參數(shù)資料
型號: LTC3543EDCB#PBF
廠商: LINEAR TECHNOLOGY CORP
元件分類: 穩(wěn)壓器
英文描述: 1.3 A SWITCHING REGULATOR, 2250 kHz SWITCHING FREQ-MAX, PDSO6
封裝: 2 X 3 MM, 0.75 MM HEIGHT, LEAD FREE, PLASTIC, MO-229, DFN-6
文件頁數(shù): 5/20頁
文件大?。?/td> 329K
代理商: LTC3543EDCB#PBF
LTC3543
13
3543fa
Using Ceramic Capacitors for CIN, COUT and C1
High value, low cost ceramic capacitors are now becoming
available in smaller case sizes. Their high ripple current,
high voltage rating and low ESR make them ideal for switch-
ing regulator applications. Because the LTC3543’s control
loop does not depend on the output capacitor’s ESR for
stable operation, ceramic capacitors can be used freely to
achieve very low output ripple and small circuit size.
However, care must be taken when ceramic 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. This ringing can couple to
the output and be mistaken as loop instability. Even worse,
the 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 resistor divider according
to the following formula:
VV
R
OUT =+
06
1
2
1
.
(4)
The external resistor divider is connected to the output
allowing remote voltage sensing as shown in Figure 3.
Efciency Considerations
The efciency 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 efciency and which change would produce
the most improvement. Efciency can be expressed as:
Efciency = 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 LTC3543 circuits: VIN quiescent current and
I2R losses. The VIN quiescent current loss dominates
the efciency loss at very low load currents whereas the
I2R loss dominates the efciency loss at medium to high
load currents. In a typical efciency plot, the efciency
curve at very low load currents can be misleading since
the actual power lost is of no consequence as illustrated
in Figure 4.
Figure 3. Setting Output Voltage
3543 F03
LTC3543
VFB
GND
R1
R2
0.6V
VOUT < 5.5V
APPLICATIONS INFORMATION
Figure 4. Power Loss vs Load Current
LOAD CURRENT (mA)
100
POWER
LOSS
(mW)
200
300
400
500
0.1
10
100
1000
3543 F04
0
1
VOUT = 1.2V
VOUT = 1.5V
VOUT = 1.8V
VOUT = 2.5V
相關(guān)PDF資料
PDF描述
LTC3543EDCB#TRM 1.3 A SWITCHING REGULATOR, 2250 kHz SWITCHING FREQ-MAX, PDSO6
LTC3543EDCB 1.3 A SWITCHING REGULATOR, 2250 kHz SWITCHING FREQ-MAX, PDSO6
LTC3544BEUD#TR 0.8 A SWITCHING REGULATOR, 2700 kHz SWITCHING FREQ-MAX, PQCC16
LTC3544EUD 0.8 A SWITCHING REGULATOR, 2700 kHz SWITCHING FREQ-MAX, PQCC16
LTC3547BEDDB 0.7 A DUAL SWITCHING CONTROLLER, 2700 kHz SWITCHING FREQ-MAX, PDSO8
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