AAT2506 Datasheet, PDF (18/26 Pages) Advanced Analogic Technologies – 1MHz Step-Down Converter/LDO Regulator

AAT2506
1MHz Step-Down Converter/LDO Regulator
R2 is 59kΩ. Although a larger value will further
reduce quiescent current, it will also increase the
impedance of the feedback node, making it more
sensitive to external noise and interference. Table 2
summarizes the resistor values for various output
voltages with R2 set to either 59kΩ for good noise
immunity or 221kΩ for reduced no load input current.
R1
=
⎛ ^VOUT
⎝ V_REF
-1^⎞⎠
·
R2
=
⎛ ^1.5V
⎝ 0.6V
-
1 ^⎞⎠
·
59kΩ
=
88.5kΩ
The AAT2506, combined with an external feedfor-
ward capacitor (C8 in Figures 2 and 5), delivers
enhanced transient response for extreme pulsed
load applications. The addition of the feedforward
capacitor typically requires a larger output capaci-
tor C1 for stability.
V_OUT (V)
0.8
0.9
1.0
1.1
1.2
1.3
1.4
1.5
1.8
1.85
2.0
2.5
3.3
R2 = 59kΩ
R1 (kΩ)
19.6
29.4
39.2
49.9
59.0
68.1
78.7
88.7
118
124
137
187
267
R2 = 221kΩ
R1 (kΩ)
75
113
150
187
221
261
301
332
442
464
523
715
1000
Table 2: Adjustable Resistor Values For Use
With 0.6V Step-Down Converter.
VOUTBUCK
3
2
1
LDO Input
LX1
VIN1
GND
C2
10µF
C3
10µF
C7
0.01µF
C1
22µF¹
L1
Table 3
R1
C9 Table 3
U1
n/a
AAT2506
1
12
PGND SGND
R2
59k
2
11
LX
FB
3
VP
10
EN
4
9
VCC ENLDO
5
IN
8
GND
6
OUT
7
BYP
C4
4.7µF
C5
10nF
C8¹
3
2
1
Buck Enable
3
2
1
LDO Enable
GND
VOUTLDO
Figure 5: AAT2506 Evaluation Board Schematic.
1. For step-down converter, enhanced transient configuration C8 = 100pF and C1 = 10uF.
18
2506.2005.12.1.0