TC682COA

TC682 Inverting Voltage Doubler Features: • 99.9% Voltage Conversion Efficiency • 92% Power Conversion Efficiency • Wide Input Voltage Range: - +2.4V to +5.5V • Only 3 External Capacitors Required • 185 μA Supply Current • Space-Saving 8-Pin SOIC and 8-Pin PDIP Packages General Description: The TC682 is a CMOS charge pump converter that provides an inverted doubled output from a single positive supply. An on-board 12 kHz (typical) oscillator provides the clock and only 3 external capacitors are required for full circuit implementation. Low output source impedance (typically 140Ω), provides output current up to 10 mA. The TC682 features low quiescent current and high efficiency, making it the ideal choice for a wide variety of applications that require a negative voltage derived from a single positive supply (for example: generation of -6V from a 3V lithium cell or -10V generated from a +5V logic supply). The minimum external parts count and small physical size of the TC682 make it useful in many mediumcurrent, dual voltage analog power supplies. Applications: • • • • • • • -10V from +5V Logic Supply -6V from a Single 3V Lithium Cell Portable Handheld Instruments Cellular Phones LCD Display Bias Generator Panel Meters Operational Amplifier Power Supplies Functional Block Diagram VIN +2.4V < VIN < +5.5V Device Selection Table Part Number TC682COA TC682CPA TC682EOA TC682EPA Package 8-Pin SOIC 8-Pin PDIP 8-Pin SOIC 8-Pin PDIP Operating Temp. Range 0°C to +70°C 0°C to +70°C -40°C to +85°C -40°C to +85°C VIN C1 + – C 1+ C 1– TC682 C2 + – C 2+ C 2– VOUT GND + GND All Caps = 3.3 μF VOUT = -(2 x VIN ) VOUT COUT Package Type 8-Pin PDIP C1– 1 C2+ 2 C2– 3 VOUT 4 TC682CPA TC682EPA 8 7 6 5 NC C 1+ VIN GND C 1– C 2+ C 2– VOUT 1 2 3 4 TC682COA TC682EOA 8-Pin SOIC 8 7 6 5 NC C1+ VIN GND © 2006 Microchip Technology Inc. DS21453C-page 1 TC682 1.0 ELECTRICAL CHARACTERISTICS *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 operation sections of the specifications is not implied. Exposure to Absolute Maximum Rating conditions for extended periods may affect device reliability. Absolute Maximum Ratings* VIN .......................................................................+5.8V VIN dV/dT ........................................................ 1V/μsec VOUT ...................................................................-11.6V Short-Circuit Duration - VOUT ..................... Continuous Power Dissipation (TA ≤ 70°C) 8-Pin PDIP ..............................................730 mW 8-Pin SOIC ..............................................470 mW Operating Temperature Range.............-40°C to +85°C Storage Temperature (Unbiased) .......-65°C to +150°C TC682 ELECTRICAL SPECIFICATIONS Electrical Characteristics: Over operating temperature range, VIN = +5V, test circuit Figure 3-1 unless otherwise noted. Symbol VIN IIN ROUT Parameter Supply Voltage Range Supply Current VOUT Source Resistance Min 2.4 — — — — — 90 99 Typ — 185 — 140 — 170 12 92 99.9 Max 5.5 300 400 180 230 320 — — — Units V μA Ω Test Conditions RL = 2 kΩ RL = ∞, TA = 25°C RL = ∞ IL– = 10 mA, TA = 25°C IL– = 10 mA IL– = 5 mA, VIN = 2.8V RL = 2 kΩ, TA = 25°C VOUT, RL = ∞ FOSC PEFF VOUTEFF Oscillator Frequency Power Efficiency Voltage Conversion Efficiency kHz % % DS21453C-page 2 © 2006 Microchip Technology Inc. TC682 2.0 PIN DESCRIPTION The descriptions of the pins are listed in Table 2-1. TABLE 2-1: Pin No. (8-Pin PDIP, SOIC) 1 2 3 4 5 6 7 8 PIN FUNCTION TABLE Symbol C1– C2+ C2– VOUT GND VIN C1+ NC Description Input. Capacitor C1 negative terminal. Input. Capacitor C2 positive terminal. Input. Capacitor C2 negative terminal. Output. Negative output voltage (-2VIN). Input. Ground. Input. Power supply voltage. Input. Capacitor C1 positive terminal. No connection. © 2006 Microchip Technology Inc. DS21453C-page 3 TC682 3.0 VIN (+5V) + – 7 1 2 3 C 1+ C 1– DETAILED DESCRIPTION +5V 6 VIN SW1 + – C1 SW2 V–OUT – + COUT RL SW3 + – SW4 -10V VOUT C2 – + C3 C1 TC682 C 2+ C 2– 5 VOUT 4 GND C2 + – FIGURE 3-3: Charge Pump – Phase 2 GND All Caps = 3.3 μF 3.3 Maximum Operating Limits FIGURE 3-1: TC682 Test Circuit 3.1 Phase 1 VSS charge storage – before this phase of the clock cycle, capacitor C1 is already charged to +5V. C1+ is then switched to ground and the charge in C1– is transferred to C2–. Since C2+ is at +5V, the voltage potential across capacitor C2 is now -10V. VIN = +5V The TC682 has on-chip Zener diodes that clamp VIN to approximately 5.8V, and VOUT to -11.6V. Never exceed the maximum supply voltage or excessive current will be shunted by these diodes, potentially damaging the chip. The TC682 will operate over the entire operating temperature range with an input voltage of 2V to 5.5V. 3.4 Efficiency Considerations Theoretically a charge pump voltage multiplier can approach 100% efficiency under the following conditions: • The charge pump switches have virtually no offset and are extremely low on resistance. • Minimal power is consumed by the drive circuitry. • The impedances of the reservoir and pump capacitors are negligible. For the TC682, efficiency is as shown below: Voltage Efficiency = VOUT / (-2VIN) VOUT = -2VIN + VDROP VDROP = (IOUT) (ROUT) Power Loss = IOUT (VDROP) There will be a substantial voltage difference between VOUT and -2VIN if the impedances of the pump capacitors C1 and C2 are high with respect to their respective output loads. Larger values of reservoir capacitor C3 will reduce output ripple. Larger values of both pump and reservoir capacitors improve the efficiency. See Section 4.2 “Capacitor Selection” “Capacitor Selection”. SW1 + – + C1 SW2 -5V – SW3 C2 SW4 – + VOUT C3 FIGURE 3-2: Charge Pump – Phase 1 3.2 Phase 2 VSS transfer – phase two of the clock connects the negative terminal of C2 to the negative side of reservoir capacitor C3 and the positive terminal of C2 to ground, transferring the generated -10V to C3. Simultaneously, the positive side of capacitor C1 is switched to +5V and the negative side is connected to ground. C2 is then switched to VCC and GND and Phase 1 begins again. DS21453C-page 4 © 2006 Microchip Technology Inc. TC682 4.0 4.1 TYPICAL APPLICATIONS Negative Doubling Converter Output voltage ripple is affected by C3. Typically the larger the value of C3 the less the ripple for a given load current. The formula for P-P VRIPPLE is given below: VRIPPLE = {1/[2(fPUMP x C3)] + 2(ESRC3)} (IOUT) For a 10 μF (0.5Ω ESR) capacitor for C3, fPUMP = 10 kHz and IOUT = 10 mA the peak-to-peak ripple voltage at the output will be less then 60 mV. In most applications (IOUT < = 10 mA) a 10-20 μF capacitor and 1-5 μF pump capacitors will suffice. Table 4-2 shows VRIPPLE for different values of C3 (assume 1Ω ESR). The most common application of the TC682 is as a charge pump voltage converter which provides a negative output of two times a positive input voltage (Figure 4-1). + C1 22 μF 1 C 1– C1+ 7 TABLE 4-1: TC682 6 5 GND + C3 22 μF V–OUT C2 + 2 C+ 2 22 μF 3 C– 2 4 V–OUT OUTPUT RESISTANCE VS. C1, C2 ROUT(Ω) 4085 2084 510 285 145 125 105 94 87 VIN GND VIN C1, C2 (μF) 0.05 0.10 0.47 1.00 3.30 5.00 10.00 22.00 100.00 FIGURE 4-1: Inverting Voltage Doubler 4.2 Capacitor Selection The output resistance of the TC682 is determined, in part, by the ESR of the capacitors used. An expression for ROUT is derived as shown below: ROUT = 2(RSW1 + RSW2 + ESRC1 + RSW3 + RSW4 + ESRC2) +2(RSW1 + RSW2 + ESRC1 + RSW3 + RSW4 + ESRC2) +1/(fPUMP x C1) +1/(fPUMP x C2) +ESRC3 TABLE 4-2: C3 (μF) 0.50 1.00 3.30 5.00 10.00 22.00 100.00 VRIPPLE PEAK-TO-PEAK VS. C3 (IOUT 10mA) VRIPPLE (mV) 1020 520 172 120 70 43 25 Assuming all switch resistances are approximately equal: ROUT = 16RSW + 4ESRC1 + 4ESRC2 + ESRC3 +1/(fPUMP x C1) +1/(fPUMP x C2) ROUT is typically 140Ω at +25°C with VIN = +5V and 3.3 μF low ESR capacitors. The fixed term (16RSW) is about 80-90Ω. It can be seen easily that increasing or decreasing values of C1 and C2 will affect efficiency by changing ROUT. However, be careful about ESR. This term can quickly become dominant with large electrolytic capacitors. Table 4-1 shows ROUT for various values of C1 and C2 (assume 0.5Ω ESR). C1 must be rated at 6VDC or greater while C2 and C3 must be rated at 12VDC or greater. © 2006 Microchip Technology Inc. DS21453C-page 5 TC682 4.3 Paralleling Devices 4.4 Paralleling multiple TC682s reduces the output resistance of the converter. The effective output resistance is the output resistance of a single device divided by the number of devices. As illustrated in Figure , each requires separate pump capacitors C1 and C2, but all can share a single reservoir capacitor. -5V Regulated Supply From A Single 3V Battery Figure 4-3 shows a -5V power supply using one 3V battery. The TC682 provides -6V at VOUT, which is regulated to -5V by the negative LDO. The input to the TC682 can vary from 3V to 5.5V without affecting regulation appreciably. A TC54 device is connected to the battery to detect undervoltage. This unit is set to detect at 2.7V. With higher input voltage, more current can be drawn from the outputs of the TC682. With 5V at VIN, 10 mA can be drawn from the regulated output. Assuming 150Ω source resistance for the converter, with IL–= 10 mA, the charge pump will droop 1.5V. VIN + 10 μF – C1+ C1– VIN 10 μF + – C1+ C1 – VIN TC682 + 10 μF – C2+ V–OUT C2– GND + 10 μF – C2 + C2 – TC682 V–OUT GND Negative Supply – + C–OUT 22 μF GND FIGURE 4-2: Paralleling TC682 for Lower Output Source Resistance + 10 μF – + – 3V + 10 μF – C1+ C1– VIN Ground C2+ C2– GND TC682 VSS V–OUT – 22 μF +C – OUT VIN VOUT + – 1 μF -5 Supply Negative LDO Regulator TC54VC2702Exx VIN VSS VOUT LOW BATTERY FIGURE 4-3: Negative Supply Derived from 3V Battery DS21453C-page 6 © 2006 Microchip Technology Inc. TC682 5.0 Note: TYPICAL CHARACTERISTICS The graphs and tables provided following this note are a statistical summary based on a limited number of samples and are provided for informational purposes only. The performance characteristics listed herein are not tested or guaranteed. In some graphs or tables, the data presented may be outside the specified operating range (e.g., outside specified power supply range) and therefore outside the warranted range. Circuit of Figure 3-1, C1 = C2 = COUT = 3.3 μF, TA = 25°C unless otherwise noted. Output Resistance vs. VIN 240 C1 – C3 = 3.3 µF 220 200 180 160 140 120 1 2 3 VIN (V) 4 5 6 VOUT (V) -7.5 -8.0 -8.5 -9.0 -9.5 -10.0 -10.5 0 5 10 15 LOAD CURRENT (mA) VIN = 5V VOUT vs. Load Current OUTPUT RESISTANCE (Ω) Supply Current vs. VIN 300 OUTPUT SOURCE RESISTANCE (Ω) Output Source Resistance vs. Temperature 200 180 160 140 120 100 80 -50 VIN = 5V IOUT = 10 mA NO LOAD SUPPLY CURRENT (μA) 250 200 150 100 50 1 2 3 VIN (V) 4 5 6 0 50 100 TEMPERATURE (°C) Output Ripple vs. Output Current 200 VIN = 5V OUTPUT RIPPLE (mV PK-PK) 150 C3 = 10 μF 100 50 C3 = 100 μF 0 0 5 10 OUTPUT CURRENT (mA) 15 20 © 2006 Microchip Technology Inc. DS21453C-page 7 TC682 6.0 6.1 PACKAGING INFORMATION Package Marking Information Package marking data not available at this time. 6.2 Taping Form Component Taping Orientation for 8-Pin SOIC (Narrow) Devices User Direction of Feed Pin 1 W P Standard Reel Component Orientation for 713 Suffix Device Carrier Tape, Number of Components Per Reel and Reel Size Package Carrier Width (W) Pitch (P) Part Per Full Reel Reel Size 8-Pin SOIC (N) 12 mm 8 mm 2500 13 in 6.3 Package Dimensions 8-Pin Plastic DIP Pin 1 .260 (6.60) .240 (6.10) .045 (1.14) .030 (0.76) .400 (10.16) .348 (8.84) .200 (5.08) .140 (3.56) .150 (3.81) .115 (2.92) .070 (1.78) .040 (1.02) .310 (7.87) .290 (7.37) .040 (1.02) .020 (0.51) .015 (0.38) .008 (0.20) .400 (10.16) .310 (7.87) 3° Min. .110 (2.79) .090 (2.29) .022 (0.56) .015 (0.38) Dimensions: inches (mm) DS21453C-page 8 © 2006 Microchip Technology Inc. TC682 8-Pin SOIC Pin 1 .157 (3.99) .150 (3.81) .244 (6.20) .228 (5.79) .050 (1.27) Typ. .197 (5.00) .189 (4.80) .069 (1.75) .053 (1.35) .020 (0.51) .010 (0.25) .013 (0.33) .004 (0.10) .010 (0.25) .007 (0.18) .050 (1.27) .016 (0.40) Dimensions: inches (mm) 8° Max. © 2006 Microchip Technology Inc. DS21453C-page 9 TC682 NOTES: DS21453C-page 10 © 2006 Microchip Technology Inc. TC682 THE MICROCHIP WEB SITE Microchip provides online support via our WWW site at www.microchip.com. This web site is used as a means to make files and information easily available to customers. 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