ST72521M7 View Datasheet(PDF) - STMicroelectronics

Part Name

Description

Manufacturer

ST72521M7

8-BIT MCU WITH NESTED INTERRUPTS, FLASH, 10-BIT ADC, FIVE TIMERS, SPI, SCI, I2C, CAN INTERFACE

STMicroelectronics 

ST72521M/R/AR

CLOCK CHARACTERISTICS (Cont’d)

12.5.4 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 (RCINT)

fOSC(RCEXT)

REX

CEX

|iCEX|

Parameter

Internal RC oscillator frequency

See Figure 86 and Figure 87

External RC oscillator frequency 1)

Oscillator external resistor 2)

Oscillator external capacitor

Capacitor load current 3)

Conditions

TA=25°C, VDD=5V

OSC1 = VSS or 1.5V

Min

Typ

Max

2

3.5

5.6

5 / (REX.CEX)

56

100

22

470

290

350

Unit

MHz

KΩ

pF

µA

Figure 85. Typical Application with RC oscillator

ST72XXX

INTERNAL RC

VDD

Current copy

EXTERNAL RC

REX

OSC1

CIN

RIN

VREF +

-

fOSC

CEX

OSC2 iCEX

Voltage generator

CEX discharge

Notes:

1. Data based on design simulation.

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

3. iCEX is the current needed to load the CEX capacitor while OSC1 is forced to VSS or 1.5V (RC oscillation voltage range).

Figure 86. Typical fOSC(RCINT) vs VDD

4.5

4

3.5

3

2.5

2

TA=-45C

1.5

TA=25C

1

TA=130C

0.5

0

2.35

5

5.5

VDD(V)

Figure 87. Typical fOSC(RCINT) vs TA

4

3.9

3.8

3.7

3.6

3.5

3.4

3.3

3.2

3.1

3

-45

Vdd = 2.4V

Vdd = 5V

0

25

70

130

TA(°C)

167/199

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