AAT1168 Datasheet, PDF (18/22 Pages) Advanced Analog Technology, Inc. – TRIPLE-CHANNEL TFT LCD POWER SOLUTION WITH OPERATIONAL AMPLIFIERS

Advanced Analog Technology, Inc.
May 2008
AAT1168/1168A/1168B
C
21.533µF
25.079µF
32.587µF
36.312µF
38.469µF
Table 3 K factor Table
Best Corner
Frequency
K factor
23.740 kHz
4.692
21.842 kHz
5.083
20.095 kHz
6.042
15.649 kHz
5.230
13.247 kHz
4.703
5. The output filter capacitor is chosen so C R_L pole
cancels R_C C_C zero
εR_CC_C
=
C


R_L
2

+ r_{C } ,
and
C_C
=
C
εR_C


R_L
2

+ r_{C }
ε = (1 ~ 3)
Example 3:
V_IN = 5V, V_O = 13.3V, I_O = 300mA, f_s = 1,190kHz,
V_FB = 1.233V, L = 6.65µH, G_m = 85µS,
r_L = 76.689 m Ω
r_C = 9.13m Ω , R_F = 0.7667 Ω , C_C = 1.95nF,
R_C = 7.6k Ω , C = 38.5µF, ε = 3, R_CS = 0.23V/A.
Bode Diagram
60
40
20
0
-20
-40
-90
-135
-180
-225
-270
2
3
4
5
6
10
10
10
10
10
Frequency (Hz)
Figure 7. Bode Plot of Loop Gain Using Matlab^®
Simulation
Positive and Negative LDO driver
Output Voltage Selection
The output voltage of positive LDO driver is set by a
resistive divider from the output (Vout3) to GND with
the center tap connected to the IN3, where V_IN3, the
positive LDO driver feedback regulation voltage, is
1.25V. Choose R₆ (Figure 8) between 10k Ω and
51k Ω . And calculate R₅ with the following equation.
R₅
=
R_{6 }
Vout3
V_IN3
− 1_{}
The output voltage of negative LDO driver is set by a
resistive divider from the output (VGL) to VREF with
the center tap connected to the IN2, where V_IN2, the
negative LDO driver feedback regulation voltage, is
0.25V. Choose R₉ (Figure 9) between 10k Ω and
51k Ω and calculate R₈ with the following equation.
R₈
=
R_{9 }
V_IN2 − V_GL
V_REF − V_IN2

Figure 8. The Positive LDO Driver
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