ICs for VCR AN3370K Flying-Erase IC ■ Overview Unit : mm 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. 1.778 18.24±0.3 0.5 1.1 10 ■ Features • Built-in high-accuracy, stable oscillator. • Capable of varying output current value and an oscilla- 3.0±0.3 1.65±0.25 1.1±0.25 3.5±0.25 (12.0) + 0.1 tion frequency with external constants. 0.25 – 0.05 1 6.0±0.3 10-Pin Shrunk SIL Plastic Package (10-SSIP) ■ Block Diagram Output Driver 1 2 3 OSC 4 VCC 5 6 GND 7 8 9 10 ICs for VCR AN3370K ■ Absolute Maximum Ratings (Ta=25˚C) Symbol Rating Supply voltage Parameter VCC 12.6 Unit V Power dissipation PD 500 mW Operating ambient temperature Topr – 20 to + 70 ˚C Storage temperature Tstg – 55 to +150 ˚C ■ Recommended Operating Range (Ta = 25˚C) Parameter Operating supply voltage range Symbol Range VCC 10.5V to 12.5V ■ Electrical Characteristics (VCC=12V, Ta=25˚C) Parameter Symbol Condition min typ max Supply current ICC V1= 5V 20 28 Oscillation output amplitude VO1 V1= 5V, RL= 300Ω 8 9 fO V1= 5V, RL= 300Ω 11 11.55 Oscillation output amplitude VO2 V1= 0V, RL= 300Ω Flying ON V1H Flying OFF V1L Oscillation frequency mA 12.1 MHz 10 mVPP VPP V 0.8 ■ Application Circuit 3 4 0.01 µF 5 6 7 8 68pF 56pF 33pF 4.7µH 0.01µF 100µF 9 10 1.8kΩ 0.01µF 2 OSC 5.1kΩ 1 36 3.5 Output Driver Unit 68pF 4µH Flying Control Voltage VCC=12V Note) Do not apply a voltage (0V included) to the Pin2 from the external. V ICs for VCR AN3370K ■ Pin Descriptions Pin No. 1 Pin name Typ. waveform Flying erase control pin Description I/O impedance Flying erase ON/OFF control pin. ON when 3.5V or more is applied, and OFF when 0.8V or less is applied. 3MΩ Equivalent circuit 1 30kΩ 30kΩ 30kΩ 2 2 Do not apply a voltage from the external. 3 Feedback pin to obtain a DC voltage by filtering an output signal via an external capacitor 60kΩ 30kΩ 5 Feedback pin 10kΩ 3 Power supply pin. Apply 12V typically from the external. 4 Power supply 5 Output pin 6 GND 7 Oscillation input pin 8 Reference voltage pin 9 Oscillation feedback pin 3.4V 10 Oscillation output pin 6V 6V High-frequency current 10kΩ 5 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 Generates a reference voltage of 1/2 VCC (approx. 6V) NPN Tr emitter A signal from Pin10 oscillation output is divided by the capacitor and is fed back. 3kΩ Oscillates at the frequency determined by L, C of the Pins8, 9, 10 6.2kΩ 10kΩ 3 7 8 6V 3kΩ 9 6.2kΩ 8 10 ICs for VCR AN3370K ■ Supplementary Explanation AN3370K 1 2 3 4 0.01µF 0.01µF 5 6 7 8 9 CX1 100µF 10 CX2 RX LX Flying Erase H VH= 5V 0.01µF C1 4.7µH C2 VCC=12V Erase Head L 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 = CX1 · CX2 · · · · · · · · · · · · · · · · · (1) L x· 2π CX1+ CX2 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. I5–RX 100 VCC =12V LX = 5.6µH CX1 = CX2= 68pF fosc=10.8MHz 80 I5 (mAPP) I5 60 5 0.047µF 7 50Ω RX 40 20 0 0 5 10 15 RX (kΩ) 20 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, . 1.25 to 1.4 set f2/fOSC = . • Characteristic Curve Fig. 1. 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. 25