My background is in ME but in my job as a test engineer has increasingly required me to develop some EE skills as well (which I'm actually pretty happy about). As such, I'm a relative noob but hopefully not totally clueless. I've been designing a circuit to drive 8 solenoids on a 4-cylinder automotive engine. These solenoids cause the camshafts to switch between high and low lift profiles. There are 4 solenoids on the intake side and 4 on the exhaust side. I've selected a TI DRV103H to drive each of the solenoids (they draw about 1.5 A each). Using their 'basic connections' circuit works fine on the bench for driving one of the solenoids. An image of the circuit for each solenoid is shown below:
In the above circuit VS=13.8V, Intake2_In=13.8V (I've included a divider to lower it to 5V at pin 8), and C4 is a tantalum bypass capacitor, which they recommend using. I've chosen to use the higher (22 uF) value capacitor to make it handle up to 3A if necessary. I'm designing a PCB to drive all 8 of the solenoids in sequence. There will be 8 sets of the above circuit on the board, along with connectors for power, signal inputs, and driver outputs. My intent is to use the middle two layers of the board for power (VS) and ground planes. There will most likely be overlap between the solenoid events such that more than one solenoid can/will be active at a given time. My question is around the tantalum capacitor, which is effectively connected between VS and GND in each circuit. When one or more solenoids fire, they're going to see all 8 of those capacitors connected in parallel. Will that be an issue in this circuit? Should I select a different value for each capacitor, or use a different number of them, or will it be fine the way it is? I'm close to completing the design and would appreciate any advice on this. Let me know if you require any additional information.
In the above circuit VS=13.8V, Intake2_In=13.8V (I've included a divider to lower it to 5V at pin 8), and C4 is a tantalum bypass capacitor, which they recommend using. I've chosen to use the higher (22 uF) value capacitor to make it handle up to 3A if necessary. I'm designing a PCB to drive all 8 of the solenoids in sequence. There will be 8 sets of the above circuit on the board, along with connectors for power, signal inputs, and driver outputs. My intent is to use the middle two layers of the board for power (VS) and ground planes. There will most likely be overlap between the solenoid events such that more than one solenoid can/will be active at a given time. My question is around the tantalum capacitor, which is effectively connected between VS and GND in each circuit. When one or more solenoids fire, they're going to see all 8 of those capacitors connected in parallel. Will that be an issue in this circuit? Should I select a different value for each capacitor, or use a different number of them, or will it be fine the way it is? I'm close to completing the design and would appreciate any advice on this. Let me know if you require any additional information.