LTC3838-1_15 Datasheet, PDF (41/52 Pages) Linear Technology – Dual, Fast, Accurate Step-Down DC/DC Controller with Dual Differential Output Sensing

APPLICATIONS INFORMATION
LTC3838-1
R_DFB2
R_DFB1
R_DFB1//R_DFB2
R_ITH2(2)
R_ITH1(2) ^CITH1(2)
C_ITH2(2)
V_{DFB2– SENSE2}⁺ _SENSE2^– _{DTR2 RUN2 PGOOD2 BOOST2}
V_DFB2+
TG2
SW2
BG2
V_RNG
ITH2
LTC3838-1
DRV_CC2
EXTV_CC
INTV_CC
TRACK/SS2
C_SS2
LOCALIZED
SGND TRACE
MODE/PLLIN
CLKOUT
SGND
PGND
RT
R_T
V_IN
PHASMD
C_ITH2(1)
R_ITH1(1)
R_ITH2(1)
ITH1
C_ITH1(1)
DRV_CC1
BG1
R_FB2(1)
C_SS1
R_FB1(1)
TRACK/SS1
SW1
TG1
V_OUTSENSE1+
V_{OUTSENSE1–} SENSE1⁺ SENSE1^– DTR1 RUN1 PGOOD1 BOOST1
C_B2
D_B2
R_INTVCC
C_INTVCC
C_DRVCC
D_B1
C_B1
L2
R_SENSE2
V_OUT2
MT2
MB2
CERAMIC
C_OUT2
C_VIN V_IN
R_VIN
+
C_IN
CERAMIC
PGND
C_OUT1
MT1
MB1
R_SENSE1
L1
V_OUT1
BOLD LINES INDICATE HIGH SWITCHING CURRENT. KEEP LINES TO A MINIMUM LENGTH
Figure 14. Recommended PCB Layout Diagram
38381 F14
• Keep small-signal components connected noise-sensi-
tive pins (give priority to SENSE⁺/SENSE^–, V_OUTSENSE1+/
V_{OUTSENSE1–}, V_DFB2+/V_DFB2–, RT, ITH, V_RNG pins) on
the left hand side of the IC as close to their respective
pins as possible. This minimizes the possibility of noise
coupling into these pins. If the LTC3838-1 can be placed
on the bottom side of a multilayer board, use ground
planes to isolate from the major power components on
the top side of the board, and prevent noise coupling
to noise sensitive components on the bottom side.
• Place the resistor feedback dividers close to the
V_OUTSENSE1+ and V_{OUTSENSE1–} pins for channel 1,
or V_DFB2+ and V_DFB2– pins for channel 2, so that the
feedback voltage tapped from the resistor divider will
not be disturbed by noise sources. Route remote sense
PCB traces (use a pair of wires closely together for
differential sensing) directly to the terminals of output
capacitors for best output regulation.
• Place decoupling capacitors C_ITH2 next to the ITH and
SGND pins with short, direct trace connections.
For more information www.linear.com3838-1
38381f
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