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I know the monitor pins can only read 0V-2.5V. It's somewhat unclear
on how to monitor voltages higher than 2.5V. I understand that I need
to scale my 12V and 7V rails down to under 2.5V using a resistor
network, but how exactly is that reflected in the GUI?
Also, I have -5V rail I would like to monitor. Any ideas on how to do that?
Last question. What is the source current for the rail enables?
Thanks for your help,
1. In order to monitor voltages higher than ~2.5V, use a resistive voltage divider to ensure the MON voltage remains below 2.5V. Within the user configurable parameters of the part is a scale monitor register (Vout Scale Monitor) where the user can enter the actual voltage divider value (for example 0.5 for a divide by 2 resistor network). There is a scale monitor and offset value for each rail that can be configured. Within the Fusion GUI (available on the UCD90120 product page), locate the Vout Scale Monitor and Offset fields on the Other Config tab in the scaling section.
2. A crude way to monitor negative voltages is to shift the MON input into the positive voltage domain using resistors. The downside of this is the interpretation of under and over voltage are reversed. A better way to monitor negative voltages is to use an op amp circuit to invert and scale the negative voltage into the positive side (example circuit attached ... but you would have to adjust values according to the negative voltage being monitored).
3. The GPIO pins (including ones used for ENABLES) are good for ~4mA each. See the datasheet electrical section for the voltage level specs under certain GPIO loading conditions. On our EVM, each GPIO can drive a LED with ~3.5mA simultaneously.
Thanks for the suggestions and the information.
I've been playing with the software for a little bit now and am trying to write the following logic for one of the GPO pins.
I'd like to have one output (LED) turn on if there is either a VOUT_OV_FAULT or VOUT_UV_FAULT on any of the rails. Because the logic is set up with AND gates into an OR gate, there doesn't seem to be an easy way to do this to only one output.
Is there a workaround to do this or is there a combination of some logic that I'm not seeing?
Unfortunately, the workaround would be to use two GPIOs (one for UV and one for OV) which are "wire OR'd" together to the LED. Our GEN2 sequencers (UCD90160 and UCD90120A) due out by the end of March will support much more advanced logic capabilities.
Is it possible that a sample of UCD90160 will be available before product release at the end of March?
If you contact your local TI sales office (see www.ti.com), they could arrange early sampling. FYI, there is an EVM available (orderable online) with a socket that can accomodate the UCD90160 device.
Thanks. I'm waiting to hear back from our sales rep about the early sample of UCD90160.
I already have the evaluation board. Everything seems to be working well (outside of the OV and UV fault indicator noted above).
I have some added functionality I would like to incorporate that I've been having issues with. I'm trying to use the GPI1 on the eval board to control the enables of rails 6-12. As I expected, it only controls the enables upon power-on. Is there anyway to control the enables using GPI's (not PMBus commands)?
I just switched to the GUI as if I were using the UCD90160 and saw Pin Selected States. Something tells me this is what I'm looking for. I guess I'll wait for that sample.
Regarding the IC Temp displayed in the GUI, is there anyway to set an over-temp condition for the IC like you can for individual rails?
If a rail doesn't have an external temp source defined (using another MON pin), it will default to the internal temp sensor for fault/warnings. Of course, the rail does not have to respond to the fault or warning.
FYI, UCD90160 will not support temperature (internal nor external) or current monitoring as all of the analog sampling channels are used for voltage rails (UCD90120A will still support IMON and TMON).
I wouldn't want to lose the temperature capability, so it sounds like the UCD90120A would be the way I want to go. I notice there isn't a datasheet available and it isn't an option when creating a new project in Offline Mode. Any idea when those might be available? Is the only difference between the 120 and 120A the extra logic for GPO's, or am I also getting the Pin Selected States?
At this time, "from a feature perspective refer to UCD90160 DS online. From a pinout and current/temperature feature perspective refer to UCD90120".
The new devices are being added to the Fusion GUI and should be available in several weeks.
UCD90160, UCD90120A and UCD90124A will support pin selected states.
I don't understand how and why the UCD90160 does not support current measurement. As the MON input is single ended it will need anyway a high side current sens amplifier. For the required current range the amplifier output voltage will be set in the range of the MONx input. Therefore, any current measurement will look actually as a voltage from the chip side MONx inputs. I is not clear why when selecting UCD90160 in Fusion Power Designer, the Pin Assignment menu has N/A for current (and Temperature). If a UCD90124 is selected the MONx inputs can measure current.
In order to support 16 voltage rails (and all of the associated processing functionality), the current and temperature monitor software/firmware resources (RAM, FLASH, etc.) were re-allocated.
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