LM3880: Cascading 3x LM3880 for 9 sequenced outputs

Collin Wells

Part Number: LM3880

Hello,

The LM3880 power sequencer mentions in the front-page of datasheet that it can be cascaded to three levels that control nine voltage rails. The datasheet does not show an example of this configuration. Is there any documentation explaining how to cascade these devices? Also could you explain how the cascaded sequencing works for the power down phase in reverse order?

over 3 years ago

0 Sam over 3 years ago

TI__Expert 4175 points

Hi Collin,

The way to cascade three of these devices is the same method to cascade two. Through the use of logic gates. See the following posts for how to implement a 3 cascade design.

https://e2e.ti.com/blogs_/b/powerhouse/posts/a-simple-six-channel-power-rail-sequencing-solution

https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/866462/lm3880-how-can-i-sequence-more-than-6-rails-using-lm3880/3205516?tisearch=e2e-sitesearch&keymatch=lm3880%252520cascade#3205516

The power down sequence will work in the same way as using a single device just with more than 3 rails. This is because of the OR gates you see in the following posts tied to the EN pin of the all the cascaded devices except the last device. Just keep in mind, between FLAG 3 of DEVICE 1 and FLAG 1 of DEVICE2 there will be an additional 120 ms delay due to glitch filter of the EN pin. This delay will also be present from FLAG 3 of DEVICE 2 and FLAG 1 of DEVICE 3.

Please let me know if you have any further questions.

Best regards,

Samuel Gradinaru

Power management

Power management forum

LM3880: Cascading 3x LM3880 for 9 sequenced outputs