JN516X Datasheet, PDF (13/94 Pages) NXP Semiconductors – IEEE802.15.4 Wireless Microcontroller

2.2.5 Analogue Peripherals
The ADC requires a reference voltage to use as part of its operation. It can use either an internal reference voltage
or an external reference connected to VREF. This voltage is referenced to analogue ground and the performance of
the analogue peripherals is dependent on the quality of this reference.
There are four ADC inputs and a pair of comparator inputs. ADC1 has a designated input pin but ADC2 uses the
same pin as VREF, invalidating its use as an ADC pin when an external reference voltage is required. The remaining
2 ADC channels are shared with the digital I/Os DIO0 and DIO1 and connect to pins 16 and 17. When these two
ADC channels are selected, the corresponding DIOs must be configured as Inputs with their pull-ups disabled.
Similarly, the comparator shares pins 1 and 2 with DIO16 and DIO17, so when the comparator is selected these pins
must be configured as Inputs with their pull-ups disabled. The analogue I/O pins on the JN516x can have signals
applied up to 0.3v higher than VDD1. A schematic view of the analogue I/O cell is shown in Figure 3. Figure 4
demonstrates a special case, where a digital I/O pin doubles as an input to analogue devices. This applies to ADC3,
ADC4, COMP1P and COMP1M.
In reset, sleep and deep sleep, the analogue peripherals are all off. In sleep, the comparator may optionally be used
as a wakeup source.
Unused ADC and comparator inputs should not be left unconnected, for example connected to analogue ground.
VDD1
Analogue
Peripheral
Analogue
I/O Pin
VSSA
Figure 3: Analogue I/O Cell
2.2.6 Digital Input/Output
For the DC properties of these pins see Section 19.2.3.
When used in their primary function all Digital Input/Output pins are bi-directional and are connected to weak internal
pull up resistors (50kΩ nominal) that can be disabled. When used in their secondary function (selected when the
appropriate peripheral block is enabled through software library calls), their direction is fixed by the function. The pull
up resistor is enabled or disabled independently of the function and direction; the default state from reset is enabled.
A schematic view of the digital I/O cell is in Figure 4. The dotted lines through resistor RESD represent a path that
exists only on DIO0, DIO1, DIO16 and DIO17 which are also inputs to the ADC (ADC3, ADC4) and Comparator
(COMP1P, COMP1M) respectively. To use these DIO pins for their analogue functions, the DIO must be set as an
Input with its pull-up resistor, RPU, disabled.
© NXP Laboratories UK 2013
JN-DS-JN516x v1.1 Production
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