APM32F103TBU7-R datasheet(53/78 Pages) GEEHY

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P a g e 52

Symbol

Parameter

Condition

Minimum

value

Typical

value

Maximu

m value

Unit

Sampling time

fADC = 14MHz

0.107

17.1

μs

1.5

239.5

1/fADC

tCONV

Total conversion time (including

sampling time)

fADC = 14MHz

μs

14~252 (sampling tS + gradually

approaching 12.5

1/fADC

Guaranteed by comprehensive evaluation and not tested in production.

Cparasitic refers to the parasitic capacitance (about 7PF) on the PCB (related to the welding and

PCB layout quality) and the pad. Large Cparasitic value will reduce the conversion accuracy. The

solution is to reduce fADC.

Figure 19 Typical Application of ADC

RADC(1)

CADC(1)

VDD

IL±1μA

VAIN

RAIN(1)

0.6V

AINx

寄生电容

12bit

转换器

GND

The calculation formula for maximum value of external input impedance is as follows:

Formula 1: Maximum RAIN formula

RAIN<

-RADC

Where fADC=14MHZ, CADC=12PF (Table41), RADC=1kΩ (Table41); the relationship

between TS and RAIN under the condition of 0.25LSB sampling error accuracy is shown in the

following table:

Table42 Maximum RAIN at fADC=14MHz (1)

TS (cycle)

tS（

μs）

Maximum RAIN

(kΩ)

Converter

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