Mystery ICs ( a399 and A30p) - Page 1
Forum section: electronics / beginners

author: lartsu
author_rank: Contributor
timestamp: February 06, 2014, 11:44:42 am
content: I had been searching back and forth without success for find out details for two components.The SMD chips have labels a399 and A30p (U2 and U3 labels in PCB).All advises are welcome!

author: electronics man
author_rank: Frequent Contributor
timestamp: February 06, 2014, 11:53:02 am
content: What product are they from

author: amyk
author_rank: Super Contributor
timestamp: February 06, 2014, 12:39:21 pm
content: Either aSPX8863LDO or aMP1523constant current boost converter, or possibly one of each...

author: valentinc
author_rank: Regular Contributor
timestamp: February 06, 2014, 02:58:56 pm
content: One of the pins of each chip goes directly to each of the inductors... So they might be some kind of DC-DC converter controllers with integrated switch... One strange thing is that there is no diode on the PCB... The other pin of the inductor goes directly to the capacitor... Could you post a larger area of the PCB ?

author: lartsu
author_rank: Contributor
timestamp: February 06, 2014, 07:37:32 pm
content: The board is broken DTV-board. Something was burned when antenna power supply was accidentally connected wrong way and it was feeding 12 VDC via SMA connector to the board.The video decoder MST720 gets voltages but left side of the board is totally dead (CT216T DVB decoder, SDRAM, FLASH).U2 and U3 get 5 VDC (pin 5, bottom left).

author: valentinc
author_rank: Regular Contributor
timestamp: February 06, 2014, 11:18:36 pm
content: Where is the power input connector ? That 2 pin connector on the bottom of the board go where ?

author: poorchava
author_rank: Super Contributor
timestamp: February 07, 2014, 09:32:25 am
content: QuoteExcuse me, but howdafukk does one push dc parrel jack into sma socket?! I'd sat there's no goddamn way.As for the IC my money would be definitely at some integrated buck converters. 4u7 inductor suggests something of relatively high frequency. Diode can be integrated as well, either as a diode or synchronous rectification mosfet.But since that's a DTVm board, those chips can be from a company you've never heard about.

author: valentinc
author_rank: Regular Contributor
timestamp: February 07, 2014, 09:58:09 am
content: There is the only possibility that they are buck converters... And the diode can be integrated, because it's between the output and ground... If it was a boost converter, as amyk suggested, the diode was between the inductor and the load (which is in parallel with the capacitor), which meant that there was no direct connection between the inductor and capacitor...And judgind by the fact that there are no external feedback resistors, it's a fixed voltage buck converter... The capacitors are rated a 6.3V... So it's obvious that the 2 voltages that they output is lower than that (3.3V and 1.2V maybe)...Measure the voltage across the 2 capacitors, what do you get ?

author: lartsu
author_rank: Contributor
timestamp: February 07, 2014, 10:13:36 pm
content: I have measured the voltages over capasitors. See the picture.Back side of PCB there is test point with label + 1V1 and voltage is 0 to GND for right side (A30p).

author: poorchava
author_rank: Super Contributor
timestamp: February 07, 2014, 11:24:24 pm
content: It could be a core voltage for a CPU or something. 0V means that obviously the rail doesn't work. Either the regulator is blown, or it does not get enable signal (which may be one of the thinner traces going to regulators. You could measure that, but enable/shutdown signals may sam as well be active-high as they can be active-low and there's no way to know without a datasheet.

author: valentinc
author_rank: Regular Contributor
timestamp: February 07, 2014, 11:45:30 pm
content: I found something: according to this site,http://www.s-manuals.com/smd/a3,the only possible one (for both A30p and A399) is the APS1006ET5-1.8 or N6200M5G-1.8 (SOT-25 packages)... Both are 1.8V Buck regulators... I don't see clearly on the first picture, the + of the capacitor goes to pin 1 and 2 ? Or it goes to pin5 (Vfb) through an internal layer ?

author: lartsu
author_rank: Contributor
timestamp: February 08, 2014, 02:38:47 pm
content: I did some debugging...(updated).Does this make sense to you?All ideas are welcome.

author: Monkeh
author_rank: Super Contributor
timestamp: February 08, 2014, 03:13:13 pm
content: Quote from: poorchava on February 07, 2014, 09:32:25 amI'd say you should look into how masthead amplifiers are supplied.

author: lartsu
author_rank: Contributor
timestamp: February 08, 2014, 03:53:58 pm
content: Looking into masthead amplifier power supply connection doesn't bring this board alive any more. :-)

author: Monkeh
author_rank: Super Contributor
timestamp: February 08, 2014, 03:58:54 pm
content: Quote from: lartsu on February 08, 2014, 03:53:58 pmNo, but it'll educate him.

author: lartsu
author_rank: Contributor
timestamp: February 08, 2014, 04:44:01 pm
content: Now he knows how to connect thishttp://www.televes.com/en/node/8149and I would like to find the bug(s) from board.

author: valentinc
author_rank: Regular Contributor
timestamp: February 08, 2014, 06:13:41 pm
content: It seems like what you have marked corresponds to the datasheet... Pin 2 is indeed ground, Pin 4 is Vin (5V), Pin 1(the orange line) is the Enable pin (which must be HIGH in order to start the converter), Pin 3 is the switch output, that goes directly to the inductor, the only pin that I'm not sure it corresponds is Pin 5 (feedback) which should be connected to the point between the inductor and the + of the capacitor (is the green one in your picture)... Figure out where goes that green one... If it goes to the + of the capacitor, then almost for sure, that is the part number...

author: lartsu
author_rank: Contributor
timestamp: February 08, 2014, 10:13:02 pm
content: Yep, you were right. The other side started to get power when the RUN-pin (1) got hard wired 5 V.My next 'suspicion' is operation amplifier (3414) next to video decoder chip.I have measured the voltages from it pins1 500 mV2 500 mV3 -10 V4 +5 V5 500 mV6 500 mV

author: valentinc
author_rank: Regular Contributor
timestamp: February 08, 2014, 10:51:34 pm
content: Something is not right... If this is the TI TL3414A op-amp pin 4 is -Vcc and you have +5V on that pin... You should have 0V... (GND)... And also, if the op-amp is used as an amplifier (with negative feedback) the voltage at pin 2 should be more or less equal to the voltage at pin 3... (they may differ by the offset voltage, which is specified in the datasheet to be maximum 5mV)...Why do you suspect this part ?

author: lartsu
author_rank: Contributor
timestamp: February 09, 2014, 07:42:48 am
content: Yes, I made a mistake.Here are the measured voltages with correct pin numbering:I have measured the voltages from "3414" pins1 OUT1 0,5 V2 IN1- 0,5 V3 IN+ 0,3 V4 VCC- -9.9 V5 IN2+ 0,5 V6 IN2- 0,5V7 OUT2 0,5 V8 Vcc+ 5 V

author: valentinc
author_rank: Regular Contributor
timestamp: February 09, 2014, 02:06:40 pm
content: What exactly is wrong with this board ? Does it have speakers ? That 2 bottom connectors with 2 pins are connected to something... I asked you in earlier posts... To what exactly ? I ask you this because, before we suspect that op-amp, we must first know what it's purpose... Or if it's even an op-amp, or used as an op-amp... It could also be used as a comparator...