---
# System prepended metadata

title: Regular Meeting (2022.12.26)
tags: [Regular Meeting, DeWei]

---

# Regular Meeting (2022.12.26)

* New 48 fanout board: 2 solutions


## New 48 fanout board

### Sol 1:

* OPA: [AD8397](https://www.analog.com/media/en/technical-documentation/data-sheets/ad8397.pdf)
  * 2 OPAs in a package
  * BW: 69MHz, Slew Rate: 53V/us
  * Controlled ON/OFF by LDO(ADP125)
    * 8 channels a group
  * Higher current supplies is necessary 
    * LDO needs \>400mA current output 
      * \[4.5V/(50ohm + 50ohm)\] \* 8channels = 360mA
  * Lower PSRR aka higher noise
    * Caused by LDO ADP125
* LDO: [ADP125](https://www.analog.com/media/en/technical-documentation/data-sheets/adp124_125.pdf)
  * 500mA max output
  * Must add 2 *setup resistor*
  * Noise (worse than sol 1)
    * ![](https://i.imgur.com/oCRuEBr.png)

### Sol 2:

* OPA: [AD8655](https://www.analog.com/media/en/technical-documentation/data-sheets/ad8655_8656.pdf)
  * 1 OPAs in a package
  * BW: 28MHz, Slew Rate: 11V/us
* LDO: [LP5907](https://www.ti.com/lit/gpn/lp5907)
  * 250mA max output
  * No *setup resistor* necessart
  * Noise (better than sol 1)
    * ![](https://i.imgur.com/XwjSCyq.png)

### Summery about sol 1 and sol 2

* Higher system bandwidth performance(e.g. slew rate, R/F time) would reduce PSRR aka noise rised. If that's fine, select AD8397(sol 1)
* Higher system PSRR would reduce bandwidth performance. If that's fine, select AD8655(sol 2)
* Because I control OPA output ON/OFF with EN of LDO:
  * ON/OFF 4 channels minimum-> Select AD8655(sol 2)
  * ON/OFF 8 channels minimum-> Select AD8397(sol 1)

### Common part

* PSU
  * EU terminated
  * USB 5V with CLC filter
    * No filter: 200mVpp ripple
    * With filter: 100mVpp ripple
    * 4.5V output for LDO
* Switch 8/4 channel of a OPA
  * Odd/Even channels
  * *DIP Switch* with *EN of LDO*

###### tags: `Regular Meeting` `DeWei`