TDA9881TS/V2-T NXP Semiconductors, TDA9881TS/V2-T Datasheet - Page 8

• Manufacturer Part Number: TDA9881TS/V2-T
• Description: Modulator / Demodulator IF DEMODULATOR
• Manufacturer: NXP Semiconductors

Specifications of TDA9881TS/V2-T

• Package / Case: SSOP-24
• Maximum Operating Temperature: + 70 C
• Maximum Power Dissipation: 385 mW
• Minimum Operating Temperature: - 20 C
• Modulation Type: Quadrature
• Mounting Style: SMD/SMT
• Operating Supply Voltage: 5 V
• Supply Current: 63 mA
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: TDA9881TS/V2,518

Philips Semiconductors
9397 750 13417
Product data sheet
8.4 FPLL detector
8.5 VCO and divider
8.6 AFC and digital acquisition help circuit
The VIF amplifier output signal is fed to a frequency detector and a phase detector via a
limiting amplifier to remove the video AM.
During acquisition the frequency detector produces a current that is proportional to the
frequency difference between the VIF and the VCO signal. After frequency lock-in the
phase detector produces a current that is proportional to the phase difference between
the VIF and the VCO signal. The currents from the frequency and phase detector are
charged into the loop filter which controls the VIF VCO and locks it to the frequency and
phase of the VIF carrier.
The VCO of the VIF FPLL operates as an integrated low radiation relaxation oscillator at
twice the picture carrier frequency. The control voltage, required to tune the VCO to
actually double the picture carrier frequency, is generated at the loop filter by the
frequency phase detector. The possible frequency range is 50 MHz to 140 MHz (typical
value).
The oscillator frequency is divided-by-two to provide two differential square wave signals
with exactly 90 degrees phase difference, independent of the frequency, for use in the
FPLL detectors, the video demodulator and the single reference QSS or intercarrier mixer.
Each relaxation oscillator of the VIF PLL and FM PLL demodulator has a wide frequency
range. To prevent false locking of the PLLs, with respect to the catching range, the digital
acquisition help circuit provides an individual control until the frequency of the VCO is
within the preselected standard dependent lock-in window of the PLL.
The VIF carrier frequencies 38.0 MHz, 38.9 MHz (M/N, B/G, I and D/K standard) and
45.75 MHz, 58.75 MHz (NTSC standard) can be selected via pin VIF0 and pin QSSO with
resistor; see
The FM carrier frequencies can be selected via pin FM0 and pin FM1; see
The in-window and out-window control at the FM PLL can additionally be used to mute the
audio stage (if auto mute is selected via pin AMUTE0); see
The principle working of the digital acquisition help circuit is as follows: The PLL VCO
output is connected to a downcounter which has a predefined start value (standard
dependent). The VCO frequency clocks the downcounter for a fixed gate time. Thereafter,
the downcounter stop value is analyzed. In the event that the stop value is higher (lower)
than the expected value range, the VCO frequency will be lower (higher) than the required
lock-in window frequency range. A positive (negative) control current is injected into the
PLL loop filter which causes the VCO frequency to be increased (decreased) and a new
counting cycle starts.
The gate time as well as the control logic of the acquisition help circuit is dependent on the
precision of the reference signal at pin REF. Operation as a crystal oscillator is possible as
well as connecting this input via a serial capacitor to an external reference frequency e.g.
the tuning system oscillator.
Table
4.
Rev. 01 — 16 November 2004
Alignment-free vision and FM sound IF PLL demodulator
© Koninklijke Philips Electronics N.V. 2004. All rights reserved.
Table
6.
TDA9881
Table
5.
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