Datasheet

I
Lmax
+ I
outmax
)
DI
L
2
DI
L
+ Vout
1 *
Vout
Vin
L ƒ
c
1
= = 50kHz
2 (1μH 10μF)
f
p´ ´ ´
TPS62065, TPS62067
SLVS833B –MARCH 2010–REVISED NOVEMBER 2013 www.ti.com
OUTPUT FILTER DESIGN (INDUCTOR AND OUTPUT CAPACITOR)
The internal compensation network of TPS6206x is optimized for a LC output filter with a corner frequency of:
The part operates with nominal inductors of 1.0µH to 1.2 µH and with 10µF to 22µF small X5R and X7R ceramic
capacitors. Please refer to the lists of inductors and capacitors. The part is optimized for a 1.0µH inductor and
10µF output capacitor.
Inductor Selection
The inductor value has a direct effect on the ripple current. 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
.
Equation 1 calculates the maximum inductor current in PWM mode under static load conditions. The saturation
current of the inductor should be rated higher than the maximum inductor current as calculated with Equation 2.
This is recommended because during heavy load transient the inductor current rises above the calculated value.
(1)
(2)
With:
f = Switching Frequency (3MHz typical)
L = Inductor Value
ΔI
L
= Peak-to-Peak inductor ripple current
I
Lmax
= Maximum Inductor current
A more conservative approach is to select the inductor current rating just for the switch current limit I
LIMF
of the
converter.
The total losses of the coil have a strong impact on the efficiency of the DC/DC conversion and 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
Table 1. List of Inductors
DIMENSIONS [mm
3
] INDUCTANCE μH INDUCTOR TYPE SUPPLIER
3.2 x 2.5 x 1.0 max 1.0 LQM32PN (MLCC) Murata
3.7 x 4 x 1.8 max 1.0 LQH44 (wire wound) Murata
4.0 x 4.0 x 2.6 max 1.2 NRG4026T (wire wound) Taiyo Yuden
3.5 x 3.7 x 1.8 max 1.2 DE3518 (wire wound) TOKO
Output Capacitor Selection
The advanced fast-response voltage mode control scheme of the TPS6206x allows the use of tiny ceramic
capacitors. Ceramic capacitors with low ESR values have the lowest output voltage ripple and are
recommended. The output capacitor requires either an X7R or X5R dielectric. Y5V and Z5U dielectric capacitors,
aside from their wide variation in capacitance over temperature, become resistive at high frequencies and may
not be used. For most applications a nominal 10µF or 22µF capacitor is suitable. At small ceramic capacitors, the
DC-bias effect decreases the effective capacitance. Therefore a 22µF capacitor can be used for output voltages
higher than 2V, see list of capacitors.
18 Submit Documentation Feedback Copyright © 2010–2013, Texas Instruments Incorporated
Product Folder Links :TPS62065 TPS62067