Generating required voltages

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Dear all
I have finally found a reasonable priced 7" tft lcd!
I want to be sure how to connect it to LCP1788.I have a few questions, Do you have any idea what I should do?

1- I need to generate 10.4v for analog power
2- I need to generate 16v for VGH
3- I need to generate -7v for VGL
4- Where should I connect the Vcom? I have no idea!
5- I need to power the LCD with a 3.3v and connects it's RGB and VS and HS signals to LPC1788.

6- should tie other inputs either to 3.3 or gnd for proper operation.

Any comments are well come,including suggestions for DC/DC convertors!

You can see the attached data sheet.

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You've noted the voltages, what are the currents?

Search out the friendly arm schematics, there's an example of the circuitry involved.

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Do you know the exact link?
How should i connect the Vcom terminal?
The currents are less than 200ma

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How hard is it to googles on the interwebs for "friendlyarm schematics" which is exactly what i did.

What did i get?
http://www.friendlyarm.net/downl...

Is there some cultural aversion to searching? If in doubt, googles first, ask on forums later.

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there is no AT070TN92 TFT used on any of their boards!

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Get some wool and a plastic comb.. comb like crazy.. if insufficient current parallel more combs

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Quote:
Get some wool and a plastic comb.. comb like crazy.. if insufficient current parallel more combs

you are such an idiot!

I have found a suitable single cheap circuit!
But what should i do with Vcom terminal!?

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Look at the schematics for the 3.5" and 4.3" lcds - you might get some ideas. Whilst it's not your specific lcd panel, there's similarities. Now, where is that spoon.

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Sigh!

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Ali_dehbidi wrote:
4- Where should I connect the Vcom? I have no idea!

I expect that you are concerned because Vcom is included in table 3.1.1. Typical Operation Conditions
as Input signal voltage with an operating value of TBD, along with DVdd, AVdd, Vgh and Vgl which have Min, Typ and Max values.

You need a newer, completed data sheet.

This link has an (embedded flashplayer) Innolux application note, version E, dated 2010/1/27
includes table 3.2. Power Operation Conditions that specifies Vcom as Min 3.8V, Typ 4.0V and Max 4.2V.
The included schematics develop all required voltages.
-- Schematic 5.2 Vcom Reference Cicuit (has pot adj - may be contrast control)
-- Schematic 5.3 Backlight Driver Reference Circuit
-- Schematic 5.4 DC/DC Reference Circuit
http://wenku.baidu.com/view/398eef6d58fafab069dc0296.html?from=related

This AT070TN82 data sheet gives a typical value for Vcom in table 3.2. Typical Operation Conditions.
http://elinux.org/images/0/09/At070tn82.pdf

The schematic at this site shows generate Vcomin for AT070TN92 Vcom (circled item page 10).
http://elinux.org/images/5/53/Lookbook-schematics.pdf

For your google-fu ------
Beware that google has recently abandoned use of the boolean + operator - people are pissed.
Now you have to place double quotes around each 'must find' item.

Stan

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Thanks a lot guys for answering specially Stan. Do you think my recommended circuit can do the job?is there any thing simpler!?

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Last Edited: Sat. Nov 5, 2011 - 08:51 AM
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There is another question?
What is your opinion about the lcd cost? I mean how much do you think it's reasonable and how much are you willing to pay to buy one of them?

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It's cheaper because it does not have a DC/DC converter on board to generate its required voltages. A more expensive module does, so the low price is partly offset by the need to add extra components and extra engineering effort. The lack of an on board converter means it is more difficult to change to another display module, if the need arises.

Depending on in what industry you are, component obsolence might be an issue. A more expensive display module might available much longer. If your gadget is some industrial control it might need service or repairs over a period that might span decades. You don't want to tell your customer to ditch your device if it happens to break after one year and you cannot repair it because the display is no longer being manufactured.

So, there's more than just the price ;)

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Quote:
You don't want to tell your customer to ditch your device if it happens to break after one year and you cannot repair it because the display is no longer being manufactured.

Ok,what about stocking them?

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That also has its costs and only feasible if you don't sell too many devices I guess.

Keeping one spare for each gadget you sell, basically means you have to pay for two display modules per device, but just give the customer only one. So effectively you more than doubled the price of a single panel.

Of course you can play with this ratio. But it helps if you select a panel from a reputable manufacturer's official catalogue then one from some obscure web shop that bought a few thousand of them surplus.

I almost sure that every display panel in all mass-produced products is a custom one, not one you can buy from regular distribution.

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Quote:
I almost sure that every display panel in all mass-produced products is a custom one, not one you can buy from regular distribution.

What about old ks108 ones!

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