OM8373 datasheet(82/108 Pages) PHILIPS

82 / 108 page

2004 Jan 15

Philips Semiconductors

Tentative Device Speciﬁcation

TV signal processor-Teletext decoder with

embedded

µ-Controller

OM8373; OM8378

14. Measured at an input signal of 10 mVRMS. The S/N is the ratio of black-to-white amplitude to the black level noise

voltage (RMS value). B = 5 MHz. Weighted in accordance with CCIR 567.

15. The time-constant of the IF-AGC is internal and the speed of the AGC can be set via the bits AGC1 and AGC0 in

subaddress 28H. The AGC response time is also dependent on the acquisition time of the PLL demodulator. The

values given are valid for the ‘norm’ setting (AGC1-AGC0 = 0-1) and when the PLL is in lock.

16. The AFC control voltage is generated by the digital tuning system of the PLL demodulator. This system uses the

clock frequency of the

µ-Controller as a reference and is therefore very accurate. For this reason no maximum and

minimum values are given for the window sensitivity figures (parameters M.7.2 and M.7.3). The tuning information is

supplied to the tuning system via the AFA and AFB bits in output byte 02H. The AFC value is valid only when the

LOCK-bit is 1.

17. Calculation of the FM-PLL filter can be done approximately by use of the following equations:

BL−3dB = f0(1.55 − υ2)

These equations are only valid under the conditions that

υ ≤ 1 and CS >5CP.

Definitions:

K0 = VCO steepness in rad/V

KD = phase detector steepness µA/rad

R = loop filter resistor

CS = series capacitor

CP = parallel capacitor

f0 = natural frequency of PLL

BL−3dB = loop bandwidth for −3dB

υ = damping factor

Some examples for these values are given in table 146

18. f = 5.5 MHz; modulation frequency: 1 kHz,

∆f = ± 50 kHz.

19. f = 4.5/5.5 MHz; FM: 70 Hz,

± 50 kHz deviation; AM: 1.0 kHz, 30% modulation.

20. The amplitude of the output signal can be increased with 6 dB by means of the AGN bit in subaddress 29H.

21. The deemphasis pin can also be used as additional audio input. In that case the internal (demodulated FM signal)

must be switched off. This can be realised by means of the SM1/SM0 (sound mute) bits. The external signal must

be switched off when the internal signal is selected.

22. The signal-to-noise ratio is measured under the following conditions:

a) Input signal to the SNDIF pin (activated via SIF bit) with an amplitude of 100mVRMS,fMOD = 1 kHz and ∆f = 27 kHz

b) Output signal measured at the AUDEEM pin. The noise (RMS value) is measured according to the CCIR 468

definition.

23. Audio input signal 200 mVRMS. Measured with a bandwidth of 15 kHz and the audio attenuator at −6 dB.

24. Unweighted RMS value, audio input signal 500 mVRMS, audio attenuator at −6 dB.

25. Test conditions: Modulation frequency: 1 kHz,

∆f = 27 kHz, AGN = 0 and audio attenuator at -9 dB

-------

K0KD

--------------

2R K

0 KD CP

-----------------------------------

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