BQ24725AEVM-710: Not Passing Current to Load

Nickolas Vallo

Part Number: BQ24725AEVM-710

I have an issue where the BQ24725AEVM-710 is not passing current from the supply to the load.

I first set the evaluation kit up according to Figure 2 in the User Guide and fail to get the correct voltages at the test points.

ACDRV and CMSRC read as 0.

J2 also does not have the correct values.

When I hook up a load to J2(Bat, GND) no current passed to the load

When I hook up a load to J2(SYS, GND) no current is passed to the load

When I hook up a load to J2(SYS, GND) and J2(BAT, GND) no current is passed to either load.

I was hoping that someone could help identify the problem and / or point me at least in the right direction.

over 6 years ago

0 Nickolas Vallo over 6 years ago

Prodigy 150 points

Quick Note:

After the loads are hooked up to J2, the registers 0x12, 0x14, 0x15 are adjusted to match the recommended setting in the User Manual and then a few other configurations to try and get the system to work.

0 Angelo Zhang87 over 6 years ago in reply to Nickolas Vallo

TI__Genius 11850 points

Hi Nickolas,

Let's try only connecting the two power supplies (PS#1 = 19.5 V and PS#2 = 3.3 V) to the EVM. Do not connect a load or a battery yet. There is also no need to change any register settings at this point.

Do your voltage measurements match the values shown below?

Best regards,

Angelo

0 Nickolas Vallo over 6 years ago in reply to Angelo Zhang87

Prodigy 150 points

Yes, this was the first process I tried.

Just tried again: Hooked up PS1 and PS2, No registers changed.

V(TP(ACDRV, CMSRC) == 0 V

0 Angelo Zhang87 over 6 years ago in reply to Nickolas Vallo

TI__Genius 11850 points

Hi Nickolas,

What are the other voltage measurements aside from V(TP(ACDRV, CMSRC))? Do they match Section 2.4.1 in the User's Guide?

Best regards,

Angelo

0 Nickolas Vallo over 6 years ago in reply to Angelo Zhang87

Prodigy 150 points

Outside V(TP(ACDRV, CMSRC)) and V(J2) the rest match the User's Guide

0 Angelo Zhang87 over 6 years ago in reply to Nickolas Vallo

TI__Genius 11850 points

Hi Nickolas,

Can you please capture a waveform that shows VCC, ACOK, ACDRV, and CMSRC the moment that the adapter is plugged in?

Best regards,

Angelo

0 Nickolas Vallo over 6 years ago in reply to Angelo Zhang87

Prodigy 150 points

V1 (Yellow): VCC

V2 (Blue): ACOK

V3 (Purple): ACDRV

V4 (Green): CMSRC

0 Nickolas Vallo over 6 years ago in reply to Nickolas Vallo

Prodigy 150 points

Adapter Voltage was turned on at the point of the initial pulse.

Adapter Voltage was left on until after the capture provided above.

The pattern depicted above repeats itself.

0 Angelo Zhang87 over 6 years ago in reply to Nickolas Vallo

TI__Genius 11850 points

Hi Nickolas,

Thanks for sending that scope shot. However, I don't understand why your VCC (yellow) is almost 20 V even before the adapter is plugged in (rising edge of the blue ACOK waveform). There is no battery or system connected during this test, correct? Am I misunderstanding your test conditions and/or misreading your scope shot?

The conditions required for ACDRV to go 6 V above CMSRC (thus turning on ACFET and RBFET) are shown below:

I know you already mentioned that the other voltages match the User's Guide, but just to be 100% clear, please provide the following measurements while the adapter is connected:

ACOK =

ACDET =

ACDRV =

CMSRC =

VCC =

VBUS =

VSYS =

VBAT =

Best regards,

Angelo

0 Joel Hernandez II over 6 years ago in reply to Nickolas Vallo

TI__Mastermind 25800 points

Hey Nickolas,

Can you try using a 21-24V input source?

I looks like the charger attempts to turn on the two AC FETs, the input voltage droops, potentially below the 17.9V setting that's set by R15 and R14 on the ACDET pin. You mentioned you used a 19.5V input source as the User's Guide describes, but it looks like either the impedance from your input source is too high or the input source cannot immediately sustain the inrush current.

Regards,

Joel H

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BQ24725AEVM-710: Not Passing Current to Load