7805 regulator replacement (Pololu S9V11F5 and alternatives)

[Peter Higgins]

There have been several discussions and recommendations in this forum regarding switching regulator replacement options for the 7805 5V 1A regulator.

One recommendation is the Pololu S9V11F5, which has several nice features including its ability to step-up/step-down over an input voltage range of 2-16V and a continuous maximum output current is rated at 1.5A. However, this device also has one serious limitation which is that its startup current is limited to 700mA. If the startup current exceeds 700mA, the output voltage of this device will never rise above around 3.5V - which Pololu does point out near the bottom of their datasheet. While this limitation is likely not going to be encountered for new-design boards with low power consumption, this device does not work as a 7805 replacement with many "vintage" H8 boards (which I know from first-hand experience).

Another recommendation is the MPS mEZD71202A-G (6.5-24V input) or mEZD72402A-G (6.5-36V input), both of which are rated at 5V at a maximum of 2A. Unlike the Pololu S9V11F5 this device will not step-up, requiring a minimum input voltage is 6.5V. A few people here have indicated they used this device as a 7805 replacement with "vintage" H8 boards. There is no indication in the MPS datasheet that this device is unable to start up at full rated current into a resistive load (like the Pololu) - can anyone here comment on their experience?

[rand...@hotmail.com]

My favorite:

Low Cost 3 pin Switching Regulator 5V 3A (ezsbc.com)

They also have a 1A version a little cheaper but $1 more you get 3A and they both run not cool but cold.

Randy

[Steven Hirsch]

On 4/17/22 21:33, rand...@hotmail.com wrote:
> My favorite:
>
> Low Cost 3 pin Switching Regulator 5V 3A (ezsbc.com)

> <https://www.ezsbc.com/product/psu5-2/>

>
> They also have a 1A version a little cheaper but $1 more you get 3A and
> they both run not cool but cold.
>

I've already upgraded one of my H89s with the EZSBC converters. Runs
significantly cooler now.

[ocl...@earthlink.net]

Have you looked at the offerings on ezsbc.com?

 

https://www.ezsbc.com/product-category/voltage-regulators-2/

 

Paul

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[Norberto Collado]

My first choice is 7805 unless it dissipates a lot of heat. Then I go switching.

 

I tested on my H8 boards:

 

https://www.amazon.com/gp/product/B08TTVTWJG/ref=ppx_yo_dt_b_asin_title_o08_s00?ie=UTF8&psc=1 Price for two parts is about $8.09.

MPS Step Down Switching Voltage Regulator 4.5V - 36V Input, 5V Output, 2A, DC/DC Power Supply Buck Converter Module

 

 

https://www.pololu.com/product/2836 Very expensive now and about $17.00 each.

 

 

Thanks,

Norberto

 

From: "se...@googlegroups.com" <se...@googlegroups.com> on behalf of Peter Higgins <higgin...@gmail.com>
Reply-To: "se...@googlegroups.com" <se...@googlegroups.com>
Date: Sunday, April 17, 2022 at 5:08 PM
To: "se...@googlegroups.com" <se...@googlegroups.com>
Subject: [sebhc] 7805 regulator replacement (Pololu S9V11F5 and alternatives)

 

There have been several discussions and recommendations in this forum regarding switching regulator replacement options for the 7805 5V 1A regulator.

 

One recommendation is the Pololu S9V11F5, which has several nice features including its ability to step-up/step-down over an input voltage range of 2-16V and a continuous maximum output current is rated at 1.5A. However, this device also has one serious limitation which is that its startup current is limited to 700mA. If the startup current exceeds 700mA, the output voltage of this device will never rise above around 3.5V - which Pololu does point out near the bottom of their datasheet. While this limitation is likely not going to be encountered for new-design boards with low power consumption, this device does not work as a 7805 replacement with many "vintage" H8 boards (which I know from first-hand experience).

 

Another recommendation is the MPS mEZD71202A-G (6.5-24V input) or mEZD72402A-G (6.5-36V input), both of which are rated at 5V at a maximum of 2A. Unlike the Pololu S9V11F5 this device will not step-up, requiring a minimum input voltage is 6.5V. A few people here have indicated they used this device as a 7805 replacement with "vintage" H8 boards. There is no indication in the MPS datasheet that this device is unable to start up at full rated current into a resistive load (like the Pololu) - can anyone here comment on their experience?

 

 

--

[Peter Higgins]

Thank you ... I had forgotten about the EZSBC PSU-5 , which looks to be the best option.

My current project is to replace the three 7805s on a couple of CompuPro EconoRAM VI that I am restoring. The 12KB of RAM on that board is provided by 96 2102 1Kb RAM chips. Each board draws over 3A, and the normal H9 L-bracket heatsink was never inadequate to provide sufficient cooling for this board - it gets hot enough to cause a serious burn.

[dwight]

Although, not getting rid of the heat, you can always use a large ceramic bypass resistor. Most of the power goes through the resistor and the regulator only needs to control a smaller amount of power.

The commonly available size is the 10 watt size. A couple of those can bypass 15 Watts if mounted in free air. Just save some of the power for the regulators.

Dwight

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From: se...@googlegroups.com <se...@googlegroups.com> on behalf of Peter Higgins <higgin...@gmail.com>

Sent: Sunday, April 17, 2022 9:42 PM
To: SEBHC <se...@googlegroups.com>
Subject: [sebhc] Re: 7805 regulator replacement (Pololu S9V11F5 and alternatives)

 

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[Terry Smedley]

Peter:

I have used the mEZD72401A-G to replace all of the linear regulators on legacy as well as  new cards for the H8.  This made an enormous difference in internal heat generation.  For legacy cards, I used the mEZDs on the WH8-37, H8-4,. H17, and Trionyx Z-H8 CPU.

As close as I could come to your full-load scenario, I put an 8ohm resistive load across the output, and when power was applied the regulator instantly came to 4.95v at about 620ma.   For fun, I paralleled two 8-ohm resistive loads, and the regulator instantly came up to full rated current (0.96A) at 4v.

Terry

[Rob]

Norby mentioned the

MPS Step Down Switching Voltage Regulator 4.5V - 36V Input, 5V Output, 2A, DC/DC Power Supply Buck Converter Module

Does that mean this regulator can replace the 7805 AND work with the original 8 volt bus or if we are using a switching power supply that puts 5 volts on the bus?

Thanks

[Peter Higgins]

No - that MPS regulator cannot be used with a bus supply of only 5V. The data sheet for this component was written to cover all output voltage versions, and is easily misinterpreted. The versions of this MPS regulator designed to output 3.3V or less require a minimum input voltage of 4.5V. The version of this regulator designed to output 5V requires a minimum input voltage of 6.5V.

If you want a buck/boost regulator (that works with a bus supply of 5V or higher) you need to look at the Pololu S9V11F5 (mentioned earlier) or similar such as the S13V20F5. These Pololu devices all cost roughly twice as much as the MPS or EZSBC regulators that require a bus supply voltage higher than 5V.

[norberto...@koyado.com]

Rob,

What is the input voltage of your application? For the H8, the minimum for the 7805 is 8 Volts as it needs a difference of 3 volts to regulate or it won’t work. The MPS Step Down Switching Voltage Regulator 4.5V - 36V Input will work fine on the H8 as I’m using them in my system as it requires a minimum of 6.5Volts per their specs.  As Peter mentioned, it will not work on a 5V system and will required the Pololu regulators instead. There are so many 5V regulators out there specially in eBay and Amazon and we need to make sure that we spend wisely our money.

 

The only time I do not use the 7805 is when the circuit pulls enough current to overheat the regulator. The H67 controller is an example.

 

Thanks,

Norberto

 

From: se...@googlegroups.com <se...@googlegroups.com> On Behalf Of Peter Higgins
Sent: Monday, April 18, 2022 8:35 PM
To: SEBHC <se...@googlegroups.com>
Subject: [sebhc] Re: 7805 regulator replacement (Pololu S9V11F5 and alternatives)

 

No - that MPS regulator cannot be used with a bus supply of only 5V. The data sheet for this component was written to cover all output voltage versions, and is easily misinterpreted. The versions of this MPS regulator designed to output 3.3V or less require a minimum input voltage of 4.5V. The version of this regulator designed to output 5V requires a minimum input voltage of 6.5V.

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[Lee Hart]

On my Z80 Membership Card kit (www.sunrise-ev.com/z80.htm), I use the low-dropout LM2940CT 5v regulator as a replacement for the LM7805. By itself, this doesn't reduce heating in the 5v regulator. But it works down to 5.5vin (instead of 7.5vin for the 7805). This allows you to reduce the input voltage, which DOES significantly reduce heating.

The Z80MC draws under 250ma. At this current, the LM2940 input can be as low as 5.25v for a 5v output, and still outputs 4.75v if the input is powered with a 5v supply or USB-serial adapter. That's handy, because it's what most people use to power it.

The H89 filter capacitors on the unregulated supplies run at or even above their rated voltage. This is one cause of the frequent "KABOOM" events with the tantalums. So I've replaced the 7805's with LM2940's, and operate the H89 with a buck transformer to reduce its input voltage from 120vac to 108vac (a 120vac-to-12vac 1 amp transformer with its secondary wired in series with the input, to reduce it to 108vac). The H89 operates completely normally, and also runs significantly cooler.

Something like this could work for the H8, though I haven't tried it yet.

Lee Hart

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[Rob]

Norby,

I hear what you are saying.  I like the idea of using a switching power supply that supplies the 5 volts instead of 8 volts on the back plane for a new H-8. I'm thinking if I use the Pololu regulators as I'm building these boards, then the board would be able to handle 8 volts or 5 volts as input voltage.  Am I understanding that correctly?  Of course, if I can build a board that will handle either input voltage, that would be my preference.

Looking at the Pololu regulators, it looks like they offer the S9V11F5 that is always referenced here. But that regulator lists for $19.95 each!

I also see the "S13VxF5 Step-Up/Step-Down Voltage Regulators" which are the suggested replacements for the S9V11F5 and their cost is half the cost of the S9V11F5.  Does anyone see a reason why these new regulators would have a problem replacing the S9V11F5 regulators? The new ones are a bit larger, but don't think the size difference will cause an issue.  I'm specifically looking at the S13V15F5 as a replacement since it's only $8.95 a piece. 

I agree that money is an issue, but I think using these regulators would be cheaper than building two boards, one for an input voltage of 8 volts and one for an input voltage of 5 volts.

Thoughts?

[norberto.collado koyado.com]

My new H8 boards has a jumper to short +8V to +5V for those using the 5V power supply on the H8 chassis.

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From: se...@googlegroups.com <se...@googlegroups.com> on behalf of Rob <rw...@robhome.com>
Sent: Friday, May 6, 2022 11:02 AM
To: SEBHC <se...@googlegroups.com>
Subject: Re: [sebhc] Re: 7805 regulator replacement (Pololu S9V11F5 and alternatives)

 

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[norberto.collado koyado.com]

Just a warning: I damaged one of my boards as I forgot to remove the +8V/+5V jumper before I plugged it into a +8V power supply. I need to replace all the IC's eventually. 🙁

Norberto

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To: se...@googlegroups.com <se...@googlegroups.com>

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[glenn.f...@gmail.com]

Rob: as a data point I’ll mention that your approach has worked well for me.  When I first built Rusty (with the original “Les Bird” boards) I simply soldered a wire across the regulator input and outputs on each board and this worked fine!  This is functionally the same as inserting jumpers on the 5V-8V jumpers that Norberto has provided on many of his recent boards.  But it suffers from the issue that Norberto just pointed out – sooner or later there’s a pretty good chance you’ll burn out a board if you have both PC-switching supplied H8 and one with a traditional linear supply.

 

There are many switching regulators designed as drop-in replacements for 780x style regulators (see previous discussions on this list) but the Pololus are up/down buck regulators and they function just fine with 5V inputs. Big Blue has Pololu up/down regulators on all boards plus the front panel (although arguably the front panel is the one place where the jumpers are probably fine as you are not as likely to be moving that around!)

 

So with few exceptions I have used the Pololus on boards I’ve built.  This lets me swap boards around at will.  It has worked well and my systems run incredibly cool.

 

Thanks for pointing out the S13V15F5.  Any idea why its half the price of the S9V11F5? Anyone?  Is this a new, improved generation of their product?

 

Tx!

 

• Glenn

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[rand...@hotmail.com]

TBH if using switching power supplies best to use 7.5V tweaked to 8V, any 5V regulator (linear or not) will run fine and for linear cooler than a linear based systems that usually run higher than 8V.

Keep in mind 7805's need 7.5V to run, 8V just a safety amount. and 7812/7912's need 14.5V.

Randy

[norberto.collado koyado.com]

The S13VxF5 series are good to use on the H8 boards. Much better in price and range is from 1A to 2A. 

Norby 

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[Rob]

Thanks for the feedback and insights. I’ve lived most of my life by the K.I.S.S. principle Heathkit taught me, and I know that missing a jumper would happen to me more than once. If I can avoid that problem in advance, that’s what I want to do.

Thank you!

[norberto.collado koyado.com]

For a safe and secured H8 board, it is better to use the Pololu regulators  as they will work with input voltages below 5V. It always guarantee that the IC’s gets 5V, and nothing lower.

 

Norby

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[Rob]

Ok, I’ve ordered some of the Pololu s13vF5 regulators and will give them a try.  

What about the + and - 18 volt supplies. Do those regulators need any updates if moving to a switching power supply that provides + and - 12 volts instead?

[glenn.f...@gmail.com]

So I think the only board I have that takes +/-12V is the Z80 rev4 CPU?  Not sure what it’s for? Haven’t checked the schematic… RS-232 signal??

 

Though I have Pololu regulators on the 5V line I use jumpers across the 12/18 jumpers when I use it with the PC ATX supply (which is basically almost all the time).  I have the 78L12/79L12 regulators installed to allow me to use it on a linear supply system, if need arises.

 

As I recall there are not as many buck regulator options for +/- 12V?

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[smb...@gmail.com]

Resurrecting this thread because I need more regulators and want to know if there have been any further developments..

Is there any reason to buy S9V11F5 instead of   S13V10F5  ? I ask because the former is double the cost of the latter. If the feature set is the same, then I'll  choose the cheaper of the two.

Scott

[norberto.collado koyado.com]

No. You can use the  S13V10F5. The S13V10F5 is 1A and the other is the same as a 7805 (1.5A).  The new boards will be using less than 1A.

 

Norberto

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[Douglas Miller]

There is quite a difference in the efficiency graphs between the two. I suspect the more-expensive one runs cooler - in addition to handling higher current. The efficiency graph for the cheaper one shows much less efficiency at lower current, too.

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[Peter Higgins]

The S9V11F5 is more expensive because it can function as both step-up and step-down regulator - useful if you want to swap the same board between systems that have a regulated (5V) or unregulated (8V or higher) backplane. If you only plan to use your board with an unregulated backplane per the original H8 design, there is no reason not to use the more common and less expensive version, which functions only as a step-down regulator.

[Douglas Miller]

But both are listed as step-up/step-down regulators. And are rated at input voltages below 5V (as well as above).

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[Scott Baker]

I'm assuming the low-end efficiency issue is due to the quiescent current, which looks to be 9-17ma on the S13V10 vs 0.2ma on the S9V11. It makes the chart look bad (50% efficiency), but I wonder how bad it really is? 15ma wasted times a hypothetical 10 regulators is only 150ma wasted across the whole computer.

If I do this, I might grab the 1.5A version. I realize everything here is sized to <= 1A, but it's nice to have some headroom for other projects.

Scott

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[Peter Higgins]

I missed that - thanks for pointing out that both can function as buck/boost regulators.

My recommendation (as I pointed out at the start of this discussion) still is to avoid use of the S9V11F5 in an application which presents a continuous load of over 700mA  right from the point of startup. As Pololu points out, the S9V11F5 will fail to turn on if the startup current requirement is greater than 700mA, even though after startup it is able to source up to 1.5A.

[glenn.f...@gmail.com]

They actually had a “black Friday” sale on the S9V11F5s so I picked some up, but I agree the less expensive one is probably fine for most of our needs.

 

I love the step up/down pololus since I can swap boards between traditional H8 and “ATX-powered” systems as needed…

 

• Glenn
•  

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[norberto.collado koyado.com]

So far I never had any failures with such Pololu devices.

 

Norberto

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[Steven Hirsch]

On 4/17/22 20:08, Peter Higgins wrote:
> There have been several discussions and recommendations in this forum
> regarding switching regulator replacement options for the 7805 5V 1A
> regulator.
>
> One recommendation is the Pololu S9V11F5, which has several nice features
> including its ability to step-up/step-down over an input voltage range of
> 2-16V and a continuous maximum output current is rated at 1.5A. However,
> this device also has one serious limitation which is that its startup
> current is limited to 700mA. If the startup current exceeds 700mA, the
> output voltage of this device will never rise above around 3.5V - which
> Pololu does point out near the bottom of their datasheet. While this
> limitation is likely not going to be encountered for new-design boards with
> low power consumption, this device does not work as a 7805 replacement with
> many "vintage" H8 boards (which I know from first-hand experience).
>
> Another recommendation is the MPS mEZD71202A-G (6.5-24V input) or
> mEZD72402A-G (6.5-36V input), both of which are rated at 5V at a maximum of
> 2A. Unlike the Pololu S9V11F5 this device will not step-up, requiring a
> minimum input voltage is 6.5V. A few people here have indicated they used
> this device as a 7805 replacement with "vintage" H8 boards. There is no
> indication in the MPS datasheet that this device is unable to start up at
> full rated current into a resistive load (like the Pololu) - can anyone
> here comment on their experience?

I've used regulator replacements from EzSBC in the past with good results.
Their website is gone, but he still sells on Tindie:

https://www.tindie.com/products/ddebeer/5v-1a-switch-mode-voltage-regulator/

[glenn.f...@gmail.com]

These are great if you don't ever intend to install in an ATX-powered chassis (they need 7-17V input), otherwise use a step up/down like the Pololu.

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