STM32F050C4 datasheet(71/97 Pages) STMICROELECTRONICS

71 / 97 page

STM32F050xx

Electrical characteristics

Doc ID 023683 Rev 1

71/97

Figure 22.

I/O AC characteristics definition

6.3.14

NRST pin characteristics

The NRST pin input driver uses CMOS technology. It is connected to a permanent pull-up

resistor, RPU (see Table 45: I/O static characteristics).

Unless otherwise specified, the parameters given in Table 48 are derived from tests

performed under ambient temperature and VDD supply voltage conditions summarized in

Table 15: General operating conditions.

Figure 23.

Recommended NRST pin protection

The reset network protects the device against parasitic resets.

The user must ensure that the level on the NRST pin can go below the VIL(NRST) max level specified in

Table 48. Otherwise the reset will not be taken into account by the device.

ai14131

10%

90%

50%

tr(IO)out

OUTPUT

EXT ERNAL

ON 50pF

Maximum fr equency is achieved if (tr + tf) £ 2/3)T and if the duty cycle is (45-55%)

10%

50%

90%

when loaded by 50pF

tr(IO)out

Table 48.

NRST pin characteristics

Symbol

Parameter

Conditions

Min

Typ

Max

Unit

VIL(NRST)

(1)

Guaranteed by design, not tested in production.

NRST input low level voltage

–0.3

0.8

VIH(NRST)

(1)

NRST input high level voltage

VDD+0.3

Vhys(NRST)

NRST Schmitt trigger voltage

hysteresis

200

RPU

Weak pull-up equivalent resistor(2)

The pull-up is designed with a true resistance in series with a switchable PMOS. This PMOS contribution

to the series resistance must be minimum

(~10% order)

VIN = VSS

VF(NRST)

(1)

NRST input filtered pulse

100

VNF(NRST)

(1)

NRST input not filtered pulse

300

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