Specifications

22 JN-DS-JN5148-001 1v9 © NXP Laboratories UK 2013

RESETN

JN5148

VDD

18k

470nF

Figure 12: External Reset Generation

The external resistor and capacitor provide a simple reset operation when connected to the RESETN pin.

6.2 External Reset

An external reset is generated by a low level on the RESETN pin. Reset pulses longer than the minimum pulse width

will generate a reset during active or sleep modes. Shorter pulses are not guaranteed to generate a reset. The

JN5148 is held in reset while the RESETN pin is low. When the applied signal reaches the Reset Threshold Voltage

RST

) on its positive edge, the internal reset process starts.

Multiple devices may connect to the RESETN pin in an open-collector mode. The JN5148 has an internal pull-up

resistor connect to the RESETN pin. The pin is an input for an external reset, an output during the power-on reset

and may optionally be an output during a software reset. No devices should drive the RESETN pin high.

Internal Reset

RESETN pin

Reset

Figure 13: External Reset

6.3 Software Reset

A system reset can be triggered at any time through software control, causing a full chip reset and invalidating the

RAM contents. For example this can be executed within a user’s application upon detection of a system failure. When

performing the reset, the RESETN pin is driven low for 1µsec; depending on the external components this may or

may not be visible on the pin.

In addition, the RESETN line can be driven low by the JN5148 to provide a reset to other devices in the system (e.g.

external sensors) without resetting itself. When the RESETN line is not driven it will pull back high through either the

internal pull-up resistor or any external circuitry. It is essential to ensure that the RESETN line pulls back high within

100µsec after the JN5148 stops driving the line; otherwise a system reset will occur. Due to this, careful consideration

should be taken of any capacitance on this line. For instance, the RC values recommended in section 6.1 may need

to be replaced with a suitable reset IC