Resistor values are typically 120 to 240 ohms for 3.3V opera on and 82 to 120 ohms for 2.5V
opera on.
Figure 7 - Pull Up Pull Down Termina on
Resistor values are typically for 3.3V opera on
For 2.5V opera on, the resistor to ground is 62 ohms and the resistor to supply is 240 ohms
There are numerous applica on notes on termina ng and interfacing PECL logic and the two most common methods are a single resistor to ground, Figure 6,
and a pull-up/pull-down scheme as shown in Figure 7. An AC coupling capacitor is op onal, depending on the applica on and the input logic requirements of
the next stage.
One of the most important considera ons is termina ng the Output and Complementary Outputs equally. An unused output should not be le un-
terminated, and if one of the two outputs is le open it will result in excessive ji er on both. PC board layout must take this and 50 ohm impedance matching
into account. Load matching and power supply noise are the main contributors to ji er related problems.
LVDS Applica on Diagrams
+3.3V
OE or NC
10nF
1nF
1
6
+3.3V
OE or NC
10nF
1nF
1
6
10nF
OE or NC
2
5
100
3
4
10nF
OE or NC
2
5
Receiver
100
Receiver
3
4
Figure 8 - LVDS to LVDS, internal 100Ω
Some LVDS structures have an internal 100 ohm resistor on the
input and do not need addi onal components.
Figure 9 - LVDS to LVDS, External 100Ω and AC block ing caps
One of the most important considera ons is termina ng the Output and Complementary Outputs equally. An unused output should not be le un-
terminated, and if one of the two outputs is le open it will result in excessive ji er on both. PC board layout must take this and 50 ohm impedance matching
into account. Load matching and power supply noise are the main contributors to ji er related problems.
在全世界范围内，双音多频DTMF(Dual Tone MultiFrequency)信令逐渐使用在按键式电话机上，因其提供更高的拨号速率， 迅速取代了传统转盘式电话机使用的拨号脉冲信令。近年来，D T M F 也应用在交互式控制中，如语言菜单、语言邮件、来电显示、电话银行和A T M终端等。在芯片内部没有内置D T M F 产生器时，用普通D/A 甚至于用4~5 个普通I/O 口和简单的电阻...[详细]
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