Datasheet

LM2717-ADJ
SNVS407C –DECEMBER 2005–REVISED MARCH 2013 www.ti.com
Note that the values calculated here give a good baseline for stability and will work well with most applications.
The values in some cases may need to be adjusted some for optimum stability or the values may need to be
adjusted depending on a particular applications bandwidth requirements.
LAYOUT CONSIDERATIONS
The LM2717-ADJ 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 20, 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(3)
and R
FB2(4)
, 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 DT3316 series www.coilcraft.com
800-3222645
TDK SLF10145 series www.component.tdk.com
847-803-6100
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
MuRata High capacitance MLCC ceramic www.murata.com
16 Submit Documentation Feedback Copyright © 2005–2013, Texas Instruments Incorporated
Product Folder Links: LM2717-ADJ