LM2744EVAL National Semiconductor, LM2744EVAL Datasheet - Page 19

• Manufacturer Part Number: LM2744EVAL
• Description: BOARD EVALUATION LM2744
• Manufacturer: National Semiconductor
• Series: PowerWise®r

Specifications of LM2744EVAL

• Main Purpose: DC/DC, Step Down
• Outputs And Type: 1, Non-Isolated
• Voltage - Output: 1.2V
• Current - Output: 3.5A
• Voltage - Input: 1.8 ~ 5.5V
• Regulator Topology: Buck
• Frequency - Switching: 1MHz
• Board Type: Fully Populated
• Utilized Ic / Part: LM2744
• Lead Free Status / RoHS Status: Not applicable / Not applicable
• Power - Output: -

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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