AAT1405 Advanced Analogic Technologies, Inc., AAT1405 Datasheet - Page 14

• Manufacturer Part Number: AAT1405
• Description: 4 Channel Led Backlight Driver With Integrated Boost And High Frequency Direct Pwm Dimming
• Manufacturer: Advanced Analogic Technologies, Inc.

The ESR zero of the output capacitor (see Figure 3) can
be calculated by:
Where:
C
R
R
capacitor.
The right half plane (RHP) zero can be calculated by:
14
SwitchReg
VIN
4
O
ESR
is the output filter capacitor
is the equivalent load resistor value
Figure 3: AAT1405 Equivalent Output Stage.
is the equivalent series resistance of the output
TM
L1
4 Channel LED Backlight Driver with Integrated Boost and High Frequency Direct PWM Dimming
f
Z_ESR
f
Z_ESR
=
2π · L
=
2π · R
1
· I
V
1
ESR
IN
OUT
2
· C
· V
4
OUT
D1
ESR
C4
w w w . a n a l o g i c t e c h . c o m
It is recommended to design the bandwidth to one
decade lower than the frequency of RHP zero to guaran-
tee the loop stability. A series capacitor and resistor
network (R1 and C3) connected to the COMP pin sets the
pole and zero which are given by:
Where:
C
R
R
(2.97MΩ).
A 15nF (C3) capacitor and a 5kΩ (R1) resistor in series
are chosen for optimum phase margin and fast transient
response.
3
1
EA
is the compensation capacitor
is the compensation resistor
is the output resistance of the error amplifier
f
P_COM
f
Z_COM
PRODUCT DATASHEET
=
=
2π · R
2π · R
AAT1405
1
1
EA
1
· C
· C
3
3
1405.2010.06.1.0