CARACTÉRISTIQUES

Built-in Two Zero-Drift, Rail-to-Rail Chopper Amplifiers

2.7V to 5.5V Input Voltage Range

1.5A Driving Capability

1% Accuracy 2.5V Internal Reference Output

TEC Voltage and Current Monitoring

Independent Programmable Heating and Cooling Current Limit

Programmable Maximum TEC Voltage

Default 2MHz Switching Frequency

Synchronization from 1.85MHz to 3.25MHz

Capable of NTC, PTC and RTD Thermal Sensors

3.5mm × 4mm × 1.3mm LGA Package

 

 CANDIDATURES

TEC Temperature Control

Optical Networking System, Optical Module

LiDAR System

 

DESCRIPTION

The LTM4663 is a complete 1.5A µModule® Thermoelectric Cooler (TEC) regulator in a tiny 3.5mm × 4mm × 1.3mm LGA package. Included in the package are the TEC controller, linear power stage, switching regulator, inductor and all support components.

Operating over an input voltage range of 2.7V to 5.5V, the LTM4663 supports a 1.5A continuous sink or source current capability. Only input and output capacitors are needed. The LTM4663 has two zero drift, rail-to-rail chop per amplifiers to serve as the thermistor input amplifier and the temperature feedback control loop.

The LTM4663 supports NTC, PTC thermistors and resis tive temperature detectors (RTD). The maximum cooling and heating currents can be programmed independently as well as the maximum TEC voltage.

The LTM4663 is available in LGA RoHS compliant terminal finish.

 

FONCTIONNEMENT

The LTM4663 is a complete Thermoelectric Cooler (TEC) µModule regulator that sets, stabilizes and monitors TEC temperature. It can deliver up to 1.5A of sinking or sourcing current with external input and output capac itors. Operating over 2.7V to 5.5V input voltage range, the LTM4663 controls an internal FET H-bridge whereby the direction of the current fed through the TEC can be either positive (for cooling mode), or negative (for heating mode).

The LTM4663 has two self-correcting, auto-zeroing amplifiers(Chopper 1 and Chopper 2) to linearize the thermal sensor input and to form an analog temperature feedback control loop. With the zero drift chopper ampli fiers, extremely good long-term temperature stability is maintained via an autonomous temperature control loop. See Figure 18 for an overview of how to configure the analog PID control, while see Figure 19 for configuring the digital PID control.

The LTM4663 can also be configured for use in a soft ware controlled PID loop. In this scenario, the Chopper 1 amplifier can configure as a thermistor input amplifier connected to an external temperature measurement ana log-to-digital converter (ADC). The Chopper 2 amplifier is used as a buffer for the external digital-to-analog con verter (DAC), which controls the temperature setpoint. Connect the DAC to TSET and short the PAMPN and PAMPOUT pins together. See Figure 19 for an overview of how to configure the LTM4463 external circuitry for digital PID control.

To provide good efficiency and small solution size, the LTM4663 utilizes a PWM switching mode power supply on one side of the H-bridge while a linear power stage on the other side. A default 2MHz switching frequency and a 10µF capacitor maintains less than 1% of the worst-case output voltage ripple across the TEC.

The maximum voltage across the TEC and the current flowing through the TEC are set by using the VLIM/SD and ILIM pins. The maximum cooling and heating currents can be set independently to allow asymmetric cooling and heating limits. The real time TEC voltage and current can be monitored using VTEC and ITEC pins

 

THÉORIE DU FONCTIONNEMENT

The LTM4663 has two half-bridge type power stages, a PWM switching mode regulator and a linear power stage, to allow current flow in or out of the TEC device connected in between.

The object temperature is measured from an external thermal sensor. The sensed temperature (voltage) is fed back to the LTM4663 at TFB pin to complete a closed thermal control loop. The thermistor input amplifier gains the thermistor sensed voltage, then outputs to the PID compensation amplifier. The PID compensation amplifier then compensates a feedback loop response to drive both the PWM switching mode regulator and the linear power stage to drive the TEC to heat up or cool down the object.