iPhone 4 CDMA board backlight IC pin 1 - GSM-Forum

drshock · 03-23-2014, 04:39

So noob question here I guess, I usually work on PC boards but looking to fix my own iPhone since I have the right gear to do so. I have a water damaged CDMA board with an obviously burnt and partially cracked backlight IC. No writing on the burnt IC is visible, but in the GSM schematic it is called Q1_PMU.

I have successfully removed part of the EMI shielding to get at and remove this IC already and have the pads ready to mount the new IC.

I've taken another of similar IC off of a deceased iPod Touch 4th gen board to try, but that donor IC has no legible pin 1 marking on it either, in fact I can't make out anything written on the top but maybe a "T" or "J" and an "8", its very faint marking.

I have not done this specific repair before, and am not familiar with this particular IC. Is the pin/pad 1 orientation on this particular IC always to the upper left of any readable stamped manufacturers text or at another position? Thx.

drshock · 03-23-2014, 23:55

OK I found the datasheet for this IC, Fairchild Semi FDFME3N311ZT, and answered my own question. Pin 1 is across from to the notched side of the middle "K" pad. And you can locate pin 1 and 3 on the CDMA board by following these two traces into the coil next to it. Phone is working again like a charm. Easy fix.

03-23-2014, 04:39	#1 (permalink)
drshock Junior Member Join Date: Feb 2014 Location: USA Posts: 5 Member: 2137277 Status: Offline Thanks Meter: 0	iPhone 4 CDMA board backlight IC pin 1 So noob question here I guess, I usually work on PC boards but looking to fix my own iPhone since I have the right gear to do so. I have a water damaged CDMA board with an obviously burnt and partially cracked backlight IC. No writing on the burnt IC is visible, but in the GSM schematic it is called Q1_PMU. I have successfully removed part of the EMI shielding to get at and remove this IC already and have the pads ready to mount the new IC. I've taken another of similar IC off of a deceased iPod Touch 4th gen board to try, but that donor IC has no legible pin 1 marking on it either, in fact I can't make out anything written on the top but maybe a "T" or "J" and an "8", its very faint marking. I have not done this specific repair before, and am not familiar with this particular IC. Is the pin/pad 1 orientation on this particular IC always to the upper left of any readable stamped manufacturers text or at another position? Thx.

03-23-2014, 23:55	#2 (permalink)
drshock Junior Member Join Date: Feb 2014 Location: USA Posts: 5 Member: 2137277 Status: Offline Thanks Meter: 0	OK I found the datasheet for this IC, Fairchild Semi FDFME3N311ZT, and answered my own question. Pin 1 is across from to the notched side of the middle "K" pad. And you can locate pin 1 and 3 on the CDMA board by following these two traces into the coil next to it. Phone is working again like a charm. Easy fix.