Datasheet

Data Sheet ADP1874/ADP1875
Rev. A | Page 39 of 44
DIFFERENTIAL SENSING
Because the ADP1874/ADP1875 operate in valley current-mode
control, a differential voltage reading is taken across the drain
and source of the lower side MOSFET. The drain of the lower
side MOSFET should be connected as close as possible to the SW
pin (Pin 15) of the IC. Likewise, the source should be connected
as close as possible to the PGND pin (Pin 13) of the IC. When
possible, both of these track lines should be narrow and away
from any other active device or voltage/current path.
09347-087
LAYER 1: SENSE LINE FOR SW
(DRAIN OF LOWER MOSFET)
LAYER 1: SENSE LINE FOR PGND
(SOURCE OF LOWER MOSFET)
PGND
SW
Figure 96. Drain/Source Tracking Tapping of the Lower Side MOSFET for CS
Amp Differential Sensing (Yellow Sense Line on Layer 2).
Differential sensing should also be employed between the
outermost output capacitor and the feedback resistor divider
(see Figure 93 and Figure 94). Connect the positive terminal of
the output capacitor to the top resistor (R
T
). Connect the negative
terminal of the output capacitor to the negative terminal of the
bottom resistor, which connects to the analog ground plane as
well. Both of these track lines, as previously mentioned, should
be narrow and away from any other active device or voltage/
current path.