# Power

The flexible power management of RSL15 allows for a wide range of battery voltages without the need for external power conversion. Two modes for the system supply are:

1. LDO Mode Operation (the default)
2. DC-DC Mode Operation

In both modes the battery supply voltage (VBAT) is regulated to a system supply (VCC) of 1.2 V. This supply is converted (using a charge pump) to an approximate 2.4 V analog supply voltage (VDDA), which is used to power the analog blocks (excluding the RF Blocks). These supplies are used as inputs to several additional supply voltages:

- VDDFLASH is a regulated voltage used to power the flash for erase and program operations.
- VDDRF is a regulated voltage used to supply the RF system.
- VDDC is a regulated voltage used for the internal digital blocks, excluding digital memories (ROM, RAM, flash) and GPIOs.
- VDDM is a regulated voltage used for the memory (ROM, RAM, flash) blocks.
- VDDPA is a regulated voltage used to supply the RF power amplifier (used in RF TX mode). The VDDPA level depends on the output power level selected.

All power supplies are trimmed by onsemi as part of the device manufacturing process.

VDDO is a power supply input to RSL15 and constitutes the logical high level for the digital I/Os, i.e., if VDDO is connected to VBAT, the GPIO signal swing is between GND and VBAT.

For more information about power supplies, see Power Supply Overview.

For HAL firmware information related to power supply, see the RSL15 Firmware Reference: Power Supply.

## Power Management Unit (PMU) Battery Monitoring and Resets

The RSL15 Power Management Unit (PMU) prevents system brown-outs in case the battery voltage dips below the specified minimum voltage required for reliable operation.

The PMU does this by:

1. Monitoring the power supply and safely shutting down the system if needed
2. Preventing possible damage to RSL15 when the battery is inserted or removed
3. Allowing operation across wide temperature and voltage ranges at low power consumption

The PMU automatically resets the internal systems during power supply disruptions, such as insufficient battery voltage or battery insertion/removal. Upon power supply rise (such as battery insertion), the system is held in Power-On-Reset until sufficient internal voltages are reached and stabilized. When POR is released, the boot ROM execution begins using the RC clock at 3 MHz.

A reset can also be issued by:

- Assertion of the nRESET pin
- Software triggers
- Watchdog timer expiration
- Invalid or missing clock detected by the clock detector

For more information about power management, see Power Management Unit. For more information about resets, see Resets.

## Power Modes Overview

The power modes are available to reduce power consumption while maintaining system responsiveness. The low power modes are Sleep Mode and Standby Mode. Smart Sense is a low-power feature that works as a subset of other power modes, and Idle Mode is a subset of Standby Mode.

- Sleep Mode is the lowest power mode, but with the longest wakeup time.
  - Smart Sense Mode takes advantage of the low power capability of Sleep Mode, but also allows some digital and analog peripherals to remain active with minimal processor intervention. Smart Sense Mode allows RSL15 to not only remain responsive to external events, but also to monitor and acquire data from external sensors with very low system-level power consumption.
- Standby Mode is low power, but with a faster wakeup time than Sleep Mode.
  - Idle Mode allows for some power savings with the fastest wakeup time through disabling internal clocks.

Smart Sense, Sleep, and Standby Modes have the ability of RAM retention (a configurable amount of RAM to be retained), and allow for configurable wakeup sources. Wakeup sources include:

- GPIO transition (pin-based wakeup)
- RTC Timer
- Analog comparator
- Threshold trigger or sample FIFO full detections in the ultra-low power data acquisition block

For more information about power modes, see Power Modes.

For HAL firmware information related to power modes, see the RSL15 Firmware Reference: HAL Power Modes.