GM5115H データシートの表示（PDF） - Genesis Microchip

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GM5115H

OnPanel LCD Panel Controller

Genesis Microchip 

*** Genesis Microchip Confidential ***

gm5115/25 Preliminary Data Sheet

The gm5115 TCLK oscillator circuitry is a custom designed circuit to support the use of an

external oscillator or a crystal resonator to generate a reference frequency source for the gm5115

device.

4.1.1 Using the Internal Oscillator with External Crystal

The first option for providing a clock reference is to use the internal oscillator with an external

crystal. The oscillator circuit is designed to provide a very low jitter and very low harmonic clock

to the internal circuitry of the gm5115. An Automatic Gain Control (AGC) is used to insure

startup and operation over a wide range of conditions. The oscillator circuit also minimizes the

overdrive of the crystal, which reduces the aging of the crystal.

When the gm5115/25 is in reset, the state of the ROM_ADDR13 pin (pin number 10) is sampled.

If the pin is left unconnected (internal pull-down) then internal oscillator is enabled. In this mode

a crystal resonator is connected between TCLK (pin 152) and the XTAL (pin 151) with the

appropriately sized loading capacitors CL1 and CL2. The size of CL1 and CL2 are determined from

the crystal manufacturer’s specification and by compensating for the parasitic capacitance of the

gm5115/25 device and the printed circuit board traces. The loading capacitors are terminated to

the analog VDD power supply. This connection increases the power supply rejection ratio when

compared to terminating the loading capacitors to ground.

Vdda

CL1

152

TCLK

Vdda

CL2

151

XTAL

gm5115/25

Vdd

100 K

180 uA

OSC_OUT

TCLK Distribution

10

N/C

ROM_ADDR13

Internal Pull Down

Resistor

~ 60K

Reset State Logic

Internal Oscillator Enable

Figure 4.

Using the Internal Oscillator with External Crystal

June 2002

11

C5115-DAT-01H

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