Voltage Range Specifications for MAGPIO, SIM Interface, nRESET, ENABLE and SWD Interface

[ShaunR]

Hello,

I have been looking through Nordic's documentation for the nRF9160 and trying to find voltage ranges for several pins but am having no luck. Can someone please answer the following questions:

What are the VIH and VIL ranges for the following input pins:

nRESET, ENABLE, SWDCLK

What are the VOH and VOL ranges for the following output pins:

SIM_RST, SIM_CLK

What are the VIH, VIL, VOH, and VOL ranges for the following bidirectional pins:

MAGPIO(2-0), SWDIO, SIM_IO

Thanks for your time!

[Amanda Hsieh]

Hi Shaun, 

The ENABLE pin is connected to VDD. Please see the Operating conditions

The Reset pin has an always-on internal pull-up resistor connected to nRF9160 internal voltage typically of 2.2 V level. The value of the pull-up resistor is given in Pin reset.

The SWDCLK is Digital input and SIM_RST, SIM_CLK, SWDIO, and SIM_IO are Digital I/O.  Please see the GPIO Electrical specification.

The MAGPIO, please see the Operating conditions

All pins that are purely controlled by the application controller is referenced to VDD_GPIO, while pins controlled by the modem are described in the operating conditions.

-Amanda H.

[ShaunR]

Hi Amanda,

Thanks for the response to my questions!

Sounds good about the SWD pins, but I am still wondering about the rest of the pins I mentioned and their VIL, VIH, VOL and VOH ranges. In my experience, most cellular module manufacturers document these ranges when applicable for each pin on the module, but I still can't find this for the following pins on the nRF9160:

ENABLE

• I understand that this pin needs to be pulled up to VDD to power on the modem.
• However, what is the minimum voltage that must be applied to this pin to start the module? As in: VIHmin = VDD - 0.3V, or something like that.

nRESET

• I understand that this pin is pulled up to 2.2V and should be driven low with an open-drain output to initiate reset.
• However, what is the VILmax for this pin? As in: VILmax = VSS + 0.3V, or something like that.
• Also, what is the maximum voltage that can be applied to this pin before something gets damaged? I understand this pin should not be driven to anything other than VSS, but this information is still good to have documented.

SIM_IO, SIM_CLK, SIM_RST

• I was able to find the VIL, VIH, VOL, and VOH for these pins in this specification: ISO/IEC 7816-3, which was mentioned on the "SIM card interface" page.
• For reference, here are the ranges I found in the ISO/IEC 7816-3 specification: VOL, VIL: 0V to 0.15*VCC_SIM and VOH, VIH: 0.7 * VCC_SIM to VCC_SIM
• I assume the values that I found in that specification are valid for the nRF9160?

MAGPIO Pins

• I see there is a VOH range listed on the "Operating conditions" page, but no VOL range. Is the VOL range documented?
• Also, are these pins just digital outputs, or are they also inputs? The "Pin assignments" page says these pins have a description of "1.8 V general purpose I/O", but the AT command to interface with these pins seems to only let you use them as digital outputs. Can you clarify this please?
• If these pins are bidirectional, then I'd like to also know the VIL and VIH ranges if that information is documented.

Thanks very much for your help!

Best Regards,

ShaunR

[Amanda Hsieh]

I am asking the internal and will be back soon. 

-Amanda H.

[Amanda Hsieh]

Hi Shaun, 

ENABLE
VIL; 0 - 0.4V max
VIH; 1.2V - Vdd

nRESET is supplied from 2.2V IO_SUPPLY.
Max voltage level IO_SUPPLY +0.3V.

SIM interface 

Verification done against ISO/IEC 7816-2 Class C.
Voltage levels;

MAGPIO Pins
Also, are these pins just digital outputs, or are they also inputs? The "Pin assignments" page says these pins have a description of "1.8 V general purpose I/O", but the AT command to interface with these pins seems to only let you use them as digital outputs. Can you clarify this please?
Yes, MAGPIO can be used as a digital input or output.

1V8 GPIO Electrical Specification

Symbol	Description	Min	Typ	Max	Units
VIH	Input high voltage	0.61xVDD	0.64xVDD	0.69xVDD	V
VIL	Input low voltage	0.31xVDD	0.36xVDD	0.40xVDD	V

This means that an input low should always be below 0.3xVDD to be sure it is recognized as a "low", while an input high should always be above 0.7xVDD to be sure it is recognized as a "high".

-Amanda H.

[ShaunR]

Hi Amanda,

Thank you for the information, and sorry for the delay in getting back to you!

Sounds good about the nRESET, ENABLE and SIM interface pins. I have another question about the MAGPIO pins, however.

The MAGPIO VIH and VIL ranges seem off to me. According to the table you sent, and assuming VDD = 5V, this would make VILmax = 0.4*5V = 2V and VIHmin = 0.61 * 5V = 3.05V.

Since these pins are fixed 1.8V referenced, these input voltage values over 1.8V do not make sense to me. Is only the output voltage of these pins referenced to 1.8V, but the input referenced to VDD as shown above?

Can you please clarify this information? Thanks again for your help!

 - ShaunR

[Amanda Hsieh]

Hi Shaun, 

The VDD in this equation is the VDD in that segment of GPIOs.
So if the supply for the GPIOs are 1.8V, this is the VDD used in the equations.
To guarantee a "low" input it should be below: VILmin = 0.3xVDD = 0.54V.
To guarantee a "high" input it should be above: VIHmax = 0.7xVDD = 1.26V.

-Amanda H.

[ShaunR]

Hi Amanda,

Gotcha, makes sense! That answers all of my questions then.

Thank you again for your help!

- ShaunR