Integration Manual
Table Of Contents
- Contents
- List of Figures
- 1. Introduction
- 2. Application PCB Consideration
- 3. Application Hardware Implementation
- 4. RF Guidelines
- 5. Regulatory Compliance Consideration
- 6. Production Testing Consideration
- 7. Regulatory and Compliance Notice
- 8. References
- 9.
- 10. Revision History
- 11. Document Details
NM180100 Hardware Integration Manual-0.9
8
3.3. Real-Time Clock
For BLE application, the current ARM Cordio BLE stack requires an external tuning fork crystal to be connected
across the XI and XO pins. A crystal-less implementation is currently being developed and until further notice by
ARM or Ambiq, it is mandatory that the RTC crystal be present in order to use the BLE transceiver. The crystal
specifications are listed in both the NM180100 datasheet [1] and the Ambiq Apollo 3 datasheet [2].
3.4. Analog to Digital Converter
The analog voltage reference of the Apollo 3 are limited to either 1.5V or 2.0V and can be configured to use an
external or the internal voltage reference. The reference voltage determines the ceiling of what the ADC can
convert. Therefore, the resolution of the ADC is defined by dividing the reference voltage by the total number of
possible conversion values which in turns is determined by the ADC precision expressed in bits. The ADC precision
can be configured to 8, 10, 12, and 14-bit.
The NM180100 uses the Apollo 3 on-chip bandgap voltage reference to simplify integration. This is because a
bandgap voltage reference is temperature independent and produces a constant voltage regardless of power
supply variations, temperature changes, and loading changes. These characteristics simplify the burden on the
designer on designing a stable voltage reference across the operating conditions of the application. Application
making use of the ADC should therefore configure the reference to make use of either the 1.5V or 2.0V internal
analog voltage reference.
At 14-bit precision and a 1.5V reference, the smallest voltage quanta that the ADC could resolve is
=
2
=
1.5
16384
= 9.155 × 10
or approximately 92uV. This voltage level is sufficiently small that it can be easily perturbed by external EMI
emissions. Applications requiring this kind of resolution should route the analog input in an inner layer and
surround the trace by ground.
Figure 6 An example IoT sensor application implementation.