Oscilloscope Tools---DIY low-cost production of oscilloscope current detection module

0. Update Notes
          Updated V2 version (not verified yet --- 2022-10-05)
IV conversion board V2---Description:
1. The IC power supply is changed from the original PMOS to a diode, which makes the shutdown current negligible without affecting the charging and discharging (the working current is about 430uA, the shutdown current is negligible)
2. According to the INA199 specification, an input protection circuit is added
3. The PCB is changed from the original 4-layer board to a 2-layer board
1.
The purpose of the oscilloscope current detection module is to make a low-cost current-to-voltage module, which is convenient for oscilloscope measurement. (The cost is about 20 yuan)
        (Sometimes when measuring a power module, it is necessary not only to test its voltage value, but also to measure the current value at the same time. Maybe you will think that there is a current probe, but my measurement needs and usage frequency are not high. It seems to be an overkill to buy a probe for this purpose, and it is also a little expensive. Therefore, a low-cost, low-frequency current and voltage module for oscilloscopes will come from this.)
          A brief short video, shared by Station B: Oscilloscope Tools---DIY Low-Cost Oscilloscope Current Detection Module_bilibili_bilibili
2. Main parameters of the module
Maximum input voltage: 26V (depends on the current detection IC, here we use the INA199A1DCKR IC) 
Maximum input current: 5A 
Measurement current accuracy: more than 10mA (depends on the VOS and sampling resistance of the current detection IC)
Measurement current frequency: about 50KHz or less (this part has not been accurately measured, INA199A says 80KHz, so don't expect to measure too high a frequency)
3. Block diagram of module system
4. Design description
A. The power supply part
adopts lithium battery power supply, which can be separated from the measured end, so that the module can be used for high-end and low-end side measurement.
        Using TYPE-C port as the power supply port, a MOS can be used to charge and switch the lithium battery, nice! (Note that a lithium battery pack with a charge and discharge protection board is required here)
B. The voltage conversion part
adopts the method of BOOT boost first, and then LDO buck. LDO adopts the ADJ adjustable version, not the fixed type, because it is convenient for later upgrades. When it is necessary to measure 10A, it is necessary to provide a 10V voltage input to the current detection IC, so that the ADJ version can flexibly adjust the voltage.
C. Output terminal
5. PCB part description
provides a 4-layer PCB board (because there is a proofing coupon, why not), it should be OK to change it to a 2-layer board. The circuit is very simple, and you can make some small changes if you need it.
6. Finally,
although the module can also be connected in series with a single power supply, it is still recommended to connect the measured GND in series, that is, connect all four terminals, which is more stable and reliable. The module has some shortcomings, and I hope you can point them out.