a Micropower Low Cost Fixed 3.3 V, 5 V, 12 V and 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 mA 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 FUNCTIONAL BLOCK DIAGRAM VIN SENSE ADP1109A-3.3: R1 = 152kV ADP1109A-5: R1 = 83kV ADP1109A-12: R1 = 29kV R2 250kV SW COMPARATOR 1.25V REFERENCE 120kHz OSCILLATOR A1 Q1 DRIVER R1 SHUTDOWN GND VIN PGND FB ADP1109A SW COMPARATOR GENERAL DESCRIPTION 1.25V REFERENCE 120kHz OSCILLATOR A1 The ADP1109A is a versatile step-up switching regulator. The device requires only minimal external components to operate as a complete switching regulator. The ADP1109A-5 can deliver 100 mA at 5 V from a 3 V input and the ADP1109A-12 can deliver 60 mA at 12 V from a 5 V input. The device also features a logic controlled shutdown capability that, when a logic low is applied, will shut down the oscillator. The 120 kHz operating frequency allows for the use of small surface mount components. Q1 DRIVER SHUTDOWN GND PGND TYPICAL APPLICATION The gated oscillator capability eliminates the need for frequency compensation. L1 33mH D1 3 VIN 5V 1 SW VIN VOUT 12V 60mA SENSE 8 ADP1109A-12 7 SHUTDOWN PGND GND 4 SHUTDOWN/PROGRAM 5 + C1 22mF 16V Flash Memory VPP Generator 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 is granted by implication or otherwise under any patent or patent rights of Analog Devices. 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 ADP1109A–SPECIFICATIONS (08C ≤ T ≤ 708C, V A IN = 3 V unless otherwise noted) Parameter Conditions VS QUIESCENT CURRENT Switch Off IQ INPUT VOLTAGE VIN COMPARATOR TRIP POINT VOLTAGE ADP1109A OUTPUT VOLTAGE ADP1109A-3.3 ADP1109A-5 ADP1109A-12 2 V ≤ VIN ≤ 3 V 2 V ≤ VIN ≤ 5 V 2 V ≤ VIN ≤ 9 V VOUT DUTY CYCLE 3.13 4.75 11.45 ADP1109A-3.3 ADP1109A-5 ADP1109A-12 OSCILLATOR FREQUENCY Full Load SWITCH-ON TIME SWITCH SATURATION VOLTAGE ADP1109A-3.3 ADP1109A-5 ADP1109A-12 ISW = 500 mA VIN = 3 V VIN = 3 V VIN = 3 V SWITCH LEAKAGE CURRENT VSW = 9 V, TA = +25°C Typ Max Units 460 580 µA 9 V 1.25 1.30 V 8 12.5 mV 3.30 5.00 12.00 3.47 5.25 12.55 V V V 15 25 60 35 50 120 mV mV mV 2 1.20 COMPARATOR HYSTERESIS OUTPUT VOLTAGE RIPPLE Min fOSC 95 120 155 kHz DC 57 67 77 % tON 3.8 5.6 7.4 µs 0.4 0.4 0.4 0.8 0.8 0.8 V V V 1 10 µA VCESAT SHUTDOWN PIN HIGH VIH 2.0 V SHUTDOWN PIN LOW VIL 0.8 V SHUTDOWN PIN INPUT CURRENT VSHUTDOWN = 4 V IIH 10 µA SHUTDOWN PIN INPUT CURRENT VSHUTDOWN = 0 V IIL 20 µA 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, VOUT . . . . . . . . . . . . . . . . . . . . –0.4 V to 20 V SW Pin Voltage . . . . . . . . . . . . . . . . . . . . . . . . –0.4 V to 50 V Shutdown Pin Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . 6.0 V Switch Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2 A Maximum Power Dissipation . . . . . . . . . . . . . . . . . . 300 mW Operating Temperature Range . . . . . . . . . . . . 0°C to +70°C Storage Temperature Range . . . . . . . . . . . . –65°C to +150°C Lead Temperature (Soldering, 10 sec) . . . . . . . . . . . +300°C *This is a stress rating only; operation beyond these limits can cause the device to be permanently damaged. –2– REV. 0 ADP1109A PIN FUNCTION DESCRIPTIONS PIN CONFIGURATIONS Pin Mnemonic Function 1 2 3 4 5 6 7 VIN NC SW PGND GND NC SHUTDOWN 8 FB(SENSE) Input Supply Voltage. No Connection. Collector Node of Power Transistor. Power Ground. Ground. No Connection. When logic low is applied to this pin, oscillator is shut down. On the ADP1109A (Adjustable), this pin goes directly to the comparator input. On the ADP1109A-3.3, ADP1109A-5 and ADP1109A-12, this pin is connected through the internal resistor that sets the output voltage. 8-Lead Plastic DIP (N-8) Package Description Package Options ADP1109AAN ADP1109AAR ADP1109AAN-3.3 ADP1109AAR-3.3 ADP1109AAN-5 ADP1109AAR-5 ADP1109AAN-12 ADP1109AAR-12 ADJ ADJ 3.3 V 3.3 V 5V 5V 12 V 12 V Plastic DIP Small Outline IC Plastic DIP Small Outline IC Plastic DIP Small Outline IC Plastic DIP Small Outline IC N-8 SO-8 N-8 SO-8 N-8 SO-8 N-8 SO-8 ADP1109A FB(SENSE)* 7 5 PGND 4 GND *FIXED VERSIONS NC = NO CONNECT 8-Lead SOIC (SO-8) VIN 1 8 FB(SENSE)* NC 2 ADP1109A 7 SHUTDOWN SW 3 TOP VIEW (Not to Scale) 6 NC 5 GND PGND 4 Output Voltage *FIXED VERSIONS NC = NO CONNECT CAUTION 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 ADP1109A 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. REV. 0 2 SHUTDOWN TOP VIEW SW 3 (Not to Scale) 6 NC NC ORDERING GUIDE Model 8 VIN 1 –3– WARNING! ESD SENSITIVE DEVICE ADP1109A 2kV MBRS130T3 20mH* VIN 3.3V 22mF MBRS130T3 10mH* 12V 60mA + VIN 5V 22mF 2N4403 + 3 SW VIN 1 3 SENSE 8 1 ADP1109A-12 4 5 7 + SHUTDOWN GND PGND 33mF** 25V *COILTRONICS CTX33-2 SUMIDA CD54-330LC **AVX TPS SERIES **AVX TPS SERIES Figure 1. 3.3 V Powered Flash Memory VPP Generator + 1mF L1 33mH* MBRS130T3 12V 35mA + 3 SW VIN 1 3 VIN 3V SENSE 8 ADP1109A-12 SHUTDOWN GND PGND 7 4 5 1 SW VIN 7 + 33mF** 25V SHUTDOWN GND GND 5 SHUTDOWN FB 8 ADP1109A 4 R2 250kV R1 + 40.3kV VOUT 9V C1 22mF** 16V SHUTDOWN *COILTRONICS CTX10-1 SUMIDA CD54-100LC *COILTRONICS CTX33-2 SUMIDA CD54-330LC **AVX TPS SERIES **AVX TPS SERIES Figure 2. 2 V Powered Flash Memory VPP Generator Figure 5. 3 V to 9 V Converter MBRS130T3 10mH* 22mF 47mF** 20V Figure 4. 5 V to 12 V Converter With Shutdown to 0 V at Output MBRS130T3 10mH* VIN 2V + SHUTDOWN *COILTRONICS CTX20-1 SUMIDA CD54-220LC 22mF 4 5 SHUTDOWN VIN 2V VOUT 12V 110mA SENSE 8 ADP1109A-12 SHUTDOWN GND PGND 7 SW VIN 5V 110mA + 3 1 SW VIN SENSE 8 ADP1109A-5 7 SHUTDOWN GND PGND 5 4 + 33mF** 10V SHUTDOWN *COILTRONICS CTX10-1 SUMIDA CD54-100LC **AVX TPS SERIES Figure 3. 2 V to 5 V Converter –4– REV. 0 ADP1109A 68 110 90 25 70 TEMPERATURE – 8C 53 –40 85 0 Figure 7. Duty Cycle vs. Temperature VCE(SAT) @ VIN = 3V AND ISW = 0.65A SWITCH-ON TIME – msec 0.50 0.45 0.40 0.35 0.30 0.25 0.20 0 25 70 TEMPERATURE – 8C VIN = 2V 550 5.0 4.5 4.0 3.5 3.0 0 25 70 TEMPERATURE – 8C 85 QUIESCENT CURRENT – mA 12.00 11.95 11.90 11.85 11.80 500 400 300 11.75 0 25 70 TEMPERATURE – 8C 85 Figure 12. 12 V Output Voltage vs. Temperature 200 1 1.2 500 450 400 350 2 4 6 8 10 12 14 16 INPUT VOLTAGE – Volts 18 20 Figure 13. Quiescent Current vs. Input Voltage –5– 250 –40 0 25 70 TEMPERATURE – 8C 85 Figure 11. Quiescent Current vs. Temperature 600 12.05 0.4 0.6 0.8 ISWITCH CURRENT – A 300 12.15 12.10 0.2 Figure 8. Saturation Voltage vs. ISWITCH Current in Step-Up Mode 5.5 Figure 10. Switch-On Time vs. Temperature 12.20 OUTPUT VOLTAGE – V 0.4 600 2.0 –40 85 Figure 9. Switch Saturation Voltage vs. Temperature REV. 0 0.6 6.0 2.5 0.15 11.70 –40 VIN = 3V 0.8 0.0 0.1 85 25 70 TEMPERATURE – 8C QUIESCENT CURRENT – mA 0 0.60 VCE(SAT) – V 59 VIN = 5V 1.0 0.2 Figure 6. Oscillator Frequency vs. Temperature 0.10 –40 62 56 70 0.55 SATURATION VOLTAGE – V 65 130 50 –40 1.4 1.2 150 DUTY CYCLE – % OSCILLATOR FREQUENCY – kHz 170 ADP1109A considered for battery powered and similar applications where the input voltage varies. APPLICATION INFORMATION THEORY OF OPERATION The ADP1109A is a flexible, low power switch-mode power supply (SMPS) controller for step-up dc/dc converter applications. This 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 µA. To minimize Electro-Magnetic Interference (EMI), a toroid or pot core type inductor is recommended. Rod core inductors are a lower-cost alternative if EMI is not a problem. Calculating the Inductor Value Selecting the proper inductor value is a simple two step process: 1. Define the operating parameters: minimum input voltage, maximum input voltage, output voltage and output current. A functional block diagram of the ADP1109A is shown on the front page. The internal 1.25 V reference is connected to one input of the comparator, while the other input is externally connected (via the FB 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 provides base drive to the internal power switch, and the switching action raises the output voltage. When 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 µA. The comparator includes a small amount of hysteresis, which ensures loop stability without requiring external components for frequency compensation. 2. Calculate the inductor value, using the equations in the following section. 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. The inductor power is calculated from the equation: ( ) ( ) P L = VOUT +V D −VIN ( MIN ) × IOUT (1) where VD is the diode forward voltage (<0.5 V for a 1N5818 Schottky). Energy is only stored in the inductor while the ADP1109A switch is ON, so the energy stored in the inductor on each switching cycle must be must be equal to or greater than: A shutdown feature permits the oscillator to be shut off. Holding SHUTDOWN low will disable the oscillator, and the ADP1109A’s quiescent current will remain 460 µA. The output voltage of the ADP1109A is set with two external resistors. Three fixed-voltage models are also available: the ADP1109A-3.3 (+3.3 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 ADP1109A, simply connect the SENSE pin (Pin 8) directly to the output voltage. PL f OSC (2) in order for the ADP1109A to regulate the output voltage. When the internal power switch turns ON, current flow in the inductor increases at the rate of: COMPONENT SELECTION General Notes on Inductor Selection () IL t = 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 transferred to the load when the switch turns off. − R't V IN 1− e L R' (3) where L is in Henrys and R' is the sum of the switch equivalent resistance (typically 0.8 Ω at +25°C) and the dc resistance of the inductor. In most applications, the voltage drop across the switch is small compared to VIN so a simpler equation can be used: To specify an inductor for the ADP1109A, the proper values of inductance, saturation current and dc resistance must be determined. This process is not difficult, and specific equations are provided in this data sheet. In general terms, however, the inductance value must be low enough to store the required amount of energy (when both input voltage and switch ON time are at a minimum) but high enough that the inductor will not saturate when both VIN and switch ON time are at their maximum values. The inductor must also store enough energy to supply the load, without saturating. Finally, the dc resistance of the inductor should be low, so that excessive power will not be wasted by heating the windings. For most ADP1109A applications, an inductor of 10 µH to 47 µH, with a saturation current rating of 300 mA to 1 A and dc resistance <0.4 Ω 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. () IL t = V IN t L (4) Replacing t in the above equation with the ON time of the ADP1109A (5.5 µs, typical) will define the peak current for a given inductor value and input voltage. At this point, the inductor energy can be calculated as follows: 1 E L = L × I 2 peak 2 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– (5) As previously mentioned, EL must be greater than PL/fOSC so that the ADP1109A can deliver the necessary power to the load. For best efficiency, peak current should be limited to 1 A or less. Higher switch currents will reduce efficiency because of increased saturation voltage in the switch. High 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 ADP1109A In practice, the inductor value is easily selected using the equations above. For example, consider a supply that will generate 12 V at 120 mA from a +5 V source. The inductor power required is, from Equation 1: Capacitor Selection For optimum performance, the ADP1109A’s output capacitor must be carefully selected. Choosing an inappropriate capacitor can result in low efficiency and/or high output ripple. PL = (12 V + 0.5 V – 5 V) × (120 mA) = 900 mW Ordinary aluminum electrolytic capacitors are inexpensive, but often have poor Equivalent Series Resistance (ESR) and Equivalent 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. Even 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 Corporation, San Diego, CA). These devices are fairly small, available with tape-and-reel packaging, and have very low ESR. On each switching cycle, the inductor must supply: P L 900 mW = = 7.5 µJ f OSC 120 kHz 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: L= V IN I L ( MAX ) t= Diode Selection 5V 5.5 µs = 45.8 µH 600 mA 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 1N4148, are appropriate. The forward voltage of the diode represents power that is not delivered to the load, so VF must also be minimized. Again, Schottky diodes are recommended. Leakage current is especially important in low current applications, where the leakage can be a significant percentage of the total quiescent current. Substituting a standard inductor value of 33 µH, with 0.2 Ω dc resistance, will produce a peak switch current of: I PEAK = 5V 1.0 Ω –1.0 Ω × 5.5 µs 33 µH 1− e = 768 mA Once the peak current is known, the inductor energy can be calculated from Equation 5: EL = ( ) ( 1 33 µH × 768 mA 2 ) 2 For most circuits, the 1N5818 is a suitable companion to the ADP1109A. This diode has a VF of 0.5 V at 1 A, 4 µA to 10 µA leakage, and fast turn-on and turn-off times. A surface mount version, the MBRS130T3, is also available. = 9.7 µJ The inductor energy of 9.7 µJ is greater than the PL/fOSC requirement of 7.5 µJ, so the 33 µH 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 current 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. For switch currents of 100 mA or less, a Schottky diode such as the BAT85 provides a VF of 0.8 V at 100 mA and leakage less than 1 µA. A similar device, the BAT54, is available in an SOT-23 package. Even lower leakage, in the 1 nA to 5 nA range, can be obtained with a 1N4148 signal diode. General purpose rectifiers, such as the 1N4001, are not suitable for ADP1109A circuits. These devices, which have turn-on times of 10 µs or more, are far too slow for switching power supply applications. Using such a diode “just to get started” will result in wasted time and effort. Even if an ADP1109A circuit appears to function with a 1N4001, the resulting performance will not be indicative of the circuit performance when the correct diode is used. Output Voltage Selection The output voltage is fed back to the ADP1109A 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. The output voltage is therefore set by the formula: R2 VOUT = 1.25 V × 1+ R1 Resistors R1 and R2 are provided internally on fixed-voltage versions of the ADP1109A. In this case, a complete dc-dc converter requires only four external components. REV. 0 –7– ADP1109A OUTLINE DIMENSIONS Dimensions shown in inches and (mm). 8-Lead Plastic DIP (N-8) 0.1968 (5.00) 0.1890 (4.80) 0.430 (10.92) 0.348 (8.84) 8 5 0.280 (7.11) 0.240 (6.10) 4 PIN 1 0.210 (5.33) MAX 0.060 (1.52) 0.015 (0.38) 0.160 (4.06) 0.115 (2.93) 0.022 (0.558) 0.100 0.070 (1.77) 0.014 (0.356) (2.54) 0.045 (1.15) BSC 0.130 (3.30) MIN SEATING PLANE 0.1574 (4.00) 0.1497 (3.80) 0.325 (8.25) 0.300 (7.62) PIN 1 0.195 (4.95) 0.115 (2.93) 0.0098 (0.25) 0.0040 (0.10) 0.015 (0.381) 0.008 (0.204) SEATING PLANE 8 5 1 4 0.2440 (6.20) 0.2284 (5.80) 0.0688 (1.75) 0.0532 (1.35) 0.0500 0.0192 (0.49) (1.27) 0.0138 (0.35) BSC 0.0196 (0.50) x 45° 0.0099 (0.25) 0.0098 (0.25) 0.0075 (0.19) 8° 0° 0.0500 (1.27) 0.0160 (0.41) PRINTED IN U.S.A. 1 C3183–8–10/97 8-Lead SOIC (SO-8) –8– REV. 0