LTC3883 Datasheet, PDF (55/112 Pages) Linear Technology – Single Phase Step-Down DC/DC Controller with Digital Power System Management

Applications Information
R_IINSNS
V_IN
R_IIN
R_IIN
R_VIN
C_VIN
IIN_SNS
VIN_SNS
TSNS
LTC3883
I_SENSE+
C1
TG
I_SENSE–
V_IN
SW
SYNC
BOOST
RUN
BG
V_SENSE+
V_SENSE–
I_TH
INTV_CC
V_DD33
V_DD25
GND
GND
LTC3883/LTC3883-1
Q1
L
R_SENSE
V_OUT
C_B
M1
M2
D1
1µF
CERAMIC
+
C_INTVCC
+
C_IN
C_OUT
3883 F26
Figure 26. Recommended Printed Circuit Layout Diagram
V_IN
R_SENSEIN
SW
L
R_SENSE
V_OUT
R_IN
C_IN
D
C_OUT
R_L
BOLD LINES INDICATE
HIGH SWITCHING
CURRENT. KEEP LINES
TO A MINIMUM LENGTH.
CURRENT WAVFORM
AT NODE
3883 F27
Figure 27. Branch Current Waveforms
the IC. Ensure accurate current sensing with Kelvin
connections at the sense resistor or inductor, whichever
is used for current sensing.
4. Is the INTV_CC decoupling capacitor connected close to
the IC, between the INTV_CC and the power ground pins?
This capacitor carries the MOSFET driver current peaks.
An additional 1µF ceramic capacitor placed immediately
next to the INTV_CC and PGND pins can help improve
noise performance substantially.
5. Keep the switching node (SW), top gate node (TG), and
boost node (BOOST) away from sensitive small-signal
nodes, especially from the voltage and current sensing
feed-back pins. All of these nodes have very large and
fast moving signals and therefore should be kept on the
“output side” of the LTC3883 and occupy minimum PC
trace area. If DCR sensing is used, place the top resistor
(Figure 18a, R1) close to the switching node.
3883f
55