SWRS258 September   2021

1. Features
2. Applications
3. Description
4. Functional Block Diagram
5. Revision History
6. Device Comparison
7. Terminal Configuration and Functions
8. Specifications
1. 8.1  Absolute Maximum Ratings
2. 8.2  ESD Ratings
3. 8.3  Recommended Operating Conditions
4. 8.4  Power Supply and Modules
5. 8.5  Power Consumption - Power Modes
6. 8.6  Power Consumption - Radio Modes
7. 8.7  Nonvolatile (Flash) Memory Characteristics
8. 8.8  Thermal Resistance Characteristics
9. 8.9  RF Frequency Bands
10. 8.10 Bluetooth Low Energy - Receive (RX)
11. 8.11 Bluetooth Low Energy - Transmit (TX)
12. 8.12 Zigbee - IEEE 802.15.4-2006 2.4 GHz (OQPSK DSSS1:8, 250 kbps) - RX
13. 8.13 Zigbee - IEEE 802.15.4-2006 2.4 GHz (OQPSK DSSS1:8, 250 kbps) - TX
14. 8.14 Timing and Switching Characteristics
1. 8.14.1 Reset Timing
2. 8.14.2 Wakeup Timing
3. 8.14.3 Clock Specifications
4. 8.14.4 Synchronous Serial Interface (SSI) Characteristics
5. 8.14.5 UART
15. 8.15 Peripheral Characteristics
2. 8.15.2 DAC
3. 8.15.3 Temperature and Battery Monitor
4. 8.15.4 Comparators
5. 8.15.5 Current Source
6. 8.15.6 GPIO
16. 8.16 Typical Characteristics
9. Detailed Description
10. 10Application, Implementation, and Layout
11. 11Device and Documentation Support
12. 12Mechanical, Packaging, and Orderable Information

#### Package Options

Refer to the PDF data sheet for device specific package drawings

• RGZ|48

## 10.2 Junction Temperature Calculation

This section shows the different techniques for calculating the junction temperature under various operating conditions. For more details, see Semiconductor and IC Package Thermal Metrics.

There are three recommended ways to derive the junction temperature from other measured temperatures:

1. From package temperature:
Equation 1. ${T}_{J}={\psi }_{\mathrm{JT}}×P+{T}_{\mathrm{case}}$
2. From board temperature:
Equation 2. ${T}_{J}={\psi }_{\mathrm{JB}}×P+{T}_{\mathrm{board}}$
3. From ambient temperature:
Equation 3. ${T}_{J}={R}_{\mathrm{\theta JA}}×P+{T}_{A}$

P is the power dissipated from the device and can be calculated by multiplying current consumption with supply voltage. Thermal resistance coefficients are found in Thermal Resistance Characteristics.

Example:

Using Equation 3, the temperature difference between ambient temperature and junction temperature is calculated. In this example, we assume a simple use case where the radio is transmitting continuously at 0 dBm output power. Let us assume the ambient temperature is 85°C and the supply voltage is 3 V. To calculate P, we need to look up the current consumption for Tx at 85°C in Figure 8-8. From the plot, we see that the current consumption is 7.8 mA. This means that P is 7.8 mA × 3 V = 23.4 mW.

The junction temperature is then calculated as:

Equation 4. ${T}_{J}=23.4\frac{°C}{W}×23.4mW+{T}_{A}=0.6°C+{T}_{A}$

As can be seen from the example, the junction temperature is 0.6 °C higher than the ambient temperature when running continuous Tx at 85°C and, thus, well within the recommended operating conditions.

For various application use cases current consumption for other modules may have to be added to calculate the appropriate power dissipation. For example, the MCU may be running simultaneously as the radio, peripheral modules may be enabled, etc. Typically, the easiest way to find the peak current consumption, and thus the peak power dissipation in the device, is to measure as described in Measuring CC13xx and CC26xx current consumption.