Datasheet

DI
L
+
V
O
V
I
V
I
* V
O
L ƒ
sw
DI
L(MAX)
+ I
O(MAX)
)
DI
L
2
TPS62660, TPS62665
www.ti.com SLVS871C –FEBRUARY 2010– REVISED JULY 2011
APPLICATION INFORMATION
INDUCTOR SELECTION
The TPS62660 series of step-down converters have been optimized to operate with an effective inductance
value in the range of 0.3μH to 1.3μH and with output capacitors in the range of 4.7μF to 10μF. The internal
compensation is optimized to operate with an output filter of L = 0.47μH and C
O
= 4.7μF. Larger or smaller
inductor values can be used to optimize the performance of the device for specific operation conditions. For more
details, see the CHECKING LOOP STABILITY section.
The inductor value affects its peak-to-peak ripple current, the PWM-to-PFM transition point, the output voltage
ripple and the efficiency. The selected inductor has to be rated for its dc resistance and saturation current. The
inductor ripple current (ΔI
L
) decreases with higher inductance and increases with higher V
I
or V
O
.
(1)
with: f
SW
= switching frequency (6 MHz typical)
L = inductor value
ΔI
L
= peak-to-peak inductor ripple current
I
L(MAX)
= maximum inductor current
In high-frequency converter applications, the efficiency is essentially affected by the inductor AC resistance (i.e.
quality factor) and to a smaller extent by the inductor DCR value. To achieve high efficiency operation, care
should be taken in selecting inductors featuring a quality factor above 25 at the switching frequency. Increasing
the inductor value produces lower RMS currents, but degrades transient response. For a given physical inductor
size, increased inductance usually results in an inductor with lower saturation current.
The total losses of the coil consist of both the losses in the DC resistance (R
(DC)
) and the following
frequency-dependent components:
• The losses in the core material (magnetic hysteresis loss, especially at high switching frequencies)
• Additional losses in the conductor from the skin effect (current displacement at high frequencies)
• Magnetic field losses of the neighboring windings (proximity effect)
• Radiation losses
The following inductor series from different suppliers have been used with the TPS62660 converters.
Table 1. List of Inductors
MANUFACTURER SERIES DIMENSIONS
LQM21PN1R0NGR 2.0 x 1.2 x 1.0 max. height
MURATA LQM21PNR54MGC 2.0 x 1.2 x 1.0 max. height
LQM2MPN1R0NG0 2.0 x 1.6 x 1.0 max. height
PANASONIC ELGTEAR82NA 2.0 x 1.2 x 1.0 max. height
TOKO MDT2012-CX1R0A 2.0 x 1.2 x 1.0 max. height
TAIYO YUDEN NM2012NR82, NM2012N1R0 2.0 x 1.2 x 1.0 max. height
FDK MIPS2012D1R0-X2 2.0 x 1.2 x 1.0 max. height
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