STR750F datasheet(57/73 Pages) STMICROELECTRONICS

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STR750F

Electrical parameters

57/71

NRSTIN and NRSTOUT pins

NRSTIN Pin Input Driver is TTL/LVTTL as for all GP I/Os. A permanent pull-up is present

which is the same as RPU (see : General characteristics on page 53)

NRSTOUT Pin Output Driver is equivalent to the O2 type driver except that it works only as

an open-drain (the P-MOS is de-activated). A permanent pull-up is present which is the

same as RPU (see : General characteristics on page 53)

Subject to general operating conditions for VDD_IO and TA unless otherwise specified.

Table 34.

NRSTIN and NRSTOUT pins

Symbol

Parameter

Conditions

Min

Typ 1)

Max

Unit

VIL(NRSTIN)

NRSTIN Input low level

voltage(1)

Data based on product characterisation, not tested in production.

0.8

VIH(NRSTIN)

NRSTIN Input high level

voltage(1)

Vhys(NRSTIN)

NRSTIN Schmitt trigger

voltage hysteresis(2)

Hysteresis voltage between Schmitt trigger switching levels.

400

VOL(NRSTIN)

NRSTOUT Output low level

voltage(3)

The IIO current sunk must always respect the absolute maximum rating specified in Section 3.2.2 and the

sum of IIO (I/O ports and control pins) must not exceed IVSS.

IIO=+2 mA

0.4

RPU(NRSTIN)

NRSTIN Weak pull-up

equivalent resistor(4)

The RPU pull-up equivalent resistor are based on a resistive transistor

VIN=VSS

VDD_IO=3.3 V 25

100

Ω

VDD_IO=5 V

100

Ω

tw(RSTL)out

Generated reset pulse

duration (visible at NRSTOUT

pin)(5)

To guarantee the reset of the device, a minimum pulse of 15 µs has to be applied to the internal reset. At

VDD_IO power-up, the built-in reset stretcher may not generate the 15 µs pulse duration while once VDD_IO

is established, an external reset pulse will be internally stretched up to 15 µs thanks to the reset pulse

stretcher.

Internal reset source

µs

th(RSTL)in

External reset pulse hold time

at NRSTIN pin(6)

The reset network (the resistor and two capacitors) protects the device against parasitic resets, especially

in noisy environments.

At VDD_IO power-up

(5)

µs

When VDD_IO is

established(5)

µs

tg(RSTL)in

maximum negative spike

duration filtered at NRSTIN

pin(7)

In fact the filter is made to ignore all incoming pulses with short duration:

- all negative spikes with a duration less than 150 ns are filtered

- all trains of negative spikes with a ratio of 1/2 are filtered. This means that all spikes with a maximum

duration of 150 ns with minimum interval between spikes of 75 ns are filtered.

Data guaranteed by design, not tested in production.

The time between two

spikes must be higher

than 1/2 of the spike

duration.

150

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