Datasheet

DocID17050 Rev 9 71/175
STM32F21xxx Electrical characteristics
174
Figure 19. Number of wait states versus f
CPU
and V
DD
range
6.3.2 VCAP1/VCAP2 external capacitor
Stabilization for the main regulator is achieved by connecting an external capacitor to the
VCAP1/VCAP2 pins. C
EXT
is specified in Table 15.
Figure 20. External capacitor C
EXT
1. Legend: ESR is the equivalent series resistance.
ai18748b
0
1
2
3
4
5
6
7
8
0 4 8
12 16 20 24 28 32 36 40 44 48 52 56 60 64 68 72 76 80 84 88 92 96
100 104 108 112 116 120
Number of Wait states
Fcpu (MHz)
Wait states vs Fcpu and VDD range
1.8 to 2.1V
2.1 to 2.4V
2.4 to 2.7V
2.7 to 3.6V
Table 15. VCAP1/VCAP2 operating conditions
(1)
1. When bypassing the voltage regulator, the two 2.2 µF V
CAP
capacitors are not required and should be
replaced by two 100 nF decoupling capacitors.
Symbol Parameter Conditions
CEXT Capacitance of external capacitor 2.2 µF
ESR ESR of external capacitor < 2 Ω
MS19044V2
ESR
R
Leak
C