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What is output capacitor for LDO Evaluation Board?
In your circuit 10µF is the actual regulator output capacitor, 4.7µH inductor + 100µF capacitor are a low-pass filter. The 0.33R might be there to dampen the LC circuit spikes at resonant frequency. The evaluation board is for a very sensitive circuit, that needs an extremely clean power source.
When does dropout voltage occur in a LDO circuit?
Dropout voltage is the input-to-output differential voltage at which the circuit ceases to regulate against further reductions in input voltage; this point occurs when the input voltage approaches the output voltage. Figure 1 shows a typical LDO regulator circuit.
What is the standby current in a LDO regulator?
Standby current is the input current drawn by a regulator when the output voltage is disabled bya shutdown signal. The reference and the error amplifier in an LDO regulator are not loadedduring the standby mode, as shown in Figure 4.
Why does the output capacitor affect the regulator?
The output capacitance also affects the regulator’s response to changes in load current. The control loop has finite large-signal bandwidth, so the output capacitor must supply most of the load current for very fast transients.
What should ESR be for low dropout regulators?
Low-dropout regulators (LDOs) from Analog Devices can operate with small, space-saving ceramic capacitors as long as they have low effective series resistance (ESR); the ESR of the output capacitor affects the stability of the LDO control loop. A minimum capacitance of 1 µF with a maximum ESR of 1 Ω is recommended to ensure stability.
What kind of resistor is used in LDO regulator?
On the evaluation board, there is a 4.7uH inductor, a 0.33 ohm resistor, and a 100 uF capacitor rather than just the 1uF recommended in the datasheet. I want to know why they used a very low value resistor together with a high value capacitor.
Why are ESR capacitors used in LC circuit?
The resistor may also be there to reduce oscillation (more correctly, “ringing”) in the LC circuit. Finally got to look at the datasheet. As @Hearth mentioned in the comments, the ADP7104 is made for use with low ESR ceramic capacitors. That makes it much more likely that the series resistor is there to reduce ringing in the filter.
How is the efficiency of a LDO regulator determined?
The efficiency of an LDO Regulator is dependent on the quiescent current and input to output voltage. Efficiency is given by: By minimizing the dropout voltage as well as the quiescent current, the efficiency of LDO can be increased. It is the maximum output voltage variation for a load current step or input voltage step.