AAT2603_08 Datasheet, PDF (21/26 Pages) Advanced Analogic Technologies – Total Power Solution for Portable Applications

PRODUCT DATASHEET
AAT2603
Total Power Solution for Portable Applications
There is a relationship between the bypass capacitor
value and the LDO regulator turn-on time. In applica-
tions where fast device turn-on time is desired, the
value of C_BYP should be reduced.
In applications where low noise performance and/or
ripple rejection are less of a concern, the bypass capac-
itor may be omitted. The fastest device turn-on time will
be realized when no bypass capacitor is used.
DC leakage on this pin can affect the LDO regulator
output noise and voltage regulation performance. For
this reason, the use of a low leakage, high quality
ceramic (NPO or C0G type) or film capacitor is highly
recommended.
Feedback Resistor Selection
Resistors R1 and R2 of Figure 2 program the output to
regulate at a voltage higher than 1.5V for LDO1/LDO2
and 1.2V for LDO3/LDO4. To limit the bias current
required for the external feedback resistor string while
maintaining good noise immunity, the minimum sug-
gested value for R2 is 100kΩ. 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. Tables 5
and 6 summarize the resistor values for various output
voltages with R2 set to 100kΩ.
R1 =
V_OUT
V_REF
-1
· R2 =
1.5V
1.2V ^{- 1 · 100kΩ = 24.9kΩ}
VFBLX
VOUTLX
R1
R2
Figure 2: AAT2603 LDO1/LDO2/LDO3/LDO4
External Resistor Output Voltage Programming.
V_OUT (V)
1.3
1.4
1.5
1.6
1.7
1.8
1.9
2
2.1
2.2
2.3
2.4
2.5
2.6
2.7
2.8
2.9
3
3.1
3.2
3.3
R2 = 100kΩ
R1 (kΩ)
8.25
16.5
24.9
33.2
41.2
49.9
59
66.5
75
82.5
90.9
100
107
118
124
133
140
150
158
165
174
Table 5: Feedback Resistor Values
for LDO3 and LDO4.
V_OUT (V)
1.5
1.6
1.7
1.8
1.9
2
2.1
2.2
2.3
2.4
2.5
2.6
2.7
2.8
2.9
3
3.1
3.2
3.3
R2 = 100kΩ
R1 (kΩ)
24.9
33.2
41.2
49.9
59
66.5
75
82.5
90.9
100
107
118
124
133
140
150
158
165
174
Table 6: Feedback Resistor Values
for LDO1 and LDO2.
2603.2008.10.1.2
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