RT8841
10mil width and put away from high (di/dt) switching
elements such as high side MOSFETs, low side
MOSFETs, phase plane etc. The circuit elements of
voltage feedback loop, such as feedback loop short
resistors and voltage loop compensation RCs, have to
be kept near the RT8841 and also away from switching
elements.
` The current sense mechanism of the RT8841 is fully
differential Kelvin sense. Therefore, the current sense
loops of the RT8841 contain two traces : the positive
traces(ISP1 to ISP4) come from the positive node of
output inductors(the node connecting phase plane) and
the negative traces (ISN1 to ISN4) come from the
negative node of output inductors(the node connecting
output plane).
DO NOT connect the current sense traces from phase
plane or output plane. Only connect these traces from
both sides of output inductors can achieve the goal of
precise Kelvin sense. The current sense feedback loops
have to be routed away from switching elements, and
the current sense RC elements have to be put near
their respective ISNor ISP pins of the RT8841 and also
away from noise switching elements. At least 10 mil
width is suggested for current sense feedback loops.
DS8841-01 April 2011
www.richtek.com
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RICHTEK [ RICHTEK TECHNOLOGY CORPORATION ]
