High Efficiency, Low Noise, Fast Transient
400mA Step-Down Converter
Typical Characteristics
No-Load Quiescent Current
vs. Input Voltage
220
210
AAT1147
Line Transient Response
(40mA to 400mA; V
IN
= 3.6V; V
OUT
= 1.8V;
C
1
= 4.7µF; C
FF
= 100pF)
2.0
1.4
1.2
1.0
0.8
0.6
0.4
0.2
400 mA
40 mA
0.0
-0.2
-0.4
-0.6
Load and Inductor Current
(bottom) (200mA/div)
Supply Current (µA)
200
190
180
170
160
150
140
130
120
2.5
3.0
3.5
85°C
Output Voltage
(top) (V)
5.0
5.5
25°C
1.9
1.8
1.7
1.6
1.5
1.4
1.3
1.2
1.1
1.0
-40°C
4.0
4.5
Input Voltage (V)
Time (25µs/div)
Line Transient Response
(40mA to 400mA; V
IN
= 3.6V;
V
OUT
= 1.8V; C
1
= 4.7µF)
Soft Start
(V
IN
= 3.6V; V
OUT
= 1.8V; I
OUT
= 400mA)
Enable and Output Voltage
(top) (V)
2.0
1.9
1.8
1.7
1.6
1.5
1.4
1.3
1.2
1.1
1.0
400mA
40mA
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
-0.2
-0.4
-0.6
5.6
4.8
4.0
3.2
2.4
1.6
0.8
0.0
-0.8
-1.6
-2.4
3.6
3.2
2.8
2.4
2.0
1.6
1.2
0.8
0.4
0.0
-0.4
Load and Inductor Current
(bottom) (200mA/div)
Inductor Current
(bottom) (A)
Output Voltage
(top) (V)
Time (25µs/div)
Time (25µs/div)
Line Response
(V
OUT
= 1.8V @ 400mA)
1.90
1.85
1.80
1.75
1.70
1.65
1.60
1.55
1.50
1.45
1.40
5.2
5.0
4.8
40
Output Ripple
(V
IN
= 3.6V; V
OUT
= 1.8V; I
OUT
= 400mA)
0.9
0.8
Output Voltage
(AC Coupled) (top) (mV)
20
0
-20
-40
-60
-80
-100
-120
Inductor Current
(bottom) (A)
Output Voltage
(top) (V)
4.6
4.4
4.2
4.0
3.8
3.6
3.4
3.2
0.7
0.6
0.5
0.4
0.3
0.2
0.1
Input Voltage
(bottom) (V)
Time (25µs/div)
Time (500ns/div)
1147.2006.05.1.0
7
ANALOGICTECH [ ADVANCED ANALOGIC TECHNOLOGIES ]
