User Manual

MAX1687/MAX1688
Step-Up DC-DC Converters with
Precise, Adaptive Current Limit for GSM
_______________________________________________________________________________________ 5
Typical Operating Characteristics (continued)
(V
IN
= +3.3V, V
OUT
= 5V, V
LIM
= 1V, Figures 6b and 7, T
A
= +25°C, unless otherwise noted.)
500mA/div
500mA/div
200mV/div
V
OUT
1ms/div
I
LX
I
LOAD
MAX1688
SWITCHING WAVEFORMS
(GSM PULSED LOAD 1A, R
CHG
= 40.2kΩ)
MAX1687/88 toc11
R
CHL
= 40.2kΩ, L = 10µH
200mA/div
0A
V
LIM = 1V
V
LIM
= 0
2µs/div
I
LX
I
LX
INDUCTOR CURRENT
MAX1687/88 toc13
200mA/div
1V/div
I
BATTERY
V
ON
10µs/div
MAX1687/88 toc15
V
ON
vs. BATTERY CURRENT
2V/div
1V/div
V
ON
V
OUT
5ms/div
MAX1687/88 toc14
POWER-UP WAVEFORM
(R
LOAD
= 15Ω C
OUT
= 2000µF)
500mA/div
500mA/div
200mV/div
V
OUT
1ms/div
I
LX
I
LOAD
MAX1688
SWITCHING WAVEFORMS
(GSM PULSED LOAD 1A, R
CHG
= 18kΩ)
MAX1687/88 toc12
R
CHG
= 18kΩ, L = 10µH
500mA/div
100mV/div
V
OUT
500µs/div
I
LX
SWITCHING WAVEFORMS
(FIXED I
LOAD
= 300mA)
MAX1687/88 toc10a