TS1582CM525 查看數據表（PDF） - TSC Corporation
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TS1582CM525 Datasheet PDF : 7 Pages
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Application Information (continued)
Protection Diodes
In normal operation TS1582 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 25A to 50A 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
If TS1582 is connected as a single supply device with
the control and power input ins shorted together the
internal diode between the output and the power input
pin will protect the control input pin.
Thermal Considerations
The TS1582 family have internal power and thermal
limiting 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 to125oC. Junction
temperature of the Power section can run up to 150oC.
Due to the thermal gradients between the power
transistor and the control circuitry there is a significant
difference in thermal 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 25oC 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 oC 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 the best possible thermal flow
this area of the package to the heat sink proper
mounting is required. Thermal compound at the
case-to-heat sink interface is recommended. A
thermally conductive spacer can be used, if the case of
the device must be electrically isolated, but its added
contribution to thermal resistance has to be considered.
TS1582 series
6-6
2003/12 rev. A
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