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| TPIC74101-Q1 Datasheet, PDF (25/32 Pages) Texas Instruments – BUCK/BOOST SWITCH-MODE REGULATOR | |||
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TPIC74101-Q1
www.ti.com
SLIS140 â OCTOBER 2011
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.
Buck Mode
⢠Select inductor ripple current ÎIL: for example ÎIL = 0.2 à IOUT
⢠Calculate inductor L
L
+
ÇVIN *
fSW
V Ç OUT
DIL
V OUT
V IN
(H)
(2)
where fSW is the regulator switching frequency.
⢠Inductor peak current
I L,max
+
IOUT
)
DIL
2
(A)
(3)
⢠Output voltage ripple
DVOUT + DIL
ÇESR ) 8
Ç 1
fSW COUT
(V (pâp))
(4)
Usually, the first term is dominant.
COUT
+
I pk(t on
8
) toff)
Vripple
(F)
(5)
Boost Mode
⢠Select inductor ripple current ÎIL: for example ÎIL = 0.2 à IIN
⢠Calculate inductor L
L
+
ÇVOUT
fSW
* VINÇ
DIL
V IN
V OUT
(H)
(6)
where fSW is the regulator switching frequency.
⢠Inductor peak current
Ip
+
IL,max
+
I IN
)
DIL
2
(A)
(7)
⢠Output voltage ripple
DVOUT + Ip
Ç Ç IOUT
ESR ) fSW
1
*
VIN
VOUT
COUT
(V(pâp))
(8)
Copyright © 2011, Texas Instruments Incorporated
Product Folder Link(s): TPIC74101-Q1
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