Datasheet ADN8834 (Analog Devices) - 14

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ADN8834 Data Sheet ANALOG PID CONTROL
The Chopper 2 amplifier is used as a buffer for the external The ADN8834 integrates two self-correcting, auto-zeroing DAC, which controls the temperature setpoint. Connect the amplifiers (Chopper 1 and Chopper 2). The Chopper 1 amplifier DAC to IN2P and short the IN2N and OUT2 pins together. See takes a thermal sensor input and converts or regulates the input Figure 27 for an overview of how to configure the ADN8834 to a linear voltage output. The OUT1 voltage is proportional to external circuitry for digital PID control. the object temperature. The OUT1 voltage is fed into the
POWERING THE CONTROLLER
compensation amplifier (Chopper 2) and is compared with a The ADN8834 operates at an input voltage range of 2.7 V to temperature setpoint voltage, which creates an error voltage that is 5.5 V that is applied to the VDD pin and the PVIN pin for the proportional to the difference. For autonomous analog temperature WLCSP (the PVINS pin and PVINL pin for the LFCSP. The control, Chopper 2 can be used to implement a PID network as VDD pin is the input power for the driver and internal reference. shown in Figure 27 to set the overal stability and response of the The PVIN input power pins are combined for both the linear thermal loop. Adjusting the PID network optimizes the step and the switching driver. Apply the same input voltage to al power response of the TEC control loop. A compromised settling time input pins: VDD and PVIN. In some circumstances, an RC low- and the maximum current ringing become available when this pass filter can be added optionally between the PVIN for the adjustment is done. To adjust the compensation network, see WLCSP (PVINS and PVINL for the LFCSP) and VDD pins to the PID Compensation Amplifier (Chopper 2) section. prevent high frequency noise from entering VDD, as shown in
DIGITAL PID CONTROL
Figure 27. The capacitor and resistor values are typically 10 Ω The ADN8834 can also be configured for use in a software and 100 nF, respectively. control ed PID loop. In this scenario, the Chopper 1 amplifier When configuring power supply to the ADN8834, keep in mind can either be left unused or configured as a thermistor input that at high current loads, the input voltage may drop substantial y amplifier connected to an external temperature measurement due to a voltage drop on the wires between the front-end power analog-to-digital converter (ADC). For more information, see supply and the PVIN for the WLCSP (PVINS and PVINL for the Thermistor Amplifier (Chopper 1) section. If Chopper 1 is the LFCSP) pin. Leave a proper voltage margin when designing left unused, tie IN1N and IN1P to AGND. the front-end power supply to maintain the performance. Minimize the trace length from the power supply to the PVIN for the WLCSP (PVINS and PVINL for the LFCSP) pin to help mitigate the voltage drop.
ENABLE COOLING AND HEATING TEC CURRENT LIMITS 2.5V VREF RC1 RC2 TEC RV1 CVDD V 0.1µF IN VOLTAGE RBP 2.7V TO 5.5V LIMIT EN/SY ILIM VDD 2.5V VREF VLIM/SD PVIN C R IN V2 10µF TEMPERATURE SET DAC IN2P TEC CURRENT READBACK ITEC LDR C TEC L_OUT TEC VOLTAGE READBACK VTEC ADN8834 0.1µF + 2.5V VREF PGNDL VREF – CVREF NTC R RA 0.1uF SFB RTH AGND L = 1µH IN1P SW C IN1N SW_OUT THERMISTER OUT1 IN2N OUT2 PGNDS F 10µF SW = 2MHz R R X B 2.5V VREF RFB TEMPERATURE READBACK
020
ADC
12954- Figure 27. TEC Controller in a Digital Temperature Control Loop (WLCSP) Rev. B | Page 14 of 27 Document Outline Features Applications Functional Block Diagram General Description Revision History Specifications Absolute Maximum Ratings Thermal Resistance ESD Caution Pin Configurations and Function Descriptions Typical Performance Characteristics Detailed Functional Block Diagram Theory of Operation Analog PID Control Digital PID Control Powering the Controller Enable and Shutdown Oscillator Clock Frequency External Clock Operation Connecting Multiple ADN8834 Devices Temperature Lock Indicator (LFCSP Only) Soft Start on Power-Up TEC Voltage/Current Monitor Voltage Monitor Current Monitor Maximum TEC Voltage Limit Using a Resistor Divider to Set the TEC Voltage Limit Maximum TEC Current Limit Using a Resistor Divider to Set the TEC Current Limit Applications Information Signal Flow Thermistor Setup Thermistor Amplifier (Chopper 1) PID Compensation Amplifier (Chopper 2) MOSFET Driver Amplifiers PWM Output Filter Requirements Inductor Selection Capacitor Selection Input Capacitor Selection Power Dissipation PWM Regulator Power Dissipation Conduction Loss (PCOND) Switching Loss (PSW) Transition Loss (PTRAN) Linear Regulator Power Dissipation PCB Layout Guidelines Block Diagrams and Signal Flow Guidelines for Reducing Noise and Minimizing Power Loss General PCB Layout Guidelines PWM Power Stage Layout Guidelines Linear Power Stage Layout Guidelines Placing the Thermistor Amplifier and PID Components Example PCB Layout Using Two Layers Outline Dimensions Ordering Guide