AAT2500 Analogic Corporation, AAT2500 Datasheet - Page 18

• Manufacturer Part Number: AAT2500
• Manufacturer: Analogic Corporation

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.
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.
R1 =
1. For step-down converter, enhanced transient configuration C8 = 100pF and C1 = 10uF.
18
V
⎛
⎝
OUTBUCK
V
V
OUT
REF
LDO Input
-1 · R2 =
⎞
⎠
3
2
1
V
OUTLDO
V
⎛
⎝
IN1
0.6V
1.5V
GND
- 1 · 59kΩ = 88.5kΩ
Figure 5: AAT2500 Evaluation Board Schematic.
⎞
⎠
C2
10µF
LX1
C3
10µF
1MHz Step-Down Converter/LDO Regulator
C1
4.7µF
Table 3
C7
0.01µF
L1
1
C4
4.7µF
1
2
3
4
5
6
Table 2: Adjustable Resistor Values For Use
PGND
LX
VP
VCC
IN
OUT
U1
AAT2500
V
OUT
1.85
0.8
0.9
1.0
1.1
1.2
1.3
1.4
1.5
1.8
2.0
2.5
ENLDO
SGND
(V)
With 0.6V Step-Down Converter.
GND
BYP
EN
FB
12
11
10
9
8
7
10nF
C5
C9
n/a
R2 = 59kΩ Ω
R1 (kΩ Ω )
Table 3
R1
19.6
29.4
39.2
49.9
59.0
68.1
78.7
88.7
124
137
187
118
R2
59k
C8
1
AAT2500
R2 = 221kΩ Ω
Buck Enable
LDO Enable
R1 (kΩ Ω )
3
2
1
3
2
1
2500.2005.08.1.9
150
187
221
261
301
332
442
464
523
715
113
75
GND