So I have a 10-36V source, and require a 5V and 15V output. A switching regulator conditions the source to 15V. It's big and expensive and because of the current levels involved (unregulated, these currents don't pass through the regulators), stacked boards are involved and it just makes board organization restrictive, and the project already requires small size, so a second switching regulator is not possible.
I have to step down the 15V from the switching regulator down to 5V. Let's say 500mA maximum (probably 200mA average. I can either use a 10V+5V LDO in series, two 5V LDOs in parallel, or use use a zener to chop off 5V and let the LDO chop off the remaining 5V. Using just one cuts too close to the thermal limit.
Any ideas which is best? I think the zener is cheapest but I can't find a large enough zener that can handle 500mA with dropping out. I think the series LDOs might have lower noise than the parallel ones, but I don't really know. But the problem with using series/parallel LDOs is that the 15V input cuts pretty close (less than 1V) or if you look at another spec, it's dead on the maximum input rating.
The LDO I am using is from Ti, the Reg103 fixed voltage version.
EDIT: JUst noticed no 10V version of the regulator exist so if I use two series regulators, I'll have to find another first stage LDO which may have a higher max input voltage.
I have to step down the 15V from the switching regulator down to 5V. Let's say 500mA maximum (probably 200mA average. I can either use a 10V+5V LDO in series, two 5V LDOs in parallel, or use use a zener to chop off 5V and let the LDO chop off the remaining 5V. Using just one cuts too close to the thermal limit.
Any ideas which is best? I think the zener is cheapest but I can't find a large enough zener that can handle 500mA with dropping out. I think the series LDOs might have lower noise than the parallel ones, but I don't really know. But the problem with using series/parallel LDOs is that the 15V input cuts pretty close (less than 1V) or if you look at another spec, it's dead on the maximum input rating.
The LDO I am using is from Ti, the Reg103 fixed voltage version.
EDIT: JUst noticed no 10V version of the regulator exist so if I use two series regulators, I'll have to find another first stage LDO which may have a higher max input voltage.
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