Datasheet
VIN
GND
EN
FB
SW
TPS62590DRV
L
V
MODE
2.2 Hm
C
OUT
10mF
C1
22pF
R1
R2
C
IN
10mF
PwrPAD
Up to 1A
V
2.5 V to 5.5 V
IN OUT
5
4
2
1
3
6
360kΩ
180kΩ
=1.8V
VIN
GND
EN
FB
SW
TPS62590DRV
L
V
MODE
2.2 Hm
C
OUT
10mF
C1
22pF
R1
R2
C
IN
10mF
PwrPAD
I
V
3.3 V to 5.5 V
IN OUT
5
4
2
1
3
6
820kΩ
182kΩ
=3.3V
OUT,max
=1A
OUT REF
R1
V = V x 1 +
R2
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TPS62590
SLVS897B –JANUARY 2009– REVISED APRIL 2011
www.ti.com
APPLICATION INFORMATION
Figure 20. TPS62590DRV Adjustable 1.8 V
Figure 21. TPS62590DRV Adjustable 3.3 V
OUTPUT VOLTAGE SETTING
The output voltage can be calculated to:
(1)
with the internal reference voltage V
REF
= 0.6V typically.
To minimize the current through the feedback divider network, R2 should be 180 kΩ or 360 kΩ. The sum of R1
and R2 should not exceed ~1MΩ, to keep the network robust against noise. An external feed forward capacitor
C1 is required for optimum load transient response. The value of C1 should be in the range between 22pF and
33pF.
Route the FB line away from noise sources, such as the inductor or the SW line.
OUTPUT FILTER DESIGN (INDUCTOR AND OUTPUT CAPACITOR)
The TPS62590 is designed to operate with inductors in the range of 1.5μH to 4.7μH and with output capacitors in
the range of 4.7μF to 22μF. The part is optimized for operation with a 2.2μH inductor and 10μF 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 1μH effective
inductance and 3.5μF effective capacitance.
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
.
The inductor selection has also impact on the output voltage ripple in PFM mode. Higher inductor values will lead
to lower output voltage ripple and higher PFM frequency, lower inductor values will lead to a higher output
voltage ripple but lower PFM frequency.
Equation 2 calculates the maximum inductor current under static load conditions. The saturation current of the
inductor should be rated higher than the maximum inductor current as calculated with Equation 3. This is
recommended because during heavy load transient the inductor current will rise above the calculated value.
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