AN3370K

ICs for VCR AN3370K Flying-Erase IC s Overview The AN3370K can amplify high-frequency current generated by the built-in oscillator and drive the Flying-erase head. This IC also allows to set an oscillation frequency and an output current optionally with external constants according to the erase head. 10 0.5 1.1 Unit : mm 18.24±0.3 s Features 0.25 – 0.05 + 0.1 tion frequency with external constants. 3.5±0.25 (12.0) 10-Pin Shrunk SIL Plastic Package (10-SSIP) s Block Diagram Output Driver OSC 1 2 3 4 5 6 7 8 9 10 VCC GND 1.1±0.25 3.0±0.3 6.0±0.3 1.65±0.25 • Built-in high-accuracy, stable oscillator. • Capable of varying output current value and an oscilla- 1 1.778 AN3370K s Absolute Maximum Ratings (Ta=25˚C) Parameter Supply voltage Power dissipation Operating ambient temperature Storage temperature Symbol VCC PD Topr Tstg Rating 12.6 500 – 20 to + 70 – 55 to +150 ICs for VCR Unit V mW ˚C ˚C s Recommended Operating Range (Ta = 25˚C) Parameter Operating supply voltage range Symbol VCC Range 10.5V to 12.5V s Electrical Characteristics (VCC=12V, Ta=25˚C) Parameter Supply current Oscillation output amplitude Oscillation frequency Oscillation output amplitude Flying ON Flying OFF Symbol ICC VO1 fO VO2 V1H V1L V1= 5V V1= 5V, RL= 300Ω V1= 5V, RL= 300Ω V1= 0V, RL= 300Ω 3.5 0.8 Condition min 20 8 11 typ 28 9 11.55 12.1 10 max 36 Unit mA VPP MHz mVPP V V s Application Circuit Output Driver OSC 1 2 3 0.01 µF 0.01µF 4 1.8kΩ 5 6 7 8 9 10 56pF 5.1kΩ 33pF 0.01µF 68pF 68pF 100µF 4.7µH 4µH Flying Control Voltage VCC=12V Note) Do not apply a voltage (0V included) to the Pin2 from the external. ICs for VCR s Pin Descriptions Pin No. Pin name Typ. waveform Description I/O impedance AN3370K Equivalent circuit 1 1 Flying erase control pin Flying erase ON/OFF control pin. ON when 3.5V or more is applied, and OFF when 0.8V or less is applied. 3MΩ 30kΩ 30kΩ 2 30kΩ 30kΩ 2 Do not apply a voltage from the external. 60kΩ 5 3 Feedback pin Feedback pin to obtain a DC voltage by filtering an output signal via an external capacitor 10kΩ 3 4 Power supply Power supply pin. Apply 12V typically from the external. 5 Output pin 6V High-frequency current 10kΩ 5 10kΩ 3 6 GND 7 Oscillation input pin It is possible to change the current which can be taken out of an output, by varying the resistor between this pin and GND. NPN Tr emitter 2V 7 8 Reference voltage pin Generates a reference voltage of 1/2 VCC (approx. 6V) NPN Tr emitter 6V 8 9 Oscillation feedback pin 3.4V A signal from Pin10 oscillation output is divided by the capacitor and is fed back. 3kΩ 3kΩ 9 10 Oscillation output pin 6V Oscillates at the frequency determined by L, C of the Pins8, 9, 10 6.2kΩ 6.2kΩ 10 8 AN3370K s Supplementary Explanation ICs for VCR AN3370K 1 2 3 0.01µF 0.01µF 4 100µF 5 6 7 8 CX1 RX LX Flying Erase H VH= 5V 4.7µH C2 VCC=12V Erase Head L C1 0.01µF 9 CX2 10 1) Internal Oscillation Frequency An internal oscillation frequency is determined by the following expression. Set CX1, CX2, and LX according to a frequency. 1 fOSC = · · · · · · · · · · · · · · · · · (1) C ·C Lx· CX1+ CX2 2π X1 X2 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 1 · · · · · · · · · (2) • Serial resonance f1 = 2π L (C1 + C2) frequency 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 L f2 = C ·C L C2 + 5 1 2π 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 I5–RX VCC =12V LX = 5.6µH CX1 = CX2= 68pF fosc=10.8MHz I5 80 I5 (mAPP) 60 5 0.047µF 7 50Ω RX 40 20 0 0 5 10 15 20 25 RX (kΩ)