VIPer20/SP/DIP - VIPer20A/ASP/ADIP
Figure 9: Oscillator
For Rt >1.2KΩ
and
Ct ≥ 15nF if FSW ≤ 40KHz
VDD
Rt
OSC
2.3
550
R – 150
-----------
---------------------
1 –
F
=
CLK
SW
R C
t
t
t
Ct
FC00050
C
t
Forbidden area
880
Ct(nF) =
Fsw(kHz)
22nF
15nF
Forbidden area
40kHz
Fsw
Oscillator frequency vs Rt and Ct
FC00030
1,000
500
Ct = 1.5 nF
Ct = 2.7 nF
Ct = 4.7 nF
300
200
Ct = 10 nF
100
50
30
1
2
3
5
10
20
30
50
Ω
Rt (k )
8/25
1