LED connection for IPPS pin in L89 GPS

IoT Modules GNSS Module
1

Hi
I am using L89 gps for one of my product and i am connecting an LED with 330 ohm resistor for the PPS.
Is that ok or do i compulsory need to use a transistor to drive that LED.

Also some of the clients compliant that there is no output sometimes but after few hours/days its started giving the data out. Confused.

also i am just using the TXD, IPPS, VCC, Vbackup, Ground pin and keep all other in open condition.

i am using 4.2v battery at Vbackup and 3,3v from 5v using AMS1117, guide me please

Edit: my power supply module can deliver 200ma in which the vbackup charger ic is tunned for 50ma and hc05 Bluetooth module needs 40ma. Is there any problem here.

2

Hi Binu_Johnson,

About PPS indicator, the EVB SCH is shown below. Please take a reference.

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3

Is there any problem when i connect a LED with a 330 ohm resistor?
Also sometimes the L89 does not give out any NMEA sentences on the output. But once i remove the Vbackup and then switch on the module then it start giving the output.

what is the problem?
i am just connecting the Vbackup, VCC, GND and TXD pins, all other pins are open connected.
Do i need to connect any other pins?
since this problem occurs at customer side its difficult for us to remove the vbackup and reconnect it.

4

Hi Binu_Johnson,

Can you show me the LED with a 330ohm resistor SCH design? Cause I’m not sure about the circuit.

About the no output problem:

  1. Is it useful to turn off and on VCC （or reset the module）without disconnect VBCKP, when the problem occurs?
  2. Does the customer strongly need the backup mode?
  3. What’s the firmware version that currently used? Query by sending $PSTMGETPAR,1500

Best regards.

5

Hi Binu_Johnson,

Please note that the V_BCKP must be powered simultaneously with the VCC or before it.

Best regards.

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6

gps led
This is the schematic for LED

About the no output problem:

  1. No even i reconnect the VCC and reset the module nothing at the output, only after removing the Vbackup and Connect Vcc again it starts giving output.
  2. It would be fine, if they get the fix soon. but not so critical
  3. Havent checked it.
  4. The Vbackup is connected to battery always.

Also can i connect the Pin7(Wakeup) to ground, is it necessary?

7

Hi Binu_Johnson,

About the schematic for LED. PPS output voltage is always lower than 3.3v . And in your schematic, PPS pin is pulled high externally. Please use a transistor to drive and refer to Reference Design.

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8

Hi Binu_Johnson,

There is no need to pull down Wakeup pin externally.

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9

Hi Binu_Johnson,

Can you try to connect VBCKP with VCC? That means VCC power supply to the two pin. And see whether the problem reappears or not.

Best regards.

10

Yes, i tried that. most time it works fine. But only one time it happen again and then i switched off the gps and switched on few minutes later and then its started giving nmea at the output.

i think better remove the vbackup battery and connect the Vcc and VBCKP. only disadvantage is it take 1 to 2 mins to get the FIX, since my product is a Bluetooth GPS and not time critical i am going to use this method.