AAT2500 Datasheet, PDF (18/26 Pages) Advanced Analogic Technologies – 1MHz Step-Down Converter/LDO Regulator

AAT2500
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 adjustable version of the AAT2500, combined
with an external feedforward 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 capacitor 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
R2 = 59kΩ
R1 (kΩ)
19.6
29.4
39.2
49.9
59.0
68.1
78.7
88.7
118
124
137
187
R2 = 221kΩ
R1 (kΩ)
75
113
150
187
221
261
301
332
442
464
523
715
Table 2: Adjustable Resistor Values For Use
With 0.6V Step-Down Converter.
V_OUTBUCK
3
2
1
LDO Input
LX1
V_IN1
GND
C2
10μF
C3
10μF
C7
0.01μF
C1
4.7μF¹
L1
Table 3
R1
C9 Table 3
U1
n/a
AAT2500
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
V_OUTLDO
Figure 5: AAT2500 Evaluation Board Schematic.
1. For step-down converter, enhanced transient configuration C8 = 100pF and C1 = 10uF.
18
2500.2006.05.1.16