LT1308B Linear Technology, LT1308B Datasheet - Page 7

• Manufacturer Part Number: LT1308B
• Description: High Current/ Micropower Single Cell/ 600kHz DC/DC Converters
• Manufacturer: Linear Technology

APPLICATIONS
DECT PHONES
The DECT standard specifies a transmit pulse 416 s in
duration. The LT1308 is capable of delivering a 400mA
pulse load from a 1.2V input with output capacitance of
100 F. Figure 11 depicts V
Figure 6’s circuit, configured for a 3.3V output by chang-
ing resistor R1 to 169k. Figure 12 shows detail of one
transmit pulse at a higher sweep speed.
L1: TOKO 636CY4R7M
FOR V
FOR V
AC COUPLED
NiCd
OR
Li-Ion
CELL
Figure 6. DC/DC Converter for GSM/DECT Application
AC COUPLED
COILTRONICS CTX5-1
I
Figure 7. GSM Load Transient Response.
100mA to 1A Transient Response for Figure 6’s Circuit.
Pulse Width = 577 s
I
200mV/DIV
LOAD
200mV/DIV
LOAD
OUT
OUT
I
L
, 1A/DIV
Figure 8. GSM Load Transient Response. Slower
Sweep Speed (1ms/DIV) Shows V
Transmit Pulses
100mA
100mA
= 5V: R1 = 309k
= 3.3V: R1 = 169k
V
V
OUT
OUT
1A
1A
C1
10 F
CERAMIC
V
V
IN
IN
= 3.6V
= 3.6V
U
SHDN
LBI
LBO
V
C
47k
LT1308
33nF
INFORMATION
U
1ms/DIV
100 s/DIV
OUT
GND
V
SW
IN
FB
transient response of
W
4.7 H
L1
100k
OUT
R1
over Several
+
1308 F08
1308 F07
D1
MBRS120
C2
100 F
U
1308F06
5V/1A OR
3.3V/300mA
I
I
LOAD
AC COUPLED
LOAD
AC COUPLED
AC COUPLED
AC COUPLED
I
I
200mV/DIV
LOAD
200mV/DIV
200mV/DIV
LOAD
200mV/DIV
I
I
L
L
, 1A/DIV
, 1A/DIV
Figure 12. DECT Load Transient Response.
Faster Sweep Speed (100 s/DIV) Details V
Inductor Current of Single DECT Transmit Pulse
400mA
100mA
400mA
100mA
50mA
Figure 11. DECT Load Transient Response.
With a Single NiCd Cell the LT1308 Provides 3.3V
with 400mA Pulsed Load. Pulse Width = 416 s
50mA
V
V
V
V
OUT
OUT
OUT
OUT
Figure 10. GSM Load Transient Response.
Faster Sweep Speed (500 s/DIV) Details V
and Inductor Current of One Transmit Pulse
Figure 9. GSM Load Transient Response.
At Low V
Serves to Hold up V
1A
1A
V
V
V
V
IN
IN
IN
IN
= 1.2V
= 2.7V
= 2.7V
= 1.2V
IN
, Large Output Capacitor (2200 F)
500 s/DIV
1ms/DIV
2ms/DIV
100 s/DIV
OUT
1308 F09
1308 F10
1308 F11
LT1308
1308 F09
OUT
OUT
and
7