Battery Charger and Step-Down
Converter for Portable Applications
Typical Characteristics – Step-Down Converter
Load Transient Response
(10mA to 250mA; V
IN
= 3.6V; V
OUT
= 1.8V;
C
OUT
= 4.7µF; C
FF
= 100pF)
2.0
1.9
2.0
1.9
AAT2556
Load Transient Response
(10mA to 250mA; V
IN
= 3.6V; V
OUT
= 1.8V; C
OUT
= 4.7µF)
1.4
Load and Inductor Current
(bottom) (200mA/div)
Load and Inductor Current
(bottom) (200mA/div)
Output Voltage
(top) (V)
1.7
1.6
1.5
1.4
1.3
1.2
Output Voltage
(top) (V)
1.8
V
O
I
O
I
LX
1.8
1.7
1.6
1.5
1.4
1.3
1.2
V
O
1.2
1.0
0.8
I
O
I
LX
0.6
0.4
0.2
0.0
-0.2
Time (25µs/div)
Time (25µs/div)
Line Response
(V
OUT
= 1.8V @ 250mA; C
FF
= 100pF)
1.90
1.85
7.0
40
Output Ripple
(V
IN
= 3.6V; V
OUT
= 1.8V; I
OUT
= 1mA)
0.07
Output Voltage
(AC Coupled) (top) (mV)
Output Voltage
(top) (V)
1.80
1.75
1.70
1.65
1.60
1.55
1.50
V
O
6.5
6.0
5.5
5.0
4.5
20
0
-20
-40
-60
-80
-100
-120
V
O
0.06
Inductor Current
(bottom) (A)
0.05
0.04
0.03
0.02
Input Voltage
(bottom) (V)
V
IN
4.0
3.5
3.0
I
L
0.01
0.00
-0.01
Time (25µs/div)
Time (2µs/div)
Output Ripple
(V
IN
= 3.6V; V
OUT
= 1.8V; I
OUT
= 250mA)
40
0.8
Output Voltage
(AC Coupled) (top) (V)
20
0
-20
-40
-60
-80
-100
-120
V
O
0.7
Inductor Current
(bottom) (A)
0.6
0.5
0.4
0.3
I
L
0.2
0.1
0.0
Time (200ns/div)
8
2556.2006.09.1.2
AAT [ ADVANCED ANALOG TECHNOLOGY, INC. ]
