ESR value of the compensating capacitor for LDO regulator

[pseudockb]

esr value

I am currently designing a LDO voltage regulator. It is well known that the ESR of the compensating capacitor contributes a zero to stabilize the system. Right now, I have a problem, i.e. I do not know what is the ESR value of a ceramic capacitor. I cannot find any information on ESR value of a ceramic capacitor. Could someone please tell me what is the typical value of the ESR of a ceramic capacitor?

I also notice that some LDO voltage regulator sold by TI are guaranteed to be stable with any capacitor regardless of the ESR value. Any circuits techniques to achieve this? Thanks.

 

[smartdream]

typical esr values

I am currently designing a LDO voltage regulator. It is well known that the ESR of the compensating capacitor contributes a zero to stabilize the system. Right now, I have a problem, i.e. I do not know what is the ESR value of a ceramic capacitor. I cannot find any information on ESR value of a ceramic capacitor. Could someone please tell me what is the typical value of the ESR of a ceramic capacitor?

I also notice that some LDO voltage regulator sold by TI are guaranteed to be stable with any capacitor regardless of the ESR value. Any circuits techniques to achieve this? Thanks.

The ESR value vary with different Capacitance and different factories, for 1uF and 2.2uF, the typical ESR
about 10mOhm~50mOhm,.

 

[Chethan]

esr value of ceramic capacitors

While simulating the LDO with output capacitor, add the wire resistance also. This wire resistance is acting in series with the ESR of the cap and so will add up. This wire resistance can be as large as 1 ohm.

 

[jutek]

pic esr capacitor

to Chethan:


what model of output capacitor and its esr do you use??

regards

 

[smartdream]

ldo esr

maybe the ESL of PCB should be taken into consideration.

 

[Chethan]

capacitor esr values

the foll doc can provide a better picture.
Normal ESR values for output capacitors are very small. But its CSR that plays a major role in stability.

CSR = RESR + Radd

 

[Chethan]

typical esr values ceramic

the foll doc can provide a better picture

 

[Vamsi Mocherla]

ldo ceramic

Hey for the Ceramic caps, the ESR values are almost zero.

Importantly, every LDO operates in a stability zone which is dependant on the ESR of the load capacitor. TI must have done the regulator which has a very wide zone of stability which takes care of the ESRs of all the available caps in the market for a given load.

 

[jutek]

esr compensation in ldo regulator

but very low ESR value means zero's location is in high frequencies. To move it to lower frequencies(better phase margin) it's needed to increase capacity, but it causes lower domain's pole frequency. Cout and regulator's Rout creates time constant which determines how fast output voltage can be change from one value to the other.

so it means a additional compensation circuit is needed, can you advice any?