LT3024IFE Просмотр технического описания (PDF) - Linear Technology
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LT3024IFE Datasheet PDF : 20 Pages
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LT3024
APPLICATIONS INFORMATION
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)
3024 F04
Figure 4. Ceramic Capacitor DC Bias Characteristics
40
20
0
X5R
–20
–40
Y5V
–60
–80
BOTH CAPACITORS ARE 16V,
–100 1210 CASE SIZE, 10μF
–50 –25 0 25 50 75
TEMPERATURE (°C)
100 125
3024 F05
Figure 5. Ceramic Capacitor Temperature Characteristics
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
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 6’s trace in response to light tapping from a pencil.
Similar vibration induced behavior can masquerade as
increased output voltage noise.
COUT = 10μF
CBYP = 0.01μF
ILOAD = 100mA
VOUT
500μV/DIV
100ms/DIV
3024 F06
Figure 6. Noise Resulting from Tapping on a Ceramic Capacitor
Thermal Considerations
The power handling capability of the device will be limited
by the maximum rated junction temperature (125°C). The
power dissipated by the device will be made up of two
components for each output:
1. Output current multiplied by the input/output voltage
differential: (IOUT)(VIN – VOUT), and
2. GND pin current multiplied by the input voltage:
(IGND)(VIN).
The ground pin current can be found by examining the
GND Pin Current curves in the Typical Performance Char-
acteristics section. Power dissipation will be equal to the
sum of the two components listed above.
The LT3024 regulator has internal thermal limiting de-
signed to protect the device during overload conditions.
For continuous normal conditions, the maximum junction
temperature rating of 125°C must not be exceeded. It is
important to give careful consideration to all sources of
thermal resistance from junction to ambient. Additional
heat sources mounted nearby must also be considered.
For surface mount devices, heat sinking is accomplished
by using the heat spreading capabilities of the PC board
3024fa
15
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