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DSPIC33EP64GS708 数据表(PDF) 18 Page - Microchip Technology |
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DSPIC33EP64GS708 数据表(HTML) 18 Page - Microchip Technology |
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18 / 484 page ![]() dsPIC33EPXXXGS70X/80X FAMILY DS70005258C-page 18 2016-2018 Microchip Technology Inc. FIGURE 2-1: RECOMMENDED MINIMUM CONNECTION 2.2.1 TANK CAPACITORS On boards with power traces running longer than six inches in length, it is suggested to use a tank capacitor for integrated circuits, including DSCs, to supply a local power source. The value of the tank capacitor should be determined based on the trace resistance that con- nects the power supply source to the device and the maximum current drawn by the device in the applica- tion. In other words, select the tank capacitor so that it meets the acceptable voltage sag at the device. Typical values range from 4.7 µF to 47 µF. 2.3 CPU Logic Filter Capacitor Connection (VCAP) A low-ESR (< 0.5Ω) capacitor is required on the VCAP pin, which is used to stabilize the voltage regulator output voltage. The VCAP pin must not be connected to VDD and must have a capacitor greater than 4.7 µF (10 µF is recommended), 16V connected to ground. The type can be ceramic or tantalum. See Section 30.0 “Electrical Characteristics” for additional information. The placement of this capacitor should be close to the VCAP pin. It is recommended that the trace length not exceed one-quarter inch (6 mm). See Section 27.4 “On-Chip Voltage Regulator” for details. 2.4 Master Clear (MCLR) Pin The MCLR pin provides two specific device functions: • Device Reset • Device Programming and Debugging. During device programming and debugging, the resistance and capacitance that can be added to the pin must be considered. Device programmers and debuggers drive the MCLR pin. Consequently, specific voltage levels (VIH and VIL) and fast signal transitions must not be adversely affected. Therefore, specific values of R and C will need to be adjusted based on the application and PCB requirements. For example, as shown in Figure 2-2, it is recom- mended that the capacitor, C, be isolated from the MCLR pin during programming and debugging operations. Place the components as shown in Figure 2-2, within one-quarter inch (6 mm) from the MCLR pin. FIGURE 2-2: EXAMPLE OF MCLR PIN CONNECTIONS Note 1: As an option, instead of a hard-wired connection, an inductor (L1) can be substituted between VDD and AVDD to improve ADC noise rejection. The inductor impedance should be less than 1 and the inductor capacity greater than 10 mA. Where: f FCNV 2 -------------- = f 1 2 LC ----------------------- = L 1 2 fC ---------------------- 2 = (i.e., ADC Conversion Rate/2) dsPIC33EP VDD VSS VSS VDD 0.1 µF Ceramic 0.1 µF Ceramic 0.1 µF Ceramic 0.1 µF Ceramic C R VDD MCLR 0.1 µF Ceramic L1(1) R1 10 µF Tantalum C R1(2) R(1) VDD MCLR dsPIC33EP JP Note 1: R 10 k is recommended. A suggested starting value is 10 k . Ensure that the MCLR pin VIH and VIL specifications are met. 2: R1 470 will limit any current flowing into MCLR from the external capacitor, C, in the event of MCLR pin breakdown due to Electrostatic Discharge (ESD) or Electrical Overstress (EOS). Ensure that the MCLR pin VIH and VIL specifications are met. |
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