Hi
I made a demonstration for DC1962C-KIT to our customer. Then they were very interested in PSM and gave us several questions as follows.
Q1. Increase the output current and after reach IOUT_OC_ FAULT_LIMIT the system enters retry mode. We wish it could enter Latch mode instead of retry. Is it possible ?
Q2. How is EEPROM's capacity of LTC297x controllers ?
Q3. If the customer would like to add another EEPROM to the controller, would it be possible ?
Q4. If the power supply for PSM controller would be broken, what would you do ? We could use another power supply to work the PSM and to check the fault log ?
Regards,
Hiroyuki
Hi Hiroyuki,
Here are your answers:
Q1: The DC1962C demo board contains three different PSM devices: LTC3880, LTC2974, and LTC2977. The LTC3880 actively controls current on a cycle-by-cycle basis, so can detect peak current and respond immediately. In the event of an overcurrent event it can re-try or latch off. You can disable the re-try fault response in the IOUT_OC_FAULT_RESPONSE register.
The LTC2974 is a power supply manager that detects voltage and current in an external power supply. It uses a high speed comparator to detect OC events, and can respond in a similar fashion to the LTC3880 when it detects an OC event. Again, use the IOUT_OC_FAULT_RESPONSE register.
The LTC2977 is broadly intended as a voltage manager. It can measure currents on odd numbered channels, if configured to do so, but it does not have the same high speed comparators as the other devices. This makes it slow to detect OC events. If you configure it to measure current on the odd numbered channels, then it can respond and you can program it to latch off using a VOUT_OV_FAULT_RESPONSE command.
Q2: The EEPROM inside of each IC is sized to contain the configuration registers, an ample fault log, and additional trim settings that are not accessible to the user. Each IC is different, according to its needs. In general the user does not need to know the total size of EEPROM on board. You can read more about this subject in this application note:
https://www.analog.com/media/en/technical-documentation/application-notes/AN145f.pdf
Q3: The EEPROM does not offer an external interface. External memory is not possible.
Q4: We do encourage users to provide power to the VDD33 pin of the ICs. This allows the DC1613 dongle or a board controller to access the parts when main power is off. This allows LTpowerPlay to access the ICs for programming and debugging purposes when main power is down. There are some good diagrams in the following datasheets:
Figure 30 & 31 on p86 of the LTC2977 datasheet
Figure 38 & 39 on p91 of the LTC2974 datasheet
Figure 28 on p59 of the LTC3880 datahseet
In addition to these answers you can get more information in these resources:
https://www.analog.com/en/design-center/ltpower-play.html
https://www.analog.com/media/en/technical-documentation/application-notes/an166f.pdf
https://www.analog.com/media/en/technical-documentation/application-notes/an152f.pdf
https://www.analog.com/media/en/technical-documentation/application-notes/an155f.pdf
https://www.analog.com/media/en/technical-documentation/application-notes/an153fb.pdf
https://www.analog.com/media/en/technical-documentation/application-notes/an135f.pdf