TPS650532 Datasheet, PDF (17/27 Pages) Texas Instruments – 5-CHANNEL POWER MGMT IC WITH TWO STEP DOWN CONVERTERS AND 3 LOW-INPUT VOLTAGE LDOs

TPS65053
TPS650531
TPS650532
www.ti.com ............................................................................................................................................. SLVS754C – MARCH 2007 – REVISED SEPTEMBER 2009
OUTPUT VOLTAGE
3.3 V
3.0 V
2.85 V
2.5 V
1.8 V
1.6 V
1.5 V
1.2 V
R1
680 kΩ
510 kΩ
560 kΩ
510 kΩ
300 kΩ
200 kΩ
300 kΩ
330 kΩ
Table 1. Typical Resistor Values
R2
150 kΩ
130 kΩ
150 kΩ
160 kΩ
150 kΩ
120 kΩ
200 kΩ
330 kΩ
NOMINAL VOLTAGE
3.32 V
2.95 V
2.84 V
2.51 V
1.80 V
1.60 V
1.50 V
1.20 V
TYPICAL CFF
47 pF
47 pF
47 pF
47 pF
47 pF
47 pF
47 pF
47 pF
OUTPUT FILTER DESIGN (INDUCTOR AND OUTPUT CAPACITOR)
Inductor Selection
The two converters operate typically with 2.2µH output inductor. Larger or smaller inductor values can be used to
optimize the performance of the device for specific operation conditions. For output voltages higher than 2.8V, an
inductor value of 3.3µH minimum should be selected, otherwise the inductor current will ramp down too fast
causing imprecise internal current measurement and therefore increased output voltage ripple under some
operating conditions in PFM mode.
The selected inductor has to be rated for its DC resistance and saturation current. The DC resistance of the
inductance will influence directly the efficiency of the converter. Therefore an inductor with lowest DC resistance
should be selected for highest efficiency.
Equation 6 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 6. This is
recommended because during heavy load transient the inductor current will rise above the calculated value.
DI_L + Vout
1
*
Vout
Vin
Lƒ
I_Lmax
+
I_out
max
)
DI_L
2
(6)
with:
f = Switching Frequency (2.25-MHz typical)
L = Inductor Value
Δ I_L = Peak-to-peak inductor ripple current
I_Lmax = Maximum Inductor current
The highest inductor current occurs at maximum Vin. Open core inductors have a soft saturation characteristic,
and they can normally handle higher inductor currents versus a comparable shielded inductor.
A more conservative approach is to select the inductor current rating just for the maximum switch current of the
corresponding converter. It must be considered, that the core material from inductor to inductor differs and will
have an impact on the efficiency especially at high switching frequencies. Refer to Table 2 and the typical
applications for possible inductors.
Inductor Type
LPS3010
LPS3015
LPS4012
VLF4012
Table 2. Tested Inductors
Inductor Value
2.2 µH
3.3 µH
2.2 µH
2.2 µH
Supplier
Coilcraft
Coilcraft
Coilcraft
TDK
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