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SI-7230 数据表(PDF) 3 Page - Sanken electric |
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SI-7230 数据表(HTML) 3 Page - Sanken electric |
3 / 5 page 52 SI-7230M Application Note s Determining the output current IO (motor coil current) The output current, IO is fixed by the following elements: RS : Current detection resistor VCC2 : Supply voltage RX : Variable current resistor To operate a motor at maximum current level, set RX to infinity (open). To compute IO when different values are used for RS and VCC2, use the approximation formula below. The maximum ripple value IOH of the output current waveform can be computed as follows: 1 IOH(max) = (0.233•VCC2–0.026) [A] RS 1 IOH(min) = (0.214•VCC2–0.021) [A] RS The graph of the equations above is shown below. s Power down mode SI-7230M can be operated in power down mode. The circuit is shown below. When transistor Tr is switched on, the reference voltage drops and the output current can be de- creased. s Surge absorption capacitor CA and CB and capacitance The upper diagram shown on the next page is the flow of the counter EMF produced by the motor coils when it charges CA and CB and the lower diagram shows the direction of the energy discharged by CA and CB. When phase A shown in the figure is off, the counter EMF (energy built-up by the coil inductance) produced by the motor coils passes through the path shown by the dotted lines and charges CA and CB. When phase A is on, the energy stored by the capacitors are discharged in the direction shown by the dotted lines in the lower left diagram on the next page. The capacitors are discharged until the voltage across their pins equal the supply voltage VCC. The peak voltage VSP across the ca- pacitors is given by the equation: L VSP =•IO + VCC C where, L : Motor coil inductance between pins 4 and 5 or pins 18 and 17 C : Capacitance of CA and CB IO : Output current An example waveform of VSP is shown in the middle figure on the next page. A VSP that can be obtained when high voltage is applied can also be produced by using the counter EMF when the coil current rises. Notes in selecting CA and CB. (1) VSP must not exceed the breakdown voltage of the hybrid IC (70V). (2) CA and CB are charged/discharged in the same rate as the phase is switched. Hence, a capacitor with excel- lent anti-ripple characteristics should be selected. Waveform of the output current IOH SI-7230M Output current IOH vs. Current detection resistor Rs 3 2 1 0 Current detection resistor Rs ( Ω) 02 13 4 IOH(max) = (0.233VCC2 – 0.026) IOH(min) = (0.214VCC2 – 0.021) 1 RS 1 RS SI-7230M Output current IOH vs. Variable current resistor Rx 3 2 1 0 Variable current resistor Rx (k Ω) 02 13 4 RS = 0.3 Ω RS = 0.6 Ω IOH(max) = VCC2 – 0.026 IOH(min) = VCC2 – 0.021 1 RS 1 RS 4.9 RX 4.843 + 1.131 5.165 + 1.107 51 RX RX Tr 9 11 13 SI-7230M |
类似零件编号 - SI-7230 |
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类似说明 - SI-7230 |
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