[EE] HV5408 Shift Register

[David Duffy (AVD)]

I'm designing this shift register into a small volume product but am
wondering about one aspect of its operation.

It has a VDD pin (10.8 - 13.2V) for the logic side and a VPP pin (8.0V -
80V) for the output switching side.

To power-up HV5308 / HV5408, perform the following
1. Connect ground
2. Apply VDD
3. Set all inputs (Data, CLK, LE, etc.) to a known
state
4. Apply VPP
5. The VPP should not fall below VDD or float during
operation.
To power-down the device, reverse the steps above.

Now, I'm actually using the same 12V supply for both VDD and VPP. Do you
think I really need to worry about the power sequencing?

I'm thinking no, because VPP will never be able to fall below VDD. Thoughts?
David...
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___________________________________________
David Duffy Audio Visual Devices P/L
Unit 8, 10 Hook St, Capalaba 4157 Australia
Ph: [phone] Fax: [phone]
Our Web Site: www.audiovisualdevices.com.au
___________________________________________

[James Cameron]

Interesting.

As there's no time specified between the three events; apply Vdd, set
all inputs, and apply Vpp, you can probably do it at the same time.

Looking through the datasheet, I can't see a good reason why Vdd and
Vpp can't rise to 12V at the same time.

In the switching waveforms there's no line for Vdd or Vpp.

[David Duffy (AVD)]

That was my thought too.  In this application I don't care if the
outputs "twitch" at start up or shut down.  I just don't want the chip
locking up or something silly like that.
David...

Post by James Cameron
Interesting.
As there's no time specified between the three events; apply Vdd, set
all inputs, and apply Vpp, you can probably do it at the same time.
Looking through the datasheet, I can't see a good reason why Vdd and
Vpp can't rise to 12V at the same time.
In the switching waveforms there's no line for Vdd or Vpp.

--
___________________________________________
David Duffy Audio Visual Devices P/L
Unit 8, 10 Hook St, Capalaba 4157 Australia
Ph: [phone] Fax: [phone]
Our Web Site: www.audiovisualdevices.com.au
___________________________________________