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ADN8831 Schematic ( PDF Datasheet ) - Analog Devices

Teilenummer ADN8831
Beschreibung Thermoelectric Cooler (TEC) Controller
Hersteller Analog Devices
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Gesamt 21 Seiten
ADN8831 Datasheet, Funktion
Data Sheet
Thermoelectric Cooler (TEC) Controller
ADN8831
FEATURES
GENERAL DESCRIPTION
Two integrated zero drift, rail-to-rail, chop amplifiers
TEC voltage and current operation monitoring
Programmable TEC maximum voltage and current
Programmable TEC current heating and cooling limits
Configurable PWM switching frequency up to 1 MHz
Power efficiency: > 90%
Temperature lock indication
Optional internal or external clock source
Clock phase adjustment for multiple drop operation
Supports negative temperature coefficient (NTC) thermistors
or positive temperature coefficient (PTC) resistance
thermal detectors (RTDs)
5 V typical and optional 3 V supplies
Standby and shutdown mode availability
Adjustable soft start feature
5 mm × 5 mm 32-lead LFCSP
APPLICATIONS
Thermoelectric cooler (TEC) temperature control
DWDM optical transceiver modules
Optical fiber amplifiers
Optical networking systems
Instruments requiring TEC temperature control
The ADN8831 is a monolithic TEC controller. It has two inte-
grated, zero drift, rail-to-rail comparators, and a PWM driver.
A unique PWM driver works with an analog driver to control
external selected MOSFETs in an H-bridge. By sensing the
thermal detector feedback from the TEC, the ADN8831 can
drive a TEC to settle the programmable temperature of a laser
diode or a passive component attached to the TEC module.
The ADN8831 supports NTC thermistors or positive tempera-
ture coefficient (PTC) RTDs. The target temperature is set as an
analog voltage input either from a DAC or from an external
resistor divider driven by a reference voltage source.
A proportional integral differential (PID) compensation
network helps to quickly and accurately stabilize the ADN8831
thermal control loop. An adjustable PID compensation network
example is described in the AN-695 Application Note, Using the
ADN8831 TEC Controller Evaluation Board. A typical reference
voltage of 2.5 V is available from the ADN8831 for thermistor
temperature sensing or for TEC voltage/current measuring and
limiting in both cooling and heating modes.
FUNCTIONAL BLOCK DIAGRAM
ILIMC ILIMH ITEC VLIM VTEC CS
IN1P
IN1N
AMPLIFIER
Chop1
OUT1
IN2P
IN2N
AMPLIFIER
Chop2
OUT2
LIMITER/MONITOR
CONTROL
REF
SOFT START
SHUTDOWN
LINEAR
MOSFET
DRIVER
PWM
MOSFET
DRIVER
OSCILLATOR
LFB
LPGATE
LNGATE
SFB
SPGATE
SNGATE
COMPSW
SW
COMPOSC
SYNCO
TMPGD VREF
SS/SB
Figure 1.
SYNCI/SD PHASE FREQ
Rev. A
Information furnished by Analog Devices is believed to be accurate and reliable. However, no
responsibilityisassumedbyAnalogDevices for itsuse,nor foranyinfringementsofpatentsor other
rights of third parties that may result from its use. Specifications subject to change without notice. No
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One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
www.analog.com
Fax: 781.461.3113 ©2005–2012 Analog Devices, Inc. All rights reserved.






ADN8831 Datasheet, Funktion
Data Sheet
Parameter1
LOGIC Controls
Logic Low Output Voltage
Logic High Output Voltage
Logic Low Input Voltage
Logic High Input Voltage
Output High Impedance
Output Low Impedance
Output High Impedance
Output Low Impedance
TEC CURRENT MEASUREMENT
ITEC Gain
ITEC Output Range High
ITEC Output Range Low
ITEC Input Range2
ITEC Bias Voltage
Maximum ITEC Driving Current
TEC VOLTAGE MEASUREMENT
VTEC Gain
VTEC Output Range2
VTEC Bias Voltage2
VTEC Output Load Resistance
VOLTAGE LIMIT
VLIM Gain
VLIM Input Range2
VLIM Input Current, Cooling
VLIM Input Current, Heating
VLIM Input Current Accuracy, Heating
CURRENT LIMIT
ILIMC Input Voltage Range
ILIMH Input Voltage Range
ILIMC Limit Threshold
ILIMH Limit Threshold
TEMPERATURE GOOD
High Threshold
Low Threshold
Symbol
VOL
VOH
VIL
VIH
AV, ITEC
VITEC, HIGH
VITEC, LOW
VCS, VLFB
VITEC, B
IOUT, TEC
AV, VTEC
VVTEC
VVTEC, B
RVTEC
AV, LIM
VVLIM
IVLIM, COOL
IVLIM, HEAT
IVLIM, HEAT
VILIMC
VILIMH
VTH, ILIMC
VTH, ILIMH
VOUT1, TH1
VOUT1, TH2
Test Conditions/Comments
TMPGD, SYNCO, IOUT = 0 A
TMPGD, SYNCO, IOUT = 0 A
VDD = 5.0 V
VDD = 5.0 V
VDD = 3.0 V
VDD = 3.0 V
(VITEC – VREF/2) / (VLFB − VCS)
No load
VLFB = VCS = 0
(VVTEC – VREF/2)/(VLFB − VSFB)
VDD = 5.0 V
VLFB = VSFB = 0 V
IVTEC = 300 μA
(VLFB − VSFB)/VVLIM
VOUT2 < VREF/2
VOUT2 > VREF/2
IVLIM/IFREQ
VITEC = 2.0 V, RS = 20 mΩ
VITEC = 0.5 V
IN2M tied to OUT2, VIN2P = 1.5 V
IN2M tied to OUT2, VIN2P = 1.5 V
1 Logic inputs meet typical CMOS I/O conditions for source/sink current (~1 µA).
2 Guaranteed by design or indirect test methods.
3 The ADN8831 does not work when the supply voltage is less than UVLO.
ADN8831
Min
Typ Max
Unit
VDD − 0.2
3
35
20
50
25
0.2
0.2
V
V
V
V
25
VDD − 0.05
0
1.10 1.20
±1.5
0.05
VDD
1.30
V/V
V
V
V
V
mA
0.23
0.25 0.28
V/V
0.05 2.5 V
1.20
1.25 1.35
V
35 Ω
5 V/V
0 VDD V
100 nA
IFREQ
mA
0.8 1.0 1.18 A/A
VREF/2
0.1
1.98
0.48
VDD − 1 V
VREF/2
V
2.0 2.02 V
0.5 0.52 V
1.55 1.60
V
1.40 1.45
V
Rev. A | Page 5 of 20

6 Page









ADN8831 pdf, datenblatt
Data Sheet
ADN8831
THEORY OF OPERATION
The ADN8831 is a single chip TEC controller that sets and
stabilizes a TEC temperature. A voltage applied to the input
of the ADN8831 corresponds to a target TEC temperature
setpoint (TEMPSET). By controlling an external FET H-bridge,
the appropriate current is then applied to the TEC to pump
heat either to or away from an object attached to the TEC.
The objective temperature is measured with a thermal sensor
attached to the TEC and the sensed temperature (voltage) is
fed back to the ADN8831 to complete a closed thermal control
loop of the TEC. For best stability, the thermal sensor is to be
closed to the object. In most laser diode modules, a TEC and a
NTC thermistor are already mounted in the same package to
regulate the laser diode temperature.
The ADN8831 integrates two self-correcting, auto-zero amplifiers
(Chop1 and Chop2). The Chop1 amplifier usually takes a thermal
sensor input and converts or regulates the input to a linear
voltage output. The OUT1 (Pin 4) voltage is proportional to the
object temperature. The OUT1 (Pin 4) voltage is fed into the
compensation amplifier (Chop2) and compared with a tempera-
ture setpoint voltage, creating an error voltage that is proportional
to the difference. When using the Chop2 amplifier, a PID
network is recommended, as shown in Figure 12.
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 is done.
Details of how to adjust the compensation network are in the
PID Compensation Amplifier (CHOP2) section. The TEC is
differentially driven in an H-bridge configuration. The ADN8831
drives external MOSFET transistors to provide the TEC current.
To further improve the power efficiency of the system, one side
of the H-bridge uses a PWM driver. Only one inductor and one
capacitor are required to filter out the switching frequency. The
other side of the H-bridge uses linear output without requiring
any additional circuitry. This proprietary configuration allows
the ADN8831 to provide efficiency of >90%. For most applica-
tions, a 4.7 μH inductor, a 22 μF capacitor, and a switching
frequency of 1 MHz, maintain less than 0.5% worst-case output
voltage ripple across a TEC.
The maximum voltage across the TEC and current flowing
through the TEC is to be set using the VLIM (Pin 31) and
ILIMC (Pin 1)/ILIMH (Pin 32). Additional details are in the
Maximum TEC Voltage Limit section and the Maximum TEC
Current Limit section.
5Ω
0.1µF
0.1µF
VDD
3.0V TO 5.5V
17.8kΩ
7.68kΩ
THERMISTOR
0.1µF 10kΩ
10kΩ
8.2kΩ 10kΩ
8.2kΩ
VREF
VLIM
ILIMC
ILIMH
10kΩ
10kΩ
IN1P
17.8kΩ
10kΩ
IN1N
OUT1
27nF
30.1kΩ
10µF
IN2N
OUT2
AVDD
PVDD
LPGATE
LFB
LNGATE
CS
COMPSW
SFB
10kΩ
SYNCI/SD
COMPOSC
SPGATE
SW
SNGATE
1kΩ
TEMPERATURE SET INPUT
IN2P
SYNCO
NC
TEC VOLTAGE OUTPUT
TEC CURRENT OUTPUT
TEMP GOOD INDICATOR
VTEC
ITEC
TMPGD
AGND
PGND
PHASE
NC
SS/SB
FREQ
0.1µF
118kΩ
NC = NO CONNECT
Figure 12. Typical Application Circuit 1
RSENSE
0.1µF
TEC
VDD
60µF
3.3µH
40µF
Rev. A | Page 11 of 20

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