Motor driving circuit substrate, motor, and pump device

A motor drive circuit substrate, including:

• a motor drive circuit disposed in a multilayer substrate, the motor drive circuit comprising:
• a power-related circuit, including a switching element that outputs a drive current;
• and
• a signal-related circuit, including a control element that supplies a signal to the switching element,
• wherein
• in the multilayer substrate, a common ground pattern is provided by integrating a ground pattern for the power-related circuit and a ground pattern for the signal-related circuit,
• the multilayer substrate includes four layers stacked in an order of a first layer, a second layer, a third layer, and a fourth layer,
• the common ground pattern includes a second conductive layer provided in the second layer, a third conductive layer provided in the third layer, and a fourth conductive layer provided in the fourth layer,
• the first layer includes at least the control element mounted therein,
• the second layer includes the second conductive layer formed over a substrate entire region,
• the third layer includes a third layer circuit including the power-related circuit formed therein and the third conductive layer formed therein to surround an outer periphery of the third layer circuit by an entire periphery of the third conductive layer,
• the fourth layer includes a fourth layer circuit including the power-related circuit formed therein and the fourth conductive layer formed therein to surround an outer periphery of the fourth layer circuit by an entire periphery of the fourth conductive layer,
• the third conductive layer includes a noise guard portion extending along an outer periphery of the power-related circuit, and
• the noise guard portion is connected to the second conductive layer and the fourth conductive layer by a plurality of through holes arranged to surround the power-related circuit.