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參數(shù)資料
| 型號(hào)： | CY28447LFXC |
| 廠商： | Silicon Laboratories Inc |
| 文件頁(yè)數(shù)： | 2/22頁(yè) |
| 文件大小： | 0K |
| 描述： | IC CLOCK CALISTOGA CK410M 72QFN |
| 標(biāo)準(zhǔn)包裝： | 240 |
| 類型： | 時(shí)鐘/頻率發(fā)生器 |
| PLL： | 是 |
| 主要目的： | Intel CPU 服務(wù)器 |
| 輸入： | LVTTL，晶體 |
| 輸出： | HCSL，LVCMOS |
| 電路數(shù)： | 1 |
| 比率 - 輸入:輸出： | 3:21 |
| 差分 - 輸入:輸出： | 無(wú)/是 |
| 頻率 - 最大： | 200MHz |
| 電源電壓： | 3.135 V ~ 3.465 V |
| 工作溫度： | 0°C ~ 85°C |
| 安裝類型： | 表面貼裝 |
| 封裝/外殼： | 72-VFQFN 裸露焊盤 |
| 供應(yīng)商設(shè)備封裝： | 72-QFN（10x10） |
| 包裝： | 托盤 |
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CY28447
...................... Document #: 38-07724 Rev *C Page 10 of 22
Calculating Load Capacitors
In addition to the standard external trim capacitors, trace
capacitance and pin capacitance must also be considered to
correctly calculate crystal loading. As mentioned previously,
the capacitance on each side of the crystal is in series with the
crystal. This means the total capacitance on each side of the
crystal must be twice the specified crystal load capacitance
(CL). While the capacitance on each side of the crystal is in
series with the crystal, trim capacitors (Ce1,Ce2) should be
calculated to provide equal capacitive loading on both sides.
As mentioned previously, the capacitance on each side of the
crystal is in series with the crystal. This means the total capac-
itance on each side of the crystal must be twice the specified
load capacitance (CL). While the capacitance on each side of
the crystal is in series with the crystal, trim capacitors
(Ce1,Ce2) should be calculated to provide equal capacitance
loading on both sides.
Use the following formulas to calculate the trim capacitor
values for Ce1 and Ce2.
CL....................................................Crystal load capacitance
CLe......................................... Actual loading seen by crystal
using standard value trim capacitors
Ce..................................................... External trim capacitors
Cs .............................................. Stray capacitance (terraced)
Ci ...........................................................Internal capacitance
(lead frame, bond wires etc.)
CLK_REQ# Description
The CLKREQ# signals are active LOW inputs used for clean
enabling and disabling selected SRC outputs. The outputs
controlled by CLKREQ# are determined by the settings in
register byte 8. The CLKREQ# signal is a de-bounced signal
in that it’s state must remain unchanged during two consec-
utive rising edges of SRCC to be recognized as a valid
assertion or deassertion. (The assertion and deassertion of
this signal is absolutely asynchronous.)
CLK_REQ[1:9]# Assertion (CLKREQ# -> LOW)
All differential outputs that were stopped are to resume normal
operation in a glitch-free manner. The maximum latency from
the assertion to active outputs is between 2 and 6 SRC clock
periods (2 clocks are shown) with all SRC outputs resuming
simultaneously. All stopped SRC outputs must be driven HIGH
within 10 ns of CLKREQ# deassertion to a voltage greater than
200 mV.
CLK_REQ[1:9]# Deassertion (CLKREQ# -> HIGH)
The impact of deasserting the CLKREQ# pins is that all SRC
outputs that are set in the control registers to stoppable via
deassertion of CLKREQ# are to be stopped after their next
transition. The final state of all stopped DIF signals is LOW,
both SRCT clock and SRCC clock outputs will not be driven.
Figure 1. Crystal Capacitive Clarification
XTAL
Ce2
Ce1
Cs1
Cs2
X1
X2
Ci1
Ci2
Clock Chip
Trace
2.8 pF
Trim
33 pF
Pin
3 to 6p
Figure 2. Crystal Loading Example
Load Capacitance (each side)
Total Capacitance (as seen by the crystal)
Ce = 2 * CL – (Cs + Ci)
Ce1 + Cs1 + Ci1
1
+
Ce2 + Cs2 + Ci2
1
()
1
=
CLe
Figure 3. CLK_REQ#[1:9] Deassertion/Assertion Waveform
SRCT(stoppable)
SRCC(free running)
SRCT(free running)
CLKREQ#X
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| CY28447LFXCT | 功能描述:時(shí)鐘發(fā)生器及支持產(chǎn)品 Calistoga System Clk Extra SRC Output RoHS:否 制造商:Silicon Labs 類型:Clock Generators 最大輸入頻率:14.318 MHz 最大輸出頻率:166 MHz 輸出端數(shù)量:16 占空比 - 最大:55 % 工作電源電壓:3.3 V 工作電源電流:1 mA 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-56 |
| CY28506OC | 制造商:Rochester Electronics LLC 功能描述:FTG FOR MOTHERBOARDS - Bulk |
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| CY28508OCT | 制造商:Cypress Semiconductor 功能描述: |
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