Fenix HP12 headlamp repair - PCB component identification, schema - Page 1
Forum section: electronics / repair

author: Libas
author_rank: Regular Contributor
timestamp: December 06, 2021, 03:13:06 am
content: Hi all,during reverse engineering of my faulty headlamp I have troubles to identify 2 major components. Please see attached pictures and schematics.Could you please help me to identify them? Component marking is BNDY and SBW7. Casing similar to SOT23-5. Marking style of IC1 (BNDY) is same style as on IC3 (C2KW, LDO regulator 3V) and also same as IC5 (THCX, temperature chip). There is an underline under the text and dots under the underline (visible on PCB photo). IC2 (SBW7) is on other side of PCB and has different marking style so its probably different manufacturer. Unfortunatelly manufacturer does not want to provide any detailed info.IC1 drives power to LED. It sends full battery voltage to gate of Q3 and Q4 when LED is OFF.

author: Libas
author_rank: Regular Contributor
timestamp: December 06, 2021, 03:14:36 am
content: ...

author: Libas
author_rank: Regular Contributor
timestamp: December 06, 2021, 03:15:52 am
content: ...

author: Libas
author_rank: Regular Contributor
timestamp: December 06, 2021, 03:18:47 am
content: .

author: Libas
author_rank: Regular Contributor
timestamp: December 06, 2021, 03:52:25 am
content: According to my codebook (SMD-codes 2012) IC3 (C2KW) could be product number S-812C30AMC-C2K. With this product number I have found 2 datasheets (manufacturer Seiko Instruments and Ablic)...but according to codebook manufacturer should be Silicon General Inc (now part of Microsemi).

author: fzabkar
author_rank: Super Contributor
timestamp: December 06, 2021, 05:13:41 am
content: The long underline, with dots underneath, appears to be a characteristic of Seiko chips.https://nation-ic.en.made-in-china.com/product/fClQDsgxXjkb/China-Electronic-Component-Integrated-Circuit-Seiko-IC-Linear-Voltage-Regulator-Sot23-3-S-1206b33-M3t1g.htmlThe first 3 letters are the product code, the 4th is the lot number:https://www.mouser.com/datasheet/2/360/S1206_E-1365753.pdfSee this database:http://www.smdmark.com/en-US/search/code?id=c2k

author: Libas
author_rank: Regular Contributor
timestamp: December 06, 2021, 05:30:43 am
content: yes fzabkar...marking style is same as in provided link.Link to database unfortunatelly without success...

author: fzabkar
author_rank: Super Contributor
timestamp: December 06, 2021, 05:34:39 am
content: This explains the relationship between Ablic and Seiko:https://www.ablic.com/en/semicon/news/2020/04/30/mm_complete/"THC" is S-5841A65D-M5T1x (x = G or U):https://www.ablic.com/en/doc/datasheet/temperature_sensor/S5841_E.pdf

author: Libas
author_rank: Regular Contributor
timestamp: December 06, 2021, 06:16:55 am
content: this looks like datasheet for the THCX:https://www.ablic.com/en/doc/datasheet/temperature_sensor/S5841_E.pdf...so it really looks like BNDY should be also by ABLIC/Seiko. Question is what type of component is it? With this info it shouldnt be so complicated to find correct datasheet here:https://www.ablic.com/en/semicon/products/

author: fzabkar
author_rank: Super Contributor
timestamp: December 06, 2021, 06:54:28 am
content: IC1 appears to be a step-down PWM controller with an external transistor.https://www.ablic.com/en/semicon/products/power-management-ic/switching-regulator/These two parts appear to match your circuit:https://www.ablic.com/en/doc/datasheet/switching_regulator/S8520_8521_E.pdfS-8521 has a "BXS" marking:http://www.eric1688.com/product.aspx?id=401973S-8520 has a "BJS" marking:https://www.techupv.com/index.php?main_page=product_info&products_id=385571IC2 appears to be sensing the LED current. Perhaps it is a comparator? Could it be something like a TS391 / TS391A?https://www.st.com/resource/en/datasheet/cd00001660.pdfOr this?https://datasheets.maximintegrated.com/en/ds/MAX9075-MAX9077.pdfhttp://ww1.microchip.com/downloads/en/DeviceDoc/MIC6270-IttyBitty-Comparator-DS20006294A.pdfhttps://asset.conrad.com/media10/add/160267/c1/-/en/001073087DS01/karta-katalogowa-1073087-uklad-scalony-liniowy-texas-instruments-tlv3201aidckt-typ-obudowy-sc-70-5.pdfIs there a date code on the PIC uC? Perhaps we can search for older Ablic/Seiko parts at the Wayback Machine?Edit:Could the "BND" part be a S-8520F18MC-BNDT2x ? This is a fixed 1.8V PWM controller.https://www.ablic.com/en/doc/datasheet/switching_regulator/S8520_8521_E.pdf(page 5)The BJS and BXS parts mentioned earlier are 3.3V devices (S-8520E33MC-BJST2G and S-8521D33MC-BXST2G).

author: Libas
author_rank: Regular Contributor
timestamp: December 06, 2021, 08:53:44 am
content: additional info to IC2 (SBW7) which may be helpful for identification....there is some sort of PWM signal measurable on PIN6 (IC6).LED OFF 0VLED disconnected 0-3V, various pulse lengths according to required LED intensityLED intensity 1 0-3V, pulse length 0.06ms (shortest pulse)LED intensity 2 0-3V, pulse length 0.5msLED intensity 3 0-3V, pulse length 0.8ms

author: fzabkar
author_rank: Super Contributor
timestamp: December 06, 2021, 09:11:43 am
content: Quote from: Libas on December 06, 2021, 08:53:44 amIs the capacitor at R3 shorted to ground?

author: Libas
author_rank: Regular Contributor
timestamp: December 06, 2021, 09:37:37 am
content: Quote from: fzabkar on December 06, 2021, 09:11:43 amSchematic is drawn based on measurements of faulty lamp...so pin to R3 measured as not grounded....pin to R5 grounded

author: Libas
author_rank: Regular Contributor
timestamp: December 07, 2021, 02:38:48 pm
content: marking details...

author: Libas
author_rank: Regular Contributor
timestamp: December 07, 2021, 04:20:04 pm
content: IC1 (BNDY) matches my measurements. During LED ON there is all the time 1.8V measured on pin 3. So function of this component is clear now.8520F18MC-BNDT2x (CMOS step-down switching regulator-controller with PWM control)https://www.ablic.com/en/doc/datasheet/switching_regulator/S8520_8521_E.pdf

author: Libas
author_rank: Regular Contributor
timestamp: December 07, 2021, 04:23:03 pm
content: So last component which is not clear now is IC2 (SBW7)When LED is ON there is of course different voltage on Anode required for different intensity levels. IC2 has to somehow cooperate with IC1 to regulate the voltage (to keep 1.8V on IC1 during various LED intensity).Any ideas?

author: fzabkar
author_rank: Super Contributor
timestamp: December 07, 2021, 06:22:46 pm
content: I think SBW7 is an op amp (same pinout as comparators). Pin 6 of the PIC outputs a PWM signal which is integrated to provide a DC reference for the op amp. This reference is compared against the LED current, and the op amp's output pin then controls the output voltage of BNDY by adding a variable DC shift to the bottom end of the voltage divider (R9 and R12).

author: fzabkar
author_rank: Super Contributor
timestamp: December 08, 2021, 04:39:42 pm
content: MCP606, Microchip, 2.5V to 6.0V Micropower CMOS Op Amp, rail-to-rail I/O, marking SBnn, SOT23-5:http://ww1.microchip.com/downloads/en/devicedoc/11177f.pdf

author: Libas
author_rank: Regular Contributor
timestamp: December 08, 2021, 05:13:49 pm
content: perfect...thanks a lot for your effort! I have the same tip from another guy on the email...so its a nice confirmationOn my second lamp this component is marked as SBEU so important are really only first two letters.

author: Libas
author_rank: Regular Contributor
timestamp: December 10, 2021, 06:57:15 pm
content: Lets move now to repair...first fault was PCB through hole which had no connection to the other side of PCB (hole next to the C2). Therefore ICs had no power.But there is unfortunately another fault. When the LED is OFF there is still voltage on LED anode (2V). Output of IC1 is full battery voltage (Q3, Q4 closed) so it looks to me like there is leak of either Q3, Q4 or IC1. Any idea how to measure without desoldering those components?I also cant find any datasheet for those PMOS transistors. Marking is C01C (or eventually AF1A). There is another transistor Q7 which has marking C00C...so I guess that one is NMOS. Could you please help to identify manufacturer? Marking style is simple text (visible on one of earlier pictures with marking details)....no other details.

author: fzabkar
author_rank: Super Contributor
timestamp: December 10, 2021, 07:59:03 pm
content: Is the enable pin of BNDY in the disabled state?As I understand the circuit, when the LED current is 0, the input to the op amp is 0V. This means that the output of the op amp will go high in order to reduce the output of BNDY. However, since BNDY also provides the supply voltage for the op amp, the minimum output voltage of BNDY must be 1.8V. Of course this only applies if BNDY is enabled by the PIC.APM2301CA, Anpec, P-ch enhancement mode MOSFET, -20V, -3A, marking C01x, SOT-23-3:http://www.hytic.net/upload/files/2013/10/ANPEC-APM2301CAC.pdfAPM2300CA, Anpec, N-ch enhancement mode MOSFET, 20V, 6A, marking C00x, SOT-23-3:http://www.hytic.net/upload/files/2013/10/ANPEC-APM2300CAC.pdf

author: Libas
author_rank: Regular Contributor
timestamp: December 11, 2021, 09:30:38 am
content: Yes...lamp is in OFF state which means:BNDY in OFF state (pin1 = 0V)BNDY output is full battery voltage (pin4)SBW7 receives NO signal from IC6 (negative input, pin4 = 0V)Q3 + Q4 should be closed (same voltage on gate and source)But there is 2V present on LED anode....which means there is voltage present on SBW7 positive input (pin3 = 1mV)....and therefore SBW7 output is high (pin1 = 2V)Basically:if BNDY input drops below 1.8V (pin3) it reduces the output voltage (driving signal or drops to zero) opens by this Q3 + Q4 to increase flow to LEDif BNDY input raise above 1.8V (pin3) it sends full battery voltage to Q3 + Q4 and closes them to reduce flowIC6 has NO feedback info about actual current flow through LED....it only sends pulses to SBW7 negative input (pulse length according to intensity level selected by user)SBW7 + BNDY then care about balancing the flow of LED currentBNDY seems to me that operates correctly....so I suspect more Q3 + Q4....or another manufacturing issue like mentioned through hole fail.

author: fzabkar
author_rank: Super Contributor
timestamp: December 11, 2021, 07:07:48 pm
content: The two AF1A MOSFETs in your diagram seem to be permanently switched on. Is this an error in your drawing?

author: Libas
author_rank: Regular Contributor
timestamp: December 12, 2021, 06:05:04 am
content: No error...On my second lamp Q1-Q4 are all marked as C01C....so all 4 are PMOS (also approved by manufacturer).If I understand it correctly...when battery is inserted (18650) the current flows only through internal diode. At some point transistor becomes open but current cannot flow in PMOS from drain to source. So current continues to flow only through diode. When battery is inserted in reverse polarity everything is blocked.

author: fzabkar
author_rank: Super Contributor
timestamp: December 12, 2021, 07:51:49 am
content: Thanks, I see now. There are two forward biased body diodes connected in parallel to provide an "ideal" diode for reverse polarity protection.

author: Libas
author_rank: Regular Contributor
timestamp: December 12, 2021, 08:59:16 am
content: but what is the reason to use internal diodes in the transistor instead of use normal diodes?

author: fzabkar
author_rank: Super Contributor
timestamp: December 12, 2021, 04:40:19 pm
content: There is no separate diode. The "body diode" is just an intrinsic feature of MOSFETs.https://www.microsemi.com/document-portal/doc_view/14692-mosfet-tutorialhttps://www.powerelectronics.com/technologies/discrete-power-semis/article/21861311/power-management-101-power-mosfet-charactertics

author: Libas
author_rank: Regular Contributor
timestamp: December 12, 2021, 06:41:59 pm
content: I mean why designer of this circuit didnt use simple diode instead of this transistor. I cant see any purpose this transistor...it doesnt switch anything. Or do I miss anything?

author: fzabkar
author_rank: Super Contributor
timestamp: December 12, 2021, 06:52:37 pm
content: The body diode can have a much lower forward voltage drop than a regular Schottky diode. However, in the present case the voltage drop is 0.4V at 1A, so I can't see much of an advantage. :-?Quote

author: Libas
author_rank: Regular Contributor
timestamp: December 13, 2021, 04:02:10 pm
content: In my local store is available IRLML6402 as a replacement for PMOS C01C. Is that suitable replacement?I have found info that "Silicon optimized for applications switching below <100kHz" ....but original transistor is driven by S-8520F18MC-BNDT2x which has according to datasheet "Oscillation frequency of 300 kHz".https://www.infineon.com/cms/en/product/power/mosfet/p-channel/irlml6402/