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参数资料
| 型号： | THS7303PW |
| 厂商： | TEXAS INSTRUMENTS INC |
| 元件分类： | 音频／视频放大 |
| 英文描述： | 3 CHANNEL, VIDEO AMPLIFIER, PDSO20 |
| 封装： | GREEN, PLASTIC, TSSOP-20 |
| 文件页数： | 36/60页 |
| 文件大小： | 1980K |
| 代理商： | THS7303PW |
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SLOS479B
– OCTOBER 2005 – REVISED MARCH 2011
I
2C DESIGN NOTES: ISSUES AND SOLUTIONS
The THS7303 requires some special attention to the I2C function that is usually not required. These are known
design issues, but there are simple work-arounds that allow the THS7303 to perform within any I2C system.
The first known I2C issue is with respect to the power-up condition. On power up, the THS7303 registers are in a
random state from device to device. The registers remain in this random state until a valid write sequence is
made to the THS7303. A total of 9 bytes of data completely configure all channels of the THS7303. Therefore,
configuring the THS7303 should be done on power-up of the system. Note that one such random state
(acknowledge state or ACK) can be engaged. While ACK is engaged, the THS7303 pulls the SDA line low and
the master cannot send data to any device on the I2C bus. To circumvent this state, at least one SCL cycle must
be completed and then the acknowledge state disengages.
While one SCL cycle normally eliminates any issues, the internal FIFO buffer may have random bits internally to
the THS7303. To completely clear all eight bits of this buffer, run 8-cycles (or 8-bits or 1-byte) on the SCL line.
While there are several different methods to run SCL cycles, the simplest is to have the master send a 0x00 hex
code to the I2C bus on power-up, ignoring any ACK state. Note that the SCL cycle should occur only after the
power-supply voltage of the THS7303 is at least 2.7 V. Failure to follow this step may cause the THS7303 to
ignore the SCL cycles.
Another known issue with the I2C function is that the internal SDA/SCL buffers are susceptible to high-frequency
noise. This noise can come from switch-mode power supplies, digital processors, or other high-frequency noise
generators. While the THS7303 includes buffers with hysterisis on the front-end, these are placed after a
low-gain CMOS buffer used as an ESD protection element. The noise susceptibility in real-world systems is very
low; however, it can be an issue in some noisy or compact systems. The simple solution, which has shown to
solve the issue, is to place a RC filter on each I2C line. Real-world results show that using a 100-
resistor in
series on each SDA/SCL line along with a 22 pF capacitor from each SDA/SCL line to ground eliminates the
noise susceptibility issue. These RC filters should be placed as close as possible to the THS7303 SDA/SCL input
pins. Other solutions have shown that not using a series resistor and only using a larger value capacitor (such as
100 pF to 220 pF) has worked, but the RC solution is more robust.
One last real-world issue that has appeared relates to the value of the pull-up resistor on the SDA and SCL lines.
While the standard allows for between 2 k
and 19 k for this pull-up resistor, practice has shown that keeping
this value lower works best. Typical values should be between 2 k
and 3.3 k, with 2.7 k being the most
common.
Copyright
2005–2011, Texas Instruments Incorporated
41
Product Folder Link(s): THS7303
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相关代理商/技术参数 |
参数描述 |
|---|---|
| THS7303PWG4 | 功能描述:视频放大器 3-Ch Low Power Video RoHS:否 制造商:ON Semiconductor 通道数量:4 电源类型: 工作电源电压:3.3 V, 5 V 电源电流: 最小工作温度: 最大工作温度: 封装 / 箱体:TSSOP-14 封装:Reel |
| THS7303PWR | 功能描述:视频放大器 3-Ch Low Power Video RoHS:否 制造商:ON Semiconductor 通道数量:4 电源类型: 工作电源电压:3.3 V, 5 V 电源电流: 最小工作温度: 最大工作温度: 封装 / 箱体:TSSOP-14 封装:Reel |
| THS7303PWRG4 | 功能描述:视频放大器 3-Ch Low Power Video RoHS:否 制造商:ON Semiconductor 通道数量:4 电源类型: 工作电源电压:3.3 V, 5 V 电源电流: 最小工作温度: 最大工作温度: 封装 / 箱体:TSSOP-14 封装:Reel |
| THS730A A2 | 制造商:Tektronix Inc 功能描述:OSCILLOSCOPE DSO/DMM 200MHZ |
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