value for in/output capacitor of LTC3564

Question

Hello 
 From the datasheet of LTC3564, it suggests both 22uf for input and output. May I know if it's possible to use 10uF? the current load should be less than 600ma. 
 Besides, are there any good choice for our purpose? 3.3-4.3Vin to 1V out, >=600ma output current, noise sensitive circuit. 
 
 Thank you very much!

MarkusHP · Accepted Answer

Hello, 
 there is no simple yes or no to your question if 10uF are possible. At least you have to find out. LTSpice simulations might help as well, but not all effects of ceramic capacitors (biasing,...) are considered in the standard model. This valuable article shines some light on this issue 
 https://www.analog.com/en/analog-dialogue/raqs/raq-issue-192.html 
 
 Back to your question: smaller Cout will increase ripple voltage, something which you want to avoid for a noise sensitive circuit, correct? 
 Smaller Cin might lead to more input ripple with negative impact on EMI as well. 
 Smaller Cout influence the control loop, hence other values of Cff (parallel to top FB resistor) might be needed for optimum stability 
 So to say you have to find out with your real hardware and test the circuit behaviour under all extreme/worst case conditions to check if smaller capacitance values degrade the desired performance too much or not. 
 
 kr 
 Markus)

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value for in/output capacitor of LTC3564