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AD995X series DDS, rig ideas
I just got some samples of the AD9952 and AD9954 DDS chips.
Both look identical, AD9954 has some extra features I don't need but can simply not program. These parts are real small, will have to find some VERY small tweezers to bend the leads and file down a soldering tip to fit. I would try to solder all the gnd and unused inputs down to a PC ground plane and bend all the power pins up flat against the top of the chip to be soldered together. The signal pins would have to be bent up halfway and fly leads soldered on to go to the rest of the circuit on perfboard. Anybody try to breadboard one of these 'dead bug' style like this? Anyone have some circuit advise on using these chips? I am thinking of using one in a single conversion transceiver. Mixers will be DBM using push pull digital drive so the DDS will drive a 74xx74 divider and be driven at twice the LO frequency. (several examples of such receiver front ends in recent ARRL HB's). IF will be 9mhz, I have 4 identical 9mzh filters, so will use 3 in rx if and 1 in tx. (got those filters at Dayton about 10 years ago... Clegg surplus). Was thinking of using 8051 series micro, the built in serial port will drive the AD98xx and AD99xx dds chips. Question....how do I convert the 5v digital io of the 8052 micro to the 1.8v levels used by the AD995x series, or is the DDS chip 5v compatible (on input maybe... what to do about output? especially on the bidirection serial line....) Was also thinking about maybe building the rig as a 6 meter single conversion with an HF transverter front end. What do you think of this idea? 73's WA2MZE |
I have mounted the 9850 and 9851 chips dead bug like this before. It is
an extremely painful process, but doable. Be very careful with the leads, I had one of the pins of a 9851 break off. You really only get to bend a pin once. Don't try bending it twice! I have mounted a lot of DIP and SOIC chips deadbug and have almost never had a pin come off (ok, maybe once, but it was kind of abused), but TSSOP packages such as this are more fragile. Except for the ground connections, which I bend over for direction connection to the ground, I bent every other pin either up or out a bit to get a little more space for the connections. I used #32 gauge enamel wire for interconnect. When mounting the device, pre-tin all leads in advance and tack the device in place by soldering the ground leads, and connecting the power leads via bypass caps. When making a connection to the part or wire to the chip, pre-tin the part and touch solder the part or wire to the pin. This is very difficult as the heat from the tip can melt an adjacent connected wire or part. It is easy to create solder bridges across pins. Solder wick or a solder sucker, or an exacto knife can be use to open up such a bridge as the solder is heated with a iron. Some time a bit of fresh solder with fresh flux helps undo the bridge. Patience, patience, patience! It is difficult to do, but it can be done, and the results can be quite rewarding. As far as 5v to 1.8v logic level conversions, the very simplest thing is to use a 2N7000 MOSFET transistor for each signal. The gate can be directly driven with the 5v signal, and the output can be pulled up to 1.8v with a 2.2K resistor. It is cool to deadbug with the surface mount version of these parts (SOT-23) and use a 805 size chip pull up resistor. The resulting "inverter" in very small! The signal will be inverted, but just keep that in mind when writing the software. I use the surface mount FETS (BSS123/2N7000) in the receiver diplexer in my home brew transceivers, and they don't take up much space! - Dan, N7VE kenneth scharf wrote: I just got some samples of the AD9952 and AD9954 DDS chips. Both look identical, AD9954 has some extra features I don't need but can simply not program. These parts are real small, will have to find some VERY small tweezers to bend the leads and file down a soldering tip to fit. I would try to solder all the gnd and unused inputs down to a PC ground plane and bend all the power pins up flat against the top of the chip to be soldered together. The signal pins would have to be bent up halfway and fly leads soldered on to go to the rest of the circuit on perfboard. Anybody try to breadboard one of these 'dead bug' style like this? Anyone have some circuit advise on using these chips? I am thinking of using one in a single conversion transceiver. Mixers will be DBM using push pull digital drive so the DDS will drive a 74xx74 divider and be driven at twice the LO frequency. (several examples of such receiver front ends in recent ARRL HB's). IF will be 9mhz, I have 4 identical 9mzh filters, so will use 3 in rx if and 1 in tx. (got those filters at Dayton about 10 years ago... Clegg surplus). Was thinking of using 8051 series micro, the built in serial port will drive the AD98xx and AD99xx dds chips. Question....how do I convert the 5v digital io of the 8052 micro to the 1.8v levels used by the AD995x series, or is the DDS chip 5v compatible (on input maybe... what to do about output? especially on the bidirection serial line....) Was also thinking about maybe building the rig as a 6 meter single conversion with an HF transverter front end. What do you think of this idea? 73's WA2MZE |
I have mounted the 9850 and 9851 chips dead bug like this before. It is
an extremely painful process, but doable. Be very careful with the leads, I had one of the pins of a 9851 break off. You really only get to bend a pin once. Don't try bending it twice! I have mounted a lot of DIP and SOIC chips deadbug and have almost never had a pin come off (ok, maybe once, but it was kind of abused), but TSSOP packages such as this are more fragile. Except for the ground connections, which I bend over for direction connection to the ground, I bent every other pin either up or out a bit to get a little more space for the connections. I used #32 gauge enamel wire for interconnect. When mounting the device, pre-tin all leads in advance and tack the device in place by soldering the ground leads, and connecting the power leads via bypass caps. When making a connection to the part or wire to the chip, pre-tin the part and touch solder the part or wire to the pin. This is very difficult as the heat from the tip can melt an adjacent connected wire or part. It is easy to create solder bridges across pins. Solder wick or a solder sucker, or an exacto knife can be use to open up such a bridge as the solder is heated with a iron. Some time a bit of fresh solder with fresh flux helps undo the bridge. Patience, patience, patience! It is difficult to do, but it can be done, and the results can be quite rewarding. As far as 5v to 1.8v logic level conversions, the very simplest thing is to use a 2N7000 MOSFET transistor for each signal. The gate can be directly driven with the 5v signal, and the output can be pulled up to 1.8v with a 2.2K resistor. It is cool to deadbug with the surface mount version of these parts (SOT-23) and use a 805 size chip pull up resistor. The resulting "inverter" in very small! The signal will be inverted, but just keep that in mind when writing the software. I use the surface mount FETS (BSS123/2N7000) in the receiver diplexer in my home brew transceivers, and they don't take up much space! - Dan, N7VE kenneth scharf wrote: I just got some samples of the AD9952 and AD9954 DDS chips. Both look identical, AD9954 has some extra features I don't need but can simply not program. These parts are real small, will have to find some VERY small tweezers to bend the leads and file down a soldering tip to fit. I would try to solder all the gnd and unused inputs down to a PC ground plane and bend all the power pins up flat against the top of the chip to be soldered together. The signal pins would have to be bent up halfway and fly leads soldered on to go to the rest of the circuit on perfboard. Anybody try to breadboard one of these 'dead bug' style like this? Anyone have some circuit advise on using these chips? I am thinking of using one in a single conversion transceiver. Mixers will be DBM using push pull digital drive so the DDS will drive a 74xx74 divider and be driven at twice the LO frequency. (several examples of such receiver front ends in recent ARRL HB's). IF will be 9mhz, I have 4 identical 9mzh filters, so will use 3 in rx if and 1 in tx. (got those filters at Dayton about 10 years ago... Clegg surplus). Was thinking of using 8051 series micro, the built in serial port will drive the AD98xx and AD99xx dds chips. Question....how do I convert the 5v digital io of the 8052 micro to the 1.8v levels used by the AD995x series, or is the DDS chip 5v compatible (on input maybe... what to do about output? especially on the bidirection serial line....) Was also thinking about maybe building the rig as a 6 meter single conversion with an HF transverter front end. What do you think of this idea? 73's WA2MZE |
In article ,
says... I just got some samples of the AD9952 and AD9954 DDS chips. Both look identical, AD9954 has some extra features I don't need but can simply not program. These parts are real small, will have to find some VERY small tweezers to bend the leads and file down a soldering tip to fit. I'm a big fan of these tweezers: http://www.folica.com/removal/rubis_costwe132.htm They have the finest tips I've ever seen, and are great for working with these sorts of parts. I would try to solder all the gnd and unused inputs down to a PC ground plane and bend all the power pins up flat against the top of the chip to be soldered together. The signal pins would have to be bent up halfway and fly leads soldered on to go to the rest of the circuit on perfboard. Anybody try to breadboard one of these 'dead bug' style like this? Note that TQFP pin spacing (0.5 mm) is half that of the AD9850/AD9851 chips that Dan Tayloe mentions. Still, it can be done, and your strategy sounds reasonable. I have hand-wired several 16-pin TSSOP 0.5- mm chips by hand without losing one. Solder-wick and a fine-tipped iron are mandatory. As Dan says, you can count on being able to bend each lead only once, so make sure you get it right! On the plus side, these chips appear to be very hard to overheat in the soldering process, probably due to low lead mass and stout internal connections. You can afford to take your time. It might not be an issue with 1.8V logic, but these chips' 3.3-volt predecessors (the AD9852 and AD9854) really got hot when operated near their maximum clock speeds. On a PC board, the traces offer a definite heat-dissipation advantage over hand-wiring. Don't assume you can run these chips full tilt until you verify that they don't overheat in your dead-bug configuration. Was thinking of using 8051 series micro, the built in serial port will drive the AD98xx and AD99xx dds chips. Question....how do I convert the 5v digital io of the 8052 micro to the 1.8v levels used by the AD995x series, or is the DDS chip 5v compatible (on input maybe... what to do about output? especially on the bidirection serial line....) Just use a resistive divider. I don't see any reason to use FETs unless programming speed is a concern. (CMOS inputs look like capacitors, so resistive dividers will slow your signal edges down and limit the speed at which you can program the chip. Some CMOS parts have a minimum- risetime requirement, but I haven't bumped up against it yet personally except for Vcc pins.) I see in the data sheet that the I/O pins can be configured for 3.3V logic levels, so that might help. Was also thinking about maybe building the rig as a 6 meter single conversion with an HF transverter front end. What do you think of this idea? Sounds like a plan! -- jm ------------------------------------------------------ http://www.qsl.net/ke5fx Note: My E-mail address has been altered to avoid spam ------------------------------------------------------ |
In article ,
says... I just got some samples of the AD9952 and AD9954 DDS chips. Both look identical, AD9954 has some extra features I don't need but can simply not program. These parts are real small, will have to find some VERY small tweezers to bend the leads and file down a soldering tip to fit. I'm a big fan of these tweezers: http://www.folica.com/removal/rubis_costwe132.htm They have the finest tips I've ever seen, and are great for working with these sorts of parts. I would try to solder all the gnd and unused inputs down to a PC ground plane and bend all the power pins up flat against the top of the chip to be soldered together. The signal pins would have to be bent up halfway and fly leads soldered on to go to the rest of the circuit on perfboard. Anybody try to breadboard one of these 'dead bug' style like this? Note that TQFP pin spacing (0.5 mm) is half that of the AD9850/AD9851 chips that Dan Tayloe mentions. Still, it can be done, and your strategy sounds reasonable. I have hand-wired several 16-pin TSSOP 0.5- mm chips by hand without losing one. Solder-wick and a fine-tipped iron are mandatory. As Dan says, you can count on being able to bend each lead only once, so make sure you get it right! On the plus side, these chips appear to be very hard to overheat in the soldering process, probably due to low lead mass and stout internal connections. You can afford to take your time. It might not be an issue with 1.8V logic, but these chips' 3.3-volt predecessors (the AD9852 and AD9854) really got hot when operated near their maximum clock speeds. On a PC board, the traces offer a definite heat-dissipation advantage over hand-wiring. Don't assume you can run these chips full tilt until you verify that they don't overheat in your dead-bug configuration. Was thinking of using 8051 series micro, the built in serial port will drive the AD98xx and AD99xx dds chips. Question....how do I convert the 5v digital io of the 8052 micro to the 1.8v levels used by the AD995x series, or is the DDS chip 5v compatible (on input maybe... what to do about output? especially on the bidirection serial line....) Just use a resistive divider. I don't see any reason to use FETs unless programming speed is a concern. (CMOS inputs look like capacitors, so resistive dividers will slow your signal edges down and limit the speed at which you can program the chip. Some CMOS parts have a minimum- risetime requirement, but I haven't bumped up against it yet personally except for Vcc pins.) I see in the data sheet that the I/O pins can be configured for 3.3V logic levels, so that might help. Was also thinking about maybe building the rig as a 6 meter single conversion with an HF transverter front end. What do you think of this idea? Sounds like a plan! -- jm ------------------------------------------------------ http://www.qsl.net/ke5fx Note: My E-mail address has been altered to avoid spam ------------------------------------------------------ |
John Miles wrote:
In article , says... I just got some samples of the AD9952 and AD9954 DDS chips. Both look identical, AD9954 has some extra features I don't need but can simply not program. These parts are real small, will have to find some VERY small tweezers to bend the leads and file down a soldering tip to fit. I'm a big fan of these tweezers: http://www.folica.com/removal/rubis_costwe132.htm They have the finest tips I've ever seen, and are great for working with these sorts of parts. I would try to solder all the gnd and unused inputs down to a PC ground plane and bend all the power pins up flat against the top of the chip to be soldered together. The signal pins would have to be bent up halfway and fly leads soldered on to go to the rest of the circuit on perfboard. Anybody try to breadboard one of these 'dead bug' style like this? Note that TQFP pin spacing (0.5 mm) is half that of the AD9850/AD9851 chips that Dan Tayloe mentions. Still, it can be done, and your strategy sounds reasonable. I have hand-wired several 16-pin TSSOP 0.5- mm chips by hand without losing one. Solder-wick and a fine-tipped iron are mandatory. As Dan says, you can count on being able to bend each lead only once, so make sure you get it right! On the plus side, these chips appear to be very hard to overheat in the soldering process, probably due to low lead mass and stout internal connections. You can afford to take your time. It might not be an issue with 1.8V logic, but these chips' 3.3-volt predecessors (the AD9852 and AD9854) really got hot when operated near their maximum clock speeds. On a PC board, the traces offer a definite heat-dissipation advantage over hand-wiring. Don't assume you can run these chips full tilt until you verify that they don't overheat in your dead-bug configuration. Since I was thinking of using a fair sized piece of PC board as a ground plane to which ALL the gnd pins would get soldered to, I might have a good enough heat sink. I could also put some silicon heat sink grease on the bottom of the chip, or glue the chip down to the pc board with heat conductive epoxy. Was thinking of using 8051 series micro, the built in serial port will drive the AD98xx and AD99xx dds chips. Question....how do I convert the 5v digital io of the 8052 micro to the 1.8v levels used by the AD995x series, or is the DDS chip 5v compatible (on input maybe... what to do about output? especially on the bidirection serial line....) Just use a resistive divider. I don't see any reason to use FETs unless programming speed is a concern. (CMOS inputs look like capacitors, so resistive dividers will slow your signal edges down and limit the speed at which you can program the chip. Some CMOS parts have a minimum- risetime requirement, but I haven't bumped up against it yet personally except for Vcc pins.) I see in the data sheet that the I/O pins can be configured for 3.3V logic levels, so that might help. Was also thinking about maybe building the rig as a 6 meter single conversion with an HF transverter front end. What do you think of this idea? Sounds like a plan! -- jm ------------------------------------------------------ http://www.qsl.net/ke5fx Note: My E-mail address has been altered to avoid spam ------------------------------------------------------ |
John Miles wrote:
In article , says... I just got some samples of the AD9952 and AD9954 DDS chips. Both look identical, AD9954 has some extra features I don't need but can simply not program. These parts are real small, will have to find some VERY small tweezers to bend the leads and file down a soldering tip to fit. I'm a big fan of these tweezers: http://www.folica.com/removal/rubis_costwe132.htm They have the finest tips I've ever seen, and are great for working with these sorts of parts. I would try to solder all the gnd and unused inputs down to a PC ground plane and bend all the power pins up flat against the top of the chip to be soldered together. The signal pins would have to be bent up halfway and fly leads soldered on to go to the rest of the circuit on perfboard. Anybody try to breadboard one of these 'dead bug' style like this? Note that TQFP pin spacing (0.5 mm) is half that of the AD9850/AD9851 chips that Dan Tayloe mentions. Still, it can be done, and your strategy sounds reasonable. I have hand-wired several 16-pin TSSOP 0.5- mm chips by hand without losing one. Solder-wick and a fine-tipped iron are mandatory. As Dan says, you can count on being able to bend each lead only once, so make sure you get it right! On the plus side, these chips appear to be very hard to overheat in the soldering process, probably due to low lead mass and stout internal connections. You can afford to take your time. It might not be an issue with 1.8V logic, but these chips' 3.3-volt predecessors (the AD9852 and AD9854) really got hot when operated near their maximum clock speeds. On a PC board, the traces offer a definite heat-dissipation advantage over hand-wiring. Don't assume you can run these chips full tilt until you verify that they don't overheat in your dead-bug configuration. Since I was thinking of using a fair sized piece of PC board as a ground plane to which ALL the gnd pins would get soldered to, I might have a good enough heat sink. I could also put some silicon heat sink grease on the bottom of the chip, or glue the chip down to the pc board with heat conductive epoxy. Was thinking of using 8051 series micro, the built in serial port will drive the AD98xx and AD99xx dds chips. Question....how do I convert the 5v digital io of the 8052 micro to the 1.8v levels used by the AD995x series, or is the DDS chip 5v compatible (on input maybe... what to do about output? especially on the bidirection serial line....) Just use a resistive divider. I don't see any reason to use FETs unless programming speed is a concern. (CMOS inputs look like capacitors, so resistive dividers will slow your signal edges down and limit the speed at which you can program the chip. Some CMOS parts have a minimum- risetime requirement, but I haven't bumped up against it yet personally except for Vcc pins.) I see in the data sheet that the I/O pins can be configured for 3.3V logic levels, so that might help. Was also thinking about maybe building the rig as a 6 meter single conversion with an HF transverter front end. What do you think of this idea? Sounds like a plan! -- jm ------------------------------------------------------ http://www.qsl.net/ke5fx Note: My E-mail address has been altered to avoid spam ------------------------------------------------------ |
kenneth scharf writes:
Was thinking of using 8051 series micro, the built in serial port will drive the AD98xx and AD99xx dds chips. Question....how do I convert the 5v digital io of the 8052 micro to the 1.8v levels used by the AD995x series, or is the DDS chip 5v compatible (on input maybe... what to do about output? especially on the bidirection serial line....) The IO lines are 3.3volt compatible-- there is a pin for that. You can get 8052 that run fine on 3.3 volts, or you can use resistors to divide down. VHC logid (and others) can also translate down just fin. 73's WA2MZE -- Steven D. Swift, , http://www.novatech-instr.com NOVATECH INSTRUMENTS, INC. P.O. Box 55997 206.301.8986, fax 206.363.4367 Seattle, Washington 98155 USA |
kenneth scharf writes:
Was thinking of using 8051 series micro, the built in serial port will drive the AD98xx and AD99xx dds chips. Question....how do I convert the 5v digital io of the 8052 micro to the 1.8v levels used by the AD995x series, or is the DDS chip 5v compatible (on input maybe... what to do about output? especially on the bidirection serial line....) The IO lines are 3.3volt compatible-- there is a pin for that. You can get 8052 that run fine on 3.3 volts, or you can use resistors to divide down. VHC logid (and others) can also translate down just fin. 73's WA2MZE -- Steven D. Swift, , http://www.novatech-instr.com NOVATECH INSTRUMENTS, INC. P.O. Box 55997 206.301.8986, fax 206.363.4367 Seattle, Washington 98155 USA |
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