KTS6027-2 datasheet(16/41 Pages) INFINEON

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Functional Description

3 - 16

KTS6027-2, KTS6029-2

Wireless Components

Specification, July 2001

3.4

Circuit Description

3.4.1

General

In the normal mode (see Table 5-7 Test modes on page 32) the IC is compatible with

KTS6027-S / KTS6029-S. An extended mode makes a reference divider ratio

of 24 (see Table 5-8 Reference divider ratio on page 32) and two additional charge pump

currents (see Table 5-9 Charge pump current on page 33) available.

3.4.2

Mixer-Oscillator block

The mixer oscillator section includes two balanced mixers (double balanced

mixer), two balanced oscillators for LOW and / or MID band and HIGH band, an

IF amplifier, a reference voltage source and a band switch.

Filters between tuner input and IC separate the TV frequency signals into two

bands. The band switching in the tuner front-end is done by using two or three

port outputs. In the selected band the signal passes a tuner input stage with

MOSFET amplifier, a double-tuned bandpass filter and is then fed to the bal-

anced mixer input of the IC which has in case of LOW / MID a high-impedance

input and in case of HIGH a low-impedance input. The input signal is mixed

there with the signal from the activated on chip oscillator to the IF frequency

which is filtered out at the balanced high-impedance output pair by means of a

parallel tuned circuit. The following SAW preamplifier has a low output imped-

ance to drive the SAW filter directly.

3.4.3

PLL block

The oscillator signal is internally DC-coupled as a differential signal to the pro-

grammable divider inputs. The signal subsequently passes through a program-

mable divider with ratio N = 256 through 32767 and is then compared in a digital

frequency / phase detector to a reference frequency fref = 31.25, 50, 62.5 or

166.7 kHz.

This frequency is derived from an unbalanced, low-impedance 4 MHz crystal

oscillator (pin XTAL) divided by R = 128, 80, 64 or 24.

The phase detector has two outputs that drive two current sources of opposite

polarity as charge pump. If the negative edge of the divided VCO signal appears

prior to the negative edge of the reference signal, the positive current source

pulses for the duration of the phase difference. In the reverse case the negative

current source pulses. If the two signals are in phase, the charge pump output

(CP) goes into the high-impedance state (PLL is locked). An active low-pass fil-

ter integrates the current pulses to generate the tuning voltage for the VCO

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