BU1425AK View Datasheet(PDF) - ROHM Semiconductor

Part Name

Description

Manufacturer

BU1425AK

NTSC / PAL digital RGB encoder

ROHM Semiconductor 

Multimedia ICs

(5) Adjustment of the DAC output level

The voltage level of the DAC output is determined by the

DAC internal output current and the DAC output external

resistor. The output current per 1 DAC bit is determined

by the external resistor of the IR pin (pin 42), as shown

below.

I (1LSB) = VVREF/RIR ∗1 / 16 [A] ... (equation 6-1)

VVREF ... Voltage generated by the regulator circuit in

the BU1425AK [V]

RIR ... External resistor for the IR pin 1200[Ω]

Consequently, when VVREF = 1.3V and RIR = 1200Ω,

a current of 67.71µA per 1LSB is output. Because the

white level of Y is a digital value of 396 (decimal value),

Internal clock (BCLK)

0

1

2

HSY

BU1425AK / BU1425AKV

the following results:

V (Y white) = 0.0677 × 396 = 26.81mA

At this point, if the DAC output external resistance is

37.5Ω, an amplitude of 1.005VP-P is obtained.

(6) YUV input mode

With the BU1425AK, setting the IM0 pin (pin 23) to

HIGH enables a 16-bit YUV input format to be support-

ed. At that time, the timing of U and V can be reversed

when data is input, using the H / L state of the Test2

pin.

The input conditions for this mode are shown below.

2n 2n + 1

Y-Data

U.V-Data

Internal clock (BCLK)

HSY

Y1 Y2 Y3 Y4 Y5

U1 V1 U3 V3 U5

Fig. 25 YUV input timing when TEST[2] = L

0

1

2

2n 2n + 1

Y-Data

U.V-Data

Y1 Y2 Y3 Y4 Y5

U1 V1 U3 V3 U5

Fig. 26 YUV input timing when TEST[2] = H

31

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