IR3721 International Rectifier, IR3721 Datasheet - Page 5

• Manufacturer Part Number: IR3721
• Description: Power Monitor IC
• Manufacturer: International Rectifier

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FUNCTIONAL DESCRIPTION
Please refer to the Functional Description Diagram
below. Power flow from the buck converter inductor is
the product of output voltage times the current I
flowing through the inductor.
Power is measured with the aid of International
Rectifier’s proprietary TruePower™ circuit. Current is
converted to a duty ratio that appears at the DI pin.
The duty ratio of the DI pin is
The full-scale current that can be measured
corresponds to a duty ratio of one.
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Vin
DI
DUTY
RATIO
Equation 1
=
(
R
CS
I
L
R
1
⋅
CS1
DCR
+
R
L
CS
I
2
Figure 1 Functional Description Diagram
L
)
C
⋅
V
DCR
CS1
R
R
R
T
CS2
Τ
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C
CS2
L
R
T
VCS
V
VO
RT
The amplitude of the DI pin is the voltage appearing
at pin VK. If a fixed voltage is applied to VK then the
output of the RC filter driven by DI will be proportional
to inductor current I
If VO is applied to V
output of the DI driven RC network will be
proportional to power. The full-scale voltage that can
be measured is established on the chip to be 1.8V.
The full scale power P
product of full-scale voltage and full scale current.
IR3721
VDD
GND
L
K
.
as shown in the figure then the
FS
that can be measured is the
DI
VK
DATA SHEET
IR3721
Power
07/14/08
Vo