05S_1XC9201/9202新規 02.09.12 15:16 ページ 550
XC9201Series
1 layer Evaluation Board
L
P-MOS
CDD
CFB
VDD Line
RFB1
1
2
3
4
5
6
7
8
CL
IC GND
SD
RSEN
Power GND
R_SS
C_SS
CIN
VIN
RFB2
R_CLK C_CLK C_GAIN
ꢀNotes on Use
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Ensure that the absolute maximum ratings of the external components and the XC9201 DC/DC IC itself are not exceeded. We recommend
that sufficient counter measures are put in place to eliminate the heat that may be generated by the external P-MOSFET as a result of
switching losses.
Try to use a P-MOSFET with as small a gate capacitance as possible in order to avoid overly large output spike voltages that may occur
(such spikes occur in proportion to gate capacitance). The performance of the XC9201 DC/DC converter is greatly influenced by not only its
own characteristics, but also by those of the external components it is used with. We recommend that you refer to the specifications of each
component to be used and take sufficient care when selecting components.
Wire external components as close to the IC as possible and use thick, short connecting wires to reduce wiring impedance. In particular,
minimize the distance between the by-pass capacitor and the IC.
Make sure that the GND wiring is as strong as possible as variations in ground potential caused by ground current at the time of switching
may result in unstable operation of the IC. Specifically, strengthen the ground wiring in the proximity of the VSS pin.
ꢀExternal Components
RSENSE Resistor
A low value resistor is defined as a resistor with a 10Ω value or lower. For RSENSE, the XC9201 series uses a resistor with a value of either
50mΩ or 100mΩ. Although resistors for RSENSE are classified as low resistance chip resistors or current limit resistors (which may give the
impression that the RSENSE resistor is expensive), it is not necessary to use expensive low resistance chip resistors as general purpose chip
resistors with values of 50mΩ or 100mΩ will do the job just as well.
When choosing the RSENSE resistor, it is important to confirm the resistor's power consumption which can be done using the following
equation:
W (Power Consumption) =I (Current) x V (Voltage)
=I (Current) x I (Current) x R (Resistance)
It is recommended that a resistor which has a power rating of more than 3 times the power consumption of RSENSE be selected (refer to the
example given below) :
(ex.) RSENSE = 100mΩ, I = 1A
I = 1A
RSENSE = 100mΩ (0.1Ω)
Power supply W = 1 x 1 x 0.1 = 0.1 [W]
0.5W, 100mΩ resistor should be used
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TOREX [ Torex Semiconductor ]
