Power

A Power object is extra information that is used for:

• ERC: by setting Pin types to power_out or power_in
• voltage compatibility checks

Another thing that is important to know is that Power is not the equivalent of a power or ground symbol on a schematic. A Power object represents a physical set of pins, not an abstract concept of power or ground.

Output Power

An output Power object defines a source of electrical power within your design.

import { Component, Power } from '@typecad/typecad';

let bt1 = new Component({ footprint: 'Battery:BatteryHolder_Keystone_3008_1x2450' });
// bt1 represents a coin cell battery holder.
// The following Power object defines its output characteristics:
let coin_cell = new Power({
    power: bt1.pin(1), // Pin 1 is the positive terminal
    gnd: bt1.pin(2),   // Pin 2 is the ground terminal
    voltage: 3.7,      // Nominal voltage of 3.7V
    direction: 'output' // Indicates this is a power source
});

In this example, coin_cell configures bt1 (a coin cell battery holder) as a power source.

• It specifies bt1.pin(1) as the positive terminal and bt1.pin(2) as the ground.
• It declares that this source provides a nominal 3.7 volts.
• Because direction is set to output, typeCAD automatically sets the type of bt1.pin(1) and bt1.pin(2) to power_out. This is important for Electrical Rules Checking (ERC).

Handling output and input Power in Components

Components like voltage regulators often have both power inputs and outputs. For instance, a voltage regulator takes an input voltage and produces a different output voltage.

A common scenario is when the input and output sides of such a component share the same ground pin. If you define separate Power objects for the input and output, and both reference the same physical pin as ground, this can lead to ERC conflicts because a pin would be assigned as power_out (from the output Power object) and potentially power_in or another type (from the input Power object).

To avoid such ERC errors for a shared ground pin, you can manually set the pin’s type to passive after the Power objects have been defined:

// Assuming U1 is a voltage regulator component
// and U1.pin(2) is the shared ground pin.

let vin = new Power({ power: U1.pin(1), gnd: U1.pin(2), voltage: 5, direction: 'input' });
let vout = new Power({ power: U1.pin(3), gnd: U1.pin(2), voltage: 3.3, direction: 'output' });

// Manually set the shared ground pin to passive to avoid ERC conflicts
U1.pin(2).type = 'passive';

This tells typeCAD that the pin is a common connection point not actively sourcing or sinking power in a way that conflicts with its dual role.

Input Power

Just as components can source power, they often need to receive it. An input Power object is used to specify the power requirements for a component or a part of your circuit.

When creating reusable typeCAD packages (e.g., a module for a specific sensor that requires power), you can define a constructor parameter for a Power object. This allows users of your package to easily connect a suitable power source.

Inside your package’s code, you can then use the properties of this input Power object to make connections. For example, if vin is an input Power object passed to your component, and U1 is an internal part that needs power:

// Assuming 'vin' is a Power object passed as a parameter (direction: 'input')
// and U1 is a component within your design that needs power.

// Connect the power line from the input Power object to U1's VCC pin
typecad.net(vin.power, U1.VCC);

// Connect the ground line from the input Power object to U1's GND pin
typecad.net(vin.gnd, U1.GND);

By using vin.power and vin.gnd, you are connecting to the pins that were defined when the input Power object (vin) was created. This ensures that your component correctly receives power according to its design.

If direction is set to input, typeCAD will automatically set the type of the associated pins to power_in for ERC purposes.

Voltage checks

A package can check that the voltage levels coming in are correct as well.

if (vin.voltage != 3.3) {
    throw new Error('Voltage must be 3.3v');
}