L89 Vbackup Rechargable battery connection

IoT Modules GNSS Module
#1

Hi
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.

Thanks
Binu

#2

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.

image
image863×466 29.5 KB

Quectel_L89_Hardware_Design_V1.1.pdf (822.5 KB)

#3

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

#4

Hi Binu_Johnson,

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

image
image857×555 56.9 KB

image
image887×690 72.4 KB

image
image850×642 46.1 KB