Richard,

Thanks for your reply. The circuit looks something like this:

                        ____ Peltier (1.7ohm)
                   ----|____|----
                   |            |
                   |            |
         L (100uH) |       C1   |   L (100uH)
              ___  |     ||     |  ___
       V1 o---UUU--o-----||-----o--UUU---o V2
                   |     ||     |
                   |            |
                   |            |
               C2 ---          --- C2
                  ---          ---
                   |            |
                  ^^^          ^^^
                  GND          GND


C1,C2 are 10uF. V1 and V2 are outputs from an H-bridge running at 
10kHz (12Vp-p, 10A). Direction of current into peltier can be changed 
(V1-V2 and V2-V1) to either heat or cool. Aim of this LC filter is to 
filter output of H-Bridge to less than 10% voltage ripple.

> ripple current
Calculated to about 150mA AC. The datasheet from manufacturer suggests 
up to 200mA is okay.

>load type
Basically resistive. Peltier module. Manufacturer's specs says 
1.70ohm.

> other filter components,
Two Inductors. Differential LC filter.

> capacitor types you are considering,
Murata: 16V,10uF in SMD1210. Dielectric X7R. Tolerance +/-10% and 
change across -55C to 125C +/-15%.

> Working temperature
Enormous amounts of forced-air cooling. So working temperature should 
be <<50C.

> consequences of failure
Ripples in the voltage across peltier, leading to quicker failure of 
module.

> actual application
Peltier heater/cooler.

Looking forward to your help,
Mohit.

----- Original Message ----- 
From: "Richard Prosser" <rhprosser@gmail.com>
To: "Microcontroller discussion list - Public." <piclist@mit.edu>
Sent: Wednesday, October 04, 2006 12:16 AM
Subject: Re: [PIC] Capacitor derating


> Mohit,
> You need to supply more information. Along the lines of ripple
> current, load type, other filter components, the capacitor types you
> are considering, working temperature, consequences of failure etc.
> etc. And a hint of the actual application may help also iin case 
> there
> are special requirements you don't know about yet.
>
> RP
>
> On 04/10/06, Mohit M. (Lists) <mohit.lists@gmail.com> wrote:
>> Hi,
>>
>> Could somebody tell me if I need to derate multi-layer ceramic
>> capacitors? Specifically, can 10uF/16V MLCC be used in filtering 
>> the
>> ouput of a 12V PWM output from an H-bridge?
>>
>> Thanks,
>> Mohit.
>>
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