1308AI Linear Technology Corporation, 1308AI Datasheet - Page 15

• Manufacturer Part Number: 1308AI
• Description: Lt1308b - Single Cell High Currentmicropower 600khz Boost Dc/dc Converter
• Manufacturer: Linear Technology Corporation

APPLICATIONS
CURRENT
GSM AND CDMA PHONES
The LT1308A/LT1308B are suitable for converting a single
Li-Ion cell to 5V for powering RF power stages in GSM or
CDMA phones. Improvements in the LT1308A/LT1308B
error amplifiers allow external compensation values to be
reduced, resulting in faster transient response compared
to the LT1308. The circuit of Figure 24 (same as Figure 1,
printed again for convenience) provides a 5V, 1A output
from a Li-Ion cell. Figure 25 details transient response at
the LT1308A operating at a V
Ripple voltage in Burst Mode operation can be seen at
10mA load. Figure 26 shows transient response of the
LT1308B under the same conditions. Note the lack of
Burst Mode ripple at 10mA load.
LOAD
C1: AVX TAJC476M010
C2: AVX TPSD227M006
500mV/DIV
Figure 24. Li-Ion to 5V Boost Converter Delivers 1A
Li-Ion
CELL
1A/DIV
500mA
50mA
Figure 23. Load Step Response with 10μF X5R
Ceramic Output Capacitor and C
V
OUT
I
+
L1
SHUTDOWN
C1
47μF
U
D1: IR 10BQ015
L1: MURATA LQH6N4R7
SHDN
V
V
IN
INFORMATION
C
200μs/DIV
U
47k
LT1308B
100pF
4.7μH
L1
IN
GND
SW
of 4.2V, 3.6V and 3V.
FB
PL
W
D1
R1
309k
R2
100k
1308 F23
+
U
1308A/B F24
C2
220μF
5V
1A
V
V
Figure 25. LT1308A Li-Ion to 5V Boost Converter
Transient Response to 1A Load Step
V
V
IN
IN
V
IN
IN
V
IN
Figure 26. LT1308B Li-Ion to 5V Boost
Converter Transient Response to 1A Load Step
IN
= 4.2V
= 3.6V
10mA
= 4.2V
= 3.6V
I
10mA
V
V
V
LOAD
I
= 3V
V
V
V
= 3V
LOAD
OUT
OUT
OUT
OUT
OUT
OUT
1A
1A
V
200mV/DIV
V
200mV/DIV
OUT
OUT
TRACES =
TRACES =
LT1308A/LT1308B
100μs/DIV
200μs/DIV
1308 F25
1308 F26
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