I need to bias 5 LCD panels, each with +5.2 V and -4.8 V. I was hoping to find a single IC that would supply enough current. Each display draws 0.8 A. The supply is 12 V, 5A. A two-IC solution could work as well.
As far as I know there is no part available that integrates a buck and a negative buck/boost in one part. So the only solution I can suggest is a dual IC solution. For buck and 4A output current, TPS5450 with 6A switch current could be a solution and for the negative output you could even use the same part in a buck/boost configuration as described in this application note: http://www.ti.com/litv/pdf/slyt286.
+5.2V and -4.8V: What type of LCD do you use?
Best regards, Brigitte
Thanks so much for your help. I'm actually interfacing to medium-sized OLED displays.
I was thinking that another way of doing it would be to use three TPS65131 chips. I would then use a 5 V DC source that I have access to through the extra 4 pins of an ATX connector. Also, using three chips, one for each pair of displays (with one display port not being used) would work well with the current PCBs I'm designing.
Any words of caution when using the TPS65131?
I just realized that your solution would cost around $20 and mine would cost $150. I wonder why the TPS65131 chips cost so much?
Technically you could also use TPS65131 3 times. I did not suggest this, because you need more ICs and more external circuitry than with 2* TPS5450.
The cost of the ICs given in the web for 1000 pieces is $2.5 for TPS5450 and $2.45 for TPS65131. So I expect you calculated the total bill of material cost. Having a look on the schematics of the two solutions, the external parts you need for the TPS5450 solution is roughly 1/3 of the external part number for the TPS65131 solution. This is reflected in the cost, therefore I expect roughly 3 times the cost with the TPS65131 solution. I do not know where the extremely high difference in your cost is coming from.
I was mistaken about the cost of the TPS65131. I was looking at the evaluation module. It seems the ICs are around the same price. But you are right about there being many more external components. I think the first solution that you mentioned is my best bet. Thanks for your help.
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