We have a design in production and we're observing a number of units with this IC exhibiting a strange behavior: The switch never fully closes and appears to remain in "in-rush control" mode, where the output voltage is at 1.86V instead of the 4+V at the input. All of our scope shots look clean: VIN is present before the ON pin is pulled up, and there are no glitches. The IC powers a circuit on an FPC with the load being the input of a boost converter, so there's about 10uF of capacitance there (nominally). Different combinations of the same IC and different FPCs exhibit / do not exhibit this behavior, so I'm led to believe that it has something to do with tolerances on the two sides.
In the attached scope shot, blue = VIN, yellow = VOUT.
Before we descend into the proverbial rabit hole, is there any known issue with this silicon?
Thanks,
Peter
Hi Peter. Do you have only capacitive load on VOUT or some resistive load as well? Please be noted that 1736 is dedicated to power up only for capacitive load and then after power up a resisitve load can be applied.
我附上相关schematic.
Hi Peter. Since your DC-DC and LDO has EN tied to VIN, that means they start to consume power once EN >VIH. After that you have additional capacitive load on VOUT side of the DC-DC + LDO also start power up. I suggest you to disconnect DC-DC from the schematic. If it helps, then definitely your DC-DC + LDO prevent 1736 normal operation.
I was suspecting it's a sequencing issue. Unfortunately, this has been fabbed by the thousands (on an FPC). But thank you for confirming.
Is it important to have current limit at 16.5mA during power up or you need just power switch with linear ramp? We can suggest SLG59M1748 as a replacement that is fully pin to pin compatible.
I was planning to evaluate a set of alternate switches with that footprint from other vendors as well. I'll add this to the list.
That said, where can this be purchased? I don't show any distributor stocking it.
http://www.silego.com/buy/index.php?main_page=advanced_search_result&sea...
Can someone from Dialog just send me a few samples of theLG59M1748C? I don't want to be stuck with 200 of them just for a validation.
I've already validated a competitive part from Toshiba.
Hi. Please advise what is your company and where are you located?
Yes, we're iBeat and we're in Silicon Valley. Who is the AFE for this area? I've never had direct contact.
You can email me directly at peter _at_ ibeat dot com or peter _at_ 100plus dot com (we're rebranding to 100Plus).
Hi Peter. I will send your request to our AFE and he will contact you soon.