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max77757 current limit problem

Category: Hardware
Product Number: MAX77757


I am using the MAX77757HEFG360+ as a LiFePO4 charger in a recent design.

The fast charge current limit is set to maximum with the IFAST resistor.

The power input and USB D+, D-, CC pins go to a USB-C connector.

1. When I tried to charge the battery, for the first few times the MAX77757 was setting the limit as described in the datasheet.

For power sources with no USB pins it was setting ~3A, but later it stopped setting 3A and is stuck to 0.5A.

For a while it responded to a strap (200R) between D+, D- and set 1.5A. Then it stopped doing this too.

2. A second example works at 3A, but has stopped responding to the D+/D- strap.

It still responds to USB signaling from USB sources, for now...

Any idea what I may be doing wrong?

Thank you,


  • Hi,

    I am not sure what is going on.   MAX77757 should set the input current limit to 3A if only power source with no USB pins connection.    Some FA needed to isolate is the setup or IC related issue.   Comparison VBUS, D+, D- CC pins signals between detection of 3A or 0.5A to see any different in the voltage/timing.   The problem is permanent or can be recovered by a power reset etc.