ADN8834ACPZ-R2 datasheet(14/27 Pages) AD

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ADN8834

Data Sheet

Rev. B | Page 14 of 27

ANALOG PID CONTROL

The ADN8834 integrates two self-correcting, auto-zeroing

amplifiers (Chopper 1 and Chopper 2). The Chopper 1 amplifier

takes a thermal sensor input and converts or regulates the input

to a linear voltage output. The OUT1 voltage is proportional to

the object temperature. The OUT1 voltage is fed into the

compensation amplifier (Chopper 2) and is compared with a

temperature setpoint voltage, which creates an error voltage that is

proportional to the difference. For autonomous analog temperature

control, Chopper 2 can be used to implement a PID network as

shown in Figure 27 to set the overall stability and response of the

thermal loop. Adjusting the PID network optimizes the step

response of the TEC control loop. A compromised settling time

and the maximum current ringing become available when this

adjustment is done. To adjust the compensation network, see

the PID Compensation Amplifier (Chopper 2) section.

DIGITAL PID CONTROL

The ADN8834 can also be configured for use in a software

controlled PID loop. In this scenario, the Chopper 1 amplifier

can either be left unused or configured as a thermistor input

amplifier connected to an external temperature measurement

analog-to-digital converter (ADC). For more information, see

the Thermistor Amplifier (Chopper 1) section. If Chopper 1 is

left unused, tie IN1N and IN1P to AGND.

The Chopper 2 amplifier is used as a buffer for the external

DAC, which controls the temperature setpoint. Connect the

DAC to IN2P and short the IN2N and OUT2 pins together. See

Figure 27 for an overview of how to configure the ADN8834

external circuitry for digital PID control.

POWERING THE CONTROLLER

The ADN8834 operates at an input voltage range of 2.7 V to

5.5 V that is applied to the VDD pin and the PVIN pin for the

WLCSP (the PVINS pin and PVINL pin for the LFCSP. The

VDD pin is the input power for the driver and internal reference.

The PVIN input power pins are combined for both the linear

and the switching driver. Apply the same input voltage to all power

input pins: VDD and PVIN. In some circumstances, an RC low-

pass filter can be added optionally between the PVIN for the

WLCSP (PVINS and PVINL for the LFCSP) and VDD pins to

prevent high frequency noise from entering VDD, as shown in

Figure 27. The capacitor and resistor values are typically 10 Ω

and 100 nF, respectively.

When configuring power supply to the ADN8834, keep in mind

that at high current loads, the input voltage may drop substantially

due to a voltage drop on the wires between the front-end power

supply and the PVIN for the WLCSP (PVINS and PVINL for

the LFCSP) pin. Leave a proper voltage margin when designing

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.

ADN8834

L = 1µH

VIN

2.7V TO 5.5V

TEC

SFB

LDR

PGNDS

PVIN

VDD

ILIM

VLIM/SD

ITEC

IN2P

VTEC

TEC

VOLTAGE

LIMIT

2.5V VREF

–

EN/SY

CSW_OUT

10µF

FSW = 2MHz

CL_OUT

0.1µF

CIN

10µF

CVDD

0.1µF

PGNDL

ENABLE

IN1N

IN1P

VREF

AGND

IN2N OUT2

OUT1

RV1

RV2

RC1

RC2

COOLING AND HEATING

TEC CURRENT LIMITS

CVREF

0.1uF

2.5V VREF

TEC VOLTAGE READBACK

TEC CURRENT READBACK

TEMPERATURE SET

RFB

RBP

NTC

THERMISTER

RTH

TEMPERATURE

READBACK

ADC

DAC

2.5V VREF

Figure 27. TEC Controller in a Digital Temperature Control Loop (WLCSP)

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