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    Automotive reverse polarity

    Hi I have attached the circuit protection. The fuse is rated at 3.7A, MF-LSMF185/33X2 hold current of 1.85A, which drops to 0.85A at 85C. The TVS is bidirectional SMC3K24CAHM5/57 this has a working voltage of 24V, clamping at 38.9V. The diode is SBR2M60S1-F, has low VF. The idea was that the...
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    Automotive reverse polarity

    I was thinking if the battery was being charged and then the charger removed? My other slight concern was that I have the VRRM of the diode at 60V, I have read that the battery can spike negative to -150V. I do have a TVS which would clamp in the input to 39V, the input max for the DCDC is 42V...
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    Automotive reverse polarity

    The fuse I am using is a PTC type, so it will reset after fault condition is removed. The TVS is for transient conditions. The reverse polarity is recommended in the DCDC buck datasheet, for example if the car battery requires changing then it is possible for leads to be connected incorrectly. I...
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    Automotive reverse polarity

    I have a fuse, then TVs before the reverse polarity diode.
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    Automotive reverse polarity

    I hav
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    Automotive reverse polarity

    Hi all, I am using 12V from a car battery to power electronics. The current consumption of my circuit is 1A max, however it will run closer to around 850mA. I need to add reverse polarity protection to my circuit. I have opted for a simple Schottky diode solution, as I am limited for PCB space...
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    DCDC converter output power

    Hi I did look at this option. However we need 5V to power some external circuitry, hence the 3V3 LDO was used. Thanks
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    DCDC converter output power

    From the 3V3 LDO output.
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    DCDC converter output power

    Hi all, I have an application described below. 12V from car battery going to Buck DCDC converter (LM53600) to generate 5V. 5V from DCDC output feeds into LDO which generates 3V3 (MCP1826) This 3V3 powers the Micro, Bluetooth and WiFi devices. To simulate current of 0.5A, I put a 5R load...
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    DC DC buck to LDO

    Hi, Thanks for your reply. I have one device that powers from 5V hence the DCDC converter, this then will power the LDO (3.3V output) that powers the micro etc. Is there any consideration i.e. would I need a diode in between the output of the buck regulator and input of the LDO? I will take a...
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    DC DC buck to LDO

    Hi all, I have an automotive application (powered from 12V car battery). I am looking to drop 12V to 5V using a DC DC buck regulator (one of my circuits require a 5V supply, then use this 5V to power a LDO at 3.3V fixed). The current will be 600mA max. Looking at low quiescent current. I am...
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    MOSFET

    Hi all, The 3V is driven from a micro, I will make sure it is a logic level FET. The 10V is the voltage I have available and is also what I am switching on the relay output.
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    MOSFET

    Hi all, I have the circuit connected below, I am using the following AQY222R2T MOS Relay. Basically I am using the MOS relay to switch an output of 10V @ 400mA. The device is AQY222R2TY I have worked out the input resistor as R = Vin - VF ---------- IF From the datasheet this works out as...
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    Tracking and layout help

    Yes, thanks. I have the answer now.
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    Tracking and layout help

    Yes, the led current is 15mA, where as the main supply is 3A. Thank you for clearing that up for me.
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    Tracking and layout help

    Hi all, Thanks for the information. I have seen the online calculator, however do I need thinner or the same track width as the supply line? I am not sure, I would think it needs to be thinner? Any advice.
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    Tracking and layout help

    Hi all, I need some advice please on a layout of PCB. I have a power track which is for a 12V 3A supply line. I need to add a led + resistor to this line as an indicator. My question is, do I need to make the track width for the led + resistor the same as the width of the supply line? Or can I...
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    USB differential signals

    Thanks. I have resolved the issue. I decided to go with a 4 layer PcB as below: 4 layer board (from the top: signal, ground, VCC,signal) I have used some online impedance calculators, 0.2mm track width and spacing is what I need to get 90 ohm impedance. My concern is that the traces don't...
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    USB differential signals

    Hi all, I am laying out a board that has a USB connector. It will be used for USB 2.0. From the connector the signals route out to a TVs clamp then to a FTDI chip. However the D+ and D- signals cross over when they go to the FDTI chip to get to the appropriate pins. How can I overcome this? Are...
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    USB filtering confusion

    Hi, thanks for your reply. I was looking at it from a layout point, I will re label the VBUS1 from the 100nF/4.7uF/Ferrite junction as 5V. This will make it more clearer. Thanks, I am sorry I will try and read the datasheets a bit more in depth.
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