SLVAEB1A March   2020  – October 2021 TLV62568 , TLV62569 , TLV62585

 

  1.   Trademarks
  2. 1Introduction
  3. 2Describing the TLV62569 Package Technologies: SOT23-5, SOT23-6, and SOT563
  4. 3Understanding Thermal Performance and Junction Temperature Estimation
    1. 3.1 Understanding Thermal Performance
    2. 3.2 Estimating Junction Temperature
  5. 4Measurement Setup and Test Results
    1. 4.1 Efficiency Measurements
    2. 4.2 Thermal Measurements
  6. 5Thermal Performance Analysis for SOT23-5, SOT23-6, and SOT563 Packages
    1. 5.1 Comparing SOT563 (DRL) and SOT23-6 (DDC)
    2. 5.2 Comparing SOT23-6 (DDC) and SOT23-5 (DBV)
    3. 5.3 Comparing SOT563 (DRL) and SOT23-5 (DBV)
  7. 6Summary
  8. 7References
  9. 8Revision History

3.2 Estimating Junction Temperature

The junction temperature of the IC is a crucial parameter for good thermal design. For further details on thermal parameters of ICs, see the Semiconductor and IC Package Thermal Metrics Application Report.

The reliable method to estimate the junction temperature of a DC/DC converter is to use the junction-to-board characterization parameter of the IC, ψJT , specified in Table 3-2 of the TLV62569 2-A High Efficiency Synchronous Buck Converter in SOT Package Data Sheet with Equation 1.

Equation 1. Tj = ψJT × PIC, diss + Tcase
Table 3-1 Variables Description for Junction Temperature Calculation
PARAMETER DESCRIPTION COMMENTS
Tj IC junction temperature Target value to calculate
Tcase IC case temperature Can be easily measured for given operating condition with a thermal camera as shown on figure 1.
ψJT Junction-to-top characterization parameter Specified in the TLV62569 2-A High Efficiency Synchronous Buck Converter in SOT Package Data Sheet. See table 1.
PIC, diss Dissipated power in the IC for the given operating conditions This parameter needs to be estimated carefully to have more reliable results (see below).

There are two options to estimate the IC power dissipation PIC,diss. The first and easiest option to estimate PIC,diss is the WEBENCH® Power Designer Tool for the required operating conditions. The second option is to use Equation 2:

Equation 2. PIC,diss = Pdiss – Pind
Table 3-2 Variables Description for IC Power Dissipation Calculation
PARAMETER DESCRIPTION COMMENTS
PIC, diss IC power dissipation
Pdiss Total dissipated power
Pdiss = (1 - n) × (Pout / η )		 Pout: Output power
η : Efficiency of the power stage – can be found in the TLV62569 2-A High Efficiency Synchronous Buck Converter in SOT Package Data Sheet or modeled in WEBENCH®
Pind DC power losses in inductor
Pind = DCR × Iout2		 DCR: inductor series resistor
This parameter can be simulated in some manufacturer's website or in WEBENCH®

It is important to model the dissipated power in the inductor to have a more reliable estimation of the junction temperature. As a general rule, it is good enough to model only the DC losses of the inductor.

Table 3-3 IC Thermal Information
THERMAL METRICDEV (5 PINS)DDC (6 PINS)DRL (6 PINS)UNIT
RθJA188.2106.2146.3°C/W
RθJC(top)137.552.951.0°C/W
RθJB41.231.227.0°C/W
ψJT31.411.32.2°C/W
ψJB40.631.627.6°C/W
RθJC(bot)N/AN/AN/A°C/W
Table 3-4 Thermal Metric of TPS563201 and TPS563202 Package
THERMAL METRIC TPS563201 TPS563202 UNIT
RθJA 92.6 137 °C/W
RθJA_Effective 53.0 65.0 °C/W
RθJC(top) 48.5 43.2 °C/W
RθJB 15.5 22.0 °C/W
ψJT 2.5 0.9 °C/W
ψJB 15.5 21.8 °C/W

In this section, the different relevance of thermal performance across EE applications were explained and the important parameters for good thermal performance evaluation were introduced. The next section focuses on the specific thermal performance of the TLV62569 across the three different packages: SOT23-5, SOT23-6, and SOT563. And introduces TPS563201 and TPS563202 performance.