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STV9211

Functional description

2.12

Preamplifier bandwidth adjustment (4 bits)

An advanced feature: preamplifier bandwidth adjustment (BW: Register 13, see I2C table 5), is

implemented on the STV9211.

The programming of this BW register is very important to get good video performances.

It must not be set its maximum value. With the following values, the optimum performances are

obtained.

For applications where rise/fall time <5.5ns, this feature offers several advantages:

Slew-rate: depending on the external capacitive load and on the peak-to-peak output voltage,

this adjustment avoids getting any slew-rate phenomenon.

Electromagnetic radiation (EMI): slowing down the signal of rise/fall time will decrease the EMI

without significantly deteriorating the rise/fall time of the CRT driver.

Video signal response: using this adjustment will allow to optimize the high frequency transient

phenomenons.

Picture boost mode: when displaying still pictures or moving video, having high video swing

can be of greater interest than rise/fall time. The preamplifier bandwidth adjustment can be

used to avoid any slew-rate phenomenon at the CRT driver output.

2.13

Amplifier bandwidth adjustment (7 bits)

The STV9211 can adjust the bandwidth of any ST video amplifier having a dedicated control pin

(CTL). The adjustment is done by I2C via Register 6 (see I2C table 2).

If not used, the AMPCTL pin must be connected to ground.

tR/tF

Preamplifier bandwidth register: BW

Binary

Decimal

5.5 ± 1 ns

1000

7.5 ± 1ns

0101

9.5 ± 1ns

0010

10 ns and below

0000

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