I'm developing my ADAU1452 Board. When compiling the project, I get an error. When checking the power supply, I noticed that the VDRIVE pin is 0.66 V instead of 1.2 V, and most likely I do not load the project, since there is no proper power for the digital part. Please help with this problem. Thanks
Firstly, congrats on your new board. Let’s see if we can troubleshoot its1.2v DVdd supply.
The ADAU1452’s 1.2v DVdd supply consists of the chip’s internal regulator driving an external PNP transistor as shown in the data sheet. The internal op-amp and PMOS device adjusts VDrive (the transistor’s base) as needed to maintain 1.2v at DVdd (the transistor’s collector). The voltage at VDrive itself is undefined — it changes with IOVdd, the transistor type and load conditions. Typically it reads about IOVdd - 0.7v, this from the PNP transistor’s Vbe drop. For example, if your IOVdd is 3.3v, VDrive should measure about 2.6v. On my ADAU1452 Eval board, the three transistor pins read: C = 1.19v, B = 2.7v, and E = 3.28v.
The very low VDrive voltage you’re measuring shows that the chip’s internal regulator is trying to increase DVdd by sinking more current at VDrive — while the external PNP transistor isn’t responding. This suggests something wrong with the external PNP transistor circuit. It could be incorrect wiring — three-pin semiconductors are so easily miswired. Or several other possibilities. With power off, a multimeter on Diode Check range should show a diode drop between IOVdd (+) and VDrive (-). If not, something’s definitely wrong with the PNP transistor or its connections.
Hi Bob, thanks for the answer! I tried to solder the aday chip, now on the VDRIVE 2.6V pin, but at the output of the 1.8 V transistor, is that a lot? I have a problem in the transistor?
I'm sorry, I'm having some difficulty understanding the measurements. Could I ask you to relate the voltages at the transistor's B, C, and E terminals with respect to ground (Vss)? Also, the type number of the transistor in use. Finally, since you mentioned re-soldering the IC -- Inspect it under magnification to insure that every pin is securely soldered without shorts to adjacent pins. Fine pitch parts like this are tricky to solder by hand.
Hi Bob! Dpak case, soldered Adau chip, even new soldered(3 times) now on leg B 0.66 v, on leg C 0.12 v, on leg E 3.29 v. I'm soldering with a heat gun.
With the E terminal at 3.29 v, the PNP transistor's forward-biased B-E junction should prevent the B terminal from going below 2.6 v. Since this junction isn't conducting with fully (3.29 - 0.66) = 2.63 v across it, it appears to be reverse-biased. This would happen, for example, if the transistor were the wrong type for this application -- perhaps a NPN. What is its type number? The STD2805 is recommended, although other PNP transistors meeting the specs described in the ADAU1452 data sheet may be used. The transistor presently on your board isn't working at all.