MP2672 STAT pin is always low (LED always on)


We are using the MP2657 in standalone mode (R on CV is 30K) to charge a 2s Li-ion battery (charge current ~0.48A**). We have a couple of questions regarding the ACOK and STAT pins.

  1. The ACOK pin as shown on the figures on pages 2 and 3 of the datasheet is driven by VCC, however, on the evaluation board schematics the ACOK is driven through a resistor from VIN. Which setting is correct? We have it connected through a 1.5K resistor from VIN and it lights up when power is present.

  2. STAT pin is always low (LED on). When we power up the device with no battery conencted both LEDs are on, STAT should be blinking at 1Hz. After connecting a battery, the charger draws current from the power supply and the battery pack gets charged. However after charge is complete after several hours (~10mA current draw to power the LEDs). STAT LED is still on (as is ACOK).

For testing we are using an external 2x18650 battery case with a switch. The final device will have the battery permanently connected. We do not require powerpath, though there are 2x22uF capacitors on the SYS pin. We are not using the NTC function so instead of a 10K NTC we just have a 10K resistor.

Do you have any suggestions on this behaviour (STAT LED always on)? The layout and schematic is as per the evaluation board, though again the charger works, there is no indication on when the charge is complete, battery fault etc. which while it still does not affect the main functionality of our device, it affects the end user experience.

**we have the ISET resistor as 24.9K (below the recommended 6K-24K range since at the time of prototpe making we only had 24.9K resistors available and the device power supply is not designed to supply more than 5W; can that be causing the STAT pin behavior? (by looking at the block diagram it shouldn’t) though we will change it to 20K and check.

Thank you in advance.

Have you tried the demo board, as a sanity check