Datasheet

HG
BOOT
I
SEN
LG
PGND
FB
V
CC
SD
PWGD
FREQ/SYNC
SS/TRACK
SGND
EAO
PGND
V
CC
= V
IN
= 3.3V
V
OUT
= 1.8V@2A
R
FB2
C
C2
R
C1
R
CS
C
SS
R
CC
C
CC
D
1
C
BOOT
Q1
C
IN
1,2
L1
+
C
C1
R
FB1
C
O
1,2
LM2745
R
C2
C
C3
R
PULL-UP
R
FADJ
C
Clk
Clk
+
K =
4.8W
4.8W + 0.6W
= 89%
K =
P
OUT
P
OUT
+ P
TOTAL
x 100%
P
CAP
=
(1.924A)
2
x 24 m:
1
2
I
RMS_RIP
= I
OUT
x
D(1 - D)
LM2745, LM2748
SNOSAL2E –APRIL 2005–REVISED APRIL 2013 www.ti.com
Here n is the number of paralleled capacitors, ESR is the equivalent series resistance of each, and P
CAP
is the
dissipation in each. So for example if we use only one input capacitor of 24 mΩ.
P
CAP
= 88.8 mW
Output Inductor Loss (P
IND
)
P
IND
= I
2
OUT
x DCR
where DCR is the DC resistance. Therefore, for example
P
IND
= (4A)
2
x 11 mΩ
P
IND
= 176 mW
Total System Efficiency
P
TOTAL
= P
FET
+ P
IC
+ P
GATE
+ P
CAP
+ P
IND
Example Circuits
Figure 33. 3.3V to 1.8V @ 2A, f
SW
= 300 kHz
26 Submit Documentation Feedback Copyright © 2005–2013, Texas Instruments Incorporated
Product Folder Links: LM2745 LM2748