LTC3421_15 Datasheet, PDF (14/16 Pages) Linear Technology – 3A, 3MHz Micropower Synchronous Boost Converter with Output Disconnect

LTC3421
APPLICATIO S I FOR ATIO
ERROR
AMP
1.22V
FB
1
V_C
24
C_C1
R_Z
Figure 3
V_OUT
R1
R2
C_C2
3421 F03
TYPICAL APPLICATIO
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.
V_IN
2.7V TO
4.2V
+
Li-Ion
L1
3µH
D1*
C1*
10µF
4
3
23
22
7
8
R1
60k
2
SHDN
ENB
V_REF
LBI
LBO
SYNC
I_LIM
SS R_T
65
21 14 15 16
V_IN SW SW SW
18
V_OUTS
17
V_OUT
19
V_OUT
20
LTC3421
V_OUT
1
FB
24
V_C
9
BURST
GND PGND PGND PGND
10 11 12 13
C2
R2
0.1µF
28k
C3
0.1µF
M1
C4
470pF
R3
10k
R4
100k
*LOCATE COMPONENTS CLOSE TO PINS
C1: TAIYO YUDEN JMK212BJ106MM
C5: TAIYO YUDEN JMK325BJ226MM
D1: MOTOROLA MBR0520L
L1: SUMIDA CDRH6D28-3R0
M1: ZETEX ZXM61P025
C6*
1µF
R5
1.13M
V_OUT
5V
1A
C5*
22µF
×2
R6
365k
3421 F04
Li-Ion to 5V Efficiency
100
90
80
Burst Mode
OPERATION
70
V_IN = 4.2V
V_IN = 3.6V
V_IN = 2.7V
60
50
40
30
20
10 ^VOUT ^{= 5V}
f_OSC = 1MHz
0
0.1
1
10
100
OUTPUT CURRENT (mA)
1000
3421 G03
Figure 4. Lithium-Ion to 5V at 1A Application with an Active Snubber Circuit
3421f
14