sysloss.utils

sysloss.utils#

Utilities.

sysLoss utility functions.

Attributes#

RHO

Copper resistance, Ohm-meter (IPC spec for copper bulk resistivity at 20°C)

TCR

Copper temperature coefficient of resistance, Ohm/°C

MILS2MM

mils to mm conversion factor

OZ2MM

oz/ft^2 (copper ounce per square feet) to mm conversion factor

Functions#

trace_res(→ float)

Calculate PCB trace resistance.

plane_res(→ float)

Calculate PCB plane resistance.

Module Contents#

RHO = 1.724e-08#

Copper resistance, Ohm-meter (IPC spec for copper bulk resistivity at 20°C)

TCR = 0.00386#

Copper temperature coefficient of resistance, Ohm/°C

MILS2MM = 0.0254#

mils to mm conversion factor

OZ2MM = 0.034798#

oz/ft^2 (copper ounce per square feet) to mm conversion factor

trace_res(*, w1_mm: float, w2_mm: float, l_mm: float, t_mm: float, rho: float = RHO, temp: float = 20.0, tcr: float = TCR) → float#

Calculate PCB trace resistance.

Trace resistance is calculated as \(R=\frac{\rho L}{A}\), where A is the cross-sectional area of the trace, L is trace length and \(\rho\) is material resistance. If the temperature is set to other than 20°C, the resistance value is adjusted with \(R_t = R \cdot (1 + tcr \cdot (temp - 20))\).

Parameters:

  • w1_mm (float) – Lower trace width in mm.

  • w2_mm (float) – Upper trace width in mm.

  • l_mm (float) – Trace length in mm.

  • t_mm (float) – Trace thickness in mm.

  • rho (float, optional) – Material resistance (Ohm-m), by default RHO.

  • temp (float, optional) – Ambient temperature, by default 20°C.

  • tcr (float, optional) – Temperature coefficient of resistance (Ohm/°C), by default TCR.

Returns:

Trace resistance (Ohm)

Return type:

float

Examples

>>> rs = trace_res(w1_mm=1, w2_mm=1, l_mm=15, t_mm=35e-3)
>>> # convert dimensions in mils and oz/ft^2 to mm by predefined constants:
>>> rs = trace_res(w1_mm=7*MILS2MM, w2_mm=6*MILS2MM, l_mm=350*MILS2MM, t_mm=2*OZ2MM, temp=50)
plane_res(*, w: float, l: float, t_mm: float, rho: float = RHO, temp: float = 20.0, tcr: float = TCR) → float#

Calculate PCB plane resistance.

Plane (or sheet) resistance is calculated as \(R=R_s \frac{L}{W}\), where W is the plane width, L is the plane length and Rs is the sheet resistance. Rs is calculated as \(R_s=\frac{\rho}{t}\), where \(\rho\) is material resistance and t is plane thickness. If the temperature is set to other than 20°C, the resistance value is adjusted with \(R_t = R \cdot (1 + tcr \cdot (temp - 20))\).

Parameters:

  • w (float) – Plane width (unitless).

  • l (float) – Plane length (unitless).

  • t_mm (float) – Plane thickness in mm.

  • rho (float, optional) – Material resistance (Ohm-m), by default RHO.

  • temp (float, optional) – Ambient temperature, by default 20°C.

  • tcr (float, optional) – Temperature coefficient of resistance (Ohm/°C), by default TCR.

Returns:

Plane resistance (Ohm)

Return type:

float

Examples

>>> rs = plane_res(w=25, l=80, t_mm=35e-3)
>>> # convert dimension oz/ft^2 to mm by predefined constant:
>>> rs = plane_res(w=800, l=500, t_mm==2*OZ2MM, temp=50)