MobileRead Forums - View Single Post - Aura H2O tps65185_int_func under-voltage on DCDC1 detected !

DomesticExtremis · 10-02-2019, 07:19 PM

Battery voltage was 4.15 to 4.1 volts after many power cycles to do the measuring.

Other than the stray voltage on VIN, I think we can see that the input power to the chip is fine and as expected, as is the regulated 3.3V to pin 45.

Pins 24,25 and 26 are for the DCDC2 negative voltage boost converter. Here too, the input voltage VIN_P (pin 24) looks fine at near battery voltage and within spec.
Pin 25 is VN_SW, the inverter output and stays resolutely at zero, after several attempts to measure it. However pin 26 does shoot up (perhaps down) to a value near the required -16V. I found it difficult to measure exactly because my meter is sluggish and the window for measuring this value is very brief. I am prepared to accept that it does attain its correct value, just that I am not able to measure before the chip reverts to standby mode.
Quite why VN_SW stays at zero I don't understand, particularly since it feed the other end of the diode to VN, so there should only be a diode drop (min 0.3V) of difference in the voltages of pins 25 and 26 (unless I misunderstand the circuit, which is eminently possible).
It may be that the diode has failed open circuit but that no error is reported because the chip measures VN and not VN_SW.

Anyhoo, moving on to pins 40,41, and 42 for the DCDC1 boost converter which should be supplying the +16V rail, there is something really weird going on. In standby mode there is a small voltage on both VB nd VB_SW. In active mode these values are slightly lower, but nowhere near in spec. Again the two pins are joined by a diode, so their voltages should not be equal. It is possible that the diode is shorted and causing the failure of the boost circuit,
However two failed diodes around the same chip at the same time seems unlikely, more likely is an internal failure in the chip.

10-02-2019, 07:19 PM	#26
DomesticExtremis Addict Posts: 243 Karma: 359054 Join Date: Nov 2012 Device: default	Battery voltage was 4.15 to 4.1 volts after many power cycles to do the measuring. Other than the stray voltage on VIN, I think we can see that the input power to the chip is fine and as expected, as is the regulated 3.3V to pin 45. Pins 24,25 and 26 are for the DCDC2 negative voltage boost converter. Here too, the input voltage VIN_P (pin 24) looks fine at near battery voltage and within spec. Pin 25 is VN_SW, the inverter output and stays resolutely at zero, after several attempts to measure it. However pin 26 does shoot up (perhaps down) to a value near the required -16V. I found it difficult to measure exactly because my meter is sluggish and the window for measuring this value is very brief. I am prepared to accept that it does attain its correct value, just that I am not able to measure before the chip reverts to standby mode. Quite why VN_SW stays at zero I don't understand, particularly since it feed the other end of the diode to VN, so there should only be a diode drop (min 0.3V) of difference in the voltages of pins 25 and 26 (unless I misunderstand the circuit, which is eminently possible). It may be that the diode has failed open circuit but that no error is reported because the chip measures VN and not VN_SW. Anyhoo, moving on to pins 40,41, and 42 for the DCDC1 boost converter which should be supplying the +16V rail, there is something really weird going on. In standby mode there is a small voltage on both VB nd VB_SW. In active mode these values are slightly lower, but nowhere near in spec. Again the two pins are joined by a diode, so their voltages should not be equal. It is possible that the diode is shorted and causing the failure of the boost circuit, However two failed diodes around the same chip at the same time seems unlikely, more likely is an internal failure in the chip. Last edited by DomesticExtremis; 10-02-2019 at 08:22 PM.