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What type of oscillator do I need?I want to buy it in my country.

It is NOT just an Oscillator.
It is a Circuit that Contains an Oscillator Circuit, PLUS Numerous Other Parts.

You Don't say Where you Live, But I DOUBT you will find Anything like this in Your Country.
And it appears you have a Definite LACK of Knowledge to make this yourself.
 
The IC is Small Enough, But it is the 6.8uH Ferrite Core Choke that will be the SPACE Problem.
True, there are some small ones depending on load current. Since OP's never specify anythi ng about their designs, I didn't recommend any caps or inductors.
 
It also requires a Few Capacitors.
And Surface Mount Tantalum Caps are Quite Small.
Check out the Data Sheet for the ICL7660.
Tantalums can't be used with the LM2731 or LM2733 I posted, the switch frequency is well above their resonant frequency. Have to use ceramics.
 
Tantalums can't be used with the LM2731 or LM2733 I posted, the switch frequency is well above their resonant frequency. Have to use ceramics.

COPIED FROM THE LM2731 DATA SHEET:

A single ceramic capacitor of value 4.7 μF to 10 μF will
provide sufficient output capacitance for most applications. If
larger amounts of capacitance are desired for improved line
support and transient response, tantalum capacitors can be
used.
 
COPIED FROM THE LM2731 DATA SHEET:

A single ceramic capacitor of value 4.7 μF to 10 μF will
provide sufficient output capacitance for most applications. If
larger amounts of capacitance are desired for improved line
support and transient response, tantalum capacitors can be
used.
Tants can be used assuming you have provided the 4.7 - 10 uF ceramic which is called out in the statement above. The Tant will add bulk capacitance, not provide switching currents. The self resonant freq of most Tants is too low for that. At 1.6 MHz switching, they are too slow to even wave as they go by.


Tantalums can be used only on the slower switching version (600 kHz) if parallelled by a ceramic.

Copied from the data sheet (which I wrote BTW):

SELECTING THE EXTERNAL CAPACITORS
The best capacitors for use with the LM2731 are multi-layer
ceramic capacitors.
They have the lowest ESR (equivalent
series resistance) and highest resonance frequency which
makes them optimum for use with high frequency switching
converters.//

In general, if electrolytics are used, it is recommended that
they be paralleled with ceramic capacitors to reduce ringing,
switching losses, and output voltage ripple




In other words: electrolytics are unsuitable for use other than adding bulk capacitance. Ceramics are needed for the switching duty. Tantalums will ring like crazy at 600 kHz and are completely useless at the 1.6 MHz frequency. If you use a Tant, you have to add a ceramic also so it's smarter just to use the ceramic.
 
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This was copied and pasted in here from the NATIONAL DATA SHEET.

SELECTING THE OUTPUT CAPACITOR


A single ceramic capacitor of value 4.7 μF to 10 μF will

provide sufficient output capacitance for most applications. If

larger amounts of capacitance are desired for improved line

support and transient response, tantalum capacitors can be

used. Aluminum electrolytics with ultra low ESR such as

Sanyo Oscon can be used, but are usually prohibitively

expensive. Typical AI electrolytic capacitors are not suitable

for switching frequencies above 500 kHz due to significant

ringing and temperature rise due to self-heating from ripple

current. An output capacitor with excessive ESR can also

reduce phase margin and cause instability.

In general, if electrolytics are used, it is recommended that

they be paralleled with ceramic capacitors to reduce ringing,

switching losses, and output voltage ripple.
----------------------------------------------------------------------------------------------------------
And I have used Tantalum caps in Many High Frequency circuit, without problems.
Much higher frequency than this.

But to each there own thinking.
 
This was copied and pasted in here from the NATIONAL DATA SHEET.

SELECTING THE OUTPUT CAPACITOR


A single ceramic capacitor of value 4.7 μF to 10 μF will

provide sufficient output capacitance for most applications. If

larger amounts of capacitance are desired for improved line

support and transient response, tantalum capacitors can be

used. Aluminum electrolytics with ultra low ESR such as

Sanyo Oscon can be used, but are usually prohibitively

expensive. Typical AI electrolytic capacitors are not suitable

for switching frequencies above 500 kHz due to significant

ringing and temperature rise due to self-heating from ripple

current. An output capacitor with excessive ESR can also

reduce phase margin and cause instability.

In general, if electrolytics are used, it is recommended that

they be paralleled with ceramic capacitors to reduce ringing,

switching losses, and output voltage ripple.
----------------------------------------------------------------------------------------------------------
And I have used Tantalum caps in Many High Frequency circuit, without problems.
Much higher frequency than this.

But to each there own thinking.

I'm not telling you how to think, I am telling you how the LM2731 part works. I am the guy who took the data on resonant frequencies for the elect caps. I recall the resonant freqs were in the 400 - 600 kHz ballpark for this size parts and that means if you use them on a switcher clocking 600 kHz they will not look capacitive, but they will ring like a resonator. Some will be functional but output noise will be severe. Guess how I learned that. You can use them as bulk capacitance in parallel with a ceramic cap. As for the 1.6 MHz switcher part, I couldn't count the number of calls I took from () who could not understand why they didn't work with Tantalum caps despite the fact the switching frequency was higher than the resonant freq of the cap which means the "capacitor" actually acted like an inductor at the switching frequency, hence not functional. It would have been better if, as I had urged, we had simply stated on the data sheet that Tantalums should not be used at all, but Marketing would never allow that and it's not strictly accurate. As long as the correct ceramic cap is present, a tant can be added since the cer cap will supply the switch current and the Tant will do nothing except supply load current during a transient. That was explicitly stated in one rev but I did not have final revision authority.

But we all need to learn so I invite you to fire up a 1.6MHz version of the 2731 and see how well it works using only tiny Tantalum caps (OP's #1 design constraint was overall size). The 600 KHz version MAY be functional with tants depending on the cap if you can stand the noise on the output. But the only thing the 1.6M version did when using Tantalum caps was generate phone calls to the applications support line.
 
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And based on the LT3527 data sheet, Linear Technology basically copied what I wrote. They are also recommending ceramics for the switch caps.
http://cds.linear.com/docs/en/datasheet/3537fd.pdf


"Output and Input Capacitor Selection
Low ESR (equivalent series resistance) capacitors should
be used to minimize the output voltage ripple. Multilayer
ceramic capacitors are an excellent choice as they have
extremely low ESR and are available in small footprints.
A 4.7μF to 10μF output capacitor is sufficient for most
boost applications. Larger values up to 22μF may be used
to obtain extremely low output voltage ripple and improve
transient response. X5R and X7R dielectric materials are
preferred for their ability to maintain capacitance over
wide voltage and temperature ranges. Y5V types should
not be used."


As I did, they mention Tantalum in context of using to provide large amounts of capacitance to support load transients:

"a tantalum capacitor may be used
in demanding applications that have large load transients."
 
Here is the reason you don't use Tantalums on a 1.6 Mhz switcher. Here is an impedance plot I found on a Kemet low impedance Tantalum cap. It goes resonant at about 500k which means at frequencies above that, it looks inductive (which is why the impedance rises with frequency). The resosnance frequency is the lowest value of the impedance curve.

Notice also that they show an impedance plot for tant paralleled by ceramic that doesn't go resonant until about 5 MHz. That parallel combination would work.

http://www.kemet.com/Lists/TechnicalArticles/Attachments/140/2007 CARTS - Low Impedance Ta Capacitors.pdf

Tant IMP.jpg
 
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