TDA4887PS datasheet(22/68 Pages) PHILIPS

22 / 68 page

2001 Oct 19

Philips Semiconductors

Product speciﬁcation

160 MHz bus-controlled monitor video

preampliﬁer

TDA4887PS

18. Gain control acts on video signals and inserted OSD video signals under I2C-bus control; subaddress 04H

(channel 1), 05H (channel 2) and 06H (channel 3; bit resolution 0.4% of gain range respectively).

19. Pedestal blanking produces an ultra black level during blanking and output clamping which is the most negative

signal at the signal output pins. The pedestal depth can be selected by bus control, subaddress 0BH. The reference

black level which should correspond to the ‘extended cut-off voltage’ at the cathodes is approximately

∆Vbl(n)(PED-VID)

higher (see Fig.5). The use of pedestal blanking with AC-coupled cathodes (control bit FPOL = 1) allows a very

simple black level restoration with a DC diode clamp instead of a complicated pulse restoration circuit.

20. The signal-to-noise ratio is calculated using the formula (range 1 to 120 MHz):

21. The following formula can be used to approximately determine the output rise/fall time for any input rise/fall time other

than 1 ns:

22. The relationship between pixel rate and signal bandwidth is f−3dB = 0.75 × fpixel, which is a compromise between

excellent and acceptable video performance. The calculation of the pixel-related rise and fall times can be done using

the formula

. Although this formula is valid for low-pass filters of first order only it is used

in most cases for simplified estimations. The pixel rate

is a good approximation for many filter types.

23. Rise and fall times depend on signal amplitude, temperature, external load, black level and supply voltage. The rise

time is affected if the top level of the signal pulse approaches the maximum output voltage level (high black level,

large signal amplitude or low supply voltage). The fall time depends on the black level (increase with decreasing

black level) and on large capacitive loads. Low-ohmic pull-down loads at the outputs helps towards smaller fall times.

Rise and fall times increase with increasing ambient (or crystal) temperature. At maximum operating temperature,

rise and fall times are approximately 0.4 ns longer than at Tamb =25 °C.

24. Transient crosstalk between any two output pins:

a) Input conditions: any channel (channel A) with nominal input signal and 1 ns rise time. The inputs of the other

two channels (channels B) are capacitively coupled to ground. Gain setting at maximum (FFH). Contrast setting

at maximum (FFH). No limiting/modulation of contrast (VLIM ≥ 4.8 V)

b) Output conditions: black level set to approximately 0.7 V for each channel at signal outputs. Output signals are

VA and VB respectively

c) Transient crosstalk suppression:

25. Crosstalk by frequency between any two output pins:

a) Input conditions: any channel (channel A) with 0.2 V (p-p) sinusoidal input signal, DC-coupled to approximately

4.3 V, no input clamping. The inputs of the other two channels (channels B) are capacitively coupled to ground.

Gain setting at maximum (FFH). Contrast setting at maximum (FFH). No limiting/modulation of contrast

(VLIM ≥ 4.8 V)

b) Output conditions: control bit FPOL = 1, subaddress 0AH set to 01H, no pedestal blanking, nominal brightness

setting. Output signals are VA and VB respectively

c) Crosstalk suppression:

----

peak-to-peak value of the maximum signal output voltage

RMS value of the noise output voltage

-------------------------------------------------------------------------------------------------------------------------------------------------------- dB

log

r/f, measured

r/f (22,19,16)

r/f, input

1 ns

[]

–

()

r/f

0.35

3dB

–

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

0.35

0.75

pixel

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

pixel

0.35

0.75

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

ct(tr)

------- dB

log

ct(f)

------- dB

log

TDA4887PS Datasheet(PDF) 22 Page - NXP Semiconductors

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