Datasheet LTM4663 (Analog Devices) - 8

link to page 19 LTM4663
OPERATION
The LTM4663 is a complete Thermoelectric Cooler (TEC) connected to an external temperature measurement ana- µModule regulator that sets, stabilizes and monitors log-to-digital converter (ADC). The Chopper 2 amplifier TEC temperature. It can deliver up to 1.5A of sinking or is used as a buffer for the external digital-to-analog con- sourcing current with external input and output capac- verter (DAC), which controls the temperature setpoint. itors. Operating over 2.7V to 5.5V input voltage range, Connect the DAC to TSET and short the PAMPN and the LTM4663 controls an internal FET H-bridge whereby PAMPOUT pins together. See Figure 19 for an overview the direction of the current fed through the TEC can be of how to configure the LTM4463 external circuitry for either positive (for cooling mode), or negative (for heating digital PID control. mode). To provide good efficiency and small solution size, the The LTM4663 has two self-correcting, auto-zeroing LTM4663 utilizes a PWM switching mode power supply amplifiers(Chopper 1 and Chopper 2) to linearize the on one side of the H-bridge while a linear power stage on thermal sensor input and to form an analog temperature the other side. A default 2MHz switching frequency and a feedback control loop. With the zero drift chopper ampli- 10µF capacitor maintains less than 1% of the worst-case fiers, extremely good long-term temperature stability is output voltage ripple across the TEC. maintained via an autonomous temperature control loop. The maximum voltage across the TEC and the current See Figure 18 for an overview of how to configure the flowing through the TEC are set by using the V analog PID control, while see Figure 19 for configuring LIM/SD and I the digital PID control. LIM pins. The maximum cooling and heating currents can be set independently to allow asymmetric cooling and The LTM4663 can also be configured for use in a soft- heating limits. The real time TEC voltage and current can ware controlled PID loop. In this scenario, the Chopper 1 be monitored using VTEC and ITEC pins. amplifier can configure as a thermistor input amplifier
APPLICATIONS INFORMATION THEORY OF OPERATION INPUT AND OUTPUT DECOUPLING CAPACITORS
The LTM4663 has two half-bridge type power stages, a Benefiting from the unique topology and the 2MHz PWM switching mode regulator and a linear power stage, default switching frequency, only one ceramic capacitor to allow current flow in or out of the TEC device connected is required at the input and output of the PWM switch- in between (see Figure 2). ing regulator to maintain less than 1% of the worst-case The object temperature is measured from an external output voltage ripple across the TEC. Additional output thermal sensor. The sensed temperature (voltage) is fed filtering may be required by the system designer if further back to the LTM4663 at T reduction of output ripples or dynamic transient spikes FB pin to complete a closed thermal control loop. The thermistor input amplifier gains is required. the thermistor sensed voltage, then outputs to the PID compensation amplifier. The PID compensation amplifier
ENABLE AND SHUTDOWN
then compensates a feedback loop response to drive both To enable the LTM4663, apply a logic high voltage to the the PWM switching mode regulator and the linear power EN/SY pin while the voltage at the V stage to drive the TEC to heat up or cool down the object. LIM/SD pin is above the maximum shutdown threshold of 0.07V. If either the EN/ SY pin voltage is set to logic low or the VLIM/SD voltage is Rev. 0 8 For more information www.analog.com Document Outline Features Applications Typical Application Description Absolute Maximum Ratings Order Information Electrical Characteristics Pin Configuration Typical Performance Characteristics Pin Functions Block Diagram Decoupling Requirements Operation Applications Information Typical Applications Package Description Package Photo Package Description Design Resources Related Parts