Other Parts Discussed in Thread: BQ24070, , LM2576
Regulator issue
For a tracking device we implement the attached power scheme
the device processor is a MT7688AN
The MT7688AN processor has a Linux operating system (openwrt) and when energizing the device with a discharged battery or without battery, the following behavior occurs, the MT7688AN starts to load the kernel and all its components, but when the modem is energized, the MT7688AN is it restarts and does not finish loading the operating system (this process is repeated indefinitely), when the BQ24070 regulator has a charged battery connected, the MT7688AN does not restart when the modem is energized, so I can assume that the problem is in the current which can supply the LMR23630 regulator or the BQ24070 regulator.
Another fact to mention is that the device's coils emit a hum when the modem is sending information.
The peak consumption of the MT7688AN together with its peripherals (memories, regulators, etc.) is 800mA, the average consumption is 300mA. The LT1963EST3.3 regulator supplies a maximum current of 1.5A, enough for the MT7688AN processor to work.
The peak consumption of the 2G modem can reach 1.6A, the average consumption is around 400mA, the SC4215A regulator supplies a maximum current of 2A, enough for the 2G modem to work.
The steps you took to identify the problem were as follows.
1. remove the battery regulator BQ24070, and feed the regulators LT1963EST3.3 (3.3v) and SC4215A (3.8v) with the 5v of the LMR23630 regulator, in this case the behavior was the same, the MT7688AN restarts when the modem is energized 2G.
When monitoring the oscilloscope I could not observe any voltage drop in the 3.3v line to which the MT7688AN is connected
2. Al replace the LMR23630 regulator with the LM2576S regulator.
With this change, the MT7688AN processor works without problems, it no longer restarts when the modem is started and no sound is heard from the device's coils.
My questions are the following:
The LMR23630 and LM2576S regulators can supply a current of 3A (according to the datasheet), when measuring the consumption of the device I obtained a maximum measurement of 0.61A with a voltage of 5v between the LMR2360 regulator and the BQ24070 regulator, this measurement is carried out with a fluke 117 multimeter in current measurement and maximum measurement configuration.
Which tells me that the consumption of the device is very far from the maximum current of the LMR23630 and LM2576S regulators.
Why does the device work correctly with the LM2576S regulator and not with the LMR23630 regulator?
What component should I add / change to the LMR23630 regulator circuit in order to use this regulator in the device?
The schematic circuit used for the LMR23630 regulator and the LM2576S regulator are those indicated by their datasheets in the example circuit.