Datasheet

LTC3421
14
3421f
5V Applications
When the output voltage is programmed above 4.3V it is
necessary to add a Schottky diode either from SW to
V
OUT
, or to a snubber network in order to maintain an
acceptable peak voltage on SW. The Schottky to the
output will provide a peak efficiency improvement but will
negate the output disconnect feature. If output disconnect
is required, the Schottky to an active snubber network is
suggested as shown in Figure 4.
Figure 4. Lithium-Ion to 5V at 1A Application with an Active Snubber Circuit
TYPICAL APPLICATIO
U
OUTPUT CURRENT (mA)
30
EFFICIENCY (%)
90
100
20
10
80
50
70
60
40
0.1 10 100 1000
3421 G03
0
1
Burst Mode
OPERATION
V
OUT
= 5V
f
OSC
= 1MHz
V
IN
= 4.2V
V
IN
= 3.6V
V
IN
= 2.7V
Li-Ion to 5V Efficiency
SHDN
ENB
V
REF
LBI
LBO
SYNC
I
LIM
V
OUTS
V
OUT
V
OUT
V
OUT
FB
V
C
BURST
V
IN
SW SW
L1
3µH
SW
18
17
19
20
1
24
9
1312111056
8
7
22
23
3
4
221141516
SS R
T
GND
LTC3421
C2
0.1µF
C3
0.1µF
C4
470pF
C5*
22µF
×2
C6*
1µF
C1*
10µF
V
IN
2.7V TO
4.2V
Li-Ion
R2
28k
R3
10k
R4
100k
R5
1.13M
M1
D1*
V
OUT
5V
1A
R6
365k
3421 F04
R1
60k
*LOCATE COMPONENTS CLOSE TO PINS
C1: TAIYO YUDEN JMK212BJ106MM
C5: TAIYO YUDEN JMK325BJ226MM
PGND PGND PGND
+
D1: MOTOROLA MBR0520L
L1: SUMIDA CDRH6D28-3R0
M1: ZETEX ZXM61P025
Figure 3
1
–
+
1.22V
C
C1
C
C2
R
Z
3421 F03
R2
R1
ERROR
AMP
FB
V
OUT
24
V
C
APPLICATIO S I FOR ATIO
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