XRP6142 Datasheet, PDF (12/17 Pages) Exar Corporation – Synchronous Step-Down Controller with DDR

XRP6142
Synchronous Step-Down Controller with DDR
Memory Termination
PCB LAYOUT GUIDELINES
The following guidelines will help attain stable
operation and reduce jitter:
1- Place all the power components; C_IN,
QT, QB, L1 and C_OUT on the same side
of the board if possible.
2- Make the loop between C_IN, QT and QB
as small as possible and use low-
impedance traces.
3- Make the loop between QB, L1 and
C_OUT as small as possible and use low-
impedance traces.
4- Place the source of QT, drain of QB and
input connection of L1 as close as
possible and use low-impedance
traces.
5- Use a short trace and connect AGND to
the thermal pad. This forms the signal
ground.
6- Use a short trace and connect PGND to
AGND.
7- Use a low-impedance trace and
connect the PGND pin to the C_OUT.
8- Place CFF, R1 and R2 close to the IC,
and connect R2 to signal ground. Use a
short trace and connect R1 to C_OUT.
9- Bypass the V_CC pin to signal ground
with a ceramic capacitor(s) as close to
the IC as possible. Connect the V_CC pin
to V_IN or an independent V_CC source
through a 10Ω resistor. This will help
filter out noise from V_CC.
© 2010 Exar Corporation
Page 12 of 17
Rev. 1.0.0