02 04 06 08 1 12 Iswrrcu CURRENT A Figure 8 Saturation Voltage vs Iswitcy Current in Step Up Mode 600 500 400 300 40 0 25 70 85 TEMPERATURE C Figure 11 Quiescent Current vs Temperature ADP1109A APPLICATION INFORMATION THEORY OF OPERATION The ADP1109A is a flexible low power switch mode power supply SM PS controller for step up dc dc converter applica tions T his device uses a gated oscillator technique to provide very high performance with low quiescent current For example more than 2 W of output power can be generated from a 5 V source while quiescent current is only 360 uA A functional block diagram of the AD 1109 is shown on the front page T he internal 1 25 V reference is connected to one input of the comparator while the other input is externally connected via the F B pin to a feedback network connected to the regulated output When the voltage at the FB pin falls below 1 25 V the 120 kHz oscillator turns on A driver amplifier pro vides base drive to the internal power switch and the switching action raises the output voltage W hen the voltage at the FB pin exceeds 1 25 V the oscillator is shut off While the oscillator is off the ADP1109A quiescent current is only 460 pA T he com parator includes a small amount of hysteresis which ensures
10. small available with tape and reel packaging and have very low ESR Diode Selection In specifying a diode consideration must be given to speed forward voltage drop and reverse leakage current When the ADP1109A switch turns off the diode must turn on rapidly if high efficiency is to be maintained Schottky rectifiers as well as fast signal diodes such as the 1N 4148 are appropriate T he forward voltage of the diode represents power that is not delivered to the load so V must also be minimized Again Schottky diodes are recommended L eakage current is especially important in low current applications where the leakage can be a significant percentage of the total quiescent current For most circuits the 1N 5818 is a suitable companion to the ADP1109A This diode has a Vp of 0 5 V at 1 A 4 uA to 10 pA leakage and fast turn on and turn off times A surface mount version the M BRS130T 3 is also available For switch currents of 100 mA or less a Schottky diode such as the BAT 85 provides a Vp of 0 8 V at 100 mA and leakage less than 1 uA A similar device the BAT 54 is available in an SOT 23 package E ven lower leakage in the 1 nA to 5 nA range can be obtained with a 1N 4148 signal diode General purpose rectifiers such as the 1N 4001 are not suitable for ADP1109A circuits T hese devices which have turn on times of 10 us or more are far too slow for switching power supply applications U sing such a diode just to get s
11. t Package Package Model Voltage Description Options ADP1109AAN ADJ Plastic DIP N 8 ADP1109AAR ADJ Small OutlinelC 50 8 ADP1109AAN 3 3 3 3 V Plastic DIP N 8 ADP1109AAR 3 3 33V Small OutlinelC SO 8 ADP1109AAN 5 5V Plastic DIP N 8 ADP1109AAR 5 5V Small OutlinelC 50 8 ADP1109AAN 12 12V Plastic DIP N 8 ADP1109AAR 12 12V Small OutlinelC SO 8 CAUTION PIN CONFIGURATIONS 8 Lead Plastic DIP N 8 TOP VIEW SW 3 ot to Scate NC PGND 4 5 GND FIXED VERSIONS NC NO CONNECT 8 Lead SOIC SO 8 FIXED VERSIONS NC NO CONNECT ESD electrostatic discharge sensitive device Electrostatic charges as high as 4000 V readily accumulate on the human body and test equipment and can discharge without detection Although the AD P 1109A features proprietary ESD protection circuitry permanent damage may occur on devices subjected to high energy electrostatic discharges Therefore proper ESD precautions are recommended to avoid performance degradation or loss of functionality WARNING cmm Aa SENSITIVE DEVICE REV 0 3 ADP1109A 20k H MBRS130T3 O 12V 60mA ADP1109A 12 7 SHUTDOWN GND PGND SHUTDOWN COILTRONICS CTX20 1 SUMIDA CD54 220LC AVX TPS SERIES Figure 1 3 3 V Powered Flash Memory VPP Generator 104H MBRS130T3 ViN O 12V 2V 35mA ADP1109A 12 7 SHUTDOWN GND PGND 33 SHUTDOWN COILTRONICS CTX10 1 SUMIDA CD54 10
12. t their maximum val ues The inductor must also store enough energy to supply the load without saturating Finally the dc resistance of the induc tor should be low so that excessive power will not be wasted by heating the windings For most ADP1109A applications an inductor of 10 uH to 47 with a saturation current rating of 300 mA to 1A and dc resistance 0 4 is suitable Ferrite core inductors that meet these specifications are available in small surface mount packages Air core inductors as well as RF chokes are unsuitable because of their low peak current ratings The ADP1109A is designed for applications where the input voltage is fairly stable such as generating 12 V from a 5 V logic supply The ADP1109A does not have an internal switch current limiting circuit so the inductor may saturate if the input voltage is too high The ADP1111 or ADP3000 should be 6 considered for battery powered and similar applications where the input voltage varies To minimize Electro M agnetic Interference EM I a toroid or pot core type inductor is recommended Rod core inductors are a lower cost alternative if EM I is not a problem Calculating the Inductor Value Selecting the proper inductor value is a simple two step process 1 D efine the operating parameters minimum input voltage maximum input voltage output voltage and output current 2 Calculate the inductor value using the equations in the fol lowing section
13. tarted will result in wasted time and effort Even if an ADP1109A circuit appears to function with a 1N 4001 the resulting performance will not be indicative of the circuit performance when the cor rect diode is used 1109 OUTLINE DIMENSIONS Dimensions shown in inches and mm amp Lead Plastic DIP N 8 0 430 10 92 gt 0 348 8 84 N 8 5 NET 0 280 7 11 0 240 6 10 0 325 8 25 528 pam 0 300 7 62 T 0 015 0 38 a MAX U H H EE 0 130 0 160 4 06 E BST 0 115 2 93 pla lai gt a 0 015 0 381 0 022 0 558 0 100 0 070 1 77 BEATING 0 008 0 204 0 014 0 356 0 045 1 15 0 1968 5 00 0 1890 4 80 8 amp Lead SOIC SO 8 1 5 0 1574 4 00 0 2440 6 20 0 1497 3 80 4 0 2284 5 80 PIN 1 0 0688 1 75 0 0196 0 50 0 0098 0 25 0 0532 1 35 0 0099 0 25 5 0 0040 0 10 x gt gt e 8 gt l la 0 0500 0 0192 0 4 0 SEATING 0 0192 0 49 0 0098 0 25 0 0 0500 1 27 PLANE 1 27 9 0138 0 35 ac 0 0138 0 35 0 0075 0 19 0 0160 0 41 REV 0 C3183 8 10 97 PRINTED IN U S A

ANALOG DEVICES ADP1109A handbook

Contents

Download Pdf Manuals

Related Search

Related Contents