There is a problem.
To make the input signal 1 Vp-p in the external video signal mode, the level of the internal video signal (character signal) must be adjusted accordingly. Perform the following setting.
|1. Internal video signal amplitude control bit||VPD = 0|
|2. Voltage applied to Vcnt pin||2.5 V|
Item 1 above can be changed by a command, but item 2 requires modification of the hardware.
The voltage of the pin cannot be changed by a command.
|- Forcibly apply 2.5 V to the VCNT pin from an external source.|
|- Insert a resistor between Vcnt and VDD (+5 V) |
to adjust the voltage applied to Vcnt to 2.5 V.
The level of VBSO pin is determined by a voltage-dividing resistor connected between the Vcnt pin and VDD (+5V).
The above two methods may be used to adjust the voltage applied to the Vcnt pin to 2.5 V.
OSD LSIs User's Manual Figure 2-9 in "2.2.3 Video signal output section"
|CMOS Operational Amplifiers|
|Bipolar Operational Amplifiers|