поискавой системы для электроныых деталей |
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TC682EPA датащи(PDF) 4 Page - Microchip Technology |
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TC682EPA датащи(HTML) 4 Page - Microchip Technology |
4 / 14 page TC682 DS21453C-page 4 © 2006 Microchip Technology Inc. 3.0 DETAILED DESCRIPTION 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 C 2 + is at +5V, the voltage potential across capacitor C2 is now -10V. FIGURE 3-2: Charge Pump – Phase 1 3.2 Phase 2 VSS transfer – phase two of the clock connects the neg- ative 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. FIGURE 3-3: Charge Pump – Phase 2 3.3 Maximum Operating Limits 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 capaci- tors 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”. (+5V) 6 7 1 2 3 5 4 RL GND + – + – + GND VIN All Caps = 3.3 μF TC682 VOUT C1+ VIN C2+ C1– C2– COUT V–OUT C1 C2 – VIN = +5V VOUT -5V SW4 SW1 SW2 SW3 C2 C3 C1 + – + + – – +5V VOUT -10V SW4 SW2 SW1 SW3 C2 C3 C1 + – + + – – |
Аналогичный номер детали - TC682EPA |
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Аналогичное описание - TC682EPA |
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