Datasheet

www.ti.com
Buck Mode
L +
ǒ
V
IN
* V
OUT
Ǔ
V
OUT
f
SW
DI
L
V
IN
(1)
I
L,max
+ I
OUT
)
DI
L
2
(2)
DV
OUT
+ DI
L
ǒ
ESR )
1
8 f
SW
C
OUT
Ǔ
(3)
C
OUT
+
I
pk
(
t
on
) t
off
)
8 V
ripple
(4)
Boost Mode
L +
ǒ
V
OUT
* V
IN
Ǔ
V
IN
f
SW
DI
L
V
OUT
(5)
I
p
+ I
L,max
+ I
IN
)
DI
L
2
(6)
DV
OUT
+ I
p
ESR )
I
OUT
ǒ
1 *
V
IN
V
OUT
Ǔ
f
SW
C
OUT
(7)
TPIC74100-Q1
BUCK/BOOST SWITCH-MODE REGULATOR
SLIS125 – DECEMBER 2006
In a two-sided PCB, it is recommended to have ground planes on both sides of the PCB to help reduce noise
and ground-loop errors. The ground connection for the input and output capacitors and IC ground should be
connected to this ground plane.
In a multilayer PCB, the ground plane is used to separate the power plane (where high switching currents and
components are placed) from the signal plane (where the feedback trace and components are) for improved
performance.
Also, arrange the components such that the switching-current loops curl in the same direction. Place the
high-current components such that during conduction, the current path is in the same direction. This prevents
magnetic field reversal caused by the traces between the two half-cycles, helping to reduce radiated EMI.
• Select inductor ripple current DIL: for example ∆ I
L
= 0.2 × I
OUT
• Calculate inductor L:
where f
SW
is the regulator switching frequency.
• Inductor peak current:
• Output voltage ripple:
Usually, the first term is dominant.
• Select inductor ripple current ∆ I
L
: for example ∆ I
L
= 0.2 × I
IN
• Calculate inductor L:
where f
SW
is the regulator switching frequency.
• Inductor peak current:
• Output voltage ripple:
25
Submit Documentation Feedback