Datasheet

LM2700

SNVS152C –MAY 2001–REVISED MARCH 2013

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LAYOUT CONSIDERATIONS

The LM2700 uses two separate ground connections, PGND for the driver and NMOS power device and AGND

for the sensitive analog control circuitry. The AGND and PGND pins should be tied directly together at the

package. The feedback and compensation networks should be connected directly to a dedicated analog ground

plane and this ground plane must connect to the AGND pin. If no analog ground plane is available then the

ground connections of the feedback and compensation networks must tie directly to the AGND pin. Connecting

these networks to the PGND can inject noise into the system and effect performance.

The input bypass capacitor C

, as shown in Figure 19, must be placed close to the IC. This will reduce copper

trace resistance which effects input voltage ripple of the IC. For additional input voltage filtering, a 100nF bypass

capacitor can be placed in parallel with C

, close to the V

pin, to shunt any high frequency noise to ground.

The output capacitor, C

OUT

, should also be placed close to the IC. Any copper trace connections for the C

OUT

capacitor can increase the series resistance, which directly effects output voltage ripple. The feedback network,

resistors R

FB1

and R

FB2

, should be kept close to the FB pin, and away from the inductor, to minimize copper

trace connections that can inject noise into the system. Trace connections made to the inductor and schottky

diode should be minimized to reduce power dissipation and increase overall efficiency. For more detail on

switching power supply layout considerations see Application Note AN-1149: Layout Guidelines for Switching

Power Supplies (literature number SNVA021).

Product Folder Links: LM2700