EngineerZone: Message List

Unused pins on AD9913

analogvm-admin@analog-vm.hosted.jivesoftware.com — Thu, 15 Nov 2012 21:37:54 GMT

Hi. I would like to use only the serial port on the AD9913. Also, I do not need multiple profiles. In this case, what should be done with the parallel port and profile select pins (ADR0/D0, ADR1/D1, ADR2/D2, PS0/ADR3/D3, PS1/ADR4/D4, PS2/ADR5/D5, ADR6/D6, ADR7/D7)?

Thanks.

AD8488 and charge amplifiers in general

analogvm-admin@analog-vm.hosted.jivesoftware.com — Wed, 27 Jun 2012 18:59:59 GMT

I'm working on an ion detector for a time-resolved mass spectrometer. The detector will employ a simple Faraday cup. Expected ion currents are in the range of 10 fA to 1 pA with a bandwidth of approximately 50 kHz.

The bandwidth makes this a difficult problem. For DC or low bandwidth applications a high-gain transimpedance amplifier is typically used. For our application a charge integrating amplifier is more appropriate.

The AD8488 has a charge amplifier front-end (well, 128 of them). Its minimum feedback capacitance of 0.45 pF would give us the gain we need. Can the AD8488 be used as a single-channel charge integrator with a reset every 5 ms?

Besides the AD8488, are there amps which are appropriate to this application (e.g. FET input, very low input bias current, very low noise)? Some off-the-shelf solutions (often called "charge sensitive preamplifiers") are hybrids that employ a discrete input FET (sometimes cooled). Any suggestions in this regard would also be appreciated.

Thanks.

http://www.analog.com/en/specialty-amplifiers/charge-integrator-amplifiers/ad8488/products/product.html#

AD9517 Jitter and AD9434 500 MSPS ADC

analogvm-admin@analog-vm.hosted.jivesoftware.com — Wed, 14 Dec 2011 17:08:11 GMT

My application will have two AD9434 12-bit, 500 MSPS ADCs running in parallel. The sample rate needs to be programmable in the range of 100 MHz - 500 MHz. I'm considering the AD9517 clock generator since it is used on the AD9434 evaluation board.

I'm trying to understand the jitter characteristics of the AD9517. The datasheet has tables for absolute and additive jitter. I'll likely use an external VCXO followed by the dividers in the AD9517. How do I estimate the total jitter? Is this simply the absolute jitter or do I add the absolute and additive?

Is there another clock generator that I should consider that may be more appropriate for my application?

Note that the input reference to the clock generator will be provided by a FPGA so its frequency will be programmable.

Andy

Re: AD9524 Unused Inputs and Outputs

analogvm-admin@analog-vm.hosted.jivesoftware.com — Tue, 13 Dec 2011 14:02:42 GMT

Matt,

Thanks!

Andy

Re: ADL5202 Input Transformer

analogvm-admin@analog-vm.hosted.jivesoftware.com — Tue, 13 Dec 2011 14:01:12 GMT

Jim,

Thanks a lot. I'll do what you suggested (which is also the approach on the ADL5202 eveluation board).

However, I would appreciate a comment in regard to the points brought up in the two articles I referenced. Specifically, the amplitude and phase imbalance induced by a transformer and their effect on SFDR. Is this only a problem at very low frequencies?

Andy

http://www.analog.com/library/analogDialogue/archives/39-04/transformer.html

http://www.analog.com/library/analogDialogue/archives/40-07/transformer.html

Re: AD9524 Unused Inputs and Outputs

analogvm-admin@analog-vm.hosted.jivesoftware.com — Tue, 13 Dec 2011 13:38:18 GMT

Matt,

The unused pins I'm asking about are REFB+, REFB-, ZD_IN+, and ZD_IN-. I'm using REFA+ and REFA- as the reference input so REFB+ and REFB- are unused. Also, I am not using the zero-delay inputs ZD_IN+ and ZD_IN-.

Andy

ADL5202 Input Transformer

analogvm-admin@analog-vm.hosted.jivesoftware.com — Tue, 13 Dec 2011 02:10:36 GMT

What is the best transformer configuration for single-ended to differential conversion into the ADL5202 in a broadband application (10 - 250 MHz)?

Its datasheet examples show a standard transformer while its evaluation board employs a transformer with a center-tapped secondary. The two articles referenced below discuss the advantages of a two-balun transfomer scheme (granted there is power loss in this case). Which apparoach best suits the ADL5202 in a wide band application? Thanks.

http://www.analog.com/library/analogDialogue/archives/39-04/transformer.html

http://www.analog.com/library/analogDialogue/archives/40-07/transformer.html

AD9524 Unused Inputs and Outputs

analogvm-admin@analog-vm.hosted.jivesoftware.com — Mon, 12 Dec 2011 22:57:00 GMT

Hello. What should be done with the REFB+/- and ZD_IN+/- inputs if they are unused? How about unused OUT+/- pins? Thanks.

Re: ADL5202 Unused Inputs

analogvm-admin@analog-vm.hosted.jivesoftware.com — Wed, 30 Nov 2011 19:14:56 GMT

Thanks!

ADL5202 Unused Inputs

analogvm-admin@analog-vm.hosted.jivesoftware.com — Wed, 30 Nov 2011 18:20:10 GMT

If using the SPI control interface on the ADL5202 can the unused parallel and up/down control inputs simply be tied to ground? Thanks.