Datasheet

LM2717
SNVS253D –MAY 2005–REVISED MARCH 2013 www.ti.com
LAYOUT CONSIDERATIONS
The LM2717 uses two separate ground connections, PGND for the drivers and boost 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
IN
, as shown in Figure 12, 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 0.1µF to 4.7µF
bypass capacitors can be placed in parallel with C
IN
, close to the V
IN
pins to shunt any high frequency noise to
ground. The output capacitors, C
OUT1
and C
OUT2
, should also be placed close to the IC. Any copper trace
connections for the C
OUTX
capacitors 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 inductors and schottky diodes 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 (SNVA021).
Application Information
Table 1. Some Recommended Inductors (Others May Be Used)
Manufacturer Inductor Contact Information
Coilcraft DO3316 and DO5022 series www.coilcraft.com
Coiltronics DRQ73 and CD1 series www.cooperet.com
Pulse P0751 and P0762 series www.pulseeng.com
Sumida CDRH8D28 and CDRH8D43 series www.sumida.com
Table 2. Some Recommended Input And Output Capacitors (Others May Be Used)
Manufacturer Capacitor Contact Information
Vishay Sprague 293D, 592D, and 595D series tantalum www.vishay.com
Taiyo Yuden High capacitance MLCC ceramic www.t-yuden.com
ESRD seriec Polymer Aluminum Electrolytic
Cornell Dubilier www.cde.com
SPV and AFK series V-chip series
High capacitance MLCC ceramic
Panasonic www.panasonic.com
EEJ-L series tantalum
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