Datasheet

LTC1773
14
1773fb
APPLICATIONS INFORMATION
WUU
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For the selection of the external MOSFETs, the R
DS(ON)
must be guaranteed at 2.5V since the LTC1773 has to
operate down to 2.7V. This requirement can be met by the
Si9801DY.
For the feedback resistors, choose R1 = 80.6k. R2 can then
be calculated from equation (2) to be:
Figure 7. Single Lithium-Ion to 2.5V/2A Regulator
R
V
R k use k
OUT
2
08
1 1 171 169=
⎛
⎝
⎜
⎞
⎠
⎟
=
.
–;
Figure 7 shows the complete circuit along with its effi-
ciency curve.
1773 F07a
+
1
2
3
4
5
10
9
8
7
6
R
SENSE
0.033Ω

33pF
200pF
0.1µF
30k
V
OUT
2.5V
2A
2.7V ≤ V
IN
≤ 4.2V
+
LTC1773
RUN/SS
SYNC/FCB
GND
SENSE
–
V
IN
TG
I
TH
V
FB
BG
SW
L1
2.5µH
Si9801DY
C
OUT
220µF
6.3V
C
IN
150µF
6.3V
169k
1%
80.6k
1%
C
IN
: SANYO POSCAP 6TPA150M
C
OUT
: AVX TPSD227M006R0100
L1: CDRH5D28
R
SENSE
: IRC LR1206-01-R033-F
V
IN
OUTPUT CURRENT (mA)
EFFICIENCY (%)
100
95
90
85
80
75
70
1 100 1000 5000
1773 F1b
10
V
IN
= 3.3V
V
OUT
= 2.5V
Efficiency Curve for Figure 7