AN79L10 stable -10V regulation troubles

S

ssylee

New Member

• Nov 5, 2007

• #1

I have tried to regulate the output voltage to be exactly -10V using the application circuit in the datasheet of AN79L10N on page 10 at https://www.ortodoxism.ro/datasheets/panasonic/SFF00006CEB.pdf .
The voltage closest to -10V that I could get to is -10V. Is there any way of getting closer to -10V? Thanks!

 

Hero999

Banned

• Nov 5, 2007

• #2

What's the problem?

You're getting -10V so obviously you're doing it correctly, unless you've made a typographical error of course.

 

S

ssylee

New Member

• Nov 5, 2007

• #3

The problem that I think I'm having is that I'm getting -10.1 V instead of right at -10 V

 

audioguru

Well-Known Member

Most Helpful Member

• Nov 5, 2007

• #4

The adjustment parts allow you to increase the output voltage of whatever the IC has as a voltage (from 9.6V to 10.4V). You cannot decrease the voltage.
The adjustment parts ruin the excellent voltage regulation of the IC.

If you want an excellent adjustable negative voltage regulator then use an LM337.

 

eblc1388

Active Member

• Nov 5, 2007

• #5

ssylee said:

The problem that I think I'm having is that I'm getting -10.1 V instead of right at -10 V

Click to expand...

The problem is you don't read the datasheet. It is perfectly normal for the regulator to output any voltage between -9.5V and -10.5V.

 

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blueroomelectronics

Well-Known Member

• Nov 6, 2007

• #6

Voltage regulators usually make average voltage references. Reference shunt diodes make excellent references.

 

S

ssylee

New Member

• Nov 6, 2007

• #7

I've taken a look at the 1N4740A zener diode. Apparently it has an error of up to 5%, which basically has the same regulation range as the -10V regulator.

 

Hero999

Banned

• Nov 6, 2007

• #8

An error of 5% means it can be between 9.5V and 10.5V and 10.1V is only 1% error so you've got a good one. Your meter probably has a tollerence of 1% so it could be between 10V and 10.2V.

 

Last edited: Nov 6, 2007

blueroomelectronics

Well-Known Member

• Nov 6, 2007

• #9

ssylee said:

I've taken a look at the 1N4740A zener diode. Apparently it has an error of up to 5%, which basically has the same regulation range as the -10V regulator.

Click to expand...

I said "reference" diode, like a TL431 2.5V precision (adjustable) reference.

 

audioguru

Well-Known Member

Most Helpful Member

• Nov 6, 2007

• #10

The 1N4740A zener diode has a tolerance of 5% at its rated current (25mA). Its voltage changes when the current and the temperature change.

A voltage regulator and voltage reference regulate their voltage very well so it barely changes when the current or temperature change.