PIN Diode Driver (8-channel) - Revision history

Dstraney: sense input current

2021-05-12T11:11:14Z

sense input current

← Older revision		Revision as of 06:11, 12 May 2021
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	# As a stand-alone load on the scanner's line: populate D2, and make sure D1 and R1 are removed		# As a stand-alone load on the scanner's line: populate D2, and make sure D1 and R1 are removed
	[[File:PIN_diode_driver_8x-conn-input-direct.png]]		[[File:PIN_diode_driver_8x-conn-input-direct.png]]
	: The sense input is electrically isolated from the rest of the circuitry and so there should be no sense connection concerns with ground loops, etc.		: The sense input is turned on by ~110 mA, to match the typical Siemens bias line current. It's electrically isolated from the rest of the circuitry and so there should be no sense connection concerns with ground loops, etc.
	Outputs can be combined into a single 800 mA output, by populating the 16 jumpers (0603-size) along the bottom edge of the PCB, and using the larger output through-hole connections near the bottom-left edge.		Outputs can be combined into a single 800 mA output, by populating the 16 jumpers (0603-size) along the bottom edge of the PCB, and using the larger output through-hole connections near the bottom-left edge.

Jaystock: /* Overview */

2020-09-17T18:47:54Z

Overview

← Older revision		Revision as of 13:47, 17 September 2020
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	[[File:PIN_diode_driver_8x.JPG\|1200px]]<br />		[[File:PIN_diode_driver_8x.JPG\|1200px]]<br />
	This PIN diode driver is intended to allow new RF coil designs to use more PIN diode channels than the Siemens scanners provide, especially for high-channel-count coil designs. Mounted to an RF coil, it takes on/off input control from an existing PIN diode line from the scanner, and drives the 8 channels in sync with the scanner's PIN diode line.		This PIN diode driver is intended to allow new RF coil designs to use more PIN diode channels than the Siemens scanners provide, especially for high-channel-count coil designs. Mounted to an RF coil, it takes on/off input control from an existing PIN diode line from the scanner, and drives the 8 channels in sync with the scanner's PIN diode line.

			Work contributed by Don Straney, Staff Electrical Engineer for the Martinos Center

	== Using the drivers ==		== Using the drivers ==

Lcravenbrightman at 16:21, 4 August 2020

2020-08-04T16:21:56Z

← Older revision		Revision as of 11:21, 4 August 2020
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	== Overview ==		== Overview ==
	[[File:PIN_diode_driver_8x.JPG\|~~1000px~~]]<br />		[[File:PIN_diode_driver_8x.JPG\|1200px]]<br />
	This PIN diode driver is intended to allow new RF coil designs to use more PIN diode channels than the Siemens scanners provide, especially for high-channel-count coil designs. Mounted to an RF coil, it takes on/off input control from an existing PIN diode line from the scanner, and drives the 8 channels in sync with the scanner's PIN diode line.		This PIN diode driver is intended to allow new RF coil designs to use more PIN diode channels than the Siemens scanners provide, especially for high-channel-count coil designs. Mounted to an RF coil, it takes on/off input control from an existing PIN diode line from the scanner, and drives the 8 channels in sync with the scanner's PIN diode line.

Lcravenbrightman: /* Overview */

2020-08-04T16:19:34Z

Overview

← Older revision		Revision as of 11:19, 4 August 2020
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	== Overview ==		== Overview ==
	[[File:PIN_diode_driver_8x.JPG]]<br />		[[File:PIN_diode_driver_8x.JPG\|1000px]]<br />
	This PIN diode driver is intended to allow new RF coil designs to use more PIN diode channels than the Siemens scanners provide, especially for high-channel-count coil designs. Mounted to an RF coil, it takes on/off input control from an existing PIN diode line from the scanner, and drives the 8 channels in sync with the scanner's PIN diode line.		This PIN diode driver is intended to allow new RF coil designs to use more PIN diode channels than the Siemens scanners provide, especially for high-channel-count coil designs. Mounted to an RF coil, it takes on/off input control from an existing PIN diode line from the scanner, and drives the 8 channels in sync with the scanner's PIN diode line.

Dstraney: Added version 1.2 files, w/notes on automated assembly service

2020-07-01T15:26:09Z

Added version 1.2 files, w/notes on automated assembly service

← Older revision		Revision as of 10:26, 1 July 2020
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	== Design files ==		== Design files ==
	Design files were created in KiCAD 5		Design files were created in KiCAD 5<br />
	[[Media:PIN_driver_8x_1.1.1.zip]]		[[Media:PIN_driver_8x_1.1.1.zip]]<br />
			[[Media:PIN_driver_8x_1.2.zip]] Contains assembly files for automated assembly, through PCB Universe or another service

Dstraney at 22:43, 25 June 2020

2020-06-25T22:43:14Z

← Older revision		Revision as of 17:43, 25 June 2020
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	'''Part substitutions''' are possible if some of the specific part numbers used in this design become unavailable. See "0 parts substitution notes.txt" in the design files.		'''Part substitutions''' are possible if some of the specific part numbers used in this design become unavailable. See "0 parts substitution notes.txt" in the design files.
	<br />There are inductors in series with each input power lines to serve as '''RF blocks'''; a high-impedance parallel resonant configuration was not possible due to the unexpectedly large/unpredictable parasitic capacitances. However, these still do provide some impedance at 100-300 Mhz.		<br />There are inductors in series with each input power lines to serve as '''RF blocks'''; a high-impedance parallel resonant configuration was not possible due to the unexpectedly large/unpredictable parasitic capacitances. However, these still do provide some impedance at 100-300 Mhz.
	'''Switching speed''' is slow, with up to 10µs turn-off time depending on configuration (8µs measured with a single large Macom PIN diode typically used for transmit switching in the RF Lab's coils). Because the Siemens scanner allows ~100µs for the switching to happen, this design is optimized for fairly low parts count, low off-state power, and robust design rather than switching speed.		<br />'''Switching speed''' is slow, with up to 10µs turn-off time depending on configuration (8µs measured with a single large Macom PIN diode typically used for transmit switching in the RF Lab's coils). Because the Siemens scanner allows ~100µs for the switching to happen, this design is optimized for fairly low parts count, low off-state power, and robust design rather than switching speed.

	== Design files ==		== Design files ==
	Design files were created in KiCAD 5		Design files were created in KiCAD 5
	[[Media:PIN_driver_8x_1.1.1.zip]]		[[Media:PIN_driver_8x_1.1.1.zip]]

Dstraney: Added notes on switching speed

2020-06-25T22:42:45Z

Added notes on switching speed

← Older revision		Revision as of 17:42, 25 June 2020
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	'''Part substitutions''' are possible if some of the specific part numbers used in this design become unavailable. See "0 parts substitution notes.txt" in the design files.		'''Part substitutions''' are possible if some of the specific part numbers used in this design become unavailable. See "0 parts substitution notes.txt" in the design files.
	<br />There are inductors in series with each input power lines to serve as '''RF blocks'''; a high-impedance parallel resonant configuration was not possible due to the unexpectedly large/unpredictable parasitic capacitances. However, these still do provide some impedance at 100-300 Mhz.		<br />There are inductors in series with each input power lines to serve as '''RF blocks'''; a high-impedance parallel resonant configuration was not possible due to the unexpectedly large/unpredictable parasitic capacitances. However, these still do provide some impedance at 100-300 Mhz.
			'''Switching speed''' is slow, with up to 10µs turn-off time depending on configuration (8µs measured with a single large Macom PIN diode typically used for transmit switching in the RF Lab's coils). Because the Siemens scanner allows ~100µs for the switching to happen, this design is optimized for fairly low parts count, low off-state power, and robust design rather than switching speed.

	== Design files ==		== Design files ==
	Design files were created in KiCAD 5		Design files were created in KiCAD 5
	[[Media:PIN_driver_8x_1.1.1.zip]]		[[Media:PIN_driver_8x_1.1.1.zip]]

Dstraney at 23:46, 16 March 2020

2020-03-16T23:46:50Z

← Older revision		Revision as of 18:46, 16 March 2020
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	* Protection consists of two SMT fuses, one for +5V and one for -15V, and "resettable" PTC fuses in the reverse-bias drivers.		* Protection consists of two SMT fuses, one for +5V and one for -15V, and "resettable" PTC fuses in the reverse-bias drivers.
	* The +5V fuse is a Schurter [https://www.digikey.com/product-detail/en/schurter-inc/3413-0219-22/486-1147-1-ND/1522979 3413.0219.22], but any 1206-size 2A fast-blow fuse will work. The -15V fuse is a Schurter [https://www.digikey.com/product-detail/en/schurter-inc/3413-0213-22/486-1141-1-ND/1522973 3413.0213.22], but any 1206-size 0.2A to 0.5A fast-blow fuse will work.		* The +5V fuse is a Schurter [https://www.digikey.com/product-detail/en/schurter-inc/3413-0219-22/486-1147-1-ND/1522979 3413.0219.22], but any 1206-size 2A fast-blow fuse will work. The -15V fuse is a Schurter [https://www.digikey.com/product-detail/en/schurter-inc/3413-0213-22/486-1141-1-ND/1522973 3413.0213.22], but any 1206-size 0.2A to 0.5A fast-blow fuse will work.
	* A red LED (one for each fuse) will light if power is applied and one of the power input fuses is blown. This can happen due to reversed power supply polarity/incorrect power supply connection, power supply over-voltage, or shorted outputs. The fuses can be de-soldered and new ones soldered in place ~~(see BOM for part numbers)~~; it is not worth the extra size/space, risk of eddy currents or image artifacts, etc. to use replaceable fuses as there are few opportunities to blow the fuses through user error once the PIN drivers are incorporated into a permanent setup.		* A red LED (one for each fuse) will light if power is applied and one of the power input fuses is blown. This can happen due to reversed power supply polarity/incorrect power supply connection, power supply over-voltage, or shorted outputs. The fuses can be de-soldered and new ones soldered in place; it is not worth the extra size/space, risk of eddy currents or image artifacts, etc. to use replaceable fuses as there are few opportunities to blow the fuses through user error once the PIN drivers are incorporated into a permanent setup.
	* Do not replace the fuses with solid jumpers! This would likely cause parts to overheat and catch on fire in case of a fault, instead of a safe blown fuse to replace.		* Do not replace the fuses with solid jumpers! This would likely cause parts to overheat and catch on fire in case of a fault, instead of a safe blown fuse to replace.
	Power connections are through a 2x2 Molex Mini-Fit Jr. connector. The pinout for this connector is shown on the top-side PCB silkscreen text next to the connector pins.		Power connections are through a 2x2 Molex Mini-Fit Jr. connector. The pinout for this connector is shown on the top-side PCB silkscreen text next to the connector pins.
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	* If a higher reverse bias is desired, change or remove the 15V TVS diode D6. The largest limitation on the reverse-bias voltage is the 30V rating of the BAT54H Schottky diodes: in operation they see about 15V+5V=20V. I wouldn't recommend using any more than -20V reverse-bias. If the BAT54H parts are replaced with a similar small-signal Schottky diode with a higher voltage rating, the driver could tolerate up to -30V reverse-bias (limited by the MMBT2222 output transistors).		* If a higher reverse bias is desired, change or remove the 15V TVS diode D6. The largest limitation on the reverse-bias voltage is the 30V rating of the BAT54H Schottky diodes: in operation they see about 15V+5V=20V. I wouldn't recommend using any more than -20V reverse-bias. If the BAT54H parts are replaced with a similar small-signal Schottky diode with a higher voltage rating, the driver could tolerate up to -30V reverse-bias (limited by the MMBT2222 output transistors).
	'''Part substitutions''' are possible if some of the specific part numbers used in this design become unavailable. See "0 parts substitution notes.txt" in the design files.		'''Part substitutions''' are possible if some of the specific part numbers used in this design become unavailable. See "0 parts substitution notes.txt" in the design files.
	There are inductors in series with each input power lines to serve as '''RF blocks'''; a high-impedance parallel resonant configuration was not possible due to the unexpectedly large/unpredictable parasitic capacitances. However, these still do provide some impedance at 100-300 Mhz.		<br />There are inductors in series with each input power lines to serve as '''RF blocks'''; a high-impedance parallel resonant configuration was not possible due to the unexpectedly large/unpredictable parasitic capacitances. However, these still do provide some impedance at 100-300 Mhz.

	== Design files ==		== Design files ==
	Design files were created in KiCAD 5		Design files were created in KiCAD 5
	[[Media:PIN_driver_8x_1.1.1.zip]]		[[Media:PIN_driver_8x_1.1.1.zip]]

Dstraney: first draft content for all sections

2020-03-16T23:43:39Z

first draft content for all sections

@@ Line 1: / Line 1: @@
 == Overview ==
 == Using the drivers ==
-== Repair notes ==
+The PIN driver can operate continuously with all channels on, at full current, without being damaged; however it does generate a reasonable amount of heat, so don't put it inside a closed box.  Mounting an insulating sheet of plastic/fiberglass/etc. 10 mm above the top of the PCB is reasonable though, to keep conductive objects and dust from falling on it.
 == Design files ==

Dstraney: Usage, repair, and build information for 8-channel PIN diode drivers

2020-03-06T14:48:20Z

Usage, repair, and build information for 8-channel PIN diode drivers

New page

== Overview ==

== Using the drivers ==

== Repair notes ==

== Design files ==