AAT1164 Datasheet, PDF (15/24 Pages) Advanced Analog Technology, Inc. – TRIPLE-CHANNEL TFT LCD POWER SOLUTION

Advanced Analog Technology, Inc.
April 2007
AAT1164/AAT1164B/AAT1164C
DESIGN PROCEDURE
Boost Converter Design
Setting the Output Voltage and Selecting
the Lead Compensation Capacitor
The output voltage of boost converter is set by the
resistor divider from the output (V_OUT1) to GND with the
center tap connected to IN1, where V_IN1, the boost
converter feedback regulation voltage is 1.233V,
Choose R₂ (Figure 2) between 5.1kΩ to 51kΩ and
calculate R₁ to satisfy the following equation.
R₁
=
R₂



V_OUT1
V_IN1

− 1_

V_OUT1
R_C
C_P
C_C
EO
24
VREF
gm
IN1 ₂₃
R₁
V_IN1
R₂
GND
GND
Figure 2. Feedback Circuit
k = ^{∆ILpeak-peak}
I_IN
η : Boost converter efficiency
k: The ratio of the inductor peak to peak ripple current to
the input DC current
V_IN: Input voltage
V_O: Output voltage
I_O: Output load current
f_S: Switching frequency
D: Duty cycle
∆I_{Lpeak–peak}: Inductor peak to peak ripple current
I_IN: Input DC current
The AAT1164 SW current limit ( I_LIM ) and inductor’s
saturation current rating ( I_LSAT ) should exceed I_L(peak),
and the inductor's DC current rating should exceed I_IN.
For the best efficiency, choose an inductor with less DC
series resistance ( r_L ).
I_LIM and I_LSAT > I_{L(peak )}
I_LDC > I_IN
I_{L(peak )}
= I_IN
+
V_IND
2Lf_S
,
I_IN
=
I_O
η(1− D)
,
Inductor Selection
The minimum inductance value is selected to make
P_DCR
≈



I_O
η(1 −
D)
²


r_L
sure that the system operates in continuous conduction
mode (CCM) for high efficiency and to prevent EMI. The
equation of inductor uses a parameter k, which is the
ratio of the inductor peak to peak ripple current to the
input DC current. The best trade-off between voltage
ripple of transient output current and permanent output
I_LDC: DC current rating of inductor
P_DCR: Power loss of inductor series resistance
C6-K1.8L
3.9µH
Table 1. Inductor Data List
r_L
DC CURRENT RATING
41mΩ
2.5A
current has a k between 0.4 and 0.5.
L ≥ ^ηVO D(1− D)^{2 ,}
kI_Of_S
D = 1− ^VIN
V_{O ,}
6.8µH
10µH
68mΩ
81mΩ
2.2A
1.8A
MITSUMI Product-Max Height:1.9mm
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