7
DEMO MANUAL DC330
LOW DROPOUT REGULATOR
Paste Mask Top
PCB LAYOUT A D FIL
U
W
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-
tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
Silkscreen Top
Component Side
Figure B4. A Ceramic Capacitor Responds to Light Pencil
Tapping. Piezoelectric Based Response Approaches 80
µ
V
P-P
Figure B3. Ceramic Capacitor Temperature Characteristics
Show Large Capacitance Shift. Effect Should Be Considered
When Determining Circuit Error Budget
Voltage and temperature coefficients are not the only
problem sources. Some ceramic capacitors have a piezo-
electric response. A piezoelectric device generates voltage
across its terminals due to mechanical stress, similar to
the way a piezoelectric accelerometer or microphone
works. For a ceramic capacitor the stress can be induced
by vibrations in the system or thermal transients. The
resulting voltages produced can cause appreciable amounts
of noise, especially when a ceramic capacitor is used for
noise bypassing. A ceramic capacitor produced Figure␣ B4’s
trace in response to light tapping from a pencil. Similar
vibration-induced behavior can masquerade as increased
output voltage noise.
TEMPERATURE (
°
C)
–50
40
20
0
–20
–40
–60
–80
–100
25
75
AN83 FB03
–25
0
50
100
125
Y5V
CHANGE IN VALUE (%)
X5R
BOTH CAPACITORS ARE 16V,
1210 CASE SIZE, 10
µ
F
200ms/DIV
AN83 FB04.tif
20
µ
V/DIV
APPLICATIO S I FOR ATIO
W
U
U
U
Downloaded from
Downloaded from
Downloaded from
Downloaded from
Downloaded from
Downloaded from
Downloaded from
