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MPC5553 数据表(PDF) 12 Page - Freescale Semiconductor, Inc |
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MPC5553 数据表(HTML) 12 Page - Freescale Semiconductor, Inc |
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12 / 66 page ![]() MPC5553 Microcontroller Data Sheet, Rev. 2.0 Electrical Characteristics Freescale Semiconductor 12 Table 8 gives the pin state for the sequence cases for all pins with pad type pad_mh (medium type) and pad_sh (slow type). 3.7.1 Input Value of Pins During POR Dependent on VDD33 When powering up the device, VDD33 must not lag the latest VDDSYN or RESET power pin (VDDEH6) by more than the VDD33 lag specification listed in Table 6, spec 8. This avoids accidentally selecting the bypass clock mode because the internal versions of PLLCFG[0:1] and RSTCFG are not powered and therefore cannot read the default state when POR negates. VDD33 can lag VDDSYN or the RESET power pin (VDDEH6), but cannot lag both by more than the VDD33 lag specification. This VDD33 lag specification applies during power up only. VDD33 has no lead or lag requirements when powering down. 3.7.2 Power-Up Sequence (VRC33 Grounded) The 1.5 V VDD power supply must rise to 1.35 V before the 3.3 V VDDSYN power supply and the RESET power supply rises above 2.0 V. This ensures that digital logic in the PLL for the 1.5 V power supply does not begin to operate below the specified operation range lower limit of 1.35 V. Because the internal 1.5 V POR is disabled, the internal 3.3 V POR or the RESET power POR must hold the device in reset. Since they can negate as low as 2.0 V, VDD must be within specification before the 3.3 V POR and the RESET POR negate. Figure 2. Power-Up Sequence (VRC33 Grounded) Table 8. Power Sequence Pin Status for Medium / Slow Pads VDDEH VDD POR Pin Status for Medium and Slow Pad Output Driver pad_mh (medium) pad_sh (slow) Low — Asserted Low VDDEH Low Asserted High impedance (Hi-Z) VDDEH VDD Asserted Hi-Z VDDEH VDD Negated Functional VDDSYN and RESET Power VDD 2.0 V 1.35 V VDD must reach 1.35 V before VDDSYN and the RESET power reach 2.0 V |
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