Preliminary Datasheet

LP3205

LP3205 – Ver. 1.0 Datasheet

Feb.-2007

Page 9 of 10

Checking Transient Response

The regulator loop response can be checked by looking at the load transient response. Switching

regulators take several cycles to respond to a step in load current. When a load step occurs, VOUT

immediately shifts by an amount equal to ∆ILOAD (ESR), where ESR is the effective series

resistance of COUT. ∆ILOAD also begins to charge or discharge COUT generating a feedback error

signal used by the regulator to return VOUT to its steady-state value. During this recovery time,

VOUT can be monitored for overshoot or ringing that would indicate a stability problem.

Layout Considerations

Follow the PCB layout guidelines for optimal performance of LP3205.

For the main current paths as indicated in bold lines, keep their traces short and wide.

Put the input capacitor as close as possible to the device pins (VIN and GND).

LX node is with high frequency voltage swing and should be kept small area. Keep analog

components away from LX node to prevent stray capacitive noise pick-up.

Connect feedback network behind the output capacitors. Keep the loop area small. Place the

feedback components near the LP3205.

Connect all analog grounds to a command node and then connect the command node to the

power ground behind the output capacitors.