LTC3858-1 Datasheet, PDF (28/38 Pages) Linear Technology – Low IQ, Dual 2-Phase Synchronous Step-Down Controller

LTC3858-1
Applications Information
SW1
D1
V_IN
R_IN
C_IN
BOLD LINES INDICATE
HIGH SWITCHING
CURRENT. KEEP LINES
TO A MINIMUM LENGTH.
SW2
D2
L1
R_{SENSE1 VOUT1}
C_OUT1
L2
R_{SENSE2 VOUT2}
C_OUT2
R_L1
R_L2
38581 F11
Figure 11. Branch Current Waveforms
for inductive coupling between C_IN, Schottky and the top
MOSFET components to the sensitive current and voltage
sensing traces. In addition, investigate common ground
path voltage pickup between these components and the
SGND pin of the IC.
An embarrassing problem, which can be missed in an
otherwise properly working switching regulator, results
when the current sensing leads are hooked up backwards.
The output voltage under this improper hookup will still
be maintained but the advantages of current mode control
will not be realized. Compensation of the voltage loop will
be much more sensitive to component selection. This
behavior can be investigated by temporarily shorting out
the current sensing resistor—don’t worry, the regulator
will still maintain control of the output voltage.
38581fb
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