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BD64547MUV データシート(PDF) 27 Page - Rohm |
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BD64547MUV データシート(HTML) 27 Page - Rohm |
27 / 39 page TSZ02201-0P2P0C001400-1-2 16.Nov.2020 Rev.006 TSZ22111 • 15 • 001 27/36 BD64547MUV © 2015 ROHM Co., Ltd. All rights reserved. www.rohm.com Precautions of Board Layout Consider the following key points when designing board layout: 1 Key points and precautions concerning the H-Bridge 1.1 VBBA, VBBB / H-Bridge Power supply Pin Motor’s drive current is flowing in it, so the wire is thick and short and has low impedance. VBBx(Note 1) may have big fluctuations due to motor back EMF, PWM switching noise, etc., so you must arrange the bypass capacitor of about over 220 μF as close to the pin as possible and adjust VBBx is stable. Increase the capacitance if needed, especially when a large current is used or motors that have great back electromotive force are used. In addition, for the purpose of reducing the power supply’s impedance in wide frequency bandwidth, parallel connection of multi-layered ceramic capacitor of 0.01 µF to 0.1 μF etc. is recommended. Extreme care must be used to make sure that VBBx does not exceed the rating even for a moment. VBBA and VBBB are shorted inside IC, so be sure to short externally VBBA and VBBB when using. If used without shorting, malfunction or destruction may occur because of concentration of current routes etc. Moreover, in the power supply pin, there is a built-in clamp component for preventing of electrostatic destruction. If steep pulse or voltage of surge exceeding the maximum absolute rating is applied, this clamp component operates. As a result, there is danger of destruction, so make sure that the maximum absolute rating is not exceeded. It is effective to mount a Zener diode about the maximum absolute rating. Also, a diode for preventing electrostatic destruction is inserted between the VBBx pin and GND pin, as a result there is the danger of IC destruction if reverse voltage is applied between the VBBx pin and GND pin, so be careful. (Note 1) x = A, B 1.2 OUTAP, OUTAM, OUTBP, OUTBM / H-Bridge output Pin Motor’s drive current is flowing in it, so the wire is thick and short and has low impedance. It is also effective to add a Schottky diode if output has big positive or negative fluctuations when large current is used, etc., for example, if counter electromotive voltage, etc. is big. Moreover, in the output pin, there is a built-in clamp component for preventing electrostatic destruction. If a steep pulse or voltage surge exceeding the maximum absolute rating is applied, this clamp component operates, but there is still the danger of destruction, so make sure that the maximum absolute rating is not exceeded. 1.3 RNFA, RNFB / H-Bridge Connection Pin of resistor for detecting of output current Connect the resistor for current detection between this pin and GND. In view of the power consumption of the current-detecting resistor, determine the resistor that W = IOUT2 x R [W] does not exceed the power dissipation of the resistor. In addition, wire has low impedance and does not have impedance in common with other GND patterns because motor’s drive current flows in the pattern through the RNFx(Note 2) pin to current-detecting resistor to GND. Do not exceed the rating because there is the possibility of circuit malfunction, etc. if the RNFx voltage has exceeded the maximum rating (0.55 V). Moreover, be careful because if the RNFx pin is shorted to GND, large current flows without normal PWM constant current control, then there is the danger that OCP or TSD will operate. If the RNFx pin is open, there is the possibility of such malfunction as output current does not flow either, so do not leave it open. (Note 2) x = A, B 2 Key points and precautions concerning the switching regulator 2.1 VBBSW1, SWOUT1 / SWREG1 power supply pins, SWREG1 output SWOUT1 is a high-voltage line and a possible source of switching noise. For that reason, the thickest, shortest, lowest-impedance wire possible should be used in the pattern design. Meanwhile, to reduce the switching current noise, the following loop should be kept as short as possible: bypass capacitor → VBBSW1 → SWOUT1 → Schottky diode → GND. To lessen the impact of coupling capacitance noise, position the FB1 feedback resistor away from the SWOUT1 pattern and components. 2.2 VINSW2, SWOUT2 / SWREG2 power supply pins, SWREG2 output SWOUT2 is a high-voltage line and a possible source of switching noise. For that reason, the thickest, shortest, lowest-impedance wire possible should be used in the pattern design. Meanwhile, to reduce the switching current noise, the following loop should be kept as short as possible: bypass capacitor → VINSW2 → SWOUT2 → GND. To lessen the impact of coupling capacitance noise, position the FB2 feedback resistor away from the SWOUT2 pattern and components. 3 Other key points and precautions 3.1 GND, PGNDSW / Ground Pin In order to reduce noise caused by the switching current and to stabilize the internal reference voltage of the IC, keep the wiring impedance from this pin as low as possible. The design should enable the lowest electrical potential in any operating state. In addition, be sure this wiring does not share common impedance with other GND patterns. |
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同様の説明 - BD64547MUV |
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