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A good PCB layout for the LM4940TSX/NOPB involves separating the analog and digital grounds, using a star-ground configuration, and placing the device close to the power supply. Additionally, it's recommended to use a 4-layer PCB with a dedicated ground plane to reduce noise and EMI.
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To ensure proper biasing, make sure to follow the recommended voltage supply and biasing scheme outlined in the datasheet. This typically involves connecting the VCC pin to a stable voltage source, and the BIAS pin to a voltage divider network that sets the desired output voltage.
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The LM4940TSX/NOPB has a maximum junction temperature of 150°C. To ensure reliable operation, it's essential to provide adequate heat sinking, such as a thermal pad or heat sink, and to follow proper PCB design guidelines to minimize thermal resistance. Additionally, consider using thermal interface materials to improve heat transfer.
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To filter out noise and ripple, you can use a combination of capacitors and resistors to create a low-pass filter. A common approach is to use a 10uF capacitor in parallel with a 10Ω resistor, followed by a 100nF capacitor in parallel with a 100Ω resistor. This helps to attenuate high-frequency noise and ripple.
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To ensure EMI and EMC compliance, follow proper PCB design guidelines, such as using a shielded enclosure, minimizing trace lengths, and using EMI filters or common-mode chokes. Additionally, consider using a metal shield or screen to enclose the device, and ensure that the device is properly grounded to prevent radiation.
LM4940TSX/NOPB datasheet
by Texas Instruments
