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| ICL828 TM Data Sheet June 2000 File Number 4835.1 Switched-Capacitor Voltage Inverter The ICL828 IC performs supply voltage conversions from positive to negative for an input range of +1.5V to +5.5V resulting in complementary output voltages of -1.5V to -5.5V. The ICL828 has a 12kHz internal oscillator and requires two capacitors to invert the supply voltage. Cascading may be made to increase the output voltage. The high efficiency (greater than 90% over most of the load-current range) and low operating current (60A typical) make these devices ideal for both battery-powered and board-level voltage conversion applications. Features * 5-Lead SOT23-5 Package * 99% Open Circuit Voltage Conversion Efficiency * Inverts Input Supply Voltage * High Power Supply Efficiency * Input Voltage Range . . . . . . . . . . . . . . . . . . +1.5V to +5.5V * May be Cascaded to Increase Output Voltage * Output Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25mA * Quiescent Current . . . . . . . . . . . . . . . . . . . . . . . . . . 60A Ordering Information PART NUMBER ICL828IH-T TEMP. RANGE (oC) -40 to 85 PACKAGE PKG. NO BRAND 828 * Pin for Pin Compatible to MAX828 * Small Package Size 5 Lead SOT23 P5.064 Applications * Simple Conversion . . . . . . . . . . . . . . . . . . . . . +5V to -5V * Voltage Multiplication . . . . . . . . . . . . . . . . . . VOUT = -nVIN * Supply Splitter - Operational Amplifiers - Bias Supplies * Hand Held Products - Cell Phones - PDAs - GPS - Pagers * LCD Panels Block Diagram NEGATIVE VOLTAGE CONVERTER OUTPUT VOLTAGE + OUT 1 C1+ 5 INPUT VOLTAGE 2 IN + 3 C1GND 4 Pinout ICL828 (SOT23) TOP VIEW OUT IN C1- 1 2 3 5 C1+ 4 GND 1 CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures. 1-888-INTERSIL or 321-724-7143 | Intersil and Design is a trademark of Intersil Corporation. | Copyright (c) Intersil Corporation 2000 ICL828 Absolute Maximum Ratings IN to GND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +6.0V, -0.3V OUT to GND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -6.0V, +0.3V OUT Output CURRENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50mA OUT Short-circuit to GND . . . . . . . . . . . . . . . . . . . . . . . . . Indefinite Thermal Information Thermal Resistance (Typical, Note 1) JA (oC/W) SOT23 Package 240 Maximum Junction Temperature (Plastic Package) . . . . . . . .150oC Maximum Storage Temperature Range . . . . . . . . . . -65oC to 150oC Maximum Lead Temperature (Soldering 10s) . . . . . . . . . . . . .300oC Operating Conditions Temperature Range . . . . . . . . . . . . . . . . . . . . . . . . . . -40oC to 85oC Supply Voltage Range . . . . . . . . . . . . . . . . . . . . . . . . 1.5V to 5.5V CAUTION: Stresses above those listed in "Absolute Maximum Ratings" may cause permanent damage to the device. This is a stress only rating and operation of the device at these or any other conditions above those indicated in the operational sections of this specification is not implied. NOTE: 1. JA is measured with the component mounted on a low effective thermal conductivity test board in free air. (See Tech Brief TB379 for details.). Electrical Specifications PARAMETER Supply Current VIN = +5V, C1 = C2 = 10F, TA = -40oC to 85oC, Unless Otherwise Specified SYMBOL ICC 25oC -40oC to 85oC TEST CONDITIONS MIN 1.25 1.5 6 95 TYP 60 1.0 98 99.9 20 MAX 90 115 5.5 20 50 65 UNITS A A V V V kHz % % Minimum Supply Voltage VCC RL = 10K, 25oC RL = 10K, -40oC to 85oC Maximum Supply Voltage Oscillator Frequency Power Efficiency Voltage Conversion Efficiency Output Resistance VCC fOSC PEFF VOUT / VIN ROUT RL = 10K -40oC to 85oC RL = 10K, 25oC RL = Open IOUT = 5mA, 25oC IOUT = 5mA, -40 to 85oC Typical Performance Curves 45 OUTPUT VOLTAGE RIPPLE (mV) 40 OUTPUT RESISTANCE () 35 30 25 20 15 10 5 0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5 500 400 300 VIN = 3.15V, VOUT = -2.5V VIN = 1.9V, VOUT = -1.5V 200 100 VIN = 4.75V, VOUT = -4.0V 0 1.5 20 40 CAPACITANCE (F) 60 80 SUPPLY VOLTAGE (V) FIGURE 1. OUTPUT RESISTANCE vs SUPPLY VOLTAGE FIGURE 2. OUTPUT VOLTAGE RIPPLE vs CAPACITANCE 2 ICL828 Typical Performance Curves 60 60 SUPPLY CURRENT (A) 80 50 VIN = 1.5V 40 ROUT () 30 VIN = 3.3V 20 10 0 -40 VIN = 5V 50 40 30 20 10 0 1.5 (Continued) 70 -30 -20 -10 0 10 20 30 40 50 60 70 2.0 2.5 3.0 3.5 4.0 4.5 5.0 TEMPERATURE (oC) SUPPLY VOLTAGE (V) FIGURE 3. ROUT vs TEMPERATURE FIGURE 4. SUPPLY CURRENT vs VOLTAGE 16 14 FREQUENCY (kHz) 12 10 VIN = 1.5V 8 6 4 2 0 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 VIN = 5V 100 95 VIN = 3.3V EFFICIENCY (%) 90 85 80 75 70 65 60 0 10 20 30 40 50 TEMPERATURE (oC) OUTPUT CURRENT (mA) VIN = 3.3V VIN = 2V VIN = 5V FIGURE 5. OSCILLATOR FREQUENCY vs TEMPERATURE FIGURE 6. EFFICIENCY vs OUTPUT CURRENT 60 VIN = 4.75V, VOUT = -4V 50 OUTPUT CURRENT (mA) SUPPLY CURRENT (A) 40 30 20 VIN = 1.9V, VOUT = -1.5V 10 0 1.5 80 70 60 50 40 30 20 10 20 40 CAPACITANCE (F) 60 80 0 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 VIN = 1.5V VIN = 3.3V VIN = 5V VIN = 3.15V, VOUT = -2.5V TEMPERATURE (oC) FIGURE 7. OUTPUT CURRENT vs CAPACITANCE FIGURE 8. SUPPLY CURRENT vs TEMPERATURE 3 ICL828 Test Circuit VIN RL VOUT 1 OUT C 1+ 5 C2 IN + 10F 4 + C1 10F 3. The impedances of the pump and reservoir capacitors are negligible at the pump frequency. 4. The losses due to the 1/fC terms is small. Energy is lost only in the transfer of charge between capacitors if a change in voltage occurs. The energy lost is defined by: 2 2 1 E = -- C 1 ( V 1 - V 2 ) 2 2 3 + C3 10F C 1- GND NOTE: VIN = +5V, C1 = C2 = C3 , TA = 25oC, unless otherwise noted. FIGURE 9. TEST CIRCUIT 2 IN S1 5 S2 Where V1 and V2 are the voltages on C1 during the pump and transfer cycles. If the impedances of C1 and C2 are relatively high at the pump frequency (refer to Figure 10) compared to the value of RL , there will be a substantial difference in the voltages V1 and V2 . Therefore it is not only desirable to make C2 as large as possible to eliminate output voltage ripple, but also to employ a correspondingly large value for C1 in order to achieve maximum efficiency of operation. Negative Voltage Converter 4 C1 C2 S3 3 S4 1 OUT V OUT = -V IN The output characteristics of the circuit on the first page can be approximated by an ideal voltage source in series with a resistance (Figure 11). The voltage source has a value of -(VIN). The output impedance (RO) is a function of the ON resistance of the internal MOS switches (shown in Figure 10), the switching frequency, the value of C1 and C2 , and the ESR (equivalent series resistance) of C1 and C2 . A good first order approximation for RO is: R O = 2 ( R sw1 + R sw3 + ESRC 1 ) + 2 ( R sw2 + R sw4 + ESRC 1 ) + 1 ( fpump ) ( C1 ) + ESRC 2 FIGURE 10. IDEALIZED NEGATIVE VOLTAGE CONVERTER Description The ICL828 contains all the necessary circuitry to complete a negative converter, utilizing two external inexpensive 10F polarized electrolytic capacitor. The mode of operation of the device may be understood by considering Figure 10 which shows an idealized negative voltage converter. Capacitor C1 is charged to a voltage, VIN , for the half cycle when switches S1 and S3 are closed (Note: switches S2 and S4 are open during this half cycle). During the second half cycle of operation, switches S2 and S4 are closed, with S1 and S2 open, thereby shifting capacitor C1 negatively by VIN Volts. Charge is then transferred from C1 to C2 such that the voltage on C2 is exactly VIN , assuming ideal switches and no load on C2 . Rsw, the switch resistance, is a function of supply voltage and temperature (see Figure 3). Careful selection of capacitors will minimize the output resistance, and low capacitor ESR will lower the ESR term. V IN + VOUT RO FIGURE 11. EQUIVALENT CIRCUIT Output Ripple ESR also affects the ripple voltage seen at the output. The total ripple is determined by 2 voltages, A and B, as shown in Figure 12. Segment A is the voltage drop across the ESR of C2 at the instant it goes from being charged by C1 (current flowing into C2) to being discharged through the load (current flowing out of C2). The magnitude of this current change is 2 x I OUT, hence the total drop is 2 x IOUT x ESRC2V. Segment B is the voltage change across C2 during time t1, the half of the cycle when C2 supplies current the Theoretical Power Efficiency Considerations In theory a voltage converter can approach 100% efficiency if certain conditions are met: 1. The driver circuitry consumes minimal power. 2. The output switches have extremely low ON resistance and virtually no offset. 4 ICL828 load. The drop at B is IOUT x t1 /C 2V. The peak-to-peak ripple voltage is the sum of these voltage drops: V 1 RIPPLE ------------------------------------------ + 2 ESRC 2 x I OUT 2 x C Xf 2 PUMP 0 t1 B Again, a low ESR capacitor will result in a higher performance output. V -(VIN) A Positive Voltage Doubling The ICL828 may be employed to achieve positive voltage doubling using the circuit shown in Figure 13. In this application, the pump inverter switches of the ICL828 are used to charge C1 to a voltage level of VIN -VF where VIN is the supply voltage and VF is the forward voltage on C1 plus the supply voltage (VIN) is applied through diode D2 to capacitor C2 . The voltage thus created on C2 becomes (2VIN) - (2VF) or twice the supply voltage minus the combined forward voltage drops of diodes D1 and D2 . The source impedance of the output (VOUT) will depend on the output current. FIGURE 12. OUTPUT RIPPLE V+ D1 1 2 3 4 5 C1 + D2 + VOUT = (2V IN) - (2VF) NOTE: D1 and D2 can be any suitable diode. C2 FIGURE 13. POSITIVE VOLTAGE DOUBLER Combined Negative Conversion and Positive Supply Doubling Figure 14 combines the functions shown on front page and Figure 13 to provide negative voltage conversion and positive voltage doubling simultaneously. This approach would be, for example, suitable for generating +9V and -5V from an existing +5V supply. In this instance capacitors C1 and C3 perform the pump and reservoir functions respectively for the generation of the negative voltage, while capacitors C2 and C4 are pump and reservoir respectively for the doubled positive voltage. There is a penalty in this configuration which combines both functions, however, in that the source impedances of the generated supplies will be somewhat higher due to the finite impedance of the common charge pump driver at pin 2 of the device. VIN VOUT = -VIN 1 2 5 D1 4 D2 VOUT = (2V IN) (VFD1) - (VFD2) + - C3 + + 3 C1 - C2 + - C4 FIGURE 14. COMBINED NEGATIVE VOLTAGE AND POSITIVE DOUBLER Cascading Devices The ICL828 may be cascaded to produce a larger multiplication supply voltage (see Figure 15). The output voltage is: VOUT = -n(VIN), where n is an integer representing the number of devices cascaded. The resulting output resistance would be approximately the sum of the individual ICL828 ROUT values. +V IN 2 3 IN 1 C1GND + C1 C4 + C3 + VOUT VOUT = - nVIN 4 3 C1 2 + 1 OUT C1+ 5 C2 1 5 OUT C1+ IN n GND 4 FIGURE 15. CASCADING TO INCREASE OUTPUT VOLTAGE 5 ICL828 Voltage Splitting The bidirectional characteristics of the switches of the ICL828 can be used to split a higher supply in half as shown below. +VIN + EFFICIENCY (%) VOUT OUT INPUT C1GND + C1 C+ (VOUT = 1/2VIN) 60 0 10 20 30 40 50 60 70 80 90 100 OUTPUT CURRENT (mA) 100 90 80 + C2 C1 = C2 = C3 = 47F 70 C3 GND - FIGURE 18. EFFICIENCY vs OUTPUT CURRENT FOR SPLIT SUPPLY APPLICATION FIGURE 16. SPLIT SUPPLY APPLICATION 2.5 OUTPUT VOLTAGE (V) The combined load will be evenly shared between the two external capacitors because the switches share the load in parallel, the output resistance is approximately half of the standard voltage inverter. VIN = 5V 2.3 2.1 Equivalent Circuit ROUT 1/2 VIN 1.9 1.7 1.5 0 10 20 30 40 50 60 70 80 90 100 OUTPUT CURRENT (mA) FIGURE 17. FIGURE 19. OUTPUT CURRENT vs OUTPUT VOLTAGE FOR SPLIT SUPPLY APPLICATIONS Typical value for ROUT in the above equivalent circuit would be 6 to 7 for an input voltage of 5V. The power efficiency for the circuit would be: PEFF = (IOUT*VOUT)/(1/2(VIN*IOUT))+(VIN*IQ) Typical values for ICL828 in this application, IQ = 22A, ROUT = 6 to 7 and VOUT = 1/2VIN*RLOAD/(ROUT + RLOAD). The ICL828 used as a voltage splitting circuit is an efficient means to providing a split supply application as shown in Figures 16 through 19. 6 ICL828 Small Outline Transistor Plastic Packages (SOT23-5) D P5.064 5 LEAD SMALL OUTLINE TRANSISTOR PLASTIC PACKAGE INCHES L e1 MILLIMETERS MIN 0.90 0.00 0.90 0.35 0.09 2.80 2.60 1.50 MAX 1.45 0.15 1.30 0.50 0.20 3.00 3.00 1.75 NOTES 3 3 4, 5 6 10o Rev. 0 10/98 SYMBOL A MIN 0.036 0.000 0.036 0.0138 0.0036 0.111 0.103 0.060 MAX 0.057 0.0059 0.051 0.0196 0.0078 0.118 0.118 0.068 E C L C L E1 A1 A2 b C e C L 0.20 (0.008) M C L C b C D E E1 e e1 0.0374 Ref 0.0748 Ref 0.004 5 0o 10o 0o 0.023 0.95 Ref 1.90 Ref 0.10 5 0.60 A A2 A1 SEATING PLANE -C- L N 0.10 (0.004) C NOTES: 1. Dimensioning and tolerances per ANSI 14.5M-1982. 2. Package conforms to EIAJ SC-74A (1992). 3. Dimensions D and E1 are exclusive of mold flash, protrusions, or gate burrs. 4. Footlength L measured at reference to seating plane. 5. "L" is the length of flat foot surface for soldering to substrate. 6. "N" is the number of terminal positions. 7. Controlling dimension: MILLIMETER. Converted inch dimensions are not necessarily exact. All Intersil semiconductor products are manufactured, assembled and tested under ISO9000 quality systems certification. Intersil semiconductor products are sold by description only. Intersil Corporation reserves the right to make changes in circuit design and/or specifications at any time without notice. Accordingly, the reader is cautioned to verify that data sheets are current before placing orders. Information furnished by Intersil is believed to be accurate and reliable. However, no responsibility is assumed by Intersil or its subsidiaries 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 Intersil or its subsidiaries. For information regarding Intersil Corporation and its products, see web site www.intersil.com Sales Office Headquarters NORTH AMERICA Intersil Corporation P. O. Box 883, Mail Stop 53-204 Melbourne, FL 32902 TEL: (321) 724-7000 FAX: (321) 724-7240 EUROPE Intersil SA Mercure Center 100, Rue de la Fusee 1130 Brussels, Belgium TEL: (32) 2.724.2111 FAX: (32) 2.724.22.05 ASIA Intersil Ltd. 8F-2, 96, Sec. 1, Chien-kuo North, Taipei, Taiwan 104 Republic of China TEL: 886-2-2515-8508 FAX: 886-2-2515-8369 7 |
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