LTC3727_15 Datasheet, PDF (27/32 Pages) Linear Technology – High Efficiency, 2-Phase Synchronous Step-Down Switching Regulators

APPLICATIO S I FOR ATIO
LTC3727/LTC3727-1
SW1
L1
R_{SENSE1 VOUT1}
+
D1
C_OUT1
R_L1
V_IN
R_IN
+
C_IN
SW2
BOLD LINES INDICATE
D2
HIGH SWITCHING
CURRENT. KEEP LINES
TO A MINIMUM LENGTH
L2
R_{SENSE2 VOUT2}
+
C_OUT2
R_L2
3727 F11
Figure 11. Branch Current Waveforms
6. Keep the switching nodes (SW1, SW2), top gate nodes
(TG1, TG2), and boost nodes (BOOST1, BOOST2) away
from sensitive small-signal nodes, especially from the
opposites channel’s voltage and current sensing feedback
pins. All of these nodes have very large and fast moving
signals and therefore should be kept on the “output side”
of the LTC3727 and occupy minimum PC trace area.
7. Use a modified “star ground” technique: a low imped-
ance, large copper area central grounding point on the
same side of the PC board as the input and output
capacitors with tie-ins for the bottom of the INTV_CC
decoupling capacitor, the bottom of the voltage feedback
resistive divider and the SGND pin of the IC.
PC Board Layout Debugging
Start with one controller on at a time. It is helpful to use
a DC-50MHz current probe to monitor the current in the
inductor while testing the circuit. Monitor the output
switching node (SW pin) to synchronize the oscilloscope
to the internal oscillator and probe the actual output
voltage as well. Check for proper performance over the
operating voltage and current range expected in the
3727fc
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