STM32L021D4 datasheet(81/114 Pages) STMICROELECTRONICS

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STM32L021x4

Electrical characteristics

Equation 1: RAIN max formula

The simplified formula above (Equation 1) is used to determine the maximum external

impedance allowed for an error below 1/4 of LSB. Here N = 12 (from 12-bit resolution).

CADC(3)

Internal sample and hold

capacitor

tCAL(3)

Calibration time

fADC = 16 MHz

5.2

µs

-83

1/fADC

WLATENCY

ADC_DR register write

latency

ADC clock = HSI16

1.5 ADC

cycles + 2

fPCLK cycles

1.5 ADC

cycles + 3

fPCLK cycles

ADC clock = PCLK/2

4.5

fPCLK

cycle

ADC clock = PCLK/4

8.5

fPCLK

cycle

tlatr(3)

Trigger conversion latency

fADC = fPCLK/2 = 16 MHz

0.266

µs

fADC = fPCLK/2

8.5

1/fPCLK

fADC = fPCLK/4 = 8 MHz

0.516

µs

fADC = fPCLK/4

16.5

1/fPCLK

fADC = fHSI16 = 16 MHz

0.252

0.260

µs

JitterADC

ADC jitter on trigger

conversion

fADC = fHSI16

-1

1/fHSI16

tS(3)

Sampling time

fADC = 16 MHz

0.093

10.03

µs

1.5

239.5

1/fADC

tSTAB(3)

Power-up time

µs

tConV(3)

Total conversion time

(including sampling time)

fADC = 16 MHz

0.875

10.81

µs

14 to 173 (tS for sampling +12.5 for

successive approximation)

1/fADC

1. VDDA minimum value can be decreased in specific temperature conditions. Refer to Table 54: RAIN max for fADC = 16

MHz.

2. A current consumption proportional to the APB clock frequency has to be added (see Table 31: Peripheral current

consumption in run or Sleep mode).

3. Guaranteed by design, not tested in production.

4. Standard channels have an extra protection resistance which depends on supply voltage. Refer to Table 54: RAIN max for

fADC = 16 MHz.

Table 53. ADC characteristics (continued)

Symbol

Parameter

Conditions

Min

Typ

Max

Unit

AIN

ADC

()

---------------------------------------------------------------- R

ADC

–

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