About power modes of PA6H

[scoltza]

I'm confused about the power modes of the globalTop PA6H GPS module.

First, there is the sleep mode activated with command pmtk161, in this one current consumption goes below than 200uA (source: http://www.gtop-tech.com/en/product/MT3339/Software_Services_21.html).

Second, the backup mode, when pin 1 VCC is disconnected/powered off; but pin 4 Vbackup is powered on.
In this mode the current consumption should be 7uA typ as stated in the datasheet.

Third, normal or power on mode with both pins powered.
Fourth, power off with no power on both pins.

Ok, that's the definition part. Now the questions,

a. Is correct that backup mode and sleep mode are different?. Or it is the same?.

b. The EASY function still working when enter backup mode and go to normal mode?. Lets say the module is in normal mode, then collects the EPO information from satellites, go to backup mode (hours, 1 day tops), and finally wake up to normal mode. The EASY/EPO information still useful?. The TTFF will be 5 seconds aprox or the module will perform a cold start?.

c. About the NRESET pin. This pin can be used to power off the module?, will it reset and erase all the EASY/EPO/other volatile data? (with Vbackup powered on). If the data is preserved then the cycle [normal mode -> backup mode (entered using NRESET pint) -> wake up (using NRESET) -> normal mode] will preserve the EASY functionality, and a power switch (a PMOS pass transistor for example) at VCC is not needed to take full advantage of the backup mode. Right?.

That's it, thank you for your time and sorry for my poor English.
Cheers.

[Horsa]

a. Is correct that backup mode and sleep mode are different?. Or it is the same?.

They are different. The official nomenclature is quite comprehensive actually.
First of all, do not confuse among "VBACKUP pin", "back-up mode" (and "standby mode").

• A powered "VBACKUP pin" retains settings, navigation data and real-time clock when the module is powered off (VCC << 3.0 V) to reduce power consumption while keeping it ready to hot-start or warm-start. This makes possible to implement simple hardware-driven power saving policies.
• "stand-by mode" (Packet Type: 161): can be exited anytime by sending any byte.
• "back-up mode @{periodic, AlwaysLocate}" (Packet Type: 225) can be exited during run-time (not during sleep-time) by sending one command ($PMTK225,0*2B<CR><LF>).
• "standby mode{periodic, AlwaysLocate}" (Packet Type: 225) can be exited anytime (during both run-time and sleep-time) by sending one command ($PMTK225,0*2B<CR><LF>).

For further reference, please read
 http://forum.trenz-electronic.de/index.php/topic,197.0.html

b. The EASY function still working when enter backup mode and go to normal mode?. Lets say the module is in normal mode, then collects the EPO information from satellites, go to backup mode (hours, 1 day tops), and finally wake up to normal mode. The EASY/EPO information still useful?. The TTFF will be 5 seconds aprox or the module will perform a cold start?.

Yes, EASY retains navigation data as long as at least one between VCC (min 3.0 V, typ 3.3 V, max 4.3 V) and VBACKUP (min 2.0 V, typ 3.0 V, max 4.3 V) are power supplied.
According documentation, "pin 4 = VBACKUP = Power Input = Backup Power Input for RTC & Navigation Data Retention". EPO are navigation data, they shall thus be retained.

• If the power-down mode lasts less than two hours, than the module will hot start.
• If the power-down mode lasts more than two hours up to the validity of the EASY data, than the module will warm start.
• Otherwise, it will cold start.

For further reference, please read
 http://www.gtop-tech.com/en/faq/4.9.-What-differentiate-between-Cold-Start-Warm-Start-and-Hot-Start/GPS_Module_Design-4_9.html

c. About the NRESET pin. This pin can be used to power off the module?, will it reset and erase all the EASY/EPO/other volatile data? (with Vbackup powered on). If the data is preserved then the cycle [normal mode -> backup mode (entered using NRESET pint) -> wake up (using NRESET) -> normal mode] will preserve the EASY functionality, and a power switch (a PMOS pass transistor for example) at VCC is not needed to take full advantage of the backup mode. Right?.

Well, the Reset pin, on almost any electronic device I know, shall be used to reset the device, not to change power operation. Unless it is explicitly documented, but it is not the case of GlobalTop modules. So, users are not supposed to use the reset line to save power consumption. They can do it under their own responsibility, but this approach is not supported.
After inquiring GlobalTop, I can tell you that the reset line does not affect  EPO, EASY, RTC, NMEA settings and user settings (= all data are retained).

[scoltza]

Hi Horsa, thank you a lot for your detailed answer.

Ok, the Vbackup pin function is clear, also the sleep mode and backup mode are not the same. Great.

Thanks for the periodic modes info, maybe I can use it to enter in backup mode using the serial UART port (without additional hardware) sending PMTK225, but of course, I will not be able to exit backup mode until run-time is reached.

About NRESET. Referring to other modules of gtop using the same chipset mt3339, this pin es a NC (not connected) (PA6C) or an enable pin (PA6B). In the last case the function is to shutdown the module as specified in the datasheet.
I was hopping that in PA6H NRESET means the same than the enable pin, but maybe not.

Ok, if I can find out something about it I will write again.
Thank you very much Horsa.

[Horsa]

About NRESET. Referring to other modules of gtop using the same chipset mt3339, this pin es a NC (not connected) (PA6C) or an enable pin (PA6B). In the last case the function is to shutdown the module as specified in the datasheet.
I was hopping that in PA6H NRESET means the same than the enable pin, but maybe not.

You can try to force an improper power saving mode by setting NReset low (10 mA), but this is not better than the following proper methods:

• add and LDO control loop and use its ENABLE pin to control power source (power saving state <30uA)
• send standby mode command to module (power saving state < 200uA)

[scoltza]

10 mA is a lot!!! - almost an active state, seems to be that the function of the pin differs of the other modules.
Adding a power switching element (an LDO as you suggest or a PMOS transistor) will be mandatory to control fully the power states of the module.
Thank you very much Horsa.