FS23 V1 output abnormal V1 output is abnormal as below waveform: C1 was VSUP,C2 was VBOS,C3 was V2;C4 was V1(power to MCU)C1 was VSUP,C2 was VBOS,C3 was V2;C4 was V1(power to MCU) 微信图片_20260813093846_286_23.jpg V1 without npnV1 without npn 微信图片_2026-08-13_095130_111.png How can I thoroughly solve the problems I am currently facing? if you want to get more information,please let me know. Re: FS23 V1 output abnormal guoweisun_0-1786680381549.png
guoweisun_1-1786680552393.png
This diagram explains the softstart conditions highlighted above. If all conditions are met, V1 starts powering on and enters the M5 timing sequence, which takes 150-500µs. If the startup fails within this time, it enters the FS state and restarts after 100ms. This is roughly the process.
Re: FS23 V1 output abnormal Could you please explain the softstart process? This section, " 19.4.6 V1UVLP monitoring chapter shows 'V1 is also monitored for V1UVLP when the device powers up after a wake-up from LPON, and during a cold start after TSOFT_START_V1. If, at the end of the softstart, V1 is still under the V1UVLP threshold, then the device goes into Fail-Safe state.'" What exactly is required for the V1 startup waveform? Thanks Re: FS23 V1 output abnormal This problem is most likely caused by V1 experiencing a startup failure during the soft boot process of OC, followed by a recovery.
The solution is to add an external tube to the V1 port and enable this function when using FS23 OTP, or you can choose our HVBUCK version.
Alternatively, you could remove some output capacitors to make the softstart smoother. I recommend choosing either of these two solutions for greater stability.
Re: FS23 V1 output abnormal 1: If PIN37 in the schematic is not used, ground it.
2: V1's load current is not large, only a maximum of 100mA. Please confirm the load at your location.
3: The decoupling capacitor of V1_IN is 1uF.
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4: In the case above, if the first startup fails and the second startup occurs, can the register M_GEN_FLAG be read to see what happened?
Let's change these things first and see the results.
Re: FS23 V1 output abnormal We measured a new waveform and found that V1 sometimes fails to start on the first try when the input is 12V. af12f0f0-afa6-40e3-881d-890516697b5a.png This is the waveform of the first startup failure. V1第一次启动未成功图V1 failed to start on the first attempt (image) This is the waveform of the second successful startup. V1第二次启动成功图V1 successfully started for the second time (image) Is this related to the undervoltage detection in V1 after a soft boot? The typical soft boot time is 300µs, and the maximum is 500µs. Why does it seem like it won't boot if it exceeds 500µs, but it seems to work if it's below 500µs? Could you please describe the soft boot process? The manual doesn't provide much information about it. Re: FS23 V1 output abnormal guoweisun_0-1786608712650.png
With 8V Vin, could you reduce the time axis of the waveform circled above? I want to see how long V1 has been running.
Can we also test the same waveform with 12V VIN?
I don't have a high and low temperature test chamber here, so I can't do too many tests. I can only rely on your results. Re: FS23 V1 output abnormal You can see below circled part.
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Re: FS23 V1 output abnormal Channel 1 was VSUP,C2 was VBOS,C3 was V2;C4 was V1(power to MCU) Re: FS23 V1 output abnormal which one indicate V1 follow up VBAT from 0? current test results show VBOS>3.06V TO V1 UPing used 13.2ms, please check Re: FS23 V1 output abnormal guoweisun_0-1786601048119.png
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A lots of confuse for your test result ,you can see when Vbat< Vsup_uv,the V1 should be stay 0,why your V1 follow up VBAT from 0? I suppose your test waveform yellow is VBAT,Green is V1,am I right? Re: FS23 V1 output abnormal This is testing. by the way, we check the manual and found 19.4.6 V1UVLP monitoring chapter shows "V1 is also monitored for V1UVLP when the device powers up after a wake up from LPON, and during a cold start after TSOFT_START_V1. If, at the end of the softstart, V1 is still under V1UVLP threshold, then the device goes into Fail-Safe state." does it mean V1 should beyond V1UVLP threshold after TSOFT_START_V1(type,300us)? in addition ,this V1 abnormal issue happened in low temperature (-30℃ ） and low Vsup power(8v)。in this condition, we increased VSUP to 12V，V1 output OK。 Re: FS23 V1 output abnormal VBOS>3.06V TO V1 UPing used 13.2msVBOS>3.06V TO V1 UPing used 13.2ms Re: FS23 V1 output abnormal You can try to disconnect MCU with V1 and test it again for example add some loading 50mA.
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