Zener diode datasheet parameters clearification

Thread Starter

ArakelTheDragon

Joined Nov 18, 2016
1,353
I am looking at this diode "1N4734A", its a 5.6V diode, but in the datasheet I want to know what is "at IZK mA" and "ZZT at IZT Ω", on page 2?
"ZZK Ω" should be the resistance of the zener, meaning 600 Ohms.

The zener is working normally on the test current of 45ma, but can work at a maximum of 162mA, so it shouldnt be a problem if I leave it at 100mA nominal current?

Edit:
Whats the minimum current under which the zener will start conducting?
 

Thread Starter

ArakelTheDragon

Joined Nov 18, 2016
1,353
The idea is to make "R4" properly, so when the "9V" battery gets discharged, there will be enough current for the transistor (1mA), the output has to be "5V", "80mA" about, all the time to power a MCU.

When I am using a shop "9V" battery with no signification what so ever (there are no mA/h on it), when is it considered discharged? Is it at "9V", "8V", at "7V"?

Since a battery has to be charged with more voltage normally, lets say for a car battery we charge with about "14V", does that mean that if the car battery is "55A/h" for 2 hours we can get "55 Ampers" per hour and than the battery will be discharged, because at "12V" its considered discharged?

That means for a "9V" battery from the shop, if its 2000mA/h, and at "7V" its considered discharged, for 2 hours I can drain "2A" and thats it? I dont believe I can draw "2 Ampers" from this battery!

Or is that battery charged to "11V" and when it gets to "9V" its discharged?
Are all batteries, including those standard ones in the shop charged to a higher voltage?
 

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Thread Starter

ArakelTheDragon

Joined Nov 18, 2016
1,353
Ok, I said there are no markings on it. Its the standard battery thats even in your multimer.

EDIT:
Yes its a PP3, does that mean I can drain 1.2A per hour for 2 hours from it
?
 

bertus

Joined Apr 5, 2008
21,947
Hello,

Did you read the notes below the table?

NOTES:
(1) The Zener impedance is derived from the 1KHZ AC voltage which results when an AC current having an RMS value equal to 10% of the Zener current (IZT or IZK)
is superimposed on IZT or IZK. Zener impedance is measured at two points to insure a sharp knee on the breakdown curve and to eliminate unstable units
(2) Valid provided that electrodes at a distance of 10mm from case are kept at ambient temperature
(3) Measured under thermal equilibrium and DC test conditions

This page will tell you something about the zener parameters:
https://www.electronics-notes.com/a...diode-datasheet-specifications-parameters.php

Bertus
 

Thread Starter

ArakelTheDragon

Joined Nov 18, 2016
1,353
I know the page about diodes that you gave me, but its a bit difficult to understand the datasheet.
What is the difference between "Zzt" and "Zzk" ? Where do I find the minimum current needed for the diode to operate, I did not see it? The test current is "45mA", the maximum current is "162mA", I dont know which is the proper resistance, "5.6V/45mA test current", is 100Ohms, but I have "600" or "5", which one should I use?

The zener diode is working in the 3rd quadrant of the graphic. Meaning it keeps the voltage stable even when the current changes. Here I dont see the volt amper characteristic.

I knew that about the 1200mA/h but I forgot.......

How much will the battery be discharged to, after 1 hour of draining 1200mA/h or 10 hours of draining 120a/h?
When I buy it, to how much is it charged?
 

Jony130

Joined Feb 17, 2009
5,351
What is the difference between "Zzt" and "Zzk" ?
Zzt is a Zener dynamic impedance/resistance at zener test current Izt (45mA).
Zzk is Zenera dynamice impedance at "knee", Zener knee current Izk (1mA)

Where do I find the minimum current needed for the diode to operate, I did not see it?
Izk is the minimum current. But at this current, the Zener diode voltage will be lower than this 5.6V.

And instead of a Zener diode try to use the TL431.
 

Jony130

Joined Feb 17, 2009
5,351
The idea is to make "R4" properly, so when the "9V" battery gets discharged, there will be enough current for the transistor (1mA), the output has to be "5V", "80mA" about, all the time to power a MCU.
So if the battery is discharged, for where do you get this additional current (80mA) to power your 5V system?
And you want to draw 100mA from the 9V battery?
 

Thread Starter

ArakelTheDragon

Joined Nov 18, 2016
1,353
When the battery is discharged too much, the voltage will drop, but until then it will work perfect. This is why I implemented a system to warn when the voltage drops under 3.3V. Until the voltage of the battery drops to under 6V, the regulator will drain 5V, 80mA, which is enough to power the MCU. Whats wrong with drawing 80mA from a PP3 battery?

Just like with any system, once the voltage drops, its over, you need a new battery.
 

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Thread Starter

ArakelTheDragon

Joined Nov 18, 2016
1,353
What is there to compare? The circuit is the same except for the transistor to regulate, putting "0.6V" in the PNP emitter, limiting the current to 2.5mA. The drop over the transistor will be 2.8V with 80mA current. Plus the reverse diode is missing.

I dont need it to be perfect, +-20mV is acceptable, the current will depend only on the MCU power need at the moment, if the MCU needs 40mA it will drain 40mA, the maximum it can drain is 80mA.
 

Bordodynov

Joined May 20, 2015
2,995
I did not lose the diode. This diode is superfluous (not needed) and it does not perform a useful function. The emitter junction of the transistor will be OK if the input power supply is short-circuited. Two circuits differ in their own current consumption. I'm used to saving energy.
 

Thread Starter

ArakelTheDragon

Joined Nov 18, 2016
1,353
Yes his circuit is better, I admit my mistake!
The MCU will not drain 80mA all the time, and even if it does the battery will last 15hours, because its 1200mA/h.
The idea is to be able to supply 80mA if the MCU needs them, but to have a stable 5V voltage no matter of the current. The MCUs resistance will change based on the consumption.

This is why we use a bipolar current generator with bipolar transistors.
 
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