[SOLVED] Using the TLE987x to control 6 Relays

Announcements

Webinar: Integrated solutions for smaller, simpler low-voltage motor control design.
Join the webinar to experience!

Tip / Sign in to post questions, reply, level up, and achieve exciting badges. Know more

cross mob
User16740
Level 1
Level 1
5 replies posted 5 questions asked First reply posted
I would like to use the TLE987x to independently manage 6 x 24V Relays.

Is it possible set setup and configure the TLE987x to independently control 6 MOSEFT using the MOSFET Driver?
0 Likes
8 Replies
Fiz
Moderator
Moderator
Moderator
First like received 50 replies posted 25 replies posted
Hi mjkinfhtx,

thank you for your interest in our products!
The TLE987x can control three half-bridges independently, but not the corresponding high-side and low-side.
Best,
Fiz
0 Likes
User16740
Level 1
Level 1
5 replies posted 5 questions asked First reply posted
Hi Fiz,

What about the statement in 27.2.2 of the UM (v1.3) 'In Normal Mode the output stage is fully controllable through the SFR registers CTRLx (x = 1, 2, 3)'?

Or do I misunderstand its meaning?

Regards,

Mark.
0 Likes
Fiz
Moderator
Moderator
Moderator
First like received 50 replies posted 25 replies posted
Hi Mark,

Yes in normal mode you can fully control each of the three half-bridge drivers via SFR CTRlL-3.
But when you try to turn on the LS and the HS of a half-bridge at the same time, the TLE987x will prevent this due to its cross-current protection, which can not be disabled.
You could use two TLE984x with its integrated relay-drivers + 4 external MOSFETs to manage your 6 relays independently.

Best,
Fiz
0 Likes
User16740
Level 1
Level 1
5 replies posted 5 questions asked First reply posted
Hi Fiz,

The TLE984x seems like a much better match. The 6 relays is not fixed as this number was chose due to the 6x HS/LS of the TLE987x.

The relays that I plan to use require a 24V PWM signal to energise the coils and require around 180mV. They are commercially available parts designed primarily for household wiring.

The Low Side Switch modules can easily cope with this current, but not the High Side.

To simplify the hardware and make use of the internal over current protection, can I use the two High Side Switches in parallel to provide the minim 180mV required by the relay coil?

Regards,

Mark.
0 Likes
Fiz
Moderator
Moderator
Moderator
First like received 50 replies posted 25 replies posted
Hi Mark,

is you target application in the automotive or industrial area?
Please check the max ratings of our devices and if they fit your application!

Best,
Fiz
0 Likes
User16740
Level 1
Level 1
5 replies posted 5 questions asked First reply posted
Hi Fiz,

It's a concept / prototype for a 24V wired Home Automation system.

There are very few devices available that can be powered directly from 24V and have 24V tolerant inputs and outputs, hence my (modified) choice of the TLE984x. These TLE984x result in a small BOM and provides good amount of diagnostics from the coil switching.

I'm trying to make the most efficient use of the TLE984x, which is why I asked about using the High Side in parallel to achieve the current requirements for the relay coil as this would allow three relays to be controlled instead of two and no need for an external MOSFET.

I'm aware that this is not part of the original use case / concept for the device, but appart from the high Side current it's a very good fit for my idea.

If the High Side can be combined into a single parallel higher current device then I can realise 5 x 24V inputs (for switches), 3 x Relay (for light / power control), with LIN (also 24V) for communication.

Regards,

Mark.
0 Likes
Fiz
Moderator
Moderator
Moderator
First like received 50 replies posted 25 replies posted
Hi Mark,

good to hear the TLE984x fits your needs!
We have to look into driver capability of the HS more closely.
Best,
Fiz
0 Likes
lock attach
Attachments are accessible only for community members.
Fiz
Moderator
Moderator
Moderator
First like received 50 replies posted 25 replies posted
Hi Mark,

you can use the TLE984x's HS driver for a relay, but you have to place a free-wheeling diode in parallel to the relay to prevent damaging the device due voltage drops, caused by the switching coil.
Check the attachment for the placement of the diode.

Best,
Fiz
3632.attach
0 Likes