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Discussion Groups | M68HC11 | High speed switch
Technical discussions about Freescale Microcontrollers: M68HC11. (Freescale Semiconductor is a Subsidiary of Motorola).
High speed switch - PFC - Feb 10 12:15:00 2005
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Dear forum, In a current project I need to switch 25volt signal lines (approx 30mA) using port pins of the HC11 (TTL). The 25V signal needs to be switched at frequencies up to 1.5MHz square wave. I have used a MC33152 high speed h-bridge to switch these lines but the maximum voltage for these devices are 16V. Anyone know of a similar device or circuit which will allow switching of a square wave at 1.5MHz and 25V? All assistance appreciated. PFC. [Non-text portions of this message have been removed] |
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Re: High speed switch - Bob Smith - Feb 10 12:51:00 2005
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You should only need 1/2 bridge drivers, not a full H bridge. See http://www.irf.com amoung others. Bob --- Avoid computer viruses, Practice safe hex --- -- Specializing in small, cost effective embedded control systems -- http://www.smithmachineworks.com/embedprod.html Robert L. (Bob) Smith Smith Machine Works, Inc. 9900 Lumlay Road Richmond, VA 23236 804/745-2608 ----- Original Message ----- From: "PFC" <> To: <> Sent: Thursday, February 10, 2005 11:15 AM Subject: [m68HC11] High speed switch > Dear forum, > In a current project I need to switch 25volt signal lines (approx 30mA) using port pins of the HC11 (TTL). The 25V signal needs to be switched at frequencies up to 1.5MHz square wave. I have used a MC33152 high speed h-bridge to switch these lines but the maximum voltage for these devices are 16V. Anyone know of a similar device or circuit which will allow switching of a square wave at 1.5MHz and 25V? > All assistance appreciated. > PFC. > > > [Non-text portions of this message have been removed] > Yahoo! Groups Sponsor > ADVERTISEMENT > -------------------------------------------------------------------------- ------ > Yahoo! Groups Links > > a.. To |
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Re: High speed switch - Paul B. Webster - Feb 10 18:44:00 2005
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On Thu, 2005-02-10 at 11:51 -0500, Bob Smith wrote: > You should only need 1/2 bridge drivers, not a full H bridge. Well of course, the MC33152 as mentioned is specifically designed for this very purpose, two lines per device, except of course, that it is only rated for operation up to 18V. It's basically a dual high-power Schmitt level-shifting non-inverting buffer. http://www.onsemi.com/pub/Collateral/MC34152-D.PDF Are not most H-bridges configured similarly? -- Cheers, Paul B. |
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Re: High speed switch - Jim Peterson - Feb 10 20:01:00 2005
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Paul, the second line of the description reads: "These devices feature low input current making them CMOS/LSTTL logic compatible, input hysteresis for fast output switching that is independent of input transition time, and two high current totem pole outputs ideally suited for driving power MOSFETs." Wouldn't you merely need to find MOSFET transisters of sufficient capacity to actually switch your higher voltage circuit? Figure 20 in the PDF has an example... hth, Jim Paul B. Webster wrote: >On Thu, 2005-02-10 at 11:51 -0500, Bob Smith wrote: >>You should only need 1/2 bridge drivers, not a full H bridge. >> >> > > Well of course, the MC33152 as mentioned is specifically designed for >this very purpose, two lines per device, except of course, that it is >only rated for operation up to 18V. It's basically a dual high-power >Schmitt level-shifting non-inverting buffer. > >http://www.onsemi.com/pub/Collateral/MC34152-D.PDF > > Are not most H-bridges configured similarly? [Non-text portions of this message have been removed] |
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Re: High speed switch - PFC - Feb 11 4:04:00 2005
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Forum, To ensure the signal lines rise to 25V and then fall to zero (or near zero) I use one side of the full bridge per line. To use a Fet on each half I would need to place two Fets on each data line. The circuit now grows and grows. I was looking for something similar to the MC33152 with higher supply voltage. PFC. ----- Original Message ----- From: "Jim Peterson" <> To: <> Sent: Friday, February 11, 2005 12:01 AM Subject: Re: [m68HC11] High speed switch > > Paul, > the second line of the description reads: > > "These devices feature low input current making them CMOS/LSTTL logic > compatible, input hysteresis for fast output switching that is > independent of input transition time, and two high current totem pole > outputs ideally suited for driving power MOSFETs." > > Wouldn't you merely need to find MOSFET transisters of sufficient > capacity to actually switch your higher voltage circuit? > > Figure 20 in the PDF has an example... > > hth, > Jim > Paul B. Webster wrote: > > >On Thu, 2005-02-10 at 11:51 -0500, Bob Smith wrote: > > > > > >>You should only need 1/2 bridge drivers, not a full H bridge. > >> > >> > > > > Well of course, the MC33152 as mentioned is specifically designed for > >this very purpose, two lines per device, except of course, that it is > >only rated for operation up to 18V. It's basically a dual high-power > >Schmitt level-shifting non-inverting buffer. > > > >http://www.onsemi.com/pub/Collateral/MC34152-D.PDF > > > > Are not most H-bridges configured similarly? > > > > > > [Non-text portions of this message have been removed] > > > Yahoo! Groups Links |
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Re: High speed switch - Paul B. Webster - Feb 11 12:52:00 2005
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On Thu, 2005-02-10 at 19:01 -0500, Jim Peterson wrote: > Wouldn't you merely need to find MOSFET transistors of sufficient > capacity to actually switch your higher voltage circuit? As you will note, I was not the original enquirer, who specifies that these are for driving "signal lines", not a motor. Driving capacitive transmission lines is not dissimilar to driving the capacitive gate of a power MOSFET, so I think he had the device correctly picked, but for, as he goes on to say, the voltage rating. In an effort to be lateral, and also from sheer and utter curiosity, I do have to ask what these "signal lines" might be and what is the significance of 25V rather than 18? -- Cheers, Paul B. |
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Re: High speed switch - Gordon Couger - Feb 12 21:12:00 2005
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A FET should work fine but a 68HC11 will not work at 1 1.5 MHz output switching frequency vvery well even over clocked to 4 MHz eclock 16 MHz Xtal frequency it takes 3 eclock cycles to get the output compare interrupt set so things would be rater messy at 1.5 MHz. Unless you use some added stuff you will have a lot of jitter and latency problems contorting over 1/4 of the eclock frequency. even at that speed thing will not be very nice and you won't have any room for much else. Gordon Couger Stillwater, OK www.couger.com/gcouger PFC wrote: > Dear forum, > In a current project I need to switch 25volt signal lines (approx 30mA) using port pins of the HC11 (TTL). The 25V signal needs to be switched at frequencies up to 1.5MHz square wave. I have used a MC33152 high speed h-bridge to switch these lines but the maximum voltage for these devices are 16V. Anyone know of a similar device or circuit which will allow switching of a square wave at 1.5MHz and 25V? > All assistance appreciated. > PFC. > > > [Non-text portions of this message have been removed] > > > Yahoo! Groups Links |
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Re: High speed switch - PFC - Feb 14 4:25:00 2005
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Forum, Answer to PaulB. The application is connecting into an existing 485 comms channel. Answer to Gorden Couger: The frequency is 1M5Hz through a driver which cleans up the HC11 output. PFC. ----- Original Message ----- From: "Paul B. Webster" <> To: <> Sent: Friday, February 11, 2005 4:52 PM Subject: Re: [m68HC11] High speed switch > > On Thu, 2005-02-10 at 19:01 -0500, Jim Peterson wrote: > > Wouldn't you merely need to find MOSFET transistors of sufficient > > capacity to actually switch your higher voltage circuit? > > As you will note, I was not the original enquirer, who specifies that > these are for driving "signal lines", not a motor. Driving capacitive > transmission lines is not dissimilar to driving the capacitive gate of a > power MOSFET, so I think he had the device correctly picked, but for, as > he goes on to say, the voltage rating. > > In an effort to be lateral, and also from sheer and utter curiosity, > I do have to ask what these "signal lines" might be and what is the > significance of 25V rather than 18? > > -- > Cheers, > Paul B. > > > Yahoo! Groups Links |
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