BIRD 45

Here is a proposal in response to a new clamping structure
that needs to be modeled.

Regards,
Neven

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BIRD ID#: 45
ISSUE TITLE: Dynamic Clamps
REQUESTER: Neven Orhanovic and Bob Ross, Interconnectix
DATE SUBMITTED: 10/31/97
DATE ACCEPTED BY IBIS OPEN FORUM:

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STATEMENT OF THE ISSUE:

A novel type of termination technique is used in today's integrated circuits.
The termination consists of a pair of built in dynamic clamps whose V-I
curves change with time. The clamp is switched "on" when needed and switched
"off" otherwise (to conserve power). When the clamp is switched "on" its V-I
curve provides more clamping than a regular static clamp and when it is
turned "off" it behaves like a normal clamp.

The "on" switching of the dynamic clamps can be triggered by an input signal
crossing a triggering threshold or by some external clock. The "off" switching
can be triggered by a built in timer or an external clock.

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STATEMENT OF THE RESOLVED SPECIFICATIONS:

The [Dynamic GND Clamp] and [Dynamic POWER Clamp] keywords are introduced
under the [Model] keyword to describe dynamic ground and power clamps,
respectively.

|==============================================================================
| Keywords: [Dynamic GND Clamp], [Dynamic POWER Clamp]
| Required: No.
| Description: Describes ground and power clamps that are switched on and off
| dynamically.
|
| Subparameters: V_trigger, V_offset,
| T_delay, T_on, T_width, T_off.
|
| Usage Rules: The [Dynamic GND Clamp] specification consists of a set of
| subparameters describing the switching characteristics of
| the clamp and a V-I curve (table). The V-I table describes
| the dynamic clamp in its "off" state. The voltages in it
| are referenced to the corresponding rail voltage (using
| the same rules as the regular ground and power clamps,
| [GND_clamp] and [POWER_clamp]). When the clamp is in its
| "on" state, the V-I curve is offset by the offset voltage
| amplitude, V_offset, described below. The switching
| characteristics are described by the following
| subparameters.
|
| V_trigger - input threshold voltage at which the dynamic
| clamp turns on. This voltage is expressed
| relative to the corresponding rail voltage.
|
| V_offset - the voltage by which the V-I curve is shifted
| in its on state.
|
| T_delay - delay time from the input crossing V_trigger
| to the beginning of the clamp turn "off" to
| "on" transition.
|
| T_on - the time it takes the clamp to transition from
| "off" to "on".
|
| T_off - the time it takes the clamp to transition from
| "on" to "off".
|
| T_width - the time during which the clamp is in its "on"
| state.
|
| These subparameters are and the resulting V-I characteristics
| of the dynamic clamp are illustrated below.
|
|
| Clamp input voltage vs. time.
|
| o o o o o
| o
| o
| o -------
| o| ^
| o | | V_trigger
| o | v time
| o o | ------- -------->
| |
| |
| | Clamp offset voltage vs. time.
| |
| | T_width
| | |<----------->|
| |
| | o o o o o o o o ---
| | o o ^
| | o o |
| | o o | V_offset
| | o o |
| | o o v time
| o o o o o o o o o o -------->
|
| T_delay
| |<----->| T_on T_off
| |<--->| |<--->|
|
|
| Clamp V-I characteristics (e.g., [Dynamic GND Clamp]):
|
| ^ I
| |
| |
| |
| |
| o o o o---x-x-x---------------> V
| o x
| o x
|
| o x <--Clamp V-I curve when in "on" state
|
| o <-- Clamp V-I curve when in "off" state
|
|------------------------------------------------------------------------------
|
| Example:
|
[Dynamic GND Clamp]
|
V_trigger = 0.4 V
V_offset = 0.9 V
T_delay = 0.5 ns
T_on = 1 ns
T_width = 6 ns
T_off = 1 ns
|
| Voltage I(typ) I(min) I(max)
|
    -5.000 -3.300e+01 -3.000e+01 -3.500e+01
    -4.000 -2.300e+01 -2.200e+01 -2.400e+01
    -3.000 -1.300e+01 -1.200e+01 -1.400e+01
    -2.000 -3.000e+00 -2.300e+00 -3.700e+00
    -1.900 -2.100e+00 -1.500e+00 -2.800e+00
    -1.800 -1.300e+00 -8.600e-01 -1.900e+00
    -1.700 -6.800e-01 -4.000e-01 -1.100e+00
    -1.600 -2.800e-01 -1.800e-01 -5.100e-01
    -1.500 -1.200e-01 -9.800e-02 -1.800e-01
    -1.400 -7.500e-02 -7.100e-02 -8.300e-02
    -1.300 -5.750e-02 -5.700e-02 -5.900e-02
    -1.200 -4.600e-02 -4.650e-02 -4.550e-02
    -1.100 -3.550e-02 -3.700e-02 -3.450e-02
    -1.000 -2.650e-02 -2.850e-02 -2.500e-02
    -0.900 -1.850e-02 -2.100e-02 -1.650e-02
    -0.800 -1.200e-02 -1.400e-02 -9.750e-03
    -0.700 -6.700e-03 -8.800e-03 -4.700e-03
    -0.600 -3.000e-03 -4.650e-03 -1.600e-03
    -0.500 -9.450e-04 -1.950e-03 -3.650e-04
    -0.400 -5.700e-05 -2.700e-04 -5.550e-06
    -0.300 -1.200e-06 -1.200e-05 -5.500e-08
    -0.200 -3.000e-08 -5.000e-07 0.000e+00
    -0.100 0.000e+00 0.000e+00 0.000e+00
     0.000 0.000e+00 0.000e+00 0.000e+00
     5.000 0.000e+00 0.000e+00 0.000e+00
|
|
[Dynamic POWER Clamp]
|
V_trigger = -0.4 V
V_offset = -0.9 V
T_delay = 0.5 ns
T_on = 1 ns
T_width = 6 ns
T_off = 1 ns
|
| Voltage I(typ) I(min) I(max)
|
    -5.000 1.150e+01 1.100e+01 1.150e+01
    -4.000 7.800e+00 7.500e+00 8.150e+00
    -3.000 4.350e+00 4.100e+00 4.700e+00
    -2.000 1.100e+00 8.750e-01 1.300e+00
    -1.900 8.000e-01 6.050e-01 1.000e+00
    -1.800 5.300e-01 3.700e-01 7.250e-01
    -1.700 2.900e-01 1.800e-01 4.500e-01
    -1.600 1.200e-01 6.850e-02 2.200e-01
    -1.500 3.650e-02 2.400e-02 6.900e-02
    -1.400 1.200e-02 1.100e-02 1.600e-02
    -1.300 6.300e-03 6.650e-03 6.100e-03
    -1.200 4.200e-03 4.750e-03 3.650e-03
    -1.100 2.900e-03 3.500e-03 2.350e-03
    -1.000 1.900e-03 2.450e-03 1.400e-03
    -0.900 1.150e-03 1.600e-03 7.100e-04
    -0.800 5.500e-04 9.150e-04 2.600e-04
    -0.700 1.200e-04 4.400e-04 5.600e-05
    -0.600 5.400e-05 1.550e-04 1.200e-05
    -0.500 1.350e-05 5.400e-05 1.300e-06
    -0.400 8.650e-07 7.450e-06 4.950e-08
    -0.300 6.250e-08 7.550e-07 0.000e+00
    -0.200 0.000e+00 8.400e-08 0.000e+00
    -0.100 0.000e+00 0.000e-08 0.000e+00
     0.000 0.000e+00 0.000e+00 0.000e+00
|
|==============================================================================

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ANALYSIS PATH/DATA THAT LED TO SPECIFICATION:

The proposal is designed to retain as much of the existing IBIS clamp syntax
as possible. The dynamic clamp V-I curve tables follow all of the
conventions of the existing V-I tables.

The overall structure is to connect a dynamic clamp to the same rail
voltage as its corresponding regular clamp. The dynamic clamps V-I
curve is shifted according to the offset voltage pulse.

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ANY OTHER BACKGROUND INFORMATION:

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Received on Fri Oct 31 18:11:07 1997