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| 型號： | SP5055S |
| 廠商： | Mitel Networks Corporation |
| 英文描述： | () |
| 中文描述： | （） |
| 文件頁數(shù)： | 1/10頁 |
| 文件大?。?/td> | 99K |
| 代理商： | SP5055S |
EXTERNAL NOISE PROBLEMS
I
2
C BUS RADIATION PROBLEMS
The main problem when designing PCBs using any I
2
C
device is that data and clock are always being transmitted and
fed to the transceivers. This can lead to problems with
radiation unless suitable precautions are taken.
Coupling from the SCL and SDA lines can often occur
where these lines are long tracks leading to the synthesiser.
The SCL and SDA lines pose particular problems as clock and
Fig.3 Layout and decoupling of synthesiser supply pins
DRIVE
V
EE
RF
RF
V
CC
P0
C
A
C
B
RF
INPUTS
GND
PLATED
THROUGH
GND
OSCILLATOR
C
B
=100n
C
A
=100p
data are always present on the I
2
C databus, regardless of
whether the synthesiser is being addressed or not. These can
couple into the synthesisier through any of the pins; it is
therefore important to ensure that all pins are decoupled
where possible. Unused ports should be taken to ground.
Small decoupling capacitors may be placed directly on the pin
to cut radiation into ports.
P7
P6
P5
P0
P3
P4
SP5055S
100p
100p
1
12V
Fig.1 Decoupling/grounding of used and unused ports
I
2
C BUS LINE FILTERING
I
2
C bus specifications permit a maximum of 400pF on the
SDA andSCL lines. This figure refers to the maximum total
capacitance present on the bus so therefore includes other
devices. Most applications use a combination of 100pF
decoupling capacitors on each line together with a series
resistor of up to 100k , depending on the clock rate.
SYNTHESISER DECOUPLING
Supplies should be decoupled as close to the chip as
possible. It is suggested that combination of 100pF and
100nF is used to give the best possible immunity against low
and high frequency noise.
Layout
Care must be taken with layout to ensure that the supply
rails are as short as possible and that no loops (either ground
or supply) exist. If the layout permits, the V
CC
line should not
be routed near the loop filter.
Grounding
The synthesiser should be taken to a clean ground
separate from the track used to ground any of the oscillators.
If possible, shielding should be introduced between the
oscillators and the synthesiser to ensure that no spurious
coupling occurs.
Fig.2 I
2
C bus line filtering
100p
330
SP5055S
SDA
SCL
100p
330
TO MICRO
AN168
TV/Satellite Synthesisers - Basic Design Guidelines
Application Note
AN168 - 2.4 June 1995
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PDF描述 |
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| SP5055 | 2.6GHz Bidirectional IIC BUS Controlled Synthesiser(2.6GHz 雙向IIC總線控制的頻率合成器) |
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| SP5502 | 1.3GHz IIC Bus 4-Address Synthesiser(1.3GHz IIC總線的頻率合成器（帶4條可編程IIC總線地址）) |
| SP5510 | 1.3GHz Bidirectional IIC Bus Controlled Synthesiser(1.3GHz 雙向IIC總線控制的頻率合成器) |
| SP5512 | 1.3GHz Bidirectional IIC Bus Controlled Synthesiser(1.3GHz 雙向IIC總線控制的頻率合成器) |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| SP5055SMP | 制造商:MITEL 制造商全稱:Mitel Networks Corporation 功能描述:2.6GHz Bidirectional I2C BUS Controlled Synthesiser |
| SP505A | 制造商:BLKBOX 功能描述: |
| SP505AB | 制造商:SIPEX 制造商全稱:Sipex Corporation 功能描述:WAN Multi-Mode Serial Transceiver |
| SP505ACF | 制造商: 功能描述: 制造商:Exar Corporation 功能描述: 制造商:undefined 功能描述: |
| SP505ACF-L | 制造商:Exar Corporation 功能描述:TRANSCEIVER MULTI MODE SMD 505 制造商:Exar 功能描述:Transceiver WAN Multi-Mode 10Mbps MQFP80 |
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