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JN-DS-JN5142 1v0
© NXP Laboratories UK 2012
17 Analogue Peripherals
The JN5142 contains a number of analogue peripherals allowing the direct connection of a wide range of external
sensors and switches.
ADC
Processor Bus
Supply Voltage
(VDD1)
Comparator 1
COMP1M (DIO17)
COMP1P (DIO16)
ADC1
VREF/ADC2
ADC3 (DIO0)
ADC4 (DIO1)
Vref
Internal Reference
Vref Select
Chip Boundary
Temp
Sensor
Figure 38: Analogue Peripherals
In order to provide good isolation from digital noise, the analogue peripherals and radio are powered by the radio
regulator, which is supplied from the analogue supply VDD1 and referenced to analogue ground VSSA.
A reference signal Vref for the ADC can be selected between an internal bandgap reference or an external voltage
reference supplied to the VREF pin. ADC input 2 cannot be used if an external reference is required as this uses the
same pin as VREF. Note also that ADC3 and ADC4 use the same pins as DIO0/SPISEL1 and DIO1/SPISEL2
respectively. These pins can only be used for the ADC if they are not required for their alternative functions.
Similarly, the comparator inputs are shared with DIO16/SIF_CLK and DIO17/SIF_D. If used for their analogue
functions, these DIOs must be put into a passive state by setting them to Inputs with their pull-ups disabled.
The ADC is clocked from a common clock source derived from the 16MHz clock
17.1 Analogue to Digital Converter
The 8-bit analogue to digital converter (ADC) uses a successive approximation design to perform high accuracy
conversions as typically required in wireless sensor network applications. It has six multiplexed single-ended input
channels: four available externally, one connected to an internal temperature sensor, and one connected to an
internal supply monitoring circuit.