TLE2426: creating a single power supply for video signal with virtual gnd

Hi Brittany,

The TLE2426 is a supply splitter intended to provide an output midpoint voltage that is one-half of V+. It is mostly used in op amp applications where instead of using a dual (+/-V ) supply, a supply that provides V+, 1/2 V+ and GND can be used. Instead of the op amp input and output being referenced to ground as with a dual supply, they become referenced to the mid-supply 1/2 V+ voltage level. For some applications that is acceptable and negates the need for an separate V- supply.

Your ADC is a high speed device with high output current drive capability (50 mA). I think you were on track with the LT1054 solution in that it provides a +/-5 V output, with an output current up to 100 mA. The internal 1.1 V drop at a 100 mA output current may be an issue. If you can power the LT1054 with a higher input voltage and then add +5 V and -5 V LDOs at the voltage converter's outputs that would result in cleaner, more stable +/-5 V output levels for the ADC.

TI has other power products that can provide the -5 V output at even higher current levels. The forum you queried about the LT1054 should be able to direct you to them.

Regards, Thomas
Precision Amplifiers Applications Engineering

Hi Thomas,

Thank you very much for your help! 

Also on a side note, why did you call the chip an ADC? I don't believe that is correct.

Hi Brittany,

That was my mistake; the device is certainly not an ADC. However, my comments apply to the multiplexer/amplifier device as well.

Sorry about any confusion that might have caused.

Regards, Thomas

Precision Amplifiers Applications

Hi Thomas, no worries. Quick question about getting a smooth voltage output. I have this schematic right here (see picture attached). Would you recommend me sending VA- through a negative voltage regulator and have the VA+ through a positive one and supply a higher voltage than 5V ? Is there anyway to smooth these voltages out with just one regulator instead of two? 

Hi Brittany,

Adding linear regulators after the LT1054 output will help reduce noise and further improve regulation. Any linear regulator LDO, requires an input voltage somewhat higher than the expected output voltage and load current. Thus, if VA+ in your schematic isn't clean and stable enough alone, it will have to be increased to a higher level before being applied to a +5 V output LDO regulator.

Reading TI's LT1054 datasheet it looks like it is capable of producing the -5 V output with +3.5 to + 15 V supply per Table 2. Again, the input voltage (VA-) to a -5 V LDO would have to be greater than -5 V. I believe the LT1054 can be set up to for an output voltage greater than -5 V, at least the equations in the datasheet suggest that.

TI has a dual +/-5 V LDO regulator capable of up to 150 mA output, the TPS7A39. It looks has high PSRR out to 2 MHz and looks like it would provide a convenient solution:

www.ti.com/.../tps7a39.pdf

The Power Products E2E support should be able to assist you with information about the LT1054 regulation, noise and capabilities. It may be that the LT1054 -5 V output, without the addition of the LDOs, is adequate for your application.

Regards, Thomas
Precision Amplifiers Applications Engineering