Datasheet

O O
RMS O
I I
V V
I I max 1
V V
æ ö
= ´ ´ -
ç ÷
è ø
O
I
O O ESR
O
V
1
V
1
V V R
L f 8 C f
-
æ ö
D = ´ ´ +
ç ÷
´ ´ ´
è ø
O
I
RMS O O
V
1
V
1
I (C ) V
L f
2 3
-
= ´ ´
´
´
TPS62110, TPS62111
TPS62112, TPS62113
www.ti.com SLVS585C –JULY 2005–REVISED OCTOBER 2012
Table 2. List of Inductors
MANUFACTURER PART NO. INDUCTANCE DC RESISTANCE SATURATION CURRENT
Coilcraft MSS6132-682 6.8 µH 65 mΩ (max) 1.5 A
HA3808-AL 6.8 µH 99 mΩ (typ) 4.4A
Epcos B82462G4682M 6.8 µH 50 mΩ (max) 1.5 A
Sumida CDRH5D28-6R2 6.2 µH 33 mΩ (typ) 1.8 A
SLF6028T-6R8M1R5 6.8 µH 35 mΩ (typ) 1.5 A
TDK
SLF7032T-6R8M1R6 6.8 µH 41 mΩ (typ) 1.6 A
7447789006 6.8 µH 44 mΩ (typ) 2.75 A
Wurth 7447779006 6.8 µH 33 mΩ (typ) 3.3 A
744053006 6.2 µH 45 mΩ (typ) 1.8 A
OUTPUT-CAPACITOR SELECTION
A 22-μF (typical) output capacitor is needed with a 6.8-μH inductor. For an output voltage greater than 5 V, a 33-
μF (minimum) output capacitor is required for stability. For best performance, a low-ESR ceramic output
capacitor is needed.
Just for completeness, the RMS ripple current is calculated as:
(4)
The overall output ripple voltage is the sum of the voltage spike caused by the output capacitor ESR plus the
voltage ripple caused by charging and discharging the output capacitor:
(5)
where the highest output-voltage ripple occurs at the highest input voltage V
I
.
INPUT-CAPACITOR SELECTION
The nature of the buck converter is a pulsating input current; therefore, a low ESR input capacitor is required for
best input voltage filtering and for minimizing the interference with other circuits caused by high input-voltage
spikes. The input capacitor should have a minimum value of 10 µF and can be increased without any limit for
better input-voltage filtering. The input capacitor should be rated for the maximum input ripple current calculated
as:
(6)
The worst-case RMS ripple current occurs at D = 0.5 and is calculated as: I
RMS
= I
O
/2. Ceramic capacitors show
a good performance because of their low ESR value, and they are less sensitive against voltage transients
compared to tantalum capacitors. Place the input capacitor as close as possible to the VIN and PGND pins of the
IC for best performance.
An additional 1 µF input capacitor is required from VINA to AGND. VIN and VINA must be connected to the
same source. An RC filter from VIN to VINA is not recommended.
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