ST72334J4B7(2003) View Datasheet(PDF) - STMicroelectronics

Part Name

Description

Manufacturer

ST72334J4B7
(Rev.:2003)

8-BIT MCU WITH SINGLE VOLTAGE FLASH MEMORY, ADC, 16-BIT TIMERS, SPI, SCI INTERFACES

STMicroelectronics 

ST72334J/N, ST72314J/N, ST72124J

CLOCK CHARACTERISTICS (Cont’d)

16.5.4 RC Oscillators

The ST7 internal clock can be supplied with an RC

oscillator. This oscillator can be used with internal

or external components (selectable by option

byte).

Symbol

fOSC

tSU(OSC)

REX

CEX

Parameter

Internal RC oscillator frequency 1)

External RC oscillator frequency 2)

Internal RC Oscillator Start-up Time 3)

External RC Oscillator Start-up Time 3)

Oscillator external resistor 4)

Oscillator external capacitor

Conditions

see Figure 71

REX=47KΩ, CEX=”0”pF

REX=47KΩ, CEX=100pF

REX=10KΩ, CEX=6.8pF

REX=10KΩ, CEX=470pF

see Figure 72

Min Typ Max Unit

3.60

5.10

MHz

1

14

2.0

1.0

6.5

ms

0.7

3.0

10

47

KΩ

0 5)

470 pF

Figure 70. Typical Application with RC oscillator

ST72XXX

INTERNAL RC

VDD

Current copy

EXTERNAL RC

REX

OSC1

CEX

OSC2

VREF +

-

Voltage generator

fOSC

CEX discharge

Figure 71. Typical Internal RC Oscillator

Figure 72. Typical External RC Oscillator

fosc [MHz]

4.3

4.2

4.1

4

-40°C

+25°C

+85°C

+125°C

fosc [MHz]

20

15

10

Rex=10KOhm

Rex=15KOhm

Rex=22KOhm

Rex=33KOhm

Rex=39KOhm

Rex=47KOhm

3.9

5

3.8

3.2

5.5

VDD [V]

0

0 6.8 22 47 100 270 470

Cex [pF]

Notes:

1. Data based on characterization results.

2. Guaranteed frequency range with the specified CEX and REX ranges taking into account the device process variation.

Data based on design simulation.

3. Data based on characterization results done with VDD nominal at 5V, not tested in production.

4. REX must have a positive temperature coefficient (ppm/°C), carbon resistors should therefore not be used.

5. Important: when no external CEX is applied, the capacitance to be considered is the global parasitic capacitance which

is subject to high variation (package, application...). In this case, the RC oscillator frequency tuning has to be done by

trying out several resistor values.

120/153

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