SNVAA70 june   2023 LM5176 , LM5176-Q1

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
    1. 1.1 Principle of the TEC
    2. 1.2 Design Specification and Key Challenge
  5. 2Tec Driver Design Using Buck-Boost Controller
    1. 2.1 System Description
    2. 2.2 Block Diagram of TEC Design With LM5176
    3. 2.3 Output Voltage Control of LM5176
  6. 3Test Result
    1. 3.1 TEC Current Versus Output Voltage
    2. 3.2 Current Ripple Measurement Through TEC Element
    3. 3.3 Start-Up
    4. 3.4 Efficiency
  7. 4Summary
  8. 5References

1.2 Design Specification and Key Challenge

In the medical in-vitro diagnostics product, the samples and reagent must stay at a stable temperature for precise detection. In the Polymerase chain reaction (PCR) instrument, a rapid temperature change (for example, from 50℃ to 90℃ in a few seconds) is necessary for the DNA amplification. In the traditional TEC control design, a step-down regulator with gate driver and H-bridge is often used. This note introduces a single chip design using a buck-boost controller to drive the TEC. Due to the requirement of heating and cooling, the key design challenges are as follows:

  • Driver for TEC needs to be able to control the current in both directions
  • Adjustable voltage control between TEC for a flexible and fast temperature change

Based on the application requirements explained previously, the design specification of the bidirectional current control for TEC are shown in Table 1-1.

Table 1-1 Design Specifications
CharacteristicSpecification
Input voltage15 V
Maximum voltage for TEC±10 V
Maximum current for TEC±4 A
Adjustable voltage for TECYes
Constant voltage driveYes