TLV4120_14 Datasheet, PDF (15/26 Pages) Texas Instruments – HIGH OUTPUT CURRENT DIFFERENTIAL DRIVE OPERATIONAL AMPLIFIER WITH SHUTDOWN

TLV4120
HIGH OUTPUT CURRENT DIFFERENTIAL DRIVE OPERATIONAL
AMPLIFIER WITH SHUTDOWN
SLOS310B − DECEMBER 2000 − REVISED SEPTEMBER 2006
APPLICATION INFORMATION
general power design considerations
When driving heavy loads at high junction temperatures there is an increased probability of electromigration
affecting the long term reliability of ICs. Therefore for this not to be an issue:
D The output current must be limited (at these high junction temperatures) or
D The junction temperature must be limited.
The maximum continuous output current at a die temperature of 150°C will be 1/3 of the current at 105°C.
The junction temperature will be dependent on the ambient temperature around the IC, thermal impedance from
the die to the ambient, and power dissipated within the IC.
T_J = T_A + θ_JA × P_DIS
Where:
P_DIS is the IC power dissipation and is equal to the output current multiplied by the voltage dropped across
the output of the IC.
θ_JA is the thermal impedance between the junction and the ambient temperature of the IC.
T_J is the junction temperature.
T_A is the ambient temperature.
Reducing one or more of these factors will result in a reduced die temperature.
The use of the MSOP PowerPAD dramatically reduces the thermal impedance from junction to case. And with
correct mounting, the reduced thermal impedance will greatly increase the IC’s permissible power dissipation
and output current handling capability. For example, the power dissipation of the PowerPAD is increased to
above 1 W. Sinusoidal and pulse-width modulated output signals will also increase the output current capability.
The equivalent dc current is proportional to the square-root of the duty cycle:
IDC(EQ) + ICont ^Ǹ(duty cycle)
CURRENT DUTY CYCLE
AT PEAK RATED CURRENT
100
70
50
EQUIVALENT DC CURRENT
AS A PERCENTAGE OF PEAK
CURRENT
100
84
71
Note that with an operational amplifier, a duty cycle of 70% will often result in the op-amp sourcing current 70%
of the time and sinking current 30%; therefore, the equivalent dc current will still be 0.84 times the continuous
current rating at a particular junction temperature.
The differential nature of the TLV4120 means that it will dissipate approximately four times the power of a
single-ended amplifier driving a similar load referenced to mid rail. The TLV4120 will however be delivering four
times the power to the load.
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