THS6022_16 Datasheet, PDF (22/44 Pages) Texas Instruments – 250-mA DUAL DIFFERENTIAL LINE DRIVER

THS6022
SLOS225D – SEPTEMBER 1998 – REVISED JULY 2007
www.ti.com
APPLICATION INFORMATION (continued)
Power Supply Restrictions
Although the THS6022 is specified for operation from power supplies of ±5 V to ±15 V (or singled-ended power
supply operation from 10 V to 30 V), and each amplifier has its own power supply pins, several precautions must
be taken to assure proper operation.
• The power supplies for each amplifier must be the same value. For example, if the driver 1 uses ±15 volts,
then the driver 2 must also use ±15 volts. Using ±15 volts for one amplifier and ±5 volts for another amplifier
is not allowed.
• To save power by powering down one of the amplifiers in the package, the following rules must be followed.
– The amplifier designated driver 1 must always receive power. This is because the internal startup circuitry
uses the power from the driver 1 device.
– The –V_CC pins from both drivers must always be at the same potential.
– Individual amplifiers are powered down by simply opening the V_CC+ connection.
The THS6022 incorporates a standard class A-B output stage. This means that some of the quiescent current is
directed to the load as the load current increases. So under heavy load conditions, accurate power dissipation
calculations are best achieved through actual measurements. For small loads, however, internal power
dissipation for each amplifier in the THS6022 can be approximated by the following formula:
ǒ Ǔ ^{ǒ Ǔ ǒ Ǔ} PD ≅ 2 VCC ICC ) VCC _ VO
VO
RL
where:
P_D = Power dissipation for one amplifier
V_CC = Split supply voltage
I_CC = Supply current for that particular amplifier
V_O = RMS output voltage of amplifier
R_L = Load resistance
To find the total THS6022 power dissipation, we simply sum up both amplifier power dissipation results.
Generally, the worst-case power dissipation occurs when the output voltage is one-half the V_CC voltage. One last
note, which is often overlooked: the feedback resistor (R_F) is also a load to the output of the amplifier and should
be taken into account for low value feedback resistors.
Device Protection Features
The THS6022 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 supply rails (±V_CC) 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 abnormal condition is fixed, the internal thermal shutdown
circuit automatically turns the device back on.
Thermal Information
The THS6022 is packaged in a thermally-enhanced PWP package, which is a member of the PowerPAD family
of packages. This package is constructed using a downset leadframe upon which the die is mounted [see
Figure 49(a) and Figure Figure 49(b)]. This arrangement results in the lead frame being exposed as a thermal
pad on the underside of the package [see Figure 49(c)]. 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.
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