Information

Electrical characteristics STM32F105xx, STM32F107xx
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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 Table 36).
Unless otherwise specified, the parameters given in Table 39 are derived from tests
performed under the ambient temperature and V
DD
supply voltage conditions summarized
in Table 9.
ai14131
t
r(IO)out
50%
90%
T
t
f(IO)out
Maximum frequency is achieved if (t + t ) < (2/3)T and if the duty cycle is (45-55%)
when loaded by 50 pF
r
f
EXTERNAL
OUTPUT
ON 50 pF
10%
50%
90%
10%
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