EVALUATION KIT AVAILABLE TC7662A CHARGE PUMP DC-TO-DC CONVERTER FEATURES GENERAL DESCRIPTION ■ ■ ■ The TC7662A is a pin-compatible upgrade to the Industry standard TC7660 charge pump voltage converter. It converts a +3V to +18V input to a corresponding –3V to –18V output using only two low-cost capacitors, eliminating inductors and their associated cost, size and EMI. In addition to a wider power supply input range (3V to 18V versus 1.5V to 10V for the TC7660), the TC7662A can source output currents as high as 40mA. The on-board oscillator operates at a nominal frequency of 12kHz. Operation below 10kHz (for lower supply current applications) is also possible by connecting an external capacitor from OSC to ground. The TC7662A directly is recommended for designs requiring greater output current and/or lower input/output voltage drop. It is available in 8-pin PDIP, and CerDIP packages in commercial and extended temperature ranges. ■ ■ ■ ■ Wide Operating Range ............................. 3V to 18V Increased Output Current .............................. 40mA Pin Compatible with ICL7662/SI7661/TC7660/ LTC1044 No External Diodes Required Low Output Impedance @ IL = 20mA ....... 40Ω Typ. No Low-Voltage Terminal Required CMOS Construction ORDERING INFORMATION Temperature Range Part No. Package TC7662ACPA TC7662AEPA TC7662AIJA TC7662AMJA 8-Pin Plastic DIP 8-Pin Plastic DIP 8-Pin CerDIP 8-Pin CerDIP 0°C to +70°C – 40°C to +85°C – 25°C to +85°C – 55°C to +125°C PIN CONFIGURATION PDIP/CerDIP NC 1 8 VDD C+ 7 OSC 2 GND 3 TC7662A C– 4 6 NC 5 VOUT NC = NO INTERNAL CONNECTION FUNCTIONAL BLOCK DIAGRAM 8 VDD I COSC TC7662A 7 + – Q F/F C Q COMPARATOR WITH HYSTERESIS LEVEL SHIFT P SW1 2 LEVEL SHIFT N SW4 CAP + + CP EXT GND 3 VREF + LEVEL SHIFT OUT 4 LEVEL SHIFT CR EXT N SW2 CAP – RL N SW3 5 VOUT © 2001 Microchip Technology Inc. DS21468 TC7662A-5 9/11/96 CHARGE PUMP DC-TO-DC CONVERTER TC7662A Package Thermal Resistance CPA, EPA θJA .............................................. 140°C/W IJA, MJA θJA .................................................. 90°C/W ABSOLUTE MAXIMUM RATINGS* Supply Voltage V DD to GND .................................... +18V Input Voltage (Any Pin) ........... (VDD + 0.3) to (V SS – 0.3) Current Into Any Pin ................................................. 10mA Operating Temperature Range C Suffix .................................................. 0°C to +70°C I Suffix .............................................. – 25°C to +85°C E Suffix ............................................. – 40°C to +85°C M Suffix .......................................... – 55°C to +125°C Power Dissipation (TA ≤ 70°C) Plastic DIP ......................................................730mW CerDIP ...........................................................800mW SOIC ........................................................................... Storage Temperature Range ................ – 65°C to +150°C Lead Temperature (Soldering, 10 sec) ................. +300°C ESD Protection ...................................................... ±2000V Output Short Circuit ................. Continuous (at 5.5V Input) * Static-sensitive device. Unused devices must be stored in conductive material. Protect devices from static discharge and static fields. Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings only and functional operation of the device at these or any other conditions above those indicated in the operational sections of the specifications is not implied. Exposure to Absolute Maximum Rating Conditions for extended periods may affect device reliability. ELECTRICAL CHARACTERISTICS: VDD = 15V, TA = +25°C (See Test Circuit), unless otherwise specified. Symbol Parameter V DD IS Supply Voltage Supply Current RO Output Source Resistance COSC PEFF Oscillator Frequency Power Efficiency VEFF Voltage Efficiency TC7662A-5 9/11/96 Test Conditions RL = ∞ V DD = +15V 0°C ≤ TA ≤ +70°C – 55°C ≤ TA ≤ +125°C V DD = +5V 0°C ≤ TA ≤ +70°C – 55°C ≤ TA ≤ +125°C IL = 20mA, V DD = +15V IL = 40mA, V DD = +15V IL = 3mA, V DD = +5V V DD = +15V RL = 2 kΩ VDD = +15V RL = ∞ Over Operating Temperature Range 2 Min Typ Max 3 — 18 V — — — — — — — — — — 93 510 560 650 190 210 210 40 50 100 12 97 700 — — — — — 50 60 125 — — µA 99 99.9 — % 96 — — © 2001 Microchip Technology Inc. Unit Ω kHz % DS21468 CHARGE PUMP DC-TO-DC CONVERTER TC7662A TEST CIRCUIT EPR NC CP + 10 µF 1 8 2 7 3 TC7662A 4 6 IS IL NC C OSC V+ (+5V) ESL C RL 5 VOUT (–5V) CR ESR + Figure 1. Capacitor Equivalent Circuit Note one of its characteristics is ESR (equivalent series resistance). This parasitic resistance winds up in series with the load. Thus, both voltage and power conversion efficiency are compromised if a low ESR capacitor is not used. For example, in the "Test Circuit", changing CP and CR capacitors from typical ESR to low ESR types, the effective converter output impedance changed from 45Ω to 40Ω, an improvement of 12%. This applies to all types of capacitors, including film types (polyester, polycarbonate etc.). Some applications information suggests that the capacitor is not critical and attributes the limiting factor to the capacitor's reactance value. Let's examine this: 10 µF APPLICATIONS INFORMATION Theory of Operation The TC7662A is a capacitive charge pump (sometimes called a switched-capacitor circuit), where four MOSFET switches control the charge and discharge of a capacitor. The functional diagram (page 1) shows how the switching action works. SW1 and SW2 are turned on simultaneously, charging C1 to the supply voltage, VDD. This assumes that the ON resistance of the MOSFETs in series with the capacitor produce a charging time (3 time constants) less than the ON time provided by the oscillator frequency, as shown: XC = X 1 and ZC = C , DS 2πf C where DS (duty cycle) = 50%. Thus, ZC ≈ 1.33Ω at f = 12kHz, where C = 10µF. For the TC7662A, f = 12,000Hz, and a typical value of C would be 10µF. This is a reactive impedance of ≈1.33Ω. If the ESR is as great as 5Ω, the reactive value is not as critical as it would first appear, since the ESR would dominate. The 5Ω value is typical of a general-purpose electrolytic capacitor. 3 (RDS(ON) C1) <C1/(0.5 fOSC). In the next cycle, SW1 and SW2 are turned OFF and, after a very short interval with all switches OFF (preventing large currents from occurring due to cross conduction), SW3 and SW4 are turned ON. The charge in C1 is then transferred to COUT, BUT WITH THE POLARITY INVERTED. In this way, a negative voltage is derived. An oscillator supplies pulses to a flip-flop that is fed to a set of level shifters. These level shifters then drive each set of switches at one-half the oscillator frequency. The oscillator has a pin that controls the frequency of oscillation. Pin 7 can have a capacitor added that is connected to ground. This will lower the frequency of the oscillator by adding capacitance to the internal timing capacitor of the TC7662A. (See Oscillator Frequency vs. CEXT, page 5.) Synchronizing The TC7662A may be synchronized by connecting pin 7 of the TC7662A through a 100k resistor in series with a diode to a negative-going pulse source. The negative pulse voltage can be +5V with a 5 microsecond duration going negative to 0V. Q Capacitors TTL 100 k In early charge pump converters, capacitors were not considered critical due to the high RDS(ON) of the MOSFET switches. In order to understand this, let’s look at a model of a typical electrolytic capacitor (Figure 1). © 2001 Microchip Technology Inc. DS21468 Q Figure 2. 3 TO PIN 7 TC7662A Synchronization TC7662A-5 9/11/96 CHARGE PUMP DC-TO-DC CONVERTER TC7662A TYPICAL APPLICATIONS Combined Negative Converter and Positive Multiplier V CP2 + 10 µF 1 8 2 7 3 6 TC7662A + VD1 V = –V 5 OUT 4 + CP1 + VD2 + + C R2 10 µF + VOUT = 2V –2VD C R1 10 µF Lowering Output Resistance by Paralleling Devices V+ CP1 + 10 µF 1 8 2 7 3 TC7662A 4 CP2 + 10 µF 6 1 8 2 7 3 5 TC7662A 4 6 5 CR 10 µF + VOUT Positive Voltage Multiplier V+ 1 8 2 7 3 6 TC7662A 4 5 VD1 VD2 + CP 10 µF VOUT = 2V+–2 VD + CR 10 µF Split V+ In Half V+ CP + 10 µF 1 8 2 7 3 TC7662A 6 5 4 CR + 100 µF TC7662A-5 9/11/96 4 V+ VOUT = 2 © 2001 Microchip Technology Inc. DS21468 CHARGE PUMP DC-TO-DC CONVERTER TC7662A TYPICAL CHARACTERISTICS CURVES Oscillator Frequency vs CEXT Supply Current vs Temperature 700 FREQUENCY (Hz) SUPPLY CURRENT (µA) TA = +25°C 10k 600 500 + V = 15V 400 300 200 V + = 5V 1k 100 100 0 –60 –40 –20 0 20 40 60 80 TEMPERATURE (°C) 10 100 120 140 18 140 OUTPUT RESISTANCE ( Ω) FREQUENCY (kHz) 20 160 16 14 12 10 8 0 20 40 60 80 TEMPERATURE (°C) 120 100 135 120 70 105 60 90 50 75 60 30 45 20 30 TA = +25°C 0 8 16 24 32 40 48 56 64 LOAD CURRENT (mA) © 2001 Microchip Technology Inc. DS21468 72 OUTPUT RESISTANCE (Ω) 150 SUPPLY CURRENT (mA) POWER CONVERSION EFFICIENCY (%) 100 SUPPLY CURRENT 0 20 40 60 80 TEMPERATURE (°C) 100 120 140 Output Resistance vs Input Voltage 110 EFFICIENCY V+ = 15V, IL = 20 mA 40 20 –60 –40 –20 100 120 140 90 V + = 5V, IL = 3 mA 60 165 10 10,000 80 Power Conversion Efficiency vs I LOAD 40 100 1000 CAPACITANCE (pF) 100 110 80 10 Output Resistance vs Temperature Frequency vs Temperature 6 –60 –40 –20 1 TA = +25°C 90 80 70 60 20 mA 50 40 30 20 10 15 0 80 0 5 2 4 6 8 10 12 14 INPUT VOLTAGE (V) 16 18 20 TC7662A-5 9/11/96 CHARGE PUMP DC-TO-DC CONVERTER TC7662A PACKAGE DIMENSIONS 8-Pin Plastic DIP PIN 1 .260 (6.60) .240 (6.10) .045 (1.14) .030 (0.76) .070 (1.78) .040 (1.02) .310 (7.87) .290 (7.37) .400 (10.16) .348 (8.84) .200 (5.08) .140 (3.56) .040 (1.02) .020 (0.51) .150 (3.81) .115 (2.92) .110 (2.79) .090 (2.29) .015 (0.38) .008 (0.20) 3° MIN. .400 (10.16) .310 (7.87) .022 (0.56) .015 (0.38) 8-Pin CerDIP .110 (2.79) .090 (2.29) PIN 1 .300 (7.62) .230 (5.84) .020 (0.51) MIN. .055 (1.40) MAX. .320 (8.13) .290 (7.37) .400 (10.16) .370 (9.40) .200 (5.08) .160 (4.06) .040 (1.02) .020 (0.51) .150 (3.81) MIN. .200 (5.08) .125 (3.18) .015 (0.38) .008 (0.20) 3° MIN. .400 (10.16) .320 (8.13) .065 (1.65) .020 (0.51) .045 (1.14) .016 (0.41) TC7662A-5 9/11/96 Dimensions: inches (mm) 6 © 2001 Microchip Technology Inc. DS21468 CHARGE PUMP DC-TO-DC CONVERTER TC7662A WORLDWIDE SALES AND SERVICE AMERICAS New York Corporate Office 150 Motor Parkway, Suite 202 Hauppauge, NY 11788 Tel: 631-273-5305 Fax: 631-273-5335 2355 West Chandler Blvd. Chandler, AZ 85224-6199 Tel: 480-792-7200 Fax: 480-792-7277 Technical Support: 480-792-7627 Web Address: http://www.microchip.com Rocky Mountain 2355 West Chandler Blvd. Chandler, AZ 85224-6199 Tel: 480-792-7966 Fax: 480-792-7456 ASIA/PACIFIC (continued) San Jose Microchip Technology Inc. 2107 North First Street, Suite 590 San Jose, CA 95131 Tel: 408-436-7950 Fax: 408-436-7955 Singapore Microchip Technology Singapore Pte Ltd. 200 Middle Road #07-02 Prime Centre Singapore, 188980 Tel: 65-334-8870 Fax: 65-334-8850 Taiwan Atlanta 6285 Northam Drive, Suite 108 Mississauga, Ontario L4V 1X5, Canada Tel: 905-673-0699 Fax: 905-673-6509 500 Sugar Mill Road, Suite 200B Atlanta, GA 30350 Tel: 770-640-0034 Fax: 770-640-0307 Microchip Technology Taiwan 11F-3, No. 207 Tung Hua North Road Taipei, 105, Taiwan Tel: 886-2-2717-7175 Fax: 886-2-2545-0139 ASIA/PACIFIC Austin EUROPE China - Beijing Australia Analog Product Sales 8303 MoPac Expressway North Suite A-201 Austin, TX 78759 Tel: 512-345-2030 Fax: 512-345-6085 Boston 2 Lan Drive, Suite 120 Westford, MA 01886 Tel: 978-692-3848 Fax: 978-692-3821 Boston Analog Product Sales Unit A-8-1 Millbrook Tarry Condominium 97 Lowell Road Concord, MA 01742 Tel: 978-371-6400 Fax: 978-371-0050 Toronto Microchip Technology Beijing Office Unit 915 New China Hong Kong Manhattan Bldg. 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