ADP1874ARQZ-0.3-R7 datasheet(39/44 Pages) AD

39 / 44 page

ADP1874/ADP1875

Rev. 0 | 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.

LAYER 1: SENSE LINE FOR SW

(DRAIN OF LOWER MOSFET)

LAYER 1: SENSE LINE FOR PGND

(SOURCE OF LOWER MOSFET)

PGND

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 (RT). 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.

ADP1874ARQZ-0.3-R7 Datasheet(PDF) 39 Page - Analog Devices