ltc3025-2 Linear Technology Corporation, ltc3025-2 Datasheet - Page 9

• Manufacturer Part Number: ltc3025-2
• Description: 500ma Micropower Vldo Linear Regulators Features
• Manufacturer: Linear Technology Corporation

applicaTions inForMaTion
Output Capacitance and Transient Response
The LTC3025-X is designed to be stable with a wide range
of ceramic output capacitors. The ESR of the output capaci-
tor affects stability, most notably with small capacitors. A
minimum output capacitor of 1µF with an ESR of 0.05Ω or
less is recommended to ensure stability. The LTC3025-X
is a micropower device and output transient response
will be a function of output capacitance. Larger values
of output capacitance decrease the peak deviations and
provide improved transient response for larger load current
changes. Note that bypass capacitors used to decouple
individual components powered by the LTC3025-X will
increase the effective output capacitor value. High ESR
tantalum and electrolytic capacitors may be used, but
a low ESR ceramic capacitor must be in parallel at the
output. There is no minimum ESR or maximum capacitor
size requirements.
Extra consideration must be given to the use of ceramic
capacitors. Ceramic capacitors are manufactured with a
variety of dielectrics, each with different behavior across
temperature and applied voltage. The most common di-
electrics used are Z5U, Y5V, X5R and X7R. The Z5U and
Y5V dielectrics are good for providing high capacitances
in a small package, but exhibit large voltage and tem-
perature coefficients as shown in Figures 3 and 4. When
used with a 2V regulator, a 1µF Y5V capacitor can lose as
much as 75% of its initial capacitance over the operating
temperature range. The X5R and X7R dielectrics result in
more stable characteristics and are usually more suitable
for use as the output capacitor. The X7R type has better
stability across temperature, while the X5R is less expensive
and is available in higher values. In all cases, the output
capacitance should never drop below 0.4µF , or instability
or degraded performance may occur.
Figure 4. Ceramic Capacitor Temperature Characteristics
Figure 3. Ceramic Capacitor DC Bias Characteristics
–100
–100
–20
–40
–60
–80
–20
–40
–60
–80
LTC3025-1/LTC3025-2/
20
20
0
0
LTC3025-3/LTC3025-4
–50
0
BOTH CAPACITORS ARE 1µF,
10V, 0603 CASE SIZE
–25
2
DC BIAS VOLTAGE (V)
TEMPERATURE (°C)
Y5V
BOTH CAPACITORS ARE 1µF,
10V, 0603 CASE SIZE
0
4
25
6
Y5V
X5R
50
X5R
8
30251234 F03
30251234 F04
75
10
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