Datasheet

STM32F105xx, STM32F107xx Electrical characteristics
Doc ID 15274 Rev 6 61/104
Figure 22. I/O AC characteristics definition
5.3.14 NRST pin characteristics
The NRST pin input driver uses CMOS technology. It is connected to a permanent pull-up
resistor, R
PU
(see Ta ble 3 6 ).
Unless otherwise specified, the parameters given in Ta ble 3 9 are derived from tests
performed under the ambient temperature and V
DD
supply voltage conditions summarized
in Ta bl e 9 .
ai14131
10%
90%
50%
t
r(IO)out
OUTPUT
EXTERNAL
ON 50pF
Maximum frequency is achieved if (t
r
+ t
f
) ≤ 2/3)T and if the duty cycle is (45-55%)
10 %
50%
90%
when loaded by 50pF
T
t
r(IO)out
Table 39. NRST pin characteristics
Symbol Parameter Conditions Min Typ Max Unit
V
IL(NRST)
(1)
1. Guaranteed by design, not tested in production.
NRST Input low level voltage –0.5 0.8
V
V
IH(NRST)
(1)
NRST Input high level voltage 2 V
DD
+0.5
V
hys(NRST)
NRST Schmitt trigger voltage
hysteresis
200 mV
R
PU
Weak pull-up equivalent resistor
(2)
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).
V
IN
= V
SS
30 40 50 kΩ
V
F(NRST)
(1)
NRST Input filtered pulse 100 ns
V
NF(NRST)
(1)
NRST Input not filtered pulse V
DD
> 2.7 V 300 ns