R/C

TTL -> ECL

Translator

D reg.

DAC

Switch

Bandgap

Reference voltage

R

OUT

G

OUT

COM

B

OUT

R

AUX

G

AUX

B

AUX

CLK

R <0,7>

G <0,7>

B <0,7>

TTL -> ECL

Translator

D reg.

DAC

Switch

Clamp

Clamp

TTL -> ECL

Translator

D reg.

DAC

Switch

Clamp

STV8438CV

BLOCK DIAGRAM

CIRCUIT DESCRIPTION

The STV8438CV is designed with 3 identical D/A

converters.Each D/Aconverter is composed of two

4-bit DACs separated by a current divider. The

elementary DAC is composed of multiple identical

current switches supplied with the same current

allowing high speed conversion rate.

DIGITAL INPUT CHANNELS

The STV8438CV supports binary coding on the 3

R, G, B, input channels when R/C pin is high. When

R/C pin is low, a 2’s complement coding is applied

to the R and B channels this provides the capability

to use the STV8438CV with luminance and chromi-

nance coded signal ; the luminance signal (usually

called Y) being applied to the G channel, the

chrominance signals (called U, V) being applied

respectively to the R and B channels.

The input range on Y signal is 0/255 and the input

range on both U, V signals is -128/+127. For both

binary coding and 2’s complement coding the out-

put voltage is in the range of 1.685V for the lowest

code to 3.315V for the highest code.

ANALOG INPUT CHANNELS

The STV8438CV provides the capability to switch

the output voltage from signals coming from the

digital channels or from signals coming from auxil-

iary analog inputs. When COM signal is low, the

auxiliary analog signals are connected to the output

amplifier internally clamped to the 16th digital step.

When COM signal is high, the digital inputsafter D/A

conversion are connected to the output amplifier.

STV8438CV

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