Datasheet

LM828
SNOS035D –MARCH 2010–REVISED MAY 2013 www.ti.com
(2)
Again, using a low ESR capacitor will result in lower ripple.
CAPACITOR SELECTION
The output resistance and ripple voltage are dependent on the capacitance and ESR values of the external
capacitors. The output voltage drop is the load current times the output resistance, and the power efficiency is
(3)
Where I
Q
(V+) is the quiescent power loss of the IC device, and I
L
2
R
out
is the conversion loss associated with the
switch on-resistance, the two external capacitors and their ESRs.
The selection of capacitors is based on the specifications of the dropout voltage (which equals I
out
R
out
), the
output voltage ripple, and the converter efficiency. Low ESR capacitors (following table) are recommended to
maximize efficiency, reduce the output voltage drop and voltage ripple.
Low ESR Capacitor Manufacturers
Manufacturer Phone Capacitor Type
Nichicon Corp. (708)-843-7500 PL & PF series, through-hole aluminum electrolytic
AVX Corp. (803)-448-9411 TPS series, surface-mount tantalum
Sprague (207)-324-4140 593D, 594D, 595D series, surface-mount tantalum
Sanyo (619)-661-6835 OS-CON series, through-hole aluminum electrolytic
Murata (800)-831-9172 Ceramic chip capacitors
Taiyo Yuden (800)-348-2496 Ceramic chip capacitors
Tokin (408)-432-8020 Ceramic chip capacitors
Other Applications
PARALLELING DEVICES
Any number of LM828s can be paralleled to reduce the output resistance. Each device must have its own
pumping capacitor C
1
, while only one output capacitor C
out
is needed as shown in Figure 13. The composite
output resistance is:
(4)
Figure 13. Lowering Output Resistance by Paralleling Devices
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