TMS320F28027, TMS320F28027-Q1, TMS320F28027F, TMS320F28027F-Q1, TMS320F28026
TMS320F28026-Q1, TMS320F28026F, TMS320F28026F-Q1, TMS320F28023
TMS320F28023-Q1, TMS320F28022, TMS320F28021, TMS320F28020, TMS320F280200
ZHCSA13P –NOVEMBER 2008 –REVISED FEBRUARY 2021
www.ti.com.cn
9.6.1 内部零引脚振荡器
F2802x 器件包含两个独立的内部零引脚振荡器。缺省情况下，两个振荡器在加电时全都打开，此时，内部振荡器
1 是默认时钟源。为了节能，用户可将不使用的振荡器断电。这些振荡器的中心频率由它们各自的振荡器调整寄存
器决定，此寄存器在校准例程中被写入作为引导ROM 执行的一部分。有关这些振荡器的更多信息，请见节8，电
气规范。
9.6.2 Crystal Oscillator Option
The on-chip crystal oscillator X1 and X2 pins are 1.8-V level signals and must never have 3.3-V level signals
applied to them. If a system 3.3-V external oscillator is to be used as a clock source, it should be connected to
the XCLKIN pin only. The X1 pin is not intended to be used as a single-ended clock input, it should be used with
X2 and a crystal.
The typical specifications for the external quartz crystal (fundamental mode, parallel resonant) are listed in 表
9-13. Furthermore, ESR range = 30 to 150 Ω.
表9-13. Typical Specifications for External Quartz Crystal(1)
FREQUENCY (MHz)
CL1 (pF)
CL2 (pF)
Rd (Ω)
2200
470
0
5
18
18
10
15
20
15
15
15
15
0
12
12
(1) Cshunt should be less than or equal to 5 pF.
XCLKIN/GPIO19/38
X1
X2
Rd
Turn off
XCLKIN path
in CLKCTL
register
Crystal
CL1
CL2
A. X1/X2 pins are available in 48-pin package only.
图9-9. Using the On-chip Crystal Oscillator
备注
1. CL1 and CL2 are the total capacitance of the circuit board and components excluding the IC and
crystal. The value is usually approximately twice the value of the crystal's load capacitance.
2. The load capacitance of the crystal is described in the crystal specifications of the manufacturers.
3. TI recommends that customers have the resonator/crystal vendor characterize the operation of
their device with the MCU chip. The resonator/crystal vendor has the equipment and expertise to
tune the tank circuit. The vendor can also advise the customer regarding the proper tank
component values that will produce proper start-up and stability over the entire operating range.
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TMS320F28026 TMS320F28026-Q1 TMS320F28026F TMS320F28026F-Q1 TMS320F28023 TMS320F28023-
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