Datasheet

1
OUT REF
2
R
V V 1
R
æ ö
= ´ +
ç ÷
è ø
DI
L
+ V
OUT
1 *
V
OUT
V
IN
L f
I
L
max + I
out
max )
DI
L
2
TPS62560, TPS62561
TPS62562
SLVS815C –JANUARY 2008–REVISED DECEMBER 2009 www.ti.com
OUTPUT VOLTAGE SETTING
For adjustable output voltage versions, the output voltage can be calculated as:
with an internal reference voltage V
REF
, typically 0.6 V.
To minimize the current through the feedback divider network, R
2
should be 180 kΩ or 360 kΩ. The sum of R
1
and R
2
should not exceed ~1 MΩ, to keep the network robust against noise. An external feed-forward capacitor,
C
1
, is required for optimum load transient response. The value of C
1
should be in the range between 22 pF and
33 pF.
In case of using the fixed output voltage version (TPS62562), V
out
has to be connected to the feedback pin FB.
Route the FB line away from noise sources, such as the inductor or the SW line.
OUTPUT FILTER DESIGN (INDUCTOR AND OUTPUT CAPACITOR)
The TPS62560 is designed to operate with inductors in the range of 1.5 μH to 4.7 μH and with output capacitors
in the range of 4.7 μF to 22 μF. The part is optimized for operation with a 2.2-μH inductor and 10-μF output
capacitor.
Larger or smaller inductor values can be used to optimize the performance of the device for specific operation
conditions. For stable operation, the L and C values of the output filter may not fall below 1 μH effective
inductance and 3.5 μF effective capacitance.
Inductor Selection
The inductor value has a direct effect on the ripple current. The selected inductor must be rated for its dc
resistance and saturation current. The inductor ripple current (ΔI
L
) decreases with higher inductance and
increases with higher V
IN
or V
OUT
.
The inductor selection also impacts the output voltage ripple in PFM mode. Higher inductor values lead to lower
output voltage ripple and higher PFM frequency; lower inductor values lead to a higher output voltage ripple but
lower PFM frequency.
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 transients the inductor current rises above the calculated
value.
(1)
(2)
where:
f = Switching frequency (2.25 MHz, typical)
L = Inductor value
ΔI
L
= Peak-to-peak inductor ripple current
I
L
max = Maximum inductor current
Table 2. List of Inductors
DIMENSIONS, mm INDUCTANCE, μH INDUCTOR TYPE SUPPLIER
2,5 × 2 × 1 max 2 MIPS2520D2R2 FDK
2,5 × 2 × 1,2 max 2 MIPSA2520D2R2 FDK
2,5 × 2 × 1 max 2.2 KSLI-252010AG2R2 Hitachi Metals
2,5 × 2 × 1,2 max 2.2 LQM2HPN2R2MJ0L Murata
3 × 3 × 1,5 max 2.2 LPS3015 2R2 Coilcraft
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Product Folder Link(s): TPS62560 TPS62561 TPS62562