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AD5142A as T-attenuator or voltage divider

March 8, 2016, 8:33 am
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Hello,

 

I just designed a moduled AGC-circuit. Amongst other things there is a fixed gain module and an adjustable attenuation moduel (AD5142A).

 

I got problems with the attenaution module. It's just a AD5142A connected as follows...

Signal goes into R_A, comes out over R_W and R_B is connected to GND (don't wonder, its german):AD5142A-Circuit_contactSupport.jpg

-> I would call it a T-attenuator and I expect a voltage dividing effect set by  R_A / R_B

 

I'm wondering why my attenuation decreases with increasing frequency when I measure the circuit with a PicoScope (power is supplied by a laboratory power supply)

The datasheet makes me think that attenuation is as expected til some Mhz (the graph is just horizontal til ~3MHz) but it just does t very low frequencies. At some kHz the amplitude starts to decrease with the frequency sweepAD5142_2k5_lowF2(1k-10M).jpgAD5142_2k5_xhighF2(1k-10M).jpg

The network analyzer shows off some exponential impedance decrease (Z11 and Z22) too what makes me pretty sure that there is something wrong. Maybe the AD5142A can't be used as a attenuator / voltage divider?

 

I wont be able to use this as an attenuator in my AGC with this behavior.

Has anyone an idea where I could be wrong or what I could improve?

 

 

Thanks and Greetings

Christian

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ADN8834 OUT2 oscillation at cooling mode only

March 2, 2016, 5:29 pm
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Hello

 

Our customer will use ADN8834 and evaluating  ADN8834CB-EVALZ.

At initial setting with his laser module including TEC and thermistor, OUT2 is oscillated.

So he aligned the C  and R around OUT2.

As the result of alignment, OUT2 is stable at 25 degreeC and heating mode but OUT2 is oscillated at cooling mode.

I describes below about his alignment.

Please let me know your advice to avoid this problem.

 

About His alignment

 

Temperature condition: 25 degreeC
TEMPSET: fixed 1.544V

His board: ADN8834CB-EVALZ

Change by below method: Cl, Cd, Cf, Rl, Rd, Rp in datasheet P.13 figure 26.

Rl：51kΩ、Rd：100kΩ、Cd：100pF、Rp：100kΩ、Cl：22µF、Cf：0.01µF

 

He aligns as below method.

1:  Short Cl and open Cd  from condition of ADN8834CB-EVALZ.

2: The retio of Rl/Rp is increased and confirm the oscillation of OUT2. Then the retio of Rl/Rp is decreased by a factor of the two.

3: Add Cl and decreas its value until OUT2 starts oscillation. Then he increases Cl by a factor of the two.

4: Short Rd and add Cd. He increases Cd until OUT2 starts oscillation.Then Cd is decreased and Rd is added.

 

Now, OUT2 is oscillated at cooling mode only in above 4.

Please let me know your advice about the problem for above method and avoiding this problem.

 

If you need any other information ,please let me know it.

 

Regards,

Terumasa

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Can ADN4604 be driven by LVDS Driver

April 6, 2016, 6:57 am
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Hi ,

 

Can ADN4604  be driven by LVDS driver. LMH0384 have equalizer inside and has 100 ohm differential output but this differential output is LVDS standard output.

 

Thanks

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I2C communication drop periodically

April 8, 2016, 11:19 am
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I am using ADUM1250 for voltage level shifter for my I2C communication between PLC(3.3v) and ADS (5v)IC. I2C communication is dropped periodically. once it stop communication i have to reset the I2C and it works again and it is stop after some time again.

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Questions about the operation of HMC721LP3E

March 27, 2016, 4:50 pm
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Hello,

 

My customer asks some questions about HMC721LP3E operation.

They say that they want to know whether the  input swing level (VIH / VIL) of HMC721LP3E affects the output swing level (VOH / VOL) or not (even though the supply voltage and VR voltage level aren't changed.).

 

Please refer below their test result and let me know your opinions.

 

They changed only input level from (-1V ~ 1V) to (-0.2V ~ 0.2V) and output swing level was changed as below.

  • VIH = 1V / VIL = -1V => VOH = 1.16V /  VOL = 585mV
  • VIH = 0.2V / VIL = -0.2V =>

        (Simulation result : VOH = 963mV /  VOL = 671mV, Proto board measure result : VOH = 90mV /  VOL = 680mV)

 

Q1) Would you clarify whether output swing level of HMC721LP3E is influenced by input swing level or not?

 

Q2) Would you let me know correlation formula if there is any correlation formula existed between input swing level and output swing level?

 

Please advise me.

 

If you have any questions, please let me know.

 

Regards,

Se-woong

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Question for AD7740

April 13, 2016, 7:50 pm
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Hi , I have a questioin about AD7740 (V-F converter) .

I use AD7740 with EX clock(1% accuracy).

I want to drive AD7740 with 1000kHz clock .

but , max CLKIN of AD7740  is 1000kHz .

Can I use AD7740 with silicon oscilator (1% accuracy ,1000kHz)?

So,  which FREQUENCY should I use as TYP CLKIN ? (990kHz ? in this case)

Or , it isn't so big deal , If 1010kHz clock come into AD7740?

 

So please anyone help.

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I am having trouble calibrating the AD5522 in FI mode.

March 30, 2016, 9:07 am
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It says in the data sheet to compute M and C but I do not understand how to compute them.  Is there anyone who has some C code to perform these computations ?  Or perhaps has an application note telling how to compute the M and C values for force I.  in the calibration steps it says to compute M and C for FI but I am having trouble computing these numbers.  Any help would be appreciated.  I figure the Eval board has software to do this so if anyone has the source code for the eval software that would be all I need.

thanks

Phil

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ADN8834 evaluation board supply current

March 14, 2016, 12:56 am
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Hello

 

Our customer will evaluate ADN8834CB-EVALZ.

He set the resistor value for setting of maximum TEC current  700mA ,

but the measurement result is not expected measurement reuslt.

We concern if we use ADN8834 correctively.

Please let me know your advice about below.

 

Change paramter

He changed Rv1:15Kohm, Rv2:10Kohm,  RC1:47Kohm and RC2:27Kohm .

(He would like to set TEC current 700mA max and Vitec =1.6V)

 

Measurement

In his system, it is difficult to measure the current through TEC directly.

So, he measured the supply current through PVIN and VDD.

(We thought that TEC current is near total current of PVIN and VDD and mearsurement reuslt will be about 700mA)

Measurement result is 250mA and Vitec=1.6V  at cooling mode.

And when TEC is heated a little more  than above condition  (Vitec  =1.6V)  ,  the supply current becomes  about 300mA.

Then  output of OUT1 is stopped ( 0V output) suddenly.

 

Question1

Is TEC current near the curernt through PVIN and VDD ?

Is above result of 250mA  standard result ?

If our setting and understanding is wrong , please let me know your advice.

 

Question 2

When TEC is heated  a little more at  maximum of Vitec as above  is the outpuf of OUT1 stopped ?

 

Please let me know your advice.

 

Regards,

Teruamsa

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ADN8831 evaluation board not stabilizing

April 20, 2016, 4:08 am
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Dear Analog devices

 

We are trying to evaluate the adn8831 chip for use in a fiber to the home product, and have therefor purchased the evaluation board.

The peltier element that we are using has an Imax=2.1 A and Umax=0.35V the thermistor is one with 10Kohm at 25 C and Stienhart-Hart- coefficients of A 1.215553e-3, B 2.192519e-4 and C 1.524069e-7.

We however have some problems is getting it to stabilize, when following the quick start found in application note AN-695, the temperature never seems to keep oscillating around the set point temperature without ever settling. This happens both when we try to control the temperature using the onboard potentiometer and if we try to set the temperature using the tempest pin.

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ADN8831 evaluation board not stabilizing

April 20, 2016, 4:08 am
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Dear Analog devices

 

We are trying to evaluate the adn8831 chip for use in a fiber to the home product, and have therefor purchased the evaluation board.

The peltier element that we are using has an Imax=2.1 A and Umax=0.35V the thermistor is one with 10Kohm at 25 C and Stienhart-Hart- coefficients of A 1.215553e-3, B 2.192519e-4 and C 1.524069e-7.

We however have some problems is getting it to stabilize, when following the quick start found in application note AN-695, the temperature never seems to keep oscillating around the set point temperature without ever settling. This happens both when we try to control the temperature using the onboard potentiometer and if we try to set the temperature using the tempest pin.

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Using SPI control on zedboard PMOD connectors

April 29, 2016, 12:20 am
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Hi,

I want to use a zedboard to control a SPI connection on PMOD. The project I'm working on already use the SPI_0 to control a device but not on PMOD. So I want to use the other connection available (SPI_1).

 

I'm using the design 2014_R1. I started with the fmcomms2 design on Vivado and I made SPI_1 as an EMIO connected to the PMOD connector JB.

 

I modified the devicetree by adding the following content :

 

    spi@e0007000 {
      compatible = "cdns,spi-r1p6", "xlnx,zynq-spi-1.00.a", "xlnx,ps7-spi-1.00.a";
      interrupt-parent = <0x1>;
      interrupts = <0x0 0x31 0x4>;
      clock-names = "ref_clk", "aper_clk", "pclk";
      clocks = <0x3 0x1a 0x3 0x23 0x3 0x23>;
      num-chip-select = <0x4>;
      reg = <0xe0007000 0x1000>;
      speed-hz = <0x5f5e100>;
      #address-cells = <0x1>;
      #size-cells = <0x0>;
      status = "okay";

 

      device@0{
        compatible = "spidev";
        reg = <0>;
        spi-max-frequency = <3125000>;
      };
    };

 

The routing seems to work but after the regeneration of the SD card, I lose the connection with SPI_0 I had before in Linux at /sys/bus/iio/devices.

 

I tried the regeneration of the SD card with and without the modification I made on the devicetree and in both cases, it doesn't work.

 

Why do I lose the control on SPI_0 when I'm trying to use SPI_1 ?

 

Regards,

Kevin

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Request HMC745LC3 IBIS model

May 3, 2016, 7:18 pm
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Hello,

 

My customer wants to use HMC745LC3 at Memory tester and they request IBIS mode of this device for SI simulation.

Would you provide a IBIS model of HMC745LC3 device?

 

Please release to me ASAP.

 

If you have any questions, please let me know.

 

Regards,

Se-woong

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ADN4604 as HDMI Switcher

May 10, 2016, 3:51 pm
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Figure 51 on page 32 of the Rev A datasheet for the ADN4604 shows a 16 input/16 output HDMI crosspoint switch.  However, I don't see how it is possible to configure the ADN4604 so that it will accept HDMI signals on the input and output HDMI compliant signal levels on the outputs. 

 

The HDMI version 1.3a specification says that standard HDMI signals are 400mV to 600mV (singled-ended) with the maximum positive swing being at AVCC (3.3V nominal).  That means that at nominal voltages an HDMI signal will swing from 2.8V to 3.3V.  See Figures 4-13 and 4-14 on page 55 of the attached HDMI specification.  This means that the common-mode voltage of an HDMI output is nominally 3.05VDC (the center line shown in Figure 4-14).

 

To be precisely compatible with the HDMI specification, VH-DC (FIgure 44, page 21 of the ADN4604 datasheet) should be VTTO and VL-DC should be 2.8VDC.  I do not see how to configure the ADN4604 to get those signal levels.  It appears to me that the output common-mode voltage for the ADN4604 will always be lower than VTTO and the output swing will be less than 800mV pk-pk.

 

Please tell me how to configure the ADN4604 to implement the application shown in Figure 51 on page 32 of the ADN4604 datasheet (Rev A) using HDMI compliant signaling.

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Does the EVAL-HMC792ALP4 come with the Digital Attenuator already attached?

May 17, 2016, 11:31 am
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Does the EVAL-HMC792ALP4 come with the Digital Attenuator already attached or do I have to solder it on myself?

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AD5522 PMU usb communication problem

May 23, 2016, 6:37 pm
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I tried to use the measurement chip AD5522 to output a constant 4V voltage。

And I setup all the needed data to the specific regs（as  data x1_reg=CCCC, gain m_reg=FFFF, offset c_reg=8000）

But none right output voltage was get.   I read back all the regs , which are just as the default config(as x1_reg=8000)

AD5522 (1).PNG

AD5522 (2).PNG

AD5522 (3).PNG

 

So  I doubted that it is a mcu comunication problem. ( QUESTION 1 )

but when i operated in the SWEEPS page as blew,  it  displayed the right output. 

so the communication works just right ???  

And in this config,  the output is clampped  on  1.21V.  ( QUESTION 2)  Actually the defualt Clamp range is from 0000 to FFFF.

AD5522 (4).PNG

Should i suppose to reload mcu firmware or any other moves ?

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Question about a DIgital PID control of ADN8833

May 25, 2016, 1:29 am
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Hello,

 

My customer is designing to use ADN8833 in their Optic module.

And they are asking some questions and your advices for implementing a DIgital PID control of ADN8833.

Please refer below questions and let me know your advices ASAP.

 

Q1) About TEC control with ADN8833 using digital PID

For control the inout voltge of CONT pin, they will refer below equations and figure in datasheet.

Would you confirm whether they can use below contents as for controling the voltage of CONT pin?

      - VVTEC = 1.25 V + 0.25 × (VLDR− VSFB), VLDR = VB− 40(VCONT−1.25 V), VSFB = VLDR + 5(VCONT −1.25 V),

     - Figure 33

PDF to JPEG 변환용.jpg

 

Q2)About requesting materias that they can refer to program MCU to control the input voltage of CONT pin (the output of DAC).

Would you provide a simulation data about the output for TEC control as the change of  input voltage values of CONT pin?

 

Q3) About requesting reference materials related digital PID control for TEC

Would you provide reference materials about digital PID control for TEC that they can refer?

Please confirm above questions and help them.

 

If you have any questions, please let me know.

 

Regards,

Se-woong

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ADM2587E absolute max rating

May 26, 2016, 12:57 am
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Hi

 

One of my customer wants to know why the Vin absolute max ratings is limited as  -9V and 14V.

They guess the limit would be +/- 9V or +/- 14V.

 

 

Regards,

Power-man

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AD5522 PMU usb communication problem

May 26, 2016, 9:39 pm
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I tried to use the measurement chip AD5522 to output a constant 4V voltage。

And I setup all the needed data to the specific regs（as  data x1_reg=CCCC, gain m_reg=FFFF, offset c_reg=8000）

But none right output voltage was get.   I read back all the regs , which are just as the default config(as x1_reg=8000)

AD5522 (1).PNG

AD5522 (2).PNG

AD5522 (3).PNG

 

So  I doubted that it is a mcu comunication problem. ( QUESTION 1 )

but when i operated in the SWEEPS page as blew,  it  displayed the right output. 

so the communication works just right ???  

And in this config,  the output is clampped  on  1.21V.  ( QUESTION 2)  Actually the defualt Clamp range is from 0000 to FFFF.

AD5522 (4).PNG

Should i suppose to reload mcu firmware or any other moves ?

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ADPD103

May 31, 2016, 6:50 am
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Sir,

 

I am currently using the Eval board from Analog Devices - ADPD103. I am having some difficulties as the schematics of it are not provided!(Kindly post the needful)

 

1. I have issues when I am connecting any external photo diode(other than the one provided on the Eval board). The Photo Diode responds to the basic tests (coarse voltage variations when rapid movements of finger is done), but when I connect an LED it shows Zero Voltage.

 

2. I tested for a series of LED ranges .i.e. green/IR . It showed a comparable PPG graph for IR LED in conjunction with a respective the respective Photo diode when adjusted the no. of pulses/ LED current etc. But for green no adjustment seemingly worked. (I was suspecting some issue with the forward voltage drops as the IR LED has a lesser forward voltage than the red LED(which is the on board sample given for testing) and green needs a higher forward voltage). I guess a little insight on the driver circuit employed will be a lot useful. Any other advice on this aspect is welcome as well.

 

3. I wanted to run two or more Photo Diode channels at the same time.The Datasheet says to modify the register 0x14 from 0555(default value) to 0445 to activate PD5/6/7/8. But in all the cases I am able to get only channel one activated .i.e. PD1/PD5. Am I missing on something?(I have checked the register 0x3C , it is not on single channel mode)

 

 

Any help at the earliest would be really appreciated.

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About ADN8834 boost output current

June 6, 2016, 10:02 am
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I need drive a TEC device (inside of a LASER module) with almost 2 Amps.

I need to know if my analysis about the OUTPUT STAGES of the ADN8834 device are correct.

I don't see any possibility (by external circuit such as Mosfet Driver) of to boost the output current (> 1.5 Amps) to the TEC device, except with a very complicated solution.

 

According the Block Diagram of ADN8834 (Thermoelectric Controller chip), ; there are two sections inside of the chip, "TEC DRIVER LINEAR STAGE" and "PWM POWER STAGE", and there is a  voltage monitoring via SFB and LDR pins. According Data Sheet, there are many constrains involved on the Output Voltage VDLR, VSFB and the selection of the Inductor then, in a general approach, I can't see how the system stability can be sustained.

 

adn8834 block diagram.jpg

 

Thanks in advance.

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