CXD2304 データシートの表示（PDF） - Sony Semiconductor

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CXD2304

8-bit 20 MSPS RGB 3-Channel D/A Converter

Sony Semiconductor 

CXD2304R

Notes on Operation

• How to select the output resistance

The CXD2304R is a D/A converter of the current output type. To obtain the output voltage connect the

resistance to the current output pins R0, G0 and B0. For specifications we have;

Output full scale voltage VFS=1.12 to 1.36 [V]

Output full scale current IFS=3.8 [mA] (typ.)

Calculate the output resistance value from the relation of VFS=IFS × ROUT. Also, 16 times resistance of the

output resistance ROUT is connected to reference current pin IREF. In some cases, however, this turns out to

be a value that does not actually exist. In such a case a value close to it can be used as a substitute.

Here please note that VFS becomes

VFS=VREF × 16ROUT/RIR.

VREF is the voltage set at the reference voltage pin VREF and ROUT is the resistance connected to the current

output pins RO, GO and BO while RIR is connected to IREF pin.

Increasing the resistance value can curb power consumption. On the other hand glitch energy and data

settling time will inversely increase. Set the most suitable value according to the desired application.

• Phase relation between data and clock

To obtain the expected performance as a D/A converter, it is necessary to set properly the phase relation

between data and clock applied from the exterior. Be sure to satisfy the provisions of the setup time (tS) and

hold time (tH) as stipulated in the Electrical Characteristics.

• Power supply and ground

To reduce noise effects separate analog and digital systems in the device periphery. For power supply pins,

both digital and analog, bypass respective grounds by using a ceramic capacitor of about 0.1 µF, as close as

possible to the pin.

• Latch up

Digital power supply and analog power supply have to be common at the PCB power supply source. This is

to prevent latch up due to voltage difference between AVDD and DVDD pins when power supply is turned ON.

• RO, GO and BO pins

The RO, GO and BO pins are the inverted current output pins described in the Pin Description. The sums

shown below become the constant value for any input data.

a) The sum of the currents output form RO and RO

b) The sum of the currents output form GO and GO

c) The sum of the currents output form BO and BO

However, the performances such as the linearity error of the inverted current output pin output current is not

guaranteed.

• Output full-scale voltage

For the applications using the RGB signal, the color balance may be broken up when the no-adjusted output

full-scale voltage is used.

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