TK14584MTL 查看數據表（PDF） - Toko America Inc

零件编号

产品描述 (功能)

生产厂家

TK14584MTL

FM IF IC

Toko America Inc  

TK14584

CIRCUIT DESCRIPTION (CONT.)

The RSSI output is a current output. It converts to a voltage by an external resistor between Pin 11 and GND. The time

constant of the RSSI output is determined by the product of the external converting resistance and parallel capacitance.

When the time constant is longer, the RSSI output is less likely to be influenced by a disturbance or component of amplitude

modulation, but the RSSI output response is slower. The external resistance and capacitance are determined by the

application.

VCC

OUTPUT

CURRENT

RSSI- OUT

Current-to-Voltage

Transformation Resistor

FIGURE 2 - RSSI OUTPUT STAGE

The slope of the RSSI curve characteristic can be modified by changing the external resistance. In this case, the maximum

range of converted RSSI output voltage is GND level to about VCC - 0.2 V (the supply voltage minus the collector saturation

voltage of the output transistor).

In addition, the temperature characteristic of the RSSI output voltage can be modified by changing the temperature

characteristic of the external resistor. Normally, the temperature characteristic of the RSSI output voltage is very stable

when using a carbon resistor or metal film resistor with a temperature characteristic of 0 to 200 ppm/ °C.

The RSSI output is trimmed individually for enhanced accuracy.

AM Demodulation by Using the RSSI Output:

Although the distortion of the RSSI output is high because it is a logarithmic detection of the IF input envelope, AM can

be demodulated simply by using the RSSI output. In this case, the input dynamic range that can demodulate AM is the

inside of the linear portion of the RSSI curve characteristic (see Figure 3B).

This method does not have a feedback loop to control the gain because an AGC amplifier is not necessary (unlike the

popularly used AM demodulation method). Therefore, it is a very useful for some applications because it does not have

the response time problem.

Figure 3A shows the AM demodulated waveform.

Page 14

January 2000 TOKO, Inc.

Share Link: