JN516X Datasheet, PDF (56/94 Pages) NXP Semiconductors – IEEE802.15.4 Wireless Microcontroller

17.1.2 Supply Monitor
The internal supply monitor allows the voltage on the analogue supply pin VDD1 to be measured. This is achieved
with a potential divider that reduces the voltage by a factor of 0.666, allowing it to fall inside the input range of the
ADC when set with an input range twice the internal voltage reference. The resistor chain that performs the voltage
reduction is disabled until the measurement is made to avoid a continuous drain on the supply.
17.1.3 Temperature Sensor
The on chip temperature sensor can be used either to provide an absolute measure of the device temperature or to
detect changes in the ambient temperature. In common with most on chip temperature sensors, it is not trimmed and
so the absolute accuracy variation is large; the user may wish to calibrate the sensor prior to use. The sensor forces
a constant current through a forward biased diode to provide a voltage output proportional to the chip die temperature
which can then be measured using the ADC. The measured voltage has a linear relationship to temperature as
described in Section 19.3.12.
Because this sensor is on chip, any measurements taken must account for the thermal time constants. For example,
if the device just came out of sleep mode the user application should wait until the temperature has stabilised before
taking a measurement.
17.2 Comparator
The JN516x contains one analogue comparator, COMP1, that is designed to have true rail-to-rail inputs and operate
over the full voltage range of the analogue supply VDD1. The hysteresis level can be set to a nominal value of 0mV,
10mV, 20mV or 40mV. The source of the negative input signal for the comparator can be set to the internal voltage
reference, the negative external pin (COMP1M, which uses the same pin as DIO17) or the positive external pin
(COMP1P, on the same pin as DIO16). The source of the positive input signal can be COMP1P or COMP1M.
DIO16 and DIO17 cannot be used if the external comparator inputs are needed. The comparator output is routed to
an internal register and can be polled, or can be used to generate interrupts. The comparator can be disabled to
reduce power consumption. DIO16 and DIO17 should be set to inputs with pull-ups disabled, when using the
comparator.
The comparator also has a low power mode where the response time of the comparator is slower than the normal
mode, but the current required is greatly reduced. These figures are specified in Section 19.3.7. It is the only mode
that may be used during sleep, where a transition of the comparator output will wake the device. The wakeup action
and the configuration for which edge of the comparator output will be active are controlled through software. In sleep
mode the negative input signal source must be configured to be driven from the external pins.
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JN-DS-JN516x v1.1 Production
© NXP Laboratories UK 2013