AN3370K Datasheet, PDF (4/4 Pages) Panasonic Semiconductor – Flying-Erase IC

AN3370K
s Supplementary Explanation
ICs for VCR
AN3370K
1
2
3
4
5
6
7
0.01µF
0.01µF
100µF
RX
Flying Erase H
VH= 5V
C1
4.7µH
8
9
10
CX1
CX2
LX
0.01µF
C2
VCC=12V
Erase Head L
1) Internal Oscillation Frequency
An internal oscillation frequency is determined by the fol-
lowing expression. Set CX1, CX2, and LX according to a fre-
quency.
fOSC =
2π
1
Lx·
CX1 ·
CX1+
CX2
CX2
· · · · · · · · · · · · · · · · · (1)
In order to obtain stable oscillation, set CX1/CX2 near 1 and
absolute value of CX1, CX2 to such a considerable extent that
an internal IC capacitance (approx. 5pF) and an external
PCB capacitance can be ignored.
2) RX
Output current amplitude from the IC is determined by the
external resistor RX of the Pin7 ; it is approximately as
shown in Fig. 1. Therefore, use within the following range.
I5=20mApp to 65mApp.
3) Do not apply the Pin1 voltage when VCC is off.
Use the Pin2 voltage open.
4) Output Dynamic Range
Since the output pin (5) dynamic range of the AN3370K is
8VPP (at VCC=12V), set a combination of C1, C2, and erase head
inductance (L) so that the following will be ensured.
I5 (mApp) × load impedance < 8VPP.
5) Serial and Parallel Resonance Points
• Serial resonance
frequency
f1 = _2π
1
· · · · · · · · · (2)
L (C1 + C2)
Since Pin5 amplitude is minimized at a point of f1, set f1
so that it will almost coincide with fOSC.
• Parallel resonance frequency
Suppose the internal capacitance of the Pin5 is
C5, then parallel resonance frequency is
f2 =
2π
L
L
C2
+
C5 · C1
C5 + C1
· · · (3)
Although an erase head current is maximized at this point,
set f2/fOSC =.. 1.25 to 1.4
• Characteristic Curve
Fig. 1.
100
80
60
40
I5–RX
VCC =12V
LX = 5.6µH
CX1 = CX2= 68pF
fosc=10.8MHz
I5
5
0.047µF
7
50Ω RX
20
0
0
5
10
15
20
25
RX (kΩ)