參數(shù)資料
型號: MPC7410VS500LE
廠商: Freescale Semiconductor
文件頁數(shù): 32/56頁
文件大?。?/td> 0K
描述: IC MPU PPC 500MHZ 360-FCCLGA
標準包裝: 44
系列: MPC74xx
處理器類型: 32-位 MPC74xx PowerPC
速度: 500MHz
電壓: 1.8V
安裝類型: 表面貼裝
封裝/外殼: 360-CLGA,F(xiàn)CCLGA
供應商設備封裝: 360-FCCLGA(25x25)
包裝: 托盤
MPC7410 RISC Microprocessor Hardware Specifications, Rev. 6.1
38
Freescale Semiconductor
System Design Information
8.4 Connection Recommendations
To ensure reliable operation, it is highly recommended to connect unused inputs to an appropriate signal level
through a resistor. Unused active low inputs should be tied to OVDD. Unused active high inputs should be connected
to GND. All NC (no connect) signals must remain unconnected.
Power and ground connections must be made to all external VDD, OVDD, L2OVDD, and GND pins of the MPC7410.
Note that power must be supplied to L2OVDD even if the L2 interface of the MPC7410 will not be used; the
remainder of the L2 interface may be left unterminated.
8.5 Output Buffer DC Impedance
The MPC7410 60x and L2 I/O drivers are characterized over process, voltage, and temperature. To measure Z0, an
external resistor is connected from the chip pad to OVDD or GND. Then, the value of each resistor is varied until
the pad voltage is OVDD/2 (see Figure 23).
The output impedance is the average of two components, the resistances of the pull-up and pull-down devices. When
data is held low, SW2 is closed (SW1 is open), and RN is trimmed until the voltage at the pad equals (L2)OVDD/2.
RN then becomes the resistance of the pull-down devices. When data is held high, SW1 is closed (SW2 is open), and
RP is trimmed until the voltage at the pad equals (L2)OVDD/2. RP then becomes the resistance of the pull-up devices.
RP and RN are designed to be close to each other in value. Then, Z0 = (RP + RN)/2.
Figure 23 describes the driver impedance measurement circuit described above.
Figure 23. Driver Impedance Measurement Circuit
Alternately, the following is another method to determine the output impedance of the MPC7410. A voltage source,
Vforce, is connected to the output of the MPC7410, as in Figure 24. Data is held low, the voltage source is set to a
value that is equal to (L2)OVDD/2, and the current sourced by Vforce is measured. The voltage drop across the
pull-down device, which is equal to (L2)OVDD/2, is divided by the measured current to determine the output
impedance of the pull-down device, RN. Similarly, the impedance of the pull-up device is determined by dividing
the voltage drop of the pull-up, (L2)OVDD/2, by the current sank by the pull-up when the data is high and Vforce is
equal to (L2)OVDD/2. This method can be employed with either empirical data from a test setup or with data from
simulation models, such as IBIS.
OVDD
OGND
RP
RN
Pad
Data
SW1
SW2
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