THS6032_14 Datasheet, PDF (14/35 Pages) Texas Instruments – LOW-POWER ADSL CENTRAL-OFFICE LINE DRIVER

THS6032
SLOS233F – APRIL 1999 – REVISED AUGUST 2009....................................................................................................................................................... www.ti.com
CLASS-AB MODE OPERATION
The class-G architecture produces sizable power dissipation savings over traditional class-AB designs while
maintaining low distortion requirements. The only drawback to the class-G design is the requirement of 4 power
supply voltages, 2 more than a typical line driver requires. In certain instances, the addition of two separate
power supplies may be cost prohibitive or PCB space prohibitive. In these cases there are two options, use a
traditional amplifier, such as a THS6012, or use the THS6032 in class-AB mode.
Using the THS6032 in class-AB mode will give several functional benefits over the THS6012. This includes
shutdown capability, low-impedance output while in shutdown state, and a slight reduction in quiescent current.
One important thing to remember is that the THS6032 running in class-AB mode, will be only about as efficient
as the THS6012. This means that the power dissipation of the THS6032 will increase dramatically and must be
accounted for. Failure to do so will result in a part which continuously overheats and may lead to failure.
To use the THS6032 in class-AB mode, the user should always connect the V_CC(L) power supply pins to GND.
The internal V_CC(L) paths were not designed for continuous full output current and could possibly fail. The V_CC(H)
paths were designed for the full output currents and thus, should be used for class-AB mode operation.
The performance of the THS6032 while in class-AB mode is very similar to the class-G mode. Figure 7 and
Figure 12 show THS6032 performance while in class-AB mode.
DEVICE PROTECTION FEATURES
The THS6032 has two built-in features that protect the device against improper operation. The first protection
mechanism is output current limiting. Should the output become shorted to ground the output current is
automatically limited to the value given in the data sheet. While this protects the output against excessive
current, the device internal power dissipation increases due to the high current and large voltage drop across the
output transistors. Continuous output shorts are not recommended and could damage the device. Additionally,
connection of the amplifier output to one of the high supply rails [ ±V_CC(H) ] can cause failure of the device and is
not recommended.
The second built-in protection feature is thermal shutdown. Should the internal junction temperature rise above
approximately +180°C, the device automatically shuts down. Such a condition could exist with improper heat
sinking or if the output is shorted to ground. When the junction temperature drops below +150°C, the internal
thermal shutdown circuit automatically turns the device back on.
THERMAL INFORMATION
The THS6032 is available in a thermally-enhanced DWP package and a VFP package, which are members of
the PowerPAD family of packages. These packages are constructed using a downset leadframe upon which the
die is mounted [see Figure 38(a) and Figure 38(b) for the DWP views]. This arrangement results in the lead
frame being exposed as a thermal pad on the underside of the package [see Figure 38©)]. Because this thermal
pad has direct thermal contact with the die, excellent thermal performance can be achieved by providing a good
thermal path away from the thermal pad.
DIE
Side View (a)
Thermal
Pad
DIE
End View (b)
Bottom View (c)
A. The thermal pad is electrically isolated from all terminals in the package.
Figure 38. Views of Thermally-Enhanced DWP Package
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