
SYNC
GND
PGND
SW
R1
560k
R2
300k
VO =3.3V
6.8 H
m
C =22 F
6.3V
O
m
VIN
LBI
C =10 F
25V
I
m
1 F
m
2
3
4
8
9
7
5
11
12
16
10
6
13
14
15
1
V =4.3Vto17V
I
VIN
EN
VINA
PGND
GND PwPD
R5
R6
AGND
TPS62110
SW
LBO
PG
R3
R7
R4
FB
Cff
10pF
NO LOAD OPERATION
THEORY OR OPERATION / DESIGN PROCEDURE
Inductor Selection
SLVS630C – APRIL 2007 – REVISED MAY 2008 .............................................................................................................................................................. www.ti.com
DETAILED DESCRIPTION (continued)
Figure 19. LBI With Increased Hysteresis
When the converter operates in the forced PWM mode and there is no load connected to the output, the
converter regulates the output voltage by allowing the inductor current to reverse for a short time.
Table 1. List of Inductors
MANUFACTURER (1)
TYPE
INDUCTANCE
DC RESISTANCE
SATURATION CURRENT
Coilcraft
MSS6132-682
6.8 H
65 mR (max)
1.5 A
Epcos
B82462G4682M
6.8 H
50 mR (max)
1.5 A
Sumida
CDRH5D28-6R2
6.2 H
33 mR (typ)
1.8 A
SLF6028T-6R8M1R5
6.8 H
35 mR (typ)
1.5 A
TDK
SLF7032T-6R8M1R6
6.8 H
41 mR (typ)
1.6 A
7447789006
6.8 H
44 mR (typ)
2.75 A
Wurth
7447779006
6.8 H
33 mR (typ)
3.3 A
744053006
6.2 H
45 mR (typ)
1.8 A
(1)
The manufacturer's part numbers are used for test purposes only.
The control loop of the TPS6211x family requires a certain value for the output inductor and the output capacitor
for stable operation. As long as the nominal value of L × C
≥ 6.2 H × 22 F, the control loop has enough phase
margin and the device is stable. Reducing the inductor value without increasing the output capacitor (or vice
versa) may cause stability problems. There are applications where it may be useful to increase the value of the
output capacitor, e.g., for a low transient output voltage change. From a stability point of view, the inductor value
could be decreased to keep the L × C product constant. However, there are drawbacks if the inductor value is
decreased. A low inductor value causes a high inductor ripple current and therefore reduces the maximum dc
output current.
Table 2 gives the advantages and disadvantages when designing the inductor and output
capacitor.
16
Copyright 2007–2008, Texas Instruments Incorporated