Hi,
The band-select relay circuit uses an NXP PCA9555 (LCSC part number C128392).
According to the spec sheet (p.20) it can supply an Ioh current of 10mA with a Voh of 4V.
The relays require 21mA of current to switch. How does this reconcile?
73,
Scott
Question about PCA9555 spec
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- Posts: 2
- Joined: 14 Jan 2022, 03:49
Re: Question about PCA9555 spec
I did some searches and found the PCA9555E which has better Ioh and Iol specs than
the standard PCA9555 part. I was not able to find the PCA9555E in stock but
the PCA9535E is compatible for this application and the DigiKey part number
PCA9535ECDTR2GOSCT-ND and it is (currently) in stock.
73,
Scott KJ7NLA
the standard PCA9555 part. I was not able to find the PCA9555E in stock but
the PCA9535E is compatible for this application and the DigiKey part number
PCA9535ECDTR2GOSCT-ND and it is (currently) in stock.
73,
Scott KJ7NLA
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- Posts: 83
- Joined: 30 Dec 2021, 20:22
Re: Question about PCA9555 spec
Page 18 indicates absolute maximum I/O current, it looks perfectly safe for 21 mA, doesn’t it? Also, it’s a short pulse.scottlbaker wrote: ↑17 Mar 2022, 14:35 Hi,
The band-select relay circuit uses an NXP PCA9555 (LCSC part number C128392).
According to the spec sheet (p.20) it can supply an Ioh current of 10mA with a Voh of 4V.
The relays require 21mA of current to switch. How does this reconcile?
73,
Scott
I’ve used my (tr)uSDX for about a month now without any trouble from relay circuit.
73,
Ian
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- Posts: 4
- Joined: 14 May 2022, 10:34
- Location: Finland
Re: Question about PCA9555 spec
So do both of you confirm that PCA9535E is compatible for this build? I already finished my first unit with proper TCA5555 but I'm building a second one and I only have this substituting parts available.
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- Posts: 4
- Joined: 14 May 2022, 10:34
- Location: Finland
Re: Question about PCA9555 spec
In case somebody ever visits this topic I can confirm that NXP PCA9535PW works for U7 on the RF board. Mouser P/N 771-PCA9535PW-T
I have also onsemi PCA9535ECDTR2G on hand and I will check if it works on later builds.
I have also onsemi PCA9535ECDTR2G on hand and I will check if it works on later builds.
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