Y caps, also called bypass caps or decoupling caps, are a type of capacitor used frequently in electronics to decouple or bypass high-frequency noise on power supply lines.

Some key things to know about Y caps:

• Placement: They are placed close to microchips/ICs, often right next to the power pins in a sideways "Y" shape which gives them the name.

• Purpose: To decouple voltage spikes and filter noise from the power supply lines which could otherwise interfere with or disrupt sensitive chips.

• Type: Usually small ceramic capacitors rated for high frequency such as multilayer ceramic chip capacitors (MLCC).

• Values: Typically range from 0.1 uF to 10 uF depending on application and chip power needs. Higher values provide more decoupling at lower frequencies.

• Lines bypassed: Usually placed between power supply rail (Vcc) and ground to filter noise coming in on the power line. Can also be used on analog/digital ground pairs.

• Effectiveness: Most effective when placed as close to the IC as possible, often right under or beside the chip. Short leads are important for good high frequency bypassing.

So in summary, Y caps are bypass/decoupling capacitors placed in a sideways Y configuration close to ICs to filter high frequency noise and transients on supply lines, improving power integrity and reducing chances of malfunction.