ST7SCR datasheet(83/101 Pages) STMICROELECTRONICS

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ST7SCR

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CLOCK AND TIMING CHARACTERISTICS (Cont’d)

14.4.3 Crystal Resonator Oscillators

The ST7 internal clock is supplied with one Crystal

resonator oscillator. All the information given in

this paragraph are based on characterization re-

sults with specified typical external componants. In

the application, the resonator and the load capaci-

tors have to be placed as close as possible to the

oscillator pins in order to minimize output distortion

and start-up stabilization time. Refer to the crystal

resonator manufacturer for more details (frequen-

cy, package, accuracy...).

Figure 41. Typical Application with a Crystal Resonator

Notes:

1. Resonator characteristics given by the crystal resonator manufacturer.

2. tSU(OSC) is the typical oscillator start-up time measured between VDD=2.8V and the fetch of the first instruction (with a

quick VDD ramp-up from 0 to 5V (<50µs).

3. The oscillator selection can be optimized in terms of supply current using an high quality resonator with small RS value.

Refer to crystal resonator manufacturer for more details.

Symbol

Parameter

Conditions

Min

Typ

Max

Unit

fOSC

Oscillator Frequency 3)

MP: Medium power oscillator

MHz

Feedback resistor

150

Ω

CL1

CL2

Recommanded load capaci-

tances versus equivalent se-

rial resistance of the crystal

resonator (RS)

See Table 5, “Recom-

mended Values for 4

MHz Crystal Resona-

tor,” on page 21

(MP oscillator)

OSCOUT driving current

VDD=5V

VIN=VSS

(MP oscillator)

1.5

3.5

Oscil.

Typical Crystal Resonator

CL1

[pF]

CL2

[pF]

tSU(osc)

[ms] 2)

Reference

Freq.

Characteristic 1)

MP JAUCH

SS3-400-30-30/30 4MHz

∆f

OSC=[±30ppm25°C,±30ppm

∆Ta], Typ. RS=60Ω

7~10

OSCOUT

OSCIN

fOSC

CL1

CL2

ST7XXX

RESONATOR

WHEN RESONATOR WITH

INTEGRATED CAPACITORS

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