BIRD 45.1 -- Dynamic clamps

Dear IBIS folks:

Here is a revision of BIRD 45 with changes that incorporate
most of your feedback.

--Neven

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BIRD ID#: 45.1
ISSUE TITLE: Dynamic Clamps
REQUESTER: Neven Orhanovic and Bob Ross, Interconnectix
DATE SUBMITTED: 10/31/97, 11/20/97
DATE ACCEPTED BY IBIS OPEN FORUM: Pending

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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. For each dynamic clamp (ground or power), three subparameters
and two keywords are used to describe the switching and V-I characteristics
of the clamp.

|==============================================================================
| 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_trigger_min, V_trigger_max
|
| Usage Rules: The [Dynamic GND Clamp] and [Dynamic PWR Clamp] specifications
| contain three subparameters and two keywords. The subparameters
| (V_trigger, V_trigger_min, V_trigger_max) specify the threshold
| clamp voltage value that causes the clamp to begin switching
| from "off" to "on" according to the [Pulse Table] section.
| These values correspond to the typical, weak (slow), and strong
| (fast) situations. The [Pulse Table] section describes the
| switching characteristics of the dynamic clamp, and the [Clamp
| Table] section gives the V-I table of the clamp in its "off"
| state. This data is used as follows.
|
| A dynamic clamp is modeled by a V-I curve that is offset
| (translated) along the voltage axis with the voltage waveform
| given in the [Pulse Table] section. The resulting dynamic V-I
| curve can be expressed as
|
| I = f( V - V_pulse(t) ),
|
| where V_pulse(t) is the offset voltage waveform described by
| the [Pulse Table] section and f(V) is the resulting V-I curve
| of the clamp in its off state, corresponding to the data
| given in the [Clamp Table] section. The [Clamp Table] data
| follows the same format and rules as the V-I curve data of
| the corresponding regular ground or power clamp ([GND Clamp],
| [POWER Clamp]). The [Pulse Table] section describes the offset
| voltage waveform and uses the same format as the [Rising
| Waveform] and [Falling Waveform] sections in driver models.
|
| Once the voltage on the clamp crosses the triggering threshold,
| the [Pulse Table] data is used to offset the V-I curve obtained
| from the [Clamp Table] section. The dependence of the offset
| pulse on the clamp voltage is illustrated below.
|
|
| Clamp voltage vs. time.
|
| o o o o
| o
| o
| o -------
| o| ^
| o | | V_trigger
| o | v time
| o o | ------------------------>
| |
| |
| |
| | Clamp offset voltage vs. time.
| |
| | o o o o
| | o o
| | o o
| | o o o o o
| | o o
| | o o time
| o o o o o o o o -------->
|
| ^
| |_ Pulse data is used from this moment on
| to offset the V-I curve.
|
|
|------------------------------------------------------------------------------
|
| Example:
|
[Dynamic GND Clamp]
|
V_trigger = 1.4V
V_trigger_min = 1.2V
V_trigger_max = 1.6V
|
[Pulse Table]
|
| Time V(typ) V(min) V(max)
|
| 0 0 0 0
| 1e-9 0 0 0
| 2e-9 0.9 0.8 1.0
| 10e-9 0.9 0.8 1.0
| 11e-9 0 0 0
|
[Clamp Table]
|
| 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 = 3.6V
V_trigger_min = 3.8V
V_trigger_max = 3.4V
|
[Pulse Table]
|
| Time V(typ) V(min) V(max)
|
| 0 0 0 0
| 1e-9 0 0 0
| 2e-9 -0.9 -1.0 -0.8
| 10e-9 -0.9 -1.0 -0.8
| 11e-9 0 0 0
|
[Clamp Table]
|
| 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 modeling approach is to decompose the dynamic clamp into its
static and dynamic portions. The static part can be modeled by a regular
clamp. The dynamic part is connected to the same rail voltage as its static
part and modeled by a V-I curve that is shifted along the voltage axis by
the offset voltage pulse.

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ANY OTHER BACKGROUND INFORMATION:

Based on a conversation with Arpad Muranyi on 11/14/97, changes were made to
include typical, minimum, and maximum values of the triggering voltage and
more general offset voltage waveforms.

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Received on Thu Nov 20 16:25:43 1997