Datasheet

OUT
IN(ripple)
SW IN
I D
V
f C
´
=
´
OUT
0.6
R2 R1
V 0.6
= ´
-
OUT
CO
2
OUT OUT
LOAD
1 s C ESR
G 4
L
1 s C (ESR DCR) s L C
DCR R
+ ´ ´
= ´
æ ö
+ ´ + ´ + + ´ ´
ç ÷
+
è ø
DP
OUT
1
f
2 L C
=
´ p ´ ´
ESR
OUT
1
f
2 ESR C
=
´ p ´ ´
( )( )
( ) ( )
EA
1 s C1 (R1 R3) 1 s R4 C2
G
C2 C3
s R1 (C2 C3) 1 s C1 R3 1 s R4
C2 C3
+ ´ ´ + + ´ ´
=
´
æ ö
´ ´ + ´ + ´ ´ ´ + ´
ç ÷
+
è ø
Z1
1
f
2 R4 C2
=
´ p ´ ´
( )
Z2
1 1
f
2 R1 R3 C1 2 R1 C1
= @
´ p ´ + ´ ´ p ´ ´
TPS53313
www.ti.com SLUSAS8 –DECEMBER 2011
To minimize the ripple current drawn from the input source, sufficient input decoupling capacitors should be
placed close to the device. The ceramic capacitor is recommended due to its low ESR and low ESL. The input
voltage ripple can be calculated as below when the total input capacitance is determined by Equation 10.
(10)
Output Voltage Setting Resistors Selection
The output voltage is programmed by the voltage-divider resistor, R1 and R2 shown in Equation 11. R1 is
connected between VFB pin and the output, and R2 is connected between the VFB pin and GND.
Recommended value for R1 is from 1k to 5k. Determine R2 using .
(11)
Compensation Design
The TPS53313 employs voltage mode control. To effectively compensate the power stage and ensure fast
transient response, Type III compensation is typically used.
(12)
The output LC filter introduces a double pole which can be calculated as shown in Equation 13.
(13)
The ESR zero of can be calculated as shown in Equation 14.
(14)
Figure 15 and Figure 16 shows the configuration of Type III compensation and typical pole and zero locations.
Equation 15 through Equation 17 describe the compensator transfer function and poles and zeros of the Type III
network.
(15)
(16)
(17)
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