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Documents
3B01: the connection between the 26-pin and 16 channel.
442 - I cannot find the datasheet for the 442 (old OPAMP Module)
751: old datasheet
Ac coupling Vs Dc coupling
AC1307E Power Supply input range
AD-MSDPD-EVB: Eval Board Datasheet
AD10200: Are the two channels fully independent?
AD10200: Channel-to-Channel isolation test with AINA2 and AINB2
AD8436 - Down conversion to 100 uV
AD8436 - Power consumption for added amplifiers
AD8436 - Power supply
AD8436 - What is unique about this device?
AD8436: output buffer with higher gain than unity
AD8436: single supply or dual supply
ADATE304 Force Voltage
ADATE318: What supply voltage do I use for VDD_THERM?
ADMP401 startup
ADMP441 output format
ADN2531: Can output be configured as current source?
ADN2685: could you send the final datasheet?
ADN2814: power consumption at 10MHz
ADN2814: Recover a 1T clock from a EFM signal
ADN2816 Evaluation Board Documentation
ADN2816: Which clock edge does the retiming block of the ADN2816 use to output data?
ADN2817 error correction
ADN2820: Optical fiber communication
ADN2830 MPD current
ADN2830: Monitor photodiode
ADN2830: CW laser diode power control
ADN2871: Differential drive circuit for driving a VCSEL Laser diode.
ADN2872: Is it possible to use 2 laser drivers in parallel to have the modulation current of 130 mA?
ADN2873: Minimum differential signal between the DATAP and DATAN
ADN2880: MAX leakage current specification of ADN2880 input
ADN2882 Evaluation Board
ADN2890/1/2 at 100Mbps?
ADN4600 Junction Temperature
ADN4600 thermal characteristics
ADN4600: Reset Power on timing
ADN469xE Evaluation Board
ADN469xE IBIS Models
ADN469xE: MLVDS and how is it different from B-LVDS and RS-485?
ADN469xE: Rise and Fall Time matching Data Rate
ADN8831 and operate DVDD with < 3v
ADN8831 EVB
ADN8831: Driving a 12V external TEC module
ADN8831: How to drive a 12V TEC?
ADN8831: how to drive an APD
ADN8831: PWM duty cycle
ADN8834: Evaluation board difference
AN-695 Q&A
Aqueous washing of ADI parts?
availability of the ADMC300 devices
Baking BGA in Tray or trays
Baking of parts in a Reel
Can ADN4604 do single ended 75Ohm input and output?
Can I connect one input to multiple outputs?
datasheet 2B35
datasheet 940, 941, 942, 943, 944, 945
datasheet error
Digital programmable power with 1.8V logic to Vout = 5V
Does changing the crosspoint connectivity affect the state of previously configured connections?
doubling ADN8810 Iout configuration query (SR#: 1202803)
EVAL-AD8436 evaluation board operation with single supply
EVAL-ADN2882-EXT
Evaluation Boards for the ADN2531
Failure probability for AD8468
How can I order Linear Circuit Design Handbook?
Maximum Recommended PMU Load Capacitance
Modell 310J
MTBF-reliability data
Other Products
Package general: What is the pin pitch of LFCSP package?
Package: 10 ld Ceramic Flat Package footprints
paste mask recommendation
PFC controller + LED driver in one package
Replacement for PMI119-883
RoHS compliant status E
RTI-850 RTI products
Shelf life for Analog parts
Shelf life of drypack used to ship Moisture/Reflow Sensitive Surface Mount Devices
Support for Mobile TV tuner parts: ADMTVxxx / IDTxxxx
Technical questions ADN8831
The unit of MTTF data on ADI web site
transistor counts for a processor to calculate the MTBF
unused inputs or outputs?
What data rates or range of data rates are supported?
What data rates protocols are supported?
Where can I find e-book versions on your seminar books to download?
Where can I find the user guide for the ADN2871/ADN2873 evaluation boards?
which register we can read to know the status of HD
Why the Analog Input Current from ?10mA to 10 mA was limited.
AN-695 Q&A
Q
We have recently purchased an ADN8831 chip with the ADN8831 Eval-z evaluation
board. We are currently trying to set up a TEC with a 10k NTC Thermistor module
following the instructions given on the AN-695 Application Note and we are
having a number of questions:
1) The PID network switches S1-5 appear to have different orientation. Could
you please confirm which are ON/OFF positions for each switch?
2) The Quick Start section on page 4 for suggests that we should measure values
of the R1-3 potentiometers after connecting the thermistor and the TEC on the
board. However, as soon as I connect these I cannot measure the pot values
accurately.
3) In the Configure setpoint temperature range section it is saying that we can
use the default values to lock a TEC with a 10k NTC thermistor at 25 degrees.
In page 5 in the same section it is given another method to set a single point
temperature instead of a range. Could you please explain what is the actual
difference between these two settings, and what is the best way to set
accurately a TEC with a 10k NTC thermistor at 25 degrees or any other
temperature?
4) In the Monitor the TEC current section it is given a formula to calculate
the current flowing through the TEC based on the Vitec voltage. However, for
Vref = 2.5 V when the Vitec drops below 1.25 the calculated current takes a
negative value. What is happening in that case?
5) When we set Vtempset at 1.25 V (correspond to 25 degrees for the 10k
thermistor we use) the Vtempout voltage continuously oscillates around the
setpoint voltage. By tuning the PID parameters we manage to reduce the
oscillation amplitude but not to get a stable output. Any ideas what might be
the problem?
A
1) The orientation has following logic: if switch ON, it adds capacitor as the
capacitors are connected in parallel.
For resistive network, if switch is On, it shorts resistor because the
resistors are connected in series. The snapshot of the board schematic
illustrates this (attached).
2) It appears the instructions in the Quick-Start section are not clear enough.
The potentiometers should be verified BEFORE connecting the thermistor. The
reason is apparent from our schematic: the thermistor completes a parallel
path between TPR1 and TPR123 that will distort the potentiometer measurement.
We revise the instructions in AN-695 accordingly.
3) The default values on the application board assume a particular thermistor
is being used that at 35C has a value of 6.9k, at 15C has a value of 14.8k and
at 25C has a value of 10k. It attempts to linearize the response over that
range. If a larger range is desired, then the thermistor values at High and Low
would be different and the resulting R1, R2 and R3 will also differ from the
"defaults". IF you select a thermistor, that has a 10k resistance at 25C, then
the default settings should produce a setpoint of 25C, but if Rhigh and Rlow
differ from the example, the range will differ.
When only a narrow temperature range is required, the linear approximation of
Vtempout and Temperature is valid and the potentiometer settings can be R1=RMID
(generally 10k) and R2=0.
Our recommendation is to initially use the default settings and verify if these
permit the required setpoint for setpoints other than 25C. If you find that
over your required temperature range Vtempout varies from 50mV (at the low
temperature) to Vref (at the high temperaure setpoint) the default values are
adequate. If your range for Vtempout is less, then your application can benefit
from adjusting the potentiometers to improve the setpoint resolution. Finally,
if you cannot achieve the required setpoint range, you will need to calculate
the potentiometer settings as appropriate for your thermistor and required
temperature range.
But first try the default settings.
4) The TEC sets in the middle of an "H Bridge". The "zero" current level of the
ITEC voltage is 1.25V. So when the current is zero, the output voltage of the
ITEC pin will be 1.25V (nominally). Likewise, the "zero" voltage output at the
VTEC pin with the TEC voltage is zero is 1.25V. When the TEMPSET voltage is
below 1.25 V, the TEC voltage will be positive (LFB>SFB), so VTEC>1.25V and
ITEC>1.25V. If the TEMPSET is above 1.25 V, the TEC voltage will be negative
(LFB<SFB), so voltage at VTEC pin<1.25V and voltage at ITEC pin <1.25V.
5) This will be very difficult to determine without more information since it
depends on the characteristics of the TEC particular and the thermal
characteristics of the object that is being controlled. It may be possible if
you provide some oscilloscope traces to show what the TEMPOUT and TEMPSET are
doing at the various compensation settings you are attempting.
Attachments:
adn8831
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