LTspice: AND-Gatter

Hallo,

1.
Unbenutzte Eingänge offen lassen damit LTspice die wegoptimieren kann.
2.
Rechter Mausklick auf das Symbol offnet ein Dialogfenster um Parameter 
einzugeben.

REF=2.5 VHIGH=5 VLOW=0
TD=5n TRISE=5n

Die Simulationsdatei(.asc) für LTspice ist im Anhang.

Gruß
Helmut

> Hallo Helmut.

> Müsste ich diese Informationen zu den Parametern nicht irgendwo in der
mitgelieferten LTspice-Doku finden?

Die ist in der Help von LTspice. Siehe Anhang
Weiterführende Help über A-devices gibt es hier.
http://ltwiki.org/?title=Undocumented_LTspice#A-Devices


> Entsprechend A5 in DIGITAL_A_DEVICES_1.ASC soll für "Ref" der Wert von
1.5 vorgesehen werden - aber

> Input threshhold "Ref" :  (Vhigh+Vlow)/2 - aber:

Wenn man "Ref" nicht angibt, dann gilt obige Formel für Ref.


> Jetzt finde ich für den CD4011 bei Vdd=15V die Werte V_IL=6V V_IH=9V -
alles typisch bei 25°C.

> Liege ich richtig mit den Annahmen V_IH -> Vhigh und V_IL -> Vlow? Dann
wäre Ref=7.5V?

Ja.

Vhigh=15 Vlow=0


> Laut Fairchild (alle Werte bei Vdd=15V):
> Propagation Delay Time, HIGH-to-LOW Level, tPHL=35n
> Propagation Delay Time, LOW-to-HIGH Level, tPLH=30n
> Transition Time, tTHL, tTLH =40n

daraus folgt:
tTLH -> Trise? Ja
tTHL -> Tfall? Ja
max(tPHL, tPLH) -> Td? Ja



--- Anhang ---

A. Special Functions
Symbol names: INV, BUF, AND, OR, XOR, SCHMITT, SCHMTBUF, SCHMTINV, 
DFLOP, VARISTOR, and MODULATE

Syntax: Annn n001 n002 n003 n004 n005 n006 n007 n008 <model> [instance 
parameters]

These are Linear Technology Corporation's proprietary special 
function/mixed mode simulation devices. Most of these and their behavior 
are undocumented as they frequently change with each new set of models 
available for LTspice. However, here we document some of them because of 
their general interest.

INV, BUF, AND, OR, and XOR are generic idealized behavioral gates. All 
gates are netlisted with eight terminals. These gates require no 
external power. Current is sourced or sunk from the complementary 
outputs, terminals 6 and 7, and returned through device common, terminal 
8. Terminals 1 through 5 are inputs. Unused inputs and outputs are to be 
connected to terminal 8. The digital device compiler recognizes that as 
a flag that that terminal is not used and removes it from the 
simulation. This leads to the potentially confusing situation where AND 
gates act differently when an input is grounded or at zero volts. If 
ground is the gate's common, then the grounded input is not at a logic 
false condition, but simply not part of the simulation. The reason that 
these gates are implemented like that is that this allows one device to 
act as 2-, 3-, 4- or 5- input gates with true, inverted, or 
complementary output with no simulation speed penalty for unused 
terminals. That is, the AND device acts as 12 different types of AND 
gates. The gates default to 0V/1V logic with a logic threshold of .5V, 
no propagation delay, and a 1Ohm output impedance. Output 
characteristics are set with these instance parameters:

Name Default Description
Vhigh 1  Logic high level
Vlow  0  Logic low level
Trise 0  Rise time
Tfall Trise Fall time
Tau  0  Output RC time constant
Cout  0  Output capacitance
Rout  1  Output impedance
Rhigh Rout  Logic high level impedance
Rlow  Rout  Logic low level impedance

Note that not all parameters can be specified on the same instance at 
the same time, e.g., the output characteristics are either a slewing 
rise time or an RC time constant, not both.

The propagation delay defaults to zero and is set with instance 
parameter Td. Input hold time is equal to the propagation delay.

The input logic threshold defaults to .5*(Vhigh+Vlow) but can be set 
with the instance parameter Ref. The hold time is equal to the 
propagation delay.

The exclusive XOR device has non-standard behavior when more than two 
inputs are used: The output is true only when exactly one of all inputs 
is true. Use the associative property of XOR's with multiple XOR devices 
to implement an XOR block with more than two inputs.

The Schmitt trigger devices have similar output characteristics as the 
gates. Their trip points are specified with instance parameters Vt and 
Vh. The low trip point is Vt-Vh and the high trip point is Vt+Vh.

The gates and Schmitt trigger devices supply no timestep information to 
the simulation engine by default. That is, they don't look when they are 
about to change state and make sure there's a timestep close to either 
side of the state change. The instance parameter tripdt can be set to 
stipulate a maximum timestep size the simulator takes across state 
changes.

The VARISTOR is a voltage controlled varistor. Its breakdown voltage is 
set by the voltage between terminals 1 and 2. Its breakdown impedance is 
specified with the instance parameter rclamp. See the example schematic 
.\examples\Educational\varistor.asc

The MODULATE device is a voltage controlled oscillator. See the example 
schematic .\examples\Educational\PLL.asc. The instantaneous oscillation 
frequency is set by the voltage on the FM input. The conversion from 
voltage to frequency is linear and set by the two instance parameters, 
mark and space. Mark is the frequency when the FM input is at 1V and 
space is the frequency when the input is at 0V. The amplitude is set by 
the voltage on the AM input and defaults to 1V if that input is 
unused(connected to the MODULATE common).

The schematic capture aspect of LTspice netlists symbols for these 
devices in a special manner. All unconnected terminals are automatically 
connected to terminal 8. Also, if terminal 8 is unconnected, then it is 
connected to node 0.

Ja die originalen A-devices benötigen immer viel weniger Rechenzeit als 
drumherum gebaute Subcircuits.

Helmut S. schrieb:
> Ja die originalen A-devices benötigen immer viel weniger Rechenzeit als
> drumherum gebaute Subcircuits.

Nachtrag

In der LTspice Yahoo group gibt es auch Libraries für CD4000 und 
74HC/74HCT im Verzeichnis Lib. Es ist zwar manchmal bequem die zu 
nehmen, aber wenn man  nur ein Gatter braucht schleppt man unnötig 
Ballast mit. Diese Libraries hatte ich vor 10 Jahren für die Yahoo group 
geschrieben.

@Flash,
danke für deinen Erfahrungsbericht und den Schaltplan.

Vermutlich war ja deine "russische" Lib die CD4000.lib von der Yahoo 
group. Das macht aber nichts. Hauptsache die Leute sind von LTspice und 
der Unterstüzung durch andere Benutzer begeistert.

Gruß
Helmut