ST72F324J2TCRE View Datasheet(PDF) - STMicroelectronics

Part Name

Description

Manufacturer

ST72F324J2TCRE

8-bit MCU for automotive, 3.8 to 5.5V operating range with 8 to 32 Kbyte Flash, 10-bit ADC, 4 timers, SPI, SCI

STMicroelectronics 

Electrical characteristics

ST72324xx-Auto

1. Any added external serial resistor will downgrade the ADC accuracy (especially for resistance greater than 10kΩ). Data

based on characterization results, not tested in production.

2. For Flash devices: Injecting negative current on any of the analog input pins significantly reduces the accuracy of any

conversion being performed on any analog input. Analog pins of ST72F324 devices can be protected against negative

injection by adding a Schottky diode (pin to ground). Injecting negative current on digital input pins degrades ADC accuracy

especially if performed on a pin close to the analog input pins. Any positive injection current within the limits specified for

IINJ(PIN) and ΣIINJ(PIN) in Section 12.9 does not affect the ADC accuracy.

Figure 85. RAIN max. vs fADC with CAIN = 0pF(1) Figure 86. Recommended CAIN and RAIN

values(2)

45

40

) 35

t(s 30

25

20

c 15

u 10

d 5

ro 0

P 0

2 MHz

1 MHz

10

30

70

CPARASITIC (pF)

1000

100

10

1

0.1

0.01

Cain 10 nF

Cain 22 nF

Cain 47 nF

0.1

1

10

fAIN(KHz)

lete 1. CPARASITIC represents the capacitance of the PCB (dependent on soldering and PCB layout quality) plus the pad

o capacitance (3pF). A high CPARASITIC value will downgrade conversion accuracy. To remedy this, fADC should be reduced.

bs 2. This graph shows that, depending on the input signal variation (fAIN), CAIN can be increased for stabilization time and

decreased to allow the use of a larger serial resistor (RAIN).

- O Figure 87. Typical A/D converter application

Product(s) VAIN

RAIN

AINx

CAIN

VDD

VT

0.6V

VT

0.6V

ST72XXX

2kΩ (max)

Ilkg

10-bit A/D

conversion

CADC

12pF

Obsolete 12.13.1 Analog power supply and reference pins

Depending on the MCU pin count, the package may feature separate VAREF and VSSA

analog power supply pins. These pins supply power to the A/D converter cell and function

as the high and low reference voltages for the conversion. In some packages, VAREF and

VSSA pins are not available (refer to Section 2 on page 15). In this case the analog supply

and reference pads are internally bonded to the VDD and VSS pins.

Separation of the digital and analog power pins allow board designers to improve A/D

performance. Conversion accuracy can be impacted by voltage drops and noise in the event

of heavily loaded or badly decoupled power supply lines (see Section 12.13.2: General PCB

design guidelines).

172/193

Doc ID 13841 Rev 1

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