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| RT8113 Datasheet, PDF (16/21 Pages) Richtek Technology Corporation – Single Phase VR11.1 PWM Controller with 7-bit VID | |||
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RT8113
Output Current Sensing
The RT8113 provides a low input offset current-sense
amplifier (CSA) to monitor the output current. The output
current of CSA (IX) is used for load line control and over-
current protection. In this inductor current sensing
topology, RS and CS must be set according to the equation
below :
L
DCR
= RS
x CS
700nA is a typical value of the CSA input offset current.
VOFS-CSA is the input offset voltage of CSA. VOFS-CSA of
the RT8113 is smaller than +/- 1.5mV. Usually, âVOFS-CSA
+ 700n x (RCSP + RS - RCSN)â is negligible except at very
light load and the equation can be simplified as the equation
below :
IX
=
IL x DCR
RCSN
Then the output current of CSA will follow the equation
below :
IX
=
IL
x
DCR
-
VOFS-CSA + 700n x
RCSN
(RCSP
+ RS
-
RCSN )
BOOT
UGATE
PHASE
LGATE
CSA: Current Sense Amplifier
+
700nA
IX
VOFS_CSA
+
-
700nA
-
VIN
R1
C1
L
R2
RS
C2
ISP
RCSP
ISN
RCSN
DCR
CS
Figure 7. Circuit for Current Sensing
www.richtek.com
16
DS8113-02 April 2011
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