>> There will be a 600W 14V TVS, with 29V max clamp voltage during the
>> surge. The question is what should be the value of the resistor between
>> the TVS and the high-side collector.
>
>
> Zero?
When the surge is negative with respect to the collector, the situation
is under control: it will be clamped to 29V and the transistor can
withstand 50V. If the surge is positive, the PNP will be driven into the
reverse active region with sort of 5V V_EBO. I can't find the TVS
forward voltage at the I_MAX and so I assumed it would be prudent to
limit the I_C a bit. Indeed, zero was my initial approach, but then some
afterthoughts started coming.
> We like TPIC6595 whan we need a lot of current-sinking drivers from an
> FPGA. It's very rugged, controlled avalanche.
I love the part. FYI, you can make 8 flybacks using the TPIC6595 by
modulating the OE. Works OK up to a MHz: I gave up here, maybe it still
can go faster. The snubber is built-in, you just connect the transformer
and call it a day.
But since a PNP per channel is one part to add to the board and the
pre-biased dual is one part as well, just by connecting pins 5 and 6 you
end up with a logic-level-driven high-side switch, eliminating the HV
shift register from the BOM. And the board must be small, so it matters.
Best regards, Piotr
Reply by Martin Rid●June 20, 20222022-06-20
Piotr Wyderski <bombald@protonmail.com> Wrote in message:r
> Hi,I need an array of high-side switches, not more than 50mA per channel. The MUN5333DW1T1G would be handy. Unfortunately, the datasheet specifies 100mA max. continuous I_C only and I can't see anything about its surge handling capabilities. What should I assume for an 8/20us ESD pulse? Does 1A looks OK? Best regards, Piotr
On Mon, 20 Jun 2022 19:39:43 +0200, Piotr Wyderski
<bombald@protonmail.com> wrote:
>jlarkin@highlandsniptechnology.com wrote:
>
>> Why use NPNs as high-side switches?
>
>The high-side switch is the PNP half. The NPN one is a level translator
>from the 2.5V FPGA enable.
>
>> Single transistors seldom include ESD protection.
>
>There will be a 600W 14V TVS, with 29V max clamp voltage during the
>surge. The question is what should be the value of the resistor between
>the TVS and the high-side collector.
Zero?
>
>> What's the application?
>
>A digitizer for an array of mechanical switches. The 20-50mA is the
>wetting current, one switch will be tested at a time in a round-robin
>fashion to limit the supply current.
>
> Best regards, Piotr
We like TPIC6595 whan we need a lot of current-sinking drivers from an
FPGA. It's very rugged, controlled avalanche. You'd still need the
PNPs.
There was a cool octal pull-up driver, UCN5815A, but it's unobtanium
now.
--
If a man will begin with certainties, he shall end with doubts,
but if he will be content to begin with doubts he shall end in certainties.
Francis Bacon
Reply by Piotr Wyderski●June 20, 20222022-06-20
jlarkin@highlandsniptechnology.com wrote:
> Why use NPNs as high-side switches?
The high-side switch is the PNP half. The NPN one is a level translator
from the 2.5V FPGA enable.
> Single transistors seldom include ESD protection.
There will be a 600W 14V TVS, with 29V max clamp voltage during the
surge. The question is what should be the value of the resistor between
the TVS and the high-side collector.
> What's the application?
A digitizer for an array of mechanical switches. The 20-50mA is the
wetting current, one switch will be tested at a time in a round-robin
fashion to limit the supply current.
Best regards, Piotr
Reply by ●June 20, 20222022-06-20
On Mon, 20 Jun 2022 18:05:23 +0200, Piotr Wyderski
<bombald@protonmail.com> wrote:
>Hi,
>
>I need an array of high-side switches, not more than 50mA per channel.
>The MUN5333DW1T1G would be handy. Unfortunately, the datasheet specifies
>100mA max. continuous I_C only and I can't see anything about its surge
>handling capabilities. What should I assume for an 8/20us ESD pulse?
>Does 1A looks OK?
>
> Best regards, Piotr
Why use NPNs as high-side switches?
Single transistors seldom include ESD protection.
What's the application?
--
Anybody can count to one.
- Robert Widlar
Reply by Piotr Wyderski●June 20, 20222022-06-20
Hi,
I need an array of high-side switches, not more than 50mA per channel.
The MUN5333DW1T1G would be handy. Unfortunately, the datasheet specifies
100mA max. continuous I_C only and I can't see anything about its surge
handling capabilities. What should I assume for an 8/20us ESD pulse?
Does 1A looks OK?
Best regards, Piotr