TK14588V 데이터 시트보기 (PDF) - Toko America Inc

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TK14588V

FM IF IC

Toko America Inc  

TK14588

CIRCUIT DESCRIPTION (CONT.)

Comparator (cont.):

Figure 11 shows the internal equivalent circuit of the comparator output stage. Because the comparator output is an open

collector, it is suitable for many interface levels. This open collector output is connected with an electrostatic discharge

protection diode at the GND side only; it is not connected with it at the power supply side in consideration of operating the

voltage over the supply voltage of this IC.

When the collector pull-up resistor value is low, high operating currents result. To prevent interference to the other circuitry,

the emitter of the output transistor is brought out independently at Pin 8.

Pin 8 is not connected with the substrate and other GND internal to the IC. Therefore, when operating this comparator,

this terminal must be connected to GND.

When the comparator is operating at high speed, the etch pattern of Pins 7 and 8 (comparator output stage) should not

be run close to the etch pattern of Pin 1 (IF input). The switching waveform of the comparator output may have an effect

on the IF input and may add noise to the zero crossing of the demodulated waveform, resulting in cross over distortion.

VCC

VCC

COMPARATOR

OUTPUT STAGE

Power Save Function:

FIGURE 11 - COMPARATOR OUTPUT STAGE

Pin 5 is the control terminal for the battery save function. The ON/OFF operation of the whole IC can be switched by

controlling the DC voltage at this terminal. Figure 12 shows the internal equivalent circuit of Pin 5.

Because it switches the bias circuit of the whole IC using the transistor in standby mode, it reduces the supply current to

near zero. As the input terminal is connected with an electrostatic discharge protection diode at GND side only, it is possible

to control the voltage above the supply voltage. It is possible to go into standby mode by disconnecting Pin 5, but it is not

recommended because Pin 5 is a high impedance and may malfunction by an external disturbance.

When Pin 5 is disconnected, a suitable capacitor should be connected between Pin 5 and GND.

VCC

BIAS

50 K

Vs

Page 18

FIGURE 12

January 2000 TOKO, Inc.

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