inverse module#

class InverseDividerConstraints(v_in, v_out, current, prec_series=<factory>, search_range=10.0, min_sources=3, query_limit=50, temp_range=Toleranced(12.5, 12.5, 12.5), base_query=<factory>)[source]#

Bases: VoltageDividerConstraints

Inverse Voltage Divider Constraints

This type defines the parameters for a voltage divider solver that attempts solve the inverse relationship that VoltageDividerConstraints.

This is typically useful for the feedback voltage divider used in LDO’s or switching converters. For example, an LDO might list specifications for the reference voltage as a tolerance over a particular temperature range. Then it is our job, as an engineer, to determine what voltage divider would cause the output of the LDO to drive a voltage in that range.

This solver allows the user to spec a v-out for the LDO’s output voltage as the objective and then the feedback reference as a the input voltage. The solver will then find the resistor combination with the right precision that keeps the LDO’s output voltage in the objective range.

Parameters:

  • v_in (Toleranced) – Input Voltage Range The inverse divider’s “input” is the middle node of the divider. This parameter is used to drive the objective voltage.

  • v_out (Toleranced) – Desired Voltage Output Range This is the objective voltage for the solver and for the inverse solver, this is the hi port voltage of the divider.

  • current (float) – Max current in amps allowed through the divider (ie from hi -> lo) This value is expected to be positive.

  • prec_series (List[float]) – Set of precision series to search By default, we search the following series: [0.20, 0.10, 0.05, 0.02, 0.01, 0.005, 0.0025, 0.001] The user can customize this series by pass an overriding series.

  • search_range (float) – Set the search range for components to select This algorithm does a pre-screening of resistor values based on the v-in, v-out, and current parameters. Then this parameter limits how far from these pre-screen values we’re willing to search to find an acceptable solution.

  • min_sources (int) – Set the minimum number of sources When pulling resistors from the database, this algorithm will limit the selection of resistors to only those components for which there are at least min-sources number of manufacturers for comparable parts. By default this value is 3.

  • query_limit (int) – Query Limiter for Results. For many resistors, there may be 1000’s of parts that match a particular query. This parameter limits the number of returned results to some max so as not to overload the parts database. The default value is 50. This value must be greater than the min-sources parameter.

  • temp_range (Toleranced) – Temperature Range for TCR evaluation. Default is 0.0 to 25.0 C.

  • base_query (ResistorQuery) – Base ResistorQuery This object allows the user to further fine tune the selected resistors as part of the solver. The global design level defaults will still apply but this can be used to override or add to the query parameters. The resistance, tolerance, or precision keys will be overridden by the solvers so any value in the base query will be ignored for those keys.

compute_objective(rh, rl, hi_dr=Toleranced(1, 0, 0), lo_dr=Toleranced(1, 0, 0))[source]#

Default compute-objective for inverse divider.

This function currently computes the objective as the inverse voltage of the voltage divider. Meaning the middle node of the divider is the “input” and the objective we are solving over is the voltage into the hi port of the divider.

Parameters:

  • rh (Toleranced) – The top resistor in the divider.

  • rl (Toleranced) – The bottom resistor in the divider.

  • hi_dr (Toleranced) – Delta-Resistance as a Toleranced with a nominal value of 1.0. This value when multiplied against the nominal hi resistance value gives the range of resistances expected for the operating temperature range.

  • lo_dr (Toleranced) – Delta-Resistance as a Toleranced with a nominal value of 1.0. This value when multiplied against the nominal lo resistance value gives the range of resistances expected for the operating temperature range.

Return type:

Toleranced

` Vobj = V-in ( 1 + (R-H / R-L) `

compute_initial_guess()[source]#

Compute an initial guess for the inverse voltage divider solution. Returns (r_hi, r_lo)

Return type:

Tuple[float, float]