Battery Charger and Step-Down
Converter for Portable Applications
Typical Characteristics – Step-Down Converter
Efficiency vs. Load
(V
OUT
= 1.8V; L = 3.3µH)
100
90
AAT2556
DC Load Regulation
(V
OUT
= 1.8V; L = 3.3µH)
1.0
V
IN
= 2.7V
V
IN
= 3.6V
V
IN
= 5.0V
Output Error (%)
Efficiency (%)
0.5
80
70
60
50
40
0.1
V
IN
= 5.5V
V
IN
= 4.2V
V
IN
= 3.6V
0.0
V
IN
= 5.5V
V
IN
= 5.0V
V
IN
= 2.7V
-0.5
V
IN
= 4.2V
1
10
100
1000
1
10
100
1000
-1.0
0.1
Output Current (mA)
Output Current (mA)
Efficiency vs. Load
(V
OUT
= 1.2V; L = 1.5µH)
100
90
1.0
DC Load Regulation
(V
OUT
= 1.2V; L = 1.5µH)
V
IN
= 2.7V
Output Error (%)
Efficiency (%)
80
70
60
50
40
30
V
IN
= 3.6V
V
IN
= 5.5V
V
IN
= 5.0V
V
IN
= 4.2V
0.1
1
10
100
1000
0.5
V
IN
= 5.0V
V
IN
= 5.5V
0.0
V
IN
= 3.6V
-0.5
V
IN
= 4.2V
V
IN
= 2.7V
1
10
100
1000
-1.0
0.1
Output Current (mA)
Output Current (mA)
Soft Start
(V
IN
= 3.6V; V
OUT
= 1.8V;
I
OUT
= 250mA; C
FF
= 100pF)
Line Regulation
(V
OUT
= 1.8V)
1.6
1.4
1.2
1.0
0.8
0.6
0.6
0.5
0.4
0.3
0.2
0.1
0.0
-0.1
-0.2
-0.3
2.5
3.0
3.5
Enable and Output Voltage
(top) (V)
5.0
4.0
3.0
2.0
1.0
0.0
-1.0
-2.0
-3.0
-4.0
-5.0
V
EN
Accuracy (%)
I
OUT
= 0mA
I
OUT
= 50mA
I
OUT
= 150mA
Inductor Current
(bottom) (A)
V
O
I
L
Time (100µs/div)
0.4
0.2
0.0
-0.2
-0.4
I
OUT
= 10mA
I
OUT
= 250mA
4.0
4.5
5.0
5.5
6.0
Input Voltage (V)
6
2556.2006.09.1.2
AAT [ ADVANCED ANALOG TECHNOLOGY, INC. ]
