TDA9207 datasheet(7/22 Pages) STMICROELECTRONICS

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TDA9207

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Figure 4. Waveforms (Drive adjustment)

4.10 Bandwidth Adjustment

A new feature: Bandwidth adjustment, has been

implemented on the TDA9207.

This function has several advantages:

– Depending on the external capacitive load and

on the peak-to-peak output voltage, the band-

width can be adjusted to avoid any slew-rate

phenomenon.

– The preamp bandwidth can be adjusted in order

to reduce electromagnetic radiation, since it is

possible to slow down the signal rise/fall time at

the CRT driver input without too much affecting

the rise/fall time at the CRT driver output.

– It is possible to optimize the ratio of the frequen-

cy response versus the CRT driver power con-

sumption for any kind of chassis, as the preamp

bandwidth adjustment also allows the adjust-

ment of the rise/fall time on the cathode (through

the CRT driver).

– In still picture mode, when a high Video swing

voltage is of greater interest than rise/fall time,

bandwidth adjustment is used to avoid any slew-

rate phenomenon at the CRT driver output and to

meet electromagnetic radiation requirements.

4.11 CRT Cathode Coupling

The powerfull multiplex capability of the TDA9207

allows to use the device with several kinds of CRT

cathode coupling.

4.11.1 AC coupling with DC restore ( Figure 5)

In this mode the output DC level (VDC) is adjusted

simultaneously for the 3 channels from 0.5 V to

2.35 V via Register 6 (4 bits). The cut-off voltage is

programmed independently for each channel from

0.17 V to 4.6 V using registers 10, 11, 12 (8 bits

each, see I2C Table 1).

HSYNC

BPCP

BLK

Video IN

BFLK

OSD IN

VCONT

Two examples of drive

adjustment (1)

VBLACK

VDC

VBRT

VOSD

VOUT1,VOUT2,VOUT3

Note :

1.Drive adjustment modifies the following voltages : VCONT,VBRT and VOSD.

Drive adjustment doesn’t modify the following voltages : VDC and VBLACK.

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