Datasheet

MAX1925/MAX1926
Switch-Mode 1-Cell Li+ Chargers
_______________________________________________________________________________________ 7
FREQUENCY vs. BATTERY VOLTAGE
MAX1925/26 toc10
BATTERY VOLTAGE (V)
SWITCHING FREQUENCY (kHz)
3.53.0
50
100
150
200
250
300
350
400
450
500
0
2.5 4.0
V
IN
= 12V
V
IN
= 8V
V
IN
= 5V
TIMER vs. CT CAPACITANCE
MAX1925/26 toc11
CT CAPACITANCE (nF)
TIMER (MINUTES)
100
0.1
1
10
100
1000
0.01
10 1000
t
FULLCHG
t
PREQUAL2
t
PREQUAL1
CHARGE CURRENT vs. TIME
MAX1925/26 toc12
TIME (h)
CHARGE CURRENT (A)
2.52.01.51.00.5
0.2
0.4
0.6
0.8
1.0
1.2
0
0 3.0
BATTERY VOLTAGE vs. TIME
MAX1925/26 toc13
TIME (h)
BATTERY VOLTAGE (A)
2.52.01.51.00.5
3.9
4.0
4.1
4.2
4.3
4.4
4.5
3.8
0 3.0
SWITCHING WAVEFORM
MAX1925/26 toc14
4µs/div
1.2A
1A
0.8A
10V
0V
100mV/
div
INDUCTOR
CURRENT
V
LX
V
BATT
V
IN
= 5V
SWITCHING WAVEFORM
MAX1925/26 toc15
1µs/div
1.2A
1.4A
1A
0.8A
10V
0V
100mV/
div
INDUCTOR
CURRENT
V
LX
V
BATT
V
IN
= 12V
CHARGE-ENABLE REPSONSE
MAX1925/26 toc16
EN
INDUCTOR
CURRENT
5V
0V
1A
0A
Typical Operating Characteristics (continued)
(Circuit of Figure 1, V
SUPPLY
= 5V, V
BATT
= 4V, T
A
= +25°C, unless otherwise noted.)