SSD1850 datasheet(22/56 Pages) ETC

22 / 56 page

SSD1850/51 Series

Rev 1.2

01/2003

SOLOMON

Oscillator Circuit

This module is an On-Chip low power RC oscillator circuitry (Figure 6). The oscillator generates the clock

for the DC-DC voltage converter. This clock is also used in the Display Timing Generator.

enable

Oscillation Circuit

enable

Buffer

Internal resistor

OSC2

OSC1

Oscillator

enable

(CL)

LCD Driving Voltage Generator and Regulator

This module generates the LCD voltage needed for display output. It takes a single supply input and

generates necessary bias voltages. It consists of:

1. 2X, 3X, 4X, 5X and 6X DC-DC voltage converter

*Note: SSD1850 works up to 5X only.

Please refer to application notes on P.42.

2. Voltage Regulator

Feedback gain control for initial LCD voltage. External resistors are connected between VSS and VR, and

between VR and VL6. These resistors are chosen to give the desired VL6 according to the following

equations:

con













ref

con

210













−

where Vref is the internally generated reference voltage with a known R1 and R2. Typical value for Vref

is 2.1V

R1 is the resistance of the resistor between VSS and VR.

R2 is the resistance of the resistors between VR and VL6.

α is the software contrast level from 0 to 63.

G = 1 if INTRS = VDD; REF = VDD

G = 0.80 if INTRS = VSS; REF = VDD

Internal pwell resistor

Figure 6. Oscillator Circuitry

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