S1D2512X01 Datasheet, PDF (34/36 Pages) Samsung semiconductor – DEFLECTION PROCESSOR FOR MULTISYNC MONITORS

S1D2512X01
DEFLECTION PROCESSOR FOR MULTISYNC MONITORS
DC/DC CONVERTER PART
This unit controls the switch-mode DC/DC converter. It converts a DC constant voltage into the B+ voltage(roughly
proportional to the horizontal frequency) necessary for the horizontal scanning. This DC/DC converter must be
configured in step-up mode. It operates very similarly to the well known UC3842.
Step-up Mode
Operating description
• The power MOS is switched-on at the middle of the horizontal Flyback.
• The power MOS is switched-off when its current reaches predetermined value. For this purpose, a sense
resistor is inserted in its source. The voltage on this resistor is sent to pin16 (ISENSE).
• The feedback (coming either from the EHV or from the Flyback) is divided to a voltage close to 4.8V and com-
pared to the internal 4.8V reference (IVREF). The difference is amplified by an error amplifier, the output of
which controls the power MOS switch-off current.
Main Features
• Switching synchronized on the horizontal frequency
• B+ voltage always higher than the DC source
• Current limited on a pulse-by-pulse basis
• The DC/DC converter is disabled:
- When V_CC or V_DD are too low,
- When X-Ray protection is latched,
- Directly through I²C bus.
• When disabled, BOUT is driven to GND by a 0.5mA current source. This feature allows to implement externally
a soft start circuit.
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