LM27762 Charge Pump with Integrated Positive and Negative LDO

H12315

LM27762 Charge Pump with Integrated Positive and Negative LDO [Copy link]

Some time ago, I used the LM27762 chip, which has a charge pump and integrated positive and negative LDO. It can output positive and negative power rails with relatively low ripple, and most importantly, it has a small area. I used this to make a board with 3.75V input and positive and negative 3.3V output, but there were batch problems when the product was made. When the negative voltage circuit of some devices has a voltage difference between the input and positive output exceeding 0.35V and the negative power supply load exceeds 5mA, the negative power supply cannot be started. At this time, disconnecting the negative power supply or reducing the input power supply voltage to 3.7V can start normally, and the load is normal after startup (maximum load 20mA).

The problem disappeared after soldering the chip. I am confused. Has anyone encountered the same problem?

Also, I remember seeing a chip similar to this LM27762, but I forgot. Are there more chips with similar functions?

wangerxian

From the phenomenon, it feels like a cold solder joint. Cold solder joints cause the resistance at the cold solder joint to increase, so the load current cannot increase when connected to the power supply.

It is possible that the chip is too small and the chip placement machine of the chip placement factory is not accurate enough, resulting in poor soldering of the chip. It is recommended to find a large factory to carry out the chip placement process.