Nominally 12 Volt Lead acid batteries typically operate in the range of When under charge, the voltage can easily get over 14V — sufficient to cause damage to sensitive 12V equipment. Voltage Regulators A voltage regulator is a device which takes an input voltage and outputs a stable fixed voltage. Variable voltage regulators are available such as the very useful LMT which the user can set to output any required voltage 1. For the more commonly required voltages of 3.
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Furthermore, a quiescent current reduction circuit has been included which reduces the ground current when the differential between the input voltage and the output voltage exceeds approximately 3V. The quiescent current with 1A of output current and an inputoutput differential of 5V is therefore only 30 mA. During line transients, such as load dump when the input voltage can momentarily exceed the specified maximum operating voltage, the regulator will automatically shut down to protect both the internal circuits and the load.
Familiar regulator features such as short circuit and thermal overload protection are also provided. Features n n n n n n n Dropout voltage typically 0. May be increased without bound to maintain regulation during transients. Locate as close as possible to the regulator. This capacitor must be rated over the same operating temperature range as the regulator and the ESR is critical; see curve.
The package markings indicated are what will appear on the actual device. Boldface limits apply over the entire operating temperature range of the indicated device. Operating Conditions are conditions under which the device functions but the specifications might not be guaranteed. For guaranteed specifications and test conditions see the Electrical Characteristics. Exceeding the maximum allowable power dissipation will cause excessive die temperature, and the regulator will go into thermal shutdown.
It is recommended that 6 vias be placed under the center pad to improve thermal performance. Note 3: ESD rating is based on the human body model, pF discharged through 1. All limits at temperature extremes are guaranteed via correlation using standard Statistical Quality Control methods.
Note 6: Output current will decrease with increasing temperature but will not drop below 1A at the maximum specified temperature. Temperature Output Voltage vs. Temperature Quiescent Current vs. Temperature Quiescent Current Quiescent Current www. Larger values of output capacitance will give improved transient response. The acceptable range of ESR plotted versus load current is shown in the graph below. It is essential that the output capacitor meet these requirements, or oscillations can result.
However, the designer must ensure that the ESR will stay inside the limits shown over the entire operating temperature range for the design. This type of capacitor is not well-suited for low temperature operation. Solid tantalum capacitors have a more stable ESR over temperature, but are more expensive than aluminum electrolytics.
A cost-effective approach sometimes used is to 13 www. To optimize the heat sinking ability of the plane and PCB, solder the tab of the package to the plane.
If two capacitors are paralleled, the effective ESR is the parallel of the two individual values. Under all possible operating conditions, the junction temperature must be within the range specified under Absolute Maximum Ratings.
To determine if a heatsink is required, the power dissipated by the regulator, PD, must be calculated. Power Dissipation Diagram The next parameter which must be calculated is the maximum allowable temperature rise, TR max.
TA max is the maximum ambient temperature which will be encountered in the application. Copper 1 ounce Area for the TO Package As shown in the figure, increasing the copper area beyond 1 square inch produces very little improvement.
Maximum Power Dissipation vs. As used herein: 1. Life support devices or systems are devices or systems which, a are intended for surgical implant into the body, or b support or sustain life, and whose failure to perform when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury to the user.
A critical component is any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness.
LM2940 direct replacement for LM7805?
Furthermore, a quiescent current reduction circuit has been included which reduces the ground current when the differential between the input voltage and the output voltage exceeds approximately 3V. The quiescent current with 1A of output current and an inputoutput differential of 5V is therefore only 30 mA. During line transients, such as load dump when the input voltage can momentarily exceed the specified maximum operating voltage, the regulator will automatically shut down to protect both the internal circuits and the load. Familiar regulator features such as short circuit and thermal overload protection are also provided. Features n n n n n n n Dropout voltage typically 0.
LM2940 DATASHEET PDF
I was using datashet above to supply 5v to my Atmegap-pu project in my automotive environment for controlling the signal that datqsheet on some lights via Mosfet. Email Required, but never shown. This capacitor must be rated over the same operating temperature range as the regulator and 2 the ESR is critical — see curve. Sign up using Email and Password. What is the input voltage? Tom Wilson 68 7. Could that contribute to the oscillation?
LM2940 12V 1A Low Dropout Regulator
Perhaps I have misunderstood this specification? Please see updated question with attached schematic. The vishay datasheet shows change of ESR with frequency. For reference, this is the LM datasheet. If you look at page 18 in its datasheet the ESR for the uF, 6.
LM2940 direct replacement for LM7805?