ADP1875 Analog Devices, ADP1875 Datasheet - Page 39

• Manufacturer Part Number: ADP1875
• Description: Synchronous Buck Controller with Constant On-Time, Valley Current Mode, and Power Saving Mode
• Manufacturer: Analog Devices

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.
Figure 96. Drain/Source Tracking Tapping of the Lower-Side MOSFET for CS
LAYER 1: SENSE LINE FOR SW
(DRAIN OF LOWER MOSFET)
Amp Differential Sensing (Yellow Sense Line on Layer 2).
SW
PGND
LAYER 1: SENSE LINE FOR PGND
(SOURCE OF LOWER MOSFET)
Rev. 0 | Page 39 of 44
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
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.
ADP1874/ADP1875
T
). Connect the negative