PJ1583CM 데이터 시트보기 (PDF) - Promax Johnton
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PJ1583CM Datasheet PDF : 6 Pages
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PJ1581/PJ1582/PJ1583
Dual Input Low Dropout Voltage Regulator
Protection Diodes
In normal operation PJ1581 family does not need any
protection diodes between the Adjust pin and the output and
from the output to the input to prevent die overstress. Internal
resistors are limiting the internal current paths on the Adjust
pin. Therefore even with bypass capacitors on the Adjust pin no
protection diode is needed to ensure device safety under
short-circuit conditions. The Adjust pin can be driver on a
transient basis +/-7V with respect to the output without any
device degradation.
A protection diode between the Output pin and Vpower pin is
not usually needed. Microsecond surge currents of 50A to
100A can be handled by the internal diode between the Output
pin and Vpower pin of the device. In normal operations it is
difficult to get those values of surge currents even with the use
of large output capacitances. Only with high value output
capacitors, such as 1000uF to 5000uF and the Vpower pin is
instantaneously shorted to ground, damage can occur. A diode
from output to input is recommended.
Figure 6. Optional Clamp Diodes Protect Against
Input Crowbar Circuits
resistance between the Control and Power sections.
Virtually all the power dissipated by the device is dissipated in
the power transistor. The temperature rise in the power
transistor will be greater than the temperature rise in the
Control section making the thermal resistance lower in the
Control section. At power levels below 12W the temperature
gradient will be less than 25℃ and the maximum ambient
temperature will be determined by the junction temperature of
the Control section. This is due to the lower maximum junction
temperature in the Control section. At power levels above 12W
the temperature gradient will be greater than 25℃ and the
maximum ambient temperature will be determined by the
Power section. In both cases the junction temperature is
determined by the total power dissipated in the device. For
most low dropout applications the power dissipation will be
less than 12W.
The power in the device is made up of two components: the
power in the output transistor and the power in the control
circuit.
The power in the control circuit is negligible.
The power in the control circuit is equal to:
Pcontrol = ( Vcontrol – Vout ) ( Icontrol )
Where Icontrol is equal Iout / 100 (typ)
The power in the out transistor is equal to:
Poutput = ( Vpower – Vout ) ( Iout )
The total power is equal to:
Ptotal = Pcontrol + Poutput
Junction-to-case thermal resistances is specified from the IC
junction to the bottom of the case directly below the die. This is
the lowest resistance path for the heat flow. In order to ensure
If PJ1581 is connected as a single supply device with the the best possible thermal flow this area of the package to the
control and power input ins shorted together the internal heat sink proper mounting is required. Thermal compound at
diode between the output and the power input pin will the case-to-heat sink interface is recommended. A thermally
protect the control input pin.
conductive spacer can be used, if the case of the device must be
Thermal Considerations
electrically isolated, but its added contribution to thermal
The PJ1581 family have internal power and thermal limiting resistance has to be considered.
circuit designed to protect the device under overload conditions.
However maximum junction temperature ratings should not be
exceeded under continuous normal load conditions. Careful
consideration must be given to all sources of thermal resistance
from junction to ambient, including junction-to-case,
case-to-heat sink interface and heat sink resistance itself.
Junction temperature of the Control section can urn up to125℃.
Junction temperature of the Power section can run up to 150℃.
Due to the thermal gradients between the power transistor and
the control circuitry there is a significant difference in thermal
5-6
2002.rev.A
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