K04RLM12 Datasheet, PDF (19/23 Pages) Texas Instruments – Operational Amplifier

www.ti.com
POWER LIMITING
OBSOLETE
K04RLM12, LM12CL
SNOSBY8D – MAY 1999 – REVISED APRIL 2013
Should the power ratings of the LM12 be exceeded, dynamic safe-area protection is activated. Waveforms with
this power limiting are shown for the LM12 driving ±26V at 30 Hz into 3Ω in series with 24 mH (θ = 45°). With an
inductive load, the output clamps to the supplies in power limit, as above. With resistive loads, the output voltage
drops in limit. Behavior with more complex RCL loads is between these extremes.
Secondary thermal limit is activated should the case temperature exceed 150°C. This thermal limit shuts down
the IC completely (open output) until the case temperature drops to about 145°C. Recovery may take several
seconds.
POWER SUPPLIES
Power op amps do not require regulated supplies. However, the worst-case output power is determined by the
low-line supply voltage in the ripple trough. The worst-case power dissipation is established by the average
supply voltage with high-line conditions. The loss in power output that can be ensured is the square of the ratio
of these two voltages.
Relatively simple off-line switching power supplies can provide voltage conversion, line isolation and 5-percent
regulation while reducing size and weight.
The regulation against ripple and line variations can provide a substantial increase in the power output that can
be specified under worst-case conditions. In addition, switching power supplies can convert low-voltage power
sources such as automotive batteries up to regulated, dual, high-voltage supplies optimized for powering power
op amps.
HEAT SINKING
A semiconductor manufacturer has no control over heat sink design. Temperature rating can only be based upon
case temperature as measured at the center of the package bottom. With power pulses of longer duration than
100 ms, case temperature is almost entirely dependent on heat sink design and the mounting of the IC to the
heat sink.
The design of heat sink is beyond the scope of this work. Convection-cooled heat sinks are available
commercially, and their manufacturers should be consulted for ratings. The preceding figure is a rough guide for
temperature rise as a function of fin area (both sides) available for convection cooling.
Copyright © 1999–2013, Texas Instruments Incorporated
Product Folder Links: K04RLM12 LM12CL
Submit Documentation Feedback
19