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I'm using this DC-DC converter +/-5V output version and I decided to use the trim up setting to get as close to 5.5V as possible. I determined the resistor value using this formula Trim up formula And got around 3.33k, which gives me about +5.56V and -5.59V. However in the datasheet it has a "Voltage adjustment range" part where it has +/-10% for dual output models, which means I can get a maximum of +/-5.5V output.

  1. Obviously I'm getting that (and a bit over), but my question is whether meeting the maximum settings of a DC-DC converter can cause any issues?
  2. Are there potential problems with 'stretching' such converters?
  3. Would they draw more current, drain the battery faster?

Battery input is a Li-Ion 14.4V.

I need this to be around 5.5V because it goes into 2 LDOs that drop the voltage to ~5V (+/-), because as I understand, the greater the difference between intput/output for LDOs, the better their operation (?).

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    \$\begingroup\$ Why bother using the LDO regulators - i.e. just set the output to +/- 5 volts? \$\endgroup\$ – Andy aka Jul 20 '17 at 6:51
  • \$\begingroup\$ What you say about the LDOs is totally wrong! The greater the difference between input and output, the more power is dissipated in the LDO and you have to be sure it doesn't exceed the package specifications. For the LDOs, you simply have to be sure the input/output difference is greater than the expected dropout voltage at your specific output current. The closer you are to this voltage, the better. \$\endgroup\$ – nickagian Jul 20 '17 at 8:55
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Usually for DC-DC regulator like this, the different fixed voltage models contain the same basic design and vary only in the resistor feedback networks to set the voltage. Since the regulator is specified for outputs up to 24V I don't see any issue with this.

However, if you are planning to use an LDO for post-regulation you need to make sure the drop out voltage is at most 0.5V (for a 5.5V to 5V LDO) for your current requirement, otherwise the LDO will go out of regulation.

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As Tony K stated, there should be no problem with adjusting the regulator as you have. Just make sure that you are above the drop out voltage for your LDOs.

However, why not simply run it at +/- 5 volts and bypass the 5V LDO's all together? With a battery powered project, any reduction in power consumption is worth examining.

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