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NCP1729 データシート(PDF) 6 Page - ON Semiconductor |
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NCP1729 データシート(HTML) 6 Page - ON Semiconductor |
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6 / 22 page  NCP1729 http://onsemi.com 6 Capacitor Selection In order to maintain the lowest output resistance and output ripple voltage, it is recommended that low ESR capacitors be used. Additionally, larger values of C1 will lower the output resistance and larger values of C2 will reduce output voltage ripple. (See Equation 3). Table 1 shows various values of C1, C2 and C3 with the corresponding output resistance values at 25 °C. Table 2 shows the output voltage ripple for various values of C1, C2 and C3. The data in Tables 1 and 2 was measured not calculated. Table 1. Output Resistance vs. Capacitance (C1 = C2 = C3), Vin = 4.75 V and Vout = −4.0 V C1 = C2 = C3 (mF) Rout (W) 0.68 55.4 1.3 36.9 3.3 26.0 7.3 25.8 10 25.5 24 25.0 50 24.0 Table 2. Output Voltage Ripple vs. Capacitance (C1 = C2 = C3), Vin = 4.75 V and Vout = −4.0 V C1 = C2 = C3 ( mF) Output Voltage Ripple (mV) 0.68 322 1.3 205 3.3 120 7.3 69 10 56 24 32 50 20 Input Supply Bypassing The input voltage, Vin should be capacitively bypassed to reduce AC impedance and minimize noise effects due to the switching internals in the device. If the device is loaded from Vout to GND, it is recommended that a large value capacitor (at least equal to C1) be connected from Vin to GND. If the device is loaded from Vin to Vout, a small (0.7 mF) capacitor between the pins is sufficient. Voltage Inverter The most common application for a charge pump is the voltage inverter (Figure 14). This application uses two or three external capacitors. The C1 (pump capacitor) and C2 (output capacitor) are required. The input bypass capacitor C3, may be necessary depending on the application. The output is equal to −Vin plus any voltage drops due to loading. Refer to Tables 1 and 2 for capacitor selection. The test setup used for the majority of the characterization is shown in Figure 14. Layout Considerations As with any switching power supply circuit, good layout practice is recommended. Mount components as close together as possible to minimize stray inductance and capacitance. Also use a large ground plane to minimize noise leakage into other circuitry. Capacitor Resources Selecting the proper type of capacitor can reduce switching loss. Low ESR capacitors are recommended. The NCP1729 was characterized using the capacitors listed in Table 3. This list identifies low ESR capacitors for the voltage inverter application. Table 3. Capacitor Types Manufacturer/Contact Part Types/Series AVX 843−448−9411 www.avxcorp.com TPS Cornell Dubilier 508−996−8561 www.cornell−dubilier.com ESRD Sanyo/Os−con 619−661−6835 www.sanyovideo.com/oscon.htm SN SVP Vishay 603−224−1961 www.vishay.com 593D 594 |
同様の部品番号 - NCP1729_06 |
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同様の説明 - NCP1729_06 |
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