參數(shù)資料
型號： MPC5646CF0CLU8
廠商： FREESCALE SEMICONDUCTOR INC
元件分類： 微控制器/微處理器
英文描述： 32-BIT, FLASH, 80 MHz, MICROCONTROLLER, PQFP176
封裝： 24 X 24 MM, 1.40 MM HEIGHT, 0.50 MM PITCH, ROHS COMPLIANT, LQFP-176
文件頁數(shù)： 88/115頁
文件大?。?/td> 783K
代理商： MPC5646CF0CLU8
MPC5646C Microcontroller Datasheet, Rev. 4
Preliminary—Subject to Change Without Notice
Electrical Characteristics
Freescale Semiconductor
74
A second aspect involving the capacitance network shall be considered. Assuming the three capacitances CF, CP1 and CP2 are
initially charged at the source voltage VA (refer to the equivalent circuit reported in Figure 16): A charge sharing phenomenon
is installed when the sampling phase is started (A/D switch close).
Figure 18. Transient behavior during sampling phase
In particular two different transient periods can be distinguished:
1.
A first and quick charge transfer from the internal capacitance CP1 and CP2 to the sampling capacitance CS occurs (CS
is supposed initially completely discharged): considering a worst case (since the time constant in reality would be
faster) in which CP2 is reported in parallel to CP1 (call CP = CP1 + CP2), the two capacitances CP and CS are in series,
and the time constant is
Eqn. 5
Equation 5 can again be simplified considering only CS as an additional worst condition. In reality, the transient is
faster, but the A/D converter circuitry has been designed to be robust also in the very worst case: the sampling time TS
is always much longer than the internal time constant:
Eqn. 6
The charge of CP1 and CP2 is redistributed also on CS, determining a new value of the voltage VA1 on the capacitance
according to Equation 7:
Eqn. 7
2.
A second charge transfer involves also CF (that is typically bigger than the on-chip capacitance) through the resistance
RL: again considering the worst case in which CP2 and CS were in parallel to CP1 (since the time constant in reality
would be faster), the time constant is:
Eqn. 8
In this case, the time constant depends on the external circuit: in particular imposing that the transient is completed
well before the end of sampling time TS, a constraints on RL sizing is obtained:
VA
VA1
VA2
t
TS
VCS
Voltage Transient on CS
V <0.5 LSB
1
2
1 < (RSW + RAD) CS << TS
2 = RL (CS + CP1 + CP2)
1
R
SW
R
AD
+
=
C
P
C
S
C
P
C
S
+
---------------------
1
R
SW
R
AD
+
C
S
T
S
V
A1
C
S
C
P1
C
P2
++
V
A
C
P1
C
P2
+
=
2
R
L
C
S
C
P1
C
P2
++
相關(guān)PDF資料
PDF描述
MPC5646CF0MMJ8 32-BIT, FLASH, 80 MHz, MICROCONTROLLER, PBGA256
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
MPC564AADPT176 功能描述:開發(fā)板和工具包 - 其他處理器 ANDORRA ADAPT RoHS:否 制造商:Freescale Semiconductor 產(chǎn)品:Development Systems 工具用于評估:P3041 核心:e500mc 接口類型:I2C, SPI, USB 工作電源電壓:
MPC564AADPT208 制造商:Freescale Semiconductor 功能描述:ANDORRA ADAPSOLDERED
MPC564AKIT176 功能描述:開發(fā)板和工具包 - 其他處理器 ANDORRA 176QFP KIT RoHS:否 制造商:Freescale Semiconductor 產(chǎn)品:Development Systems 工具用于評估:P3041 核心:e500mc 接口類型:I2C, SPI, USB 工作電源電壓:
MPC564AKIT176S 制造商:Freescale Semiconductor 功能描述:MPC564XA 176 LQFP SOCKET EVAL KIT 制造商:Freescale Semiconductor 功能描述:MPC564XA, 176 LQFP SOCKET, EVAL KIT
MPC564AKIT208 制造商:Freescale Semiconductor 功能描述:ANDORRA 208BGA KIT
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