5 / 11 page
CY2037
Document Number: 38-07354 Rev. *E
Page 5 of 11
Crystal Oscillator Tuning Circuit
CY2037 contains a unique tuning circuit to fine-tune the output frequency of the device. The tuning circuit consists of an array of eleven
load capacitors on both sides of the oscillator drive inverter. The capacitor load values are EPROM-programmable and may be
increased in small increments. As the capacitor load is increased the circuit is fine-tuned to a lower frequency. The capacitor load
values vary from 0.17 pF to 8 pF for a 100:1 total control ratio. The tuning increments are shown in Table 3. Refer to “7C8038x/7C8034x
Programming Specification” for further details.
Figure 1. Crystal Oscillator Tuning Circuit
Table 3. Crystal Oscillator Parameter
Parameter
Description
Min
Typ.
Max
Unit
Rf
Feedback resistor, VDD = 4.5–5.5V
Feedback resistor, VDD = 2.7–3.6V
0.5
1.0
2
4
3.5
9.0
M
Ω
M
Ω
Capacitors have ± 20% tolerance
Cg
Gate capacitor
13
pF
Cd
Drain capacitor
9
pF
C0
Series cap
0.27
pF
C1
Series cap
0.52
pF
C2
Series cap
1.00
pF
C3
Series cap
0.7
pF
C4
Series cap
1.4
pF
C5
Series cap
2.6
pF
C6
Series cap
5.0
pF
C7
Series cap
0.45
pF
C8
Series cap
0.85
pF
C9
Series cap
1.7
pF
C10
Series cap
3.3
pF
CD = EPROM BIT
T = TRANSISTOR
C = LOAD CAPACITOR
CD6
C6
CD5
C5
CD4
C4
CD3
C3
CD2
C2
CD1
C1
CD0
C0
CD3
C7
CD4
C8
CD5
C9
CD6
C10
External Crystal
Cgo Cdo
Rf
[+] Feedback
English ▼
English
Chinese
German
Japanese
Russian
Korean
Spanish
French
Italian
Portuguese
Polish
Vietnamese
Indian
Mexican
British
New Zealand
