lm2744mtcx National Semiconductor Corporation, lm2744mtcx Datasheet - Page 19

• Manufacturer Part Number: lm2744mtcx
• Description: Low Voltage N-channel Mosfet Synchronous Buck Regulator Controller With External Reference
• Manufacturer: National Semiconductor Corporation

There are few additional losses that are taken into account:
IC Operating Loss (P
where I
FET Gate Charging Loss (P
The value n is the total number of FETs used and Q
typical gate-source charge value, which is 3nC. For the FD-
S6898A the gate charging loss is 5.94mW.
Input Capacitor Loss (P
where,
Here n is the number of paralleled capacitors, ESR is the
equivalent series resistance of each, and P
Q-VCC
is the typical operating V
P
GATE
P
P
GATE
IC
= 1.5mA *3.3V = 4.95mW
= 2 x 3.3V x 3nC x 300kHz
P
P
IC
= n * V
IC)
GATE
= I
CAP
Q_VCC
= 5.94mW
)
CC
GATE
* Q
x V
)
GS
CC
CC
* F
,
current
OSC
CAP
is the dissipa-
GS
is the
19
tion in each. So for example if we use only one input capacitor
of 24 mΩ.
Output Inductor Loss (P
where DCR is the DC resistance. Therefore, for example
Total System Efficiency
P
P
IND
P
IND
P
CAP
IND
= (4A)
= I
IND
= 88.8mW
= 176mW
2
)
OUT
2
x 11mΩ
* DCR
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