AAT1164 Datasheet, PDF (19/24 Pages) Advanced Analog Technology, Inc. – TRIPLE-CHANNEL TFT LCD POWER SOLUTION

Advanced Analog Technology, Inc.
April 2007
AAT1164/AAT1164B/AAT1164C
Compensator design guide:
1.
Crossover
frequency f_ci
<
1
2
f_S
2. Gain margin>10dB
∘ 3. Phase margin>45
4. The L_VI(s) = 1 at crossover frequency, Therefore,
the compensator resistance, R_C is determined by:
R_C
=
V_O
V_FB
2πf_ciC_OUTR_CS
g_mk
(R_L + 2r_C )

(^1−

D)R_L
−
r
(1−
D)



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
Table 3. k Factor Table
C_OUT
Best Corner
Frequency
21.533µF
23.740kHz
25.079µF
21.842kHz
32.587µF
20.095kHz
36.312µF
15.649kHz
38.469µF
13.247kHz
k Factor
4.692
5.083
6.042
5.230
4.703
Positive and Negative LDO Driver
Output Voltage Selection
The output voltage of positive LDO driver is set by a
resistive divider from the output (V_OUT3) 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 10kΩ and 51kΩ . And
calculate R₅ with the following equation.
5. The output filter capacitor is chosen so C_OUTR_L
pole cancels R_CC_C zero
εR_CC_C
= C_OUT


R_L
2

+ r_{C } ,
and
C_C
=
C_OUT
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 mΩ
r_C = 9.13 mΩ , R_F = 0.7667 Ω , C_C = 1.95nF,
R_C = 7.6 kΩ , C_OUT = 38.5 µ F , ε = 3, R_CS = 0.23V/A.
R₅

=
R₆


V_OUT3
V_IN3

− 1_

The output voltage of negative LDO driver is set by a
resistive divider from the output (V_OUT2) to VREF with
the center tap connected to IN2, where V_IN2, the
negative LDO driver feedback regulation voltage, is
0.25V. Choose R₉ (Figure 9) between10kΩ and
51kΩ and calculate R₈ with the following equation.
R₈
=
R₉



V_IN2 − V_OUT2
V_REF − V_IN2



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