Electronic Components Datasheet Search
  English  ▼

Delete All
ON OFF
ALLDATASHEET.COM

X  

Preview PDF Download HTML

LTC3409A Datasheet(PDF) 11 Page - Linear Technology

Part No. LTC3409A
Description  600mA Low VIN Buck Regulator in 3mm 3mm DFN
Download  16 Pages
Scroll/Zoom Zoom In 100% Zoom Out
Maker  LINER [Linear Technology]
Homepage  http://www.linear.com
Logo 

LTC3409A Datasheet(HTML) 11 Page - Linear Technology

Zoom Inzoom in Zoom Outzoom out
 11 / 16 page
background image
LTC3409A
11
3409af
APPLICATIONS INFORMATION
The output ripple
ΔVOUT is determined by:
ΔVOUT =ΔIL ESR+
1
8• f • COUT
⎝⎜
⎠⎟
where f = operating frequency, COUT = output capacitance
and
ΔIL = ripple current in the inductor. For a fixed output
voltage, the output ripple is highest at maximum input
voltage since
ΔIL increases with input voltage. Aluminum
electrolytic and dry tantalum capacitors are both available
in surface mount configurations. In the case of tantalum,
it is critical that the capacitors are surge tested for use
in switching power supplies. An excellent choice is the
AVX TPS series of surface mount tantalum. These are
specially constructed and tested for low ESR so they give
the lowest ESR for a given volume. Other capacitor types
include Sanyo POSCAP, Kemet T510 and T495 series, and
Sprague 593D and 595D series. Consult the manufacturer
for other specific recommendations.
Using Ceramic Input and Output Capacitors
Higher value, lower cost ceramic capacitors are now avail-
able in smaller case sizes. Their high ripple current, high
voltage rating and low ESR make them ideal for switching
regulator applications. Because the LTC3409A’s control
loop does not depend on the output capacitor’s ESR for
stable operation, ceramic capacitors can be used to achieve
very low output ripple and small circuit size.
However, care must be taken when these capacitors are
used at the input and the output. When a ceramic capacitor
is used at the input and the power is supplied by a wall
adapter through long wires, a load step at the output can
induce ringing at the input, VIN. At best, this ringing can
couple to the output and be mistaken as loop instability. At
worst, a sudden inrush of current through the long wires
can potentially cause a voltage spike at VIN, large enough
to damage the part.
When choosing the input and output ceramic capacitors,
choose the X5R or X7R dielectric formulations. These
dielectrics have the best temperature and voltage charac-
teristics of all the ceramics for a given value and size.
Output Voltage Programming
The output voltage is set by a resistive divider according
to Equation 2:
VOUT = 0.612V 1+
R1
R2
⎝⎜
⎠⎟
(2)
The external resistive divider is connected to the output,
allowing remote voltage sensing as shown in Figure 1.
VFB
VOUT
R1
R2
3409A F01
GND
LTC3409A
Figure 1
Efficiency Considerations
The efficiency of a switching regulator is equal to the output
power divided by the input power times 100%. It is often
useful to analyze individual losses to determine what is
limiting the efficiency and which change would produce
the most improvement. Efficiency can be expressed as:
Efficiency = 100% – (L1 + L2 + L3 + ...)
where L1, L2, etc. are the individual losses as a percent-
age of input power.
Although all dissipative elements in the circuit produce
losses, two main sources usually account for most of
the losses in LTC3409A circuits: VIN quiescent current
and I2R losses. The VIN quiescent current loss dominates
the efficiency loss at very low load currents whereas the
I2R loss dominates the efficiency loss at medium to high
load currents. In a typical efficiency plot, the efficiency
curve at very low load currents can be misleading since
the actual power lost is of no consequence as illustrated
in Figure 2.


Html Pages

1  2  3  4  5  6  7  8  9  10  11  12  13  14  15  16 


Datasheet Download




Link URL




Privacy Policy
ALLDATASHEET.COM
Does ALLDATASHEET help your business so far?  [ DONATE ]  

About Alldatasheet   |   Advertisement   |   Datasheet Upload   |   Contact us   |   Privacy Policy   |   Alldatasheet API   |   Link Exchange   |   Manufacturer List
All Rights Reserved© Alldatasheet.com


Mirror Sites
English : Alldatasheet.com  |   English : Alldatasheet.net  |   Chinese : Alldatasheetcn.com  |   German : Alldatasheetde.com  |   Japanese : Alldatasheet.jp
Russian : Alldatasheetru.com  |   Korean : Alldatasheet.co.kr  |   Spanish : Alldatasheet.es  |   French : Alldatasheet.fr  |   Italian : Alldatasheetit.com
Portuguese : Alldatasheetpt.com  |   Polish : Alldatasheet.pl  |   Vietnamese : Alldatasheet.vn