npm1300 wdog and led drivers

[dave_s]

Hi,

I have a system I am redesigning to use the npm1300.  

It has a rechargeable battery, about 3-4 weeks per charge, connected to an nrf9160.

The current system has an external watchdog chip and also controls an RGB LED through 3 pwm pins

What timeout (or timeout range) does watchdog on the npm1300 have? Is it configurable through i2c?

Is it suitable to use as an external watchdog for the nrf9160?

Is it serviced over the I2C bus?

What (if any) additional power draw is used by the npm1300 if the watchdog is enabled?

For the LEDs, I see it has 3 led drivers. Is it suitable for an RGB led?

Are the led driver lines only on/off?  Or do they pwm?

Is it possible to set the LEDs to blink, like if you want green to blink at 1 hz?  Or would on/off command have to be sent to achieve blinking?

What power draw do the led drivers add?

[Andy Sinclair]

Hi.

The watchdog is I2C configurable.  The timeout can be configured from 16ms to 3 days in 16ms steps.
It can be configured to provide an interrupt, assert a /RESET output, or power cycle the SoC.

It is suitable as an external watchdog for the nRF9160.
Additional power consumption from the watchdog is approx 4uA.

More details: TIMER — Timer/monitor (nordicsemi.com)


LED spec is here: LEDDRV — LED drivers (nordicsemi.com)
The LED drivers can be used for an RGB LED.
They are not PWM controllable (on/off only), and they cannot blink autonomously, they need to be controlled by the SoC.

Andy

[frax84]

There is one info missing about LED drivers that i would like to appoint to this question. Are the LED drivers current driven? I have many hints to state this but i would like a confirm. In fact, in the datasheet is said:

The system can control an RGB LED component (or three separate LEDs) . The LED0, LED1, and LED2
pins can connect to any of the RGB LED cathodes (low-side). The anodes (common or individual) MUST
be connected to the VSYS pin

Considering that the VSYS is on the same level of VBUS and that the average VFmax of leds is in the range of 2.3V (it changes based on led color of course), this seems too much for the led to handle. Moreover, Table 25 of the npm1300 datasheet says:

Symbol          Description                             Min.       Typ.        Max.        Unit
ILED            LED driver current                                  5                       mA
VLEDn           Voltage on pin LED0, LED1, and LED2     0.5                    VSYS          V

So it seems that the LED current is stable at 5 mA and the VLED changes between 0.5 and  VSYS to allow that current.

Are my assumptions correct? Please confirm

Thank you

Frax