15

LT1308A/LT1308B

1308abfa

1A

10mA

200

μs/DIV

200mV/DIV

1308 F25

Figure 26. LT1308B Li-Ion to 5V Boost

Converter Transient Response to 1A Load Step

Figure 25. LT1308A Li-Ion to 5V Boost Converter

Transient Response to 1A Load Step

100

μs/DIV

200mV/DIV

1308 F26

1A

10mA

Figure 24. Li-Ion to 5V Boost Converter Delivers 1A

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

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.

SW

FB

LT1308B

L1

4.7

μH

D1

47k

R2

100k

R1

309k

5V

1A

100pF

1308A/B F24

C1

47

μF

C2

220

μF

Li-Ion

CELL

GND

SHDN

SHUTDOWN

C1: AVX TAJC476M010

C2: AVX TPSD227M006

+

+

D1: IR 10BQ015

L1: MURATA LQH6N4R7

500mV/DIV

200

μs/DIV

1308 F23

1A/DIV

LOAD

CURRENT

50mA

500mA

Figure 23. Load Step Response with 10

μF X5R