NXP Semiconductors
NHS3100
Temperature logger
NHS3100 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2018. All rights reserved.
Product data sheet Rev. 6.03 — 15 June 2018
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8.15 Real-Time Clock (RTC) timer
8.15.1 Features
The Real-Time Clock (RTC) block contains two counters:
• A countdown timer generating a wake-up signal when it expires
• A continuous counter that counts seconds since power-up or the last system reset
The countdown timer runs on a low speed clock and runs in an always-on power domain.
The delay, as well as a clock tuning prescaler, can be configured via the APB bus. The
RTC countdown timer generates both the deep power-down wake-up signal and the RTC
interrupt signal (wake-up interrupt 12). The deep power-down wake-up signal is always
generated, while the interrupt can be masked according to the settings in the RTCIMSC
register.
8.15.2 General description
The RTC module consists of two parts:
• The RTC core module, implementing the RTC timers themselves. This module runs in
the always-on VDD_ALON domain.
• The AMBA APB slave interface. This module allows configuration of the RTC core via
an APB bus. This module runs in the switched power domain.
8.16 Temperature sensor
8.16.1 Features
The temperature sensor block measures the chip temperature and outputs a raw value or
a calibrated value in Kelvin.
8.16.2 General description
The temperature is measured using a high-precision, zoom-ADC. The analog part is able
to measure a highly temperature-dependent X = V
be
/ ΔV
be
1
. It determines the value of
X by first applying a coarse search (successive approximation), and then a sigma-delta
in a limited range. The conversion time depends on the resolution mode as shown in
Table 15.
Table 15. Conversion time for different resolution of TSENS
Resolution (bit) Resolution (°C) Conversion time (ms)
7 ±0.8 4
8 ±0.4 7
9 ±0.2 14
10 ±0.1 26
1 V
be
is the base-emitter voltage of a bipolar transistor. Basically, the temperature sensor measures the
voltage drop over a diode formed by the base-emitter junction of a bipolar transistor. It compares the V
be
at different current levels (from which follows the ΔV
be
).
