Timer

The behavioral model of the integrated circuit timer.

blockType: AcausalElectricPowerSystems.IntegratedCircuits.Timer

Path in the library:

/Physical Modeling/Electrical/Integrated Circuits/Timer

Description

Block Timer It is a behavioral model of a timer integrated circuit such as the NE555.

The following figure shows the block implementation structure:

timer 1

Parameter Potential divider component resistance sets the values of the three resistors forming the voltage divider. The two comparator inputs have infinite input impedance and zero input capacitance. Block S-R Latch provides latch functionality with installation and reset. It includes an output capacitor and a resistor with values set according to the parameter value Propagation delay. The block simulates the output stage inverter using the block CMOS NOT. The output resistance, low-level output voltage and high-level output voltage for the CMOS valve are set in the settings window of the unit Timer. The element switch approximates a bipolar NPN transistor on a real timer as a switch with preset resistance values when switched on and off directly.

Assumptions and limitations

Behavior is described abstractly. The results are not as accurate as when using a transistor-level model.
The delay in response to a change in the input signals depends solely on the time constant of the RC resistor-capacitor circuit at the latch output. In practice, the delay has a more complex dependence on the structure of the device. Set this value based on the rise and fall time of the output pulse.
The output voltage drop is a linear function of the output current. In practice, this ratio corresponds to a push-pull pair of bipolar transistors.
The controlled switch circuit used in the unit is an approximation to the open collector circuit.
The power supply is connected inside the component, and it is assumed that the GND pin is grounded.

Ports

Conserving

# DISCH — discharge contact
electricity

Details

An undirected port connected to the timer’s discharge pin.

Program usage name

discharge_pin

# TRIG — launch contact
electricity

Details

The non-directional port associated with the timer start pin.

Program usage name

trigger_pin

# RESET — reset contact
electricity

Details

The non-directional port associated with the timer reset pin.

Program usage name

reset_pin

# OUT — output contact
electricity

Details

An undirected port connected to the timer output pin.

Program usage name

output_pin

# CONT — managing contact
electricity

Details

An undirected port connected to the timer control pin.

Program usage name

control_pin

# THRES — threshold contact
electricity

Details

An undirected port connected to the timer’s threshold pin.

Program usage name

threshold_pin

Parameters

Potential Divider

# Potential divider component resistance — resistance of the voltage divider component
Ohm | mOhm | kOhm | MOhm | GOhm

Details

A typical value for a type 555 timer is 5 Com. It can be measured directly between the positive power contact and the control contacts when the chip is not connected to the circuit.

Units	`Ohm` \| `mOhm` \| `kOhm` \| `MOhm` \| `GOhm`
Default value	`5.0 kOhm`
Program usage name	`R_divider`
Evaluatable	Yes

Discharge

# Discharge switch off-resistance — resistance of the element switch in the off state
Ohm | mOhm | kOhm | MOhm | GOhm

Details

A characteristic value is the leakage current of the discharge contact divided by the corresponding terminal voltage.

Units	`Ohm` \| `mOhm` \| `kOhm` \| `MOhm` \| `GOhm`
Default value	`5.0e8 Ohm`
Program usage name	`R_open`
Evaluatable	Yes

# Discharge switch on-resistance — resistance of the element switch during direct switching
Ohm | mOhm | kOhm | MOhm | GOhm

Details

The characteristic value is the saturation voltage of the discharge contact divided by the corresponding current.

Units	`Ohm` \| `mOhm` \| `kOhm` \| `MOhm` \| `GOhm`
Default value	`12.0 Ohm`
Program usage name	`R_closed`
Evaluatable	Yes

Outputs

# Propagation delay — propagation delay
s | ns | us | ms | min | hr | d

Details

Set this value to the rise time of the input or output pulse.

Units	`s` \| `ns` \| `us` \| `ms` \| `min` \| `hr` \| `d`
Default value	`1.0e-7 s`
Program usage name	`delay`
Evaluatable	Yes

# Output resistance — output resistance
Ohm | mOhm | kOhm | MOhm | GOhm

Details

The ratio of the output voltage drop to the output current. Set this parameter to , where — reduced high-level output voltage at output current .

Units	`Ohm` \| `mOhm` \| `kOhm` \| `MOhm` \| `GOhm`
Default value	`8.0 Ohm`
Program usage name	`R_output`
Evaluatable	Yes

# Low level output voltage — low-level output voltage
V | uV | mV | kV | MV

Details

Output voltage when the timer output signal is in a low state and no current is consumed at the output.

Units	`V` \| `uV` \| `mV` \| `kV` \| `MV`
Default value	`0.0 V`
Program usage name	`V_OL`
Evaluatable	Yes

# High level output voltage — high-level output voltage
V | uV | mV | kV | MV

Details

Output voltage when the timer output is in a high state and no current is being consumed.

Units	`V` \| `uV` \| `mV` \| `kV` \| `MV`
Default value	`14.1 V`
Program usage name	`V_OH`
Evaluatable	Yes

Supply

# Power supply voltage — Supply voltage
V | uV | mV | kV | MV

Details

Voltage value , which the block supplies internally to the timer component.

Units	`V` \| `uV` \| `mV` \| `kV` \| `MV`
Default value	`15.0 V`
Program usage name	`V_supply`
Evaluatable	Yes