# minimum zener current for break down.

Started by March 22, 2013
```Is there any minimum zener current required for it to break down or is it o=
nly dependent on voltage? For example, MMSZ5V1T1G (datasheet below) break d=
own voltage Izt1 is given at test condition as 5ma.

The following is our application and current should be limited to the volta=
ge sensing circuitry to less than 100uA. So after break down voltage of 5.6=
V, only few tens of uA will flow through the zener. Is this sufficient for =
the zener to break down and maintain the Vs - Vz for the voltage sensing ci=
rcuitry?=20

5V-30V o---/\/\/\---|<|----------/\/\/\-----GND=20
1K     Z5V6     |      47K
|
|_ _ _ /\/\/\---->> Sensing Circuit
330K=20
=20
=20

regards
Sridhar
```
```On Fri, 22 Mar 2013 05:48:54 -0700 (PDT),
sridhar09.cherukuri@gmail.com wrote:

>Is there any minimum zener current required for it to break down or is it only dependent on voltage? For example, MMSZ5V1T1G (datasheet below) break down voltage Izt1 is given at test condition as 5ma.
>
>The following is our application and current should be limited to the voltage sensing circuitry to less than 100uA. So after break down voltage of 5.6V, only few tens of uA will flow through the zener. Is this sufficient for the zener to break down and maintain the Vs - Vz for the voltage sensing circuitry?

---
No.

Vz is specified with a certain current through the Zener.

Take a look at quadrant 3 of the Cartesian plot on page 2 of the data
sheet.

---

>
>5V-30V o---/\/\/\---|<|----------/\/\/\-----GND
>            1K     Z5V6     |      47K
>                            |
>                            |_ _ _ /\/\/\---->> Sensing Circuit
>                                    330K
>
>
>
>regards
>Sridhar
--
JF
```
```On Mar 22, 8:48=A0am, sridhar09.cheruk...@gmail.com wrote:
> Is there any minimum zener current required for it to break down or is it=
only dependent on voltage? For example, MMSZ5V1T1G (datasheet below) break=
down voltage Izt1 is given at test condition as 5ma.
>
> The following is our application and current should be limited to the vol=
tage sensing circuitry to less than 100uA. So after break down voltage of 5=
.6V, only few tens of uA will flow through the zener. Is this sufficient fo=
r the zener to break down and maintain the Vs - Vz for the voltage sensing =
circuitry?
>
> 5V-30V o---/\/\/\---|<|----------/\/\/\-----GND
> =A0 =A0 =A0 =A0 =A0 =A0 1K =A0 =A0 Z5V6 =A0 =A0 | =A0 =A0 =A047K
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 |
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 |_ _ _ /\/\/\----=
>> Sensing Circuit
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 3=
30K
>
>
> regards
> Sridhar

5.6 volt regulator diodes  do not have a sharp breakdown knee.  They
are Zener diodes.  Higher voltage diodes are avalanche diodes and have
a sharp knee.  if you need a sharp knee, you may have to go to
something like TL431.

=20
Dan

```
```On Mar 22, 7:30=A0am, "dcas...@krl.org" <dcas...@krl.org> wrote:
> On Mar 22, 8:48=A0am, sridhar09.cheruk...@gmail.com wrote:
>
> > Is there any minimum zener current required for it to break down or is =
it only dependent on voltage? For example, MMSZ5V1T1G (datasheet below) bre=
ak down voltage Izt1 is given at test condition as 5ma.
>
> > The following is our application and current should be limited to the v=
oltage sensing circuitry to less than 100uA. So after break down voltage of=
5.6V, only few tens of uA will flow through the zener. Is this sufficient =
for the zener to break down and maintain the Vs - Vz for the voltage sensin=
g circuitry?
>
> > 5V-30V o---/\/\/\---|<|----------/\/\/\-----GND
> > =A0 =A0 =A0 =A0 =A0 =A0 1K =A0 =A0 Z5V6 =A0 =A0 | =A0 =A0 =A047K
> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 |
> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 |_ _ _ /\/\/\--=
-->> Sensing Circuit
> > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0=
330K
>
>
> > regards
> > Sridhar
>
> 5.6 volt regulator diodes =A0do not have a sharp breakdown knee. =A0They
> are Zener diodes. =A0Higher voltage diodes are avalanche diodes and have
> a sharp knee. =A0if you need a sharp knee, you may have to go to
> something like TL431.
>
> Dan

May be important, zeners turn on SLOWLY!

To demonstrate, try to use two zeners in the feedback of an amplifier
to make a 'square wave' generator. You'll see the zener's true
characteristics.
```
```On Fri, 22 Mar 2013 07:58:44 -0700 (PDT), Robert Macy <robert.a.macy@gmail.com>
wrote:

>On Mar 22, 7:30&#2013266080;am, "dcas...@krl.org" <dcas...@krl.org> wrote:
>> On Mar 22, 8:48&#2013266080;am, sridhar09.cheruk...@gmail.com wrote:
>>
>> > Is there any minimum zener current required for it to break down or is it only dependent on voltage? For example, MMSZ5V1T1G (datasheet below) break down voltage Izt1 is given at test condition as 5ma.
>>
>> > The following is our application and current should be limited to the voltage sensing circuitry to less than 100uA. So after break down voltage of 5.6V, only few tens of uA will flow through the zener. Is this sufficient for the zener to break down and maintain the Vs - Vz for the voltage sensing circuitry?
>>
>> > 5V-30V o---/\/\/\---|<|----------/\/\/\-----GND
>> > &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; 1K &#2013266080; &#2013266080; Z5V6 &#2013266080; &#2013266080; | &#2013266080; &#2013266080; &#2013266080;47K
>> > &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; |
>> > &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; |_ _ _ /\/\/\---->> Sensing Circuit
>> > &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; 330K
>>
>>
>> > regards
>> > Sridhar
>>
>> 5.6 volt regulator diodes &#2013266080;do not have a sharp breakdown knee. &#2013266080;They
>> are Zener diodes. &#2013266080;Higher voltage diodes are avalanche diodes and have
>> a sharp knee. &#2013266080;if you need a sharp knee, you may have to go to
>> something like TL431.
>>
>> Dan
>
>May be important, zeners turn on SLOWLY!
>
>To demonstrate, try to use two zeners in the feedback of an amplifier
>to make a 'square wave' generator. You'll see the zener's true
>characteristics.

They tend to have a lot of capacitance, and reverse recovery time. The zener
mechanism itself is pretty fast.

--

John Larkin                  Highland Technology Inc
www.highlandtechnology.com   jlarkin at highlandtechnology dot com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
VME  analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators
```
```On Friday, March 22, 2013 7:50:37 PM UTC+5:30, John Fields wrote:
> On Fri, 22 Mar 2013 05:48:54 -0700 (PDT),
>=20
> sridhar09.cherukuri@gmail.com wrote:
>=20
>=20
>=20
> >Is there any minimum zener current required for it to break down or is i=
t only dependent on voltage? For example, MMSZ5V1T1G (datasheet below) brea=
k down voltage Izt1 is given at test condition as 5ma.
>=20
> >
>=20
> >The following is our application and current should be limited to the vo=
ltage sensing circuitry to less than 100uA. So after break down voltage of =
5.6V, only few tens of uA will flow through the zener. Is this sufficient f=
or the zener to break down and maintain the Vs - Vz for the voltage sensing=
circuitry?=20
>=20
>=20
>=20
> ---
>=20
> No.
>=20
>=20
>=20
> Vz is specified with a certain current through the Zener.
>=20
>=20
>=20
> Take a look at quadrant 3 of the Cartesian plot on page 2 of the data
>=20
> sheet.
>=20
>=20
>=20
> ---
>=20
>=20
>=20
> >
>=20
> >5V-30V o---/\/\/\---|<|----------/\/\/\-----GND=20
>=20
> >            1K     Z5V6     |      47K
>=20
> >                            |
>=20
> >                            |_ _ _ /\/\/\---->> Sensing Circuit
>=20
> >                                    330K=20
>=20
> >                      =20
>=20
> >                     =20
>=20
>=20
> >
>=20
> >regards
>=20
> >Sridhar
>=20
> --=20
>=20
> JF

Thanks. That graph doesn't have any values for zener break down current. Ho=
w do I find this from the datasheet?
```
```On Fri, 22 Mar 2013 08:37:56 -0700, John Larkin
<jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:

>
>They tend to have a lot of capacitance, and reverse recovery time. The zener
>mechanism itself is pretty fast.

Claimed to be sub-ns.

```
```On 3/22/2013 3:04 PM, Spehro Pefhany wrote:
> On Fri, 22 Mar 2013 08:37:56 -0700, John Larkin
> <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:
>
>>
>> They tend to have a lot of capacitance, and reverse recovery time. The zener
>> mechanism itself is pretty fast.
>
> Claimed to be sub-ns.
>

I'd always heard it was fast too, though I've never measured it.

Good point about how the reverse recovery messes that up if it's been
forward biased.  Pease's trick of putting the Zener inside a bridge
rectifier sounds like pretty good medicine for that.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

Briarcliff Manor NY 10510 USA
+1 845 480 2058

hobbs at electrooptical dot net
http://electrooptical.net
```
```sridhar09.cherukuri@gmail.com wrote:
> Is there any minimum zener current required for it to break down or is it only dependent on voltage? For example, MMSZ5V1T1G (datasheet below) break down voltage Izt1 is given at test condition as 5ma.
>
> The following is our application and current should be limited to the voltage sensing circuitry to less than 100uA. So after break down voltage of 5.6V, only few tens of uA will flow through the zener. Is this sufficient for the zener to break down and maintain the Vs - Vz for the voltage sensing circuitry?
>
> 5V-30V o---/\/\/\---|<|----------/\/\/\-----GND
>              1K     Z5V6     |      47K
>                              |
>                              |_ _ _ /\/\/\---->>  Sensing Circuit
>                                      330K
>
>
>
> regards
> Sridhar
Zeners "work" from zero to the max rated current (and above that, but
do not do that).
The problem is, that all voltages will have a noisy and negative
resistance region.
You better characterize the particular voltage and manufacturer that
you think you want to use; you may find that there are NONE that do not
have these undesirable characteristics in such low current regions.
That is why the specs AVOID low currents and use "operating" or
similar terms, and have NO I/V curves of value.

```
```On Fri, 22 Mar 2013 13:13:14 -0800, Robert Baer
<robertbaer@localnet.com> wrote:

>sridhar09.cherukuri@gmail.com wrote:
>> Is there any minimum zener current required for it to break down or is it only dependent on voltage? For example, MMSZ5V1T1G (datasheet below) break down voltage Izt1 is given at test condition as 5ma.
>>
>> The following is our application and current should be limited to the voltage sensing circuitry to less than 100uA. So after break down voltage of 5.6V, only few tens of uA will flow through the zener. Is this sufficient for the zener to break down and maintain the Vs - Vz for the voltage sensing circuitry?
>>
>> 5V-30V o---/\/\/\---|<|----------/\/\/\-----GND
>>              1K     Z5V6     |      47K
>>                              |
>>                              |_ _ _ /\/\/\---->>  Sensing Circuit
>>                                      330K
>>
>>
>>
>> regards
>> Sridhar
>   Zeners "work" from zero to the max rated current (and above that, but
>do not do that).
>   The problem is, that all voltages will have a noisy and negative
>resistance region.
>   You better characterize the particular voltage and manufacturer that
>you think you want to use; you may find that there are NONE that do not
>have these undesirable characteristics in such low current regions.
>   That is why the specs AVOID low currents and use "operating" or
>similar terms, and have NO I/V curves of value.

Most of the Japanese parts are well specified, and the Iz currents are
reasonable (like 0.5mA and not 20mA or whatever).

Eg.

http://media.digikey.com/pdf/Data%20Sheets/Panasonic%20Semiconductors%20ICs%20PDFs/DZ2J056.pdf
5.6V nominal at 5mA, 'typical' curve down to 1uA, up to 100mA

http://rohmfs.rohm.com/en/products/databook/datasheet/discrete/diode/zener/udzs5.6b.pdf
5.6V nominal at 500uA, 'typical' curve down to 1uA, up to 10mA

Seems many designers these days would rather use a \$3 chip than a
\$0.03 zener.

Just guessing about what you are actually trying to do, but the Rohm
part looks like it might 'typically' be suitable. Maybe you could use
a higher voltage zener if your input switches between 5V and 30V- the
5.6V unit is guaranteed to have < 0.5uA at 2.5V. A 9.1V zener from
that series is guaranteed to have a reverse current of < 0.5uA at 6V
and will drop no more than 9.2V at 5mA, so at 5V in you'd have less
than 24mV to your sensing circuit, and at 30V you'd have more than