AAT1164C Advanced Analog Technology, AAT1164C Datasheet - Page 20

• Manufacturer Part Number: AAT1164C
• Description: TRIPLE-CHANNEL TFT LCD POWER SOLUTION
• Manufacturer: Advanced Analog Technology

Example 4:
For system design
V
V
Flying Capacitors
Increasing the flying capacitor (C
lower
capacitors works well in positive LDO driver. A 0.1µF
ceramic capacitor works well in negative LDO driver.
LDO Driver Diode
To achieve high efficiency, a Schottky diode should be
OUT3
OUT2
= 25V, R
= − 6V, R
output voltage ripples. The 1µF
Figure 9. The Negative LDO Driver
Figure 8. The Positive LDO Driver
5
8
= 200k , R
= 62k , R
Advanced Analog Technology, Inc.
9
6
= 10k
= 10k ,
5
, C
7
, C
–
9
) values can
–
Advanced Analog Technology, Inc . –
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ceramic
Page 20 of 24
Version 1.00
used. BAT54S (Figure 8 and 9) has fast recovery time
and low forward voltage for best efficiency.
LDO Driver Base-Emitter Resistors
For AAT1164, the minimum drive current for positive
and negative LDO drivers are 1mA, thus the minimum
base-emitter resistance can be calculated by the
following equation:
Example 5:
Output current of V
minimum base-emitter resistor can be calculated as
The minimum value can be used, however, the larger
value has the advantage of reducing quiescent current.
So we choose 6.8k to be R
Charge Pump Output Capacitor
Using low ESR ceramic capacitor to reduce the output
voltage ripple is recommended and output voltage ripple
is dominated by the capacitance value. The minimum
capacitance value can be calculated by the following
equation:
R
R
R
R
AAT1164/AAT1164B/AAT1164C
7
7
4
4
(min)
(min)
(min)
(min)
V
h
BE
fe(min)
Table 4. Pass Transistor Specifications
≥
≥
≥
≥
(max)
–
DIODES Product, Package: SOT23
V
0.65 / (( 1mA
0.5 / (( 1mA
V
BE(max)
BE(max)
OUT3
/ ((I
/ ((I
MMBT4401
−
OUT2(min)
OUT3(min)
−
and V
30mA ) / 90)
0.65V
30mA ) / 130)
130
4
.
OUT2
−
−
I ) / h
I ) / h
are 30mA, the
C
C
≥ 750
≥ 845
fe(min)
fe(min)
MMBT4403
0.5V
90
)
)
April 2007