LT1963AES8 Просмотр технического описания (PDF) - Linear Dimensions Semiconductor
Номер в каталоге
Компоненты Описание
производитель
LT1963AES8 Datasheet PDF : 28 Pages
| |||
LT1963A Series
APPLICATIONS INFORMATION
Y5V dielectrics are good for providing high capacitances in
a small package, but exhibit strong voltage and temperature
coefficients as shown in Figures 10 and 11. When used
with a 5V regulator, a 10µF Y5V capacitor can exhibit an
effective value as low as 1µF to 2µF over the operating
temperature range. The X5R and X7R dielectrics result in
more stable characteristics and are 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.
Voltage and temperature coefficients are not the only
sources of problems. Some ceramic capacitors have a
piezoelectric response. A piezoelectric device generates
voltage across its terminals due to mechanical stress,
similar to the way a piezoelectric accelerometer or micro-
phone works. For a ceramic capacitor the stress can be
induced by vibrations in the system or thermal transients.
“FREE” Resistance with PC Traces
The resistance values shown in Table 2 can easily be made
using a small section of PC trace in series with the output
capacitor. The wide range of non-critical ESR makes it
easy to use PC trace. The trace width should be sized to
handle the RMS ripple current associated with the load.
The output capacitor only sources or sinks current for a few
microseconds during fast output current transitions. There
is no DC current in the output capacitor. Worst case ripple
current will occur if the output load is a high frequency
(>100kHz) square wave with a high peak value and fast
edges (< 1µs). Measured RMS value for this case is 0.5
times the peak-to-peak current change. Slower edges or
lower frequency will significantly reduce the RMS ripple
current in the capacitor.
Table 2. PC Trace Resistors
0.5oz CU
1.0oz CU
2.0oz CU
Width
Length
Width
Length
Width
Length
10mΩ
0.011" (0.28mm)
0.102" (2.6mm)
0.006" (0.15mm)
0.110" (2.8mm)
0.006" (0.15mm)
0.224" (5.7mm)
20mΩ
0.011" (0.28mm)
0.204" (5.2mm)
0.006" (0.15mm)
0.220" (5.6mm)
0.006" (0.15mm)
0.450" (11.4mm)
30mΩ
0.011" (0.28mm)
0.307" (7.8mm)
0.006" (0.15mm)
0.330" (8.4mm)
0.006" (0.15mm)
0.670" (17mm)
20
BOTH CAPACITORS ARE 16V,
1210 CASE SIZE, 10µF
0
X5R
–20
–40
–60
Y5V
–80
–100
0 2 4 6 8 10 12 14 16
DC BIAS VOLTAGE (V)
1963A F10
Figure 10. Ceramic Capacitor DC Bias Characteristics
40
20
0
X5R
–20
–40
Y5V
–60
–80 BOTH CAPACITORS ARE 16V,
1210 CASE SIZE, 10µF
–100
–50 –25 0 25 50 75
TEMPERATURE (°C)
100 125
1963A F11
Figure 11. Ceramic Capacitor Temperature Characteristics
1963afe
17
Share Link: 