L89 Vbackup Rechargable battery connection

i am using L89 GPS module and for the Vbackup i am using a 3.7v Lithium Polymer battery.
For charging from 5v i connect 2 nos of 1N4007 diodes which reduce the 5v to 4.2v and it charge the battery well.
But the problem is once the battery get charged the current goes below 1ma and now the forward voltage drop of the diodes reduced and the 5v is applied to the Vbackup pin. Is it safe and is there any simple circuit which can charge the battery and drive the vbackup pin safely.


Hi Binu_Johnson,
I suggest you design Vbackup circuit according to the L89_Hardware_Design
Please find the document attached. Hope it helps.

Best regards.

Quectel_L89_Hardware_Design_V1.1.pdf (822.5 KB)

Hi, its working fine now.
Whats the latest firmware which support to receive broadcast message from Navic

Hi Binu_Johnson,

L89 support IRNSS, you can enable IRNSS by sending $PSTMSETCONSTMASK,1024