Strict LDO dropout (#386)

Prior, the LDO dropout would propagate to the output voltage and assume
that the LDO would track. This creates an assertion that the input
voltage is greater than the dropout. Not super strict, only checks that
the input lower bound is greater than the output lower bound + dropout.

Rationale: voltage_out is a spec, and it's not being met. Users can
change the dropout voltage in refinements to tighten bounds (eg, LDO
operating at less than max current) or allow the regulator to go into
tracking.

Also refactors out actual_target_voltage since it's no longer needed.

Author: ducky64

edg/abstract_parts/AbstractPowerConverters.py

@@ -101,25 +101,22 @@ def __init__(self) -> None:
     # these device model parameters must be provided by subtypes
     self.actual_dropout = self.Parameter(RangeExpr())
     self.actual_quiescent_current = self.Parameter(RangeExpr())
-    self.actual_target_voltage = self.Parameter(RangeExpr())
 
+    self.gnd = self.Port(Ground(), [Common])
     self.pwr_in = self.Port(VoltageSink(
-      voltage_limits=RangeExpr(),
+      voltage_limits=RangeExpr(),  # parameters set by subtype
       current_draw=RangeExpr()
     ), [Power, Input])
-    # dropout voltage is modeled to expand the tolerance range for actual output voltage
     self.pwr_out = self.Port(VoltageSource(
-      voltage_out=(  # bounds are lowest of the target voltage or dropout voltage
-        self.actual_target_voltage.lower().min(self.pwr_in.link().voltage.lower() - self.actual_dropout.upper()),
-        self.actual_target_voltage.upper().min(self.pwr_in.link().voltage.upper() - self.actual_dropout.lower()),
-      ),
+      voltage_out=self.RangeExpr(),  # parameters set by subtype
       current_limits=RangeExpr()
     ), [Output])
-    self.gnd = self.Port(Ground(), [Common])
-
     self.assign(self.pwr_in.current_draw,
                 self.pwr_out.link().current_drawn + self.actual_quiescent_current)
 
+    self.require(self.pwr_out.voltage_out.lower() + self.actual_dropout.upper() <= self.pwr_in.link().voltage.lower(),
+                 "excessive dropout")
+
 
 @abstract_block
 class SwitchingVoltageRegulator(VoltageRegulator):

edg/parts/LinearRegulators.py

@@ -31,7 +31,7 @@ def generate(self):
     assert suitable_parts, "no regulator with compatible output"
     part_output_voltage, part_number, lcsc_part = suitable_parts[0]
 
-    self.assign(self.actual_target_voltage, part_output_voltage)
+    self.assign(self.pwr_out.voltage_out, part_output_voltage)
     self.assign(self.lcsc_part, lcsc_part)
     self.assign(self.actual_basic_part, False)
     self.footprint(
@@ -89,7 +89,7 @@ def generate(self):
     assert suitable_parts, "no regulator with compatible output"
     part_output_voltage_nominal, part_number, jlc_number = suitable_parts[0]
 
-    self.assign(self.actual_target_voltage, part_output_voltage_nominal * Volt(tol=TOLERANCE))
+    self.assign(self.pwr_out.voltage_out, part_output_voltage_nominal * Volt(tol=TOLERANCE))
     self.footprint(
       'U', 'Package_TO_SOT_SMD:SOT-223-3_TabPin2',
       {
@@ -159,7 +159,7 @@ def generate(self):
     assert suitable_parts, "no regulator with compatible output"
     part_output_voltage_nominal, part_number, jlc_number = suitable_parts[0]
 
-    self.assign(self.actual_target_voltage, part_output_voltage_nominal * Volt(tol=TOLERANCE))
+    self.assign(self.pwr_out.voltage_out, part_output_voltage_nominal * Volt(tol=TOLERANCE))
     self.footprint(
       'U', 'Package_TO_SOT_SMD:SOT-23-5',
       {
@@ -204,7 +204,7 @@ def __init__(self, output_voltage: RangeLike):
     self.assign(self.pwr_out.current_limits, (0, 0.6) * Amp)
     self.assign(self.actual_quiescent_current, (50, 80) * uAmp)
     self.assign(self.actual_dropout, (0, 0.25) * Volt)  # worst-case @ 100mA Iout
-    self.assign(self.actual_target_voltage, (3.234, 3.366) * Volt)
+    self.assign(self.pwr_out.voltage_out, (3.234, 3.366) * Volt)
     self.footprint(
       'U', 'Package_TO_SOT_SMD:SOT-89-3',
       {
@@ -273,7 +273,7 @@ def generate(self):
     assert suitable_parts, "no regulator with compatible output"
     part_output_voltage, part_number, part_dropout, part_max_current, lcsc_part, basic_part = suitable_parts[0]
 
-    self.assign(self.actual_target_voltage, part_output_voltage * Volt)
+    self.assign(self.pwr_out.voltage_out, part_output_voltage * Volt)
     self.assign(self.actual_dropout, part_dropout * Volt)
     self.assign(self.pwr_out.current_limits, (0, part_max_current) * Amp)
     self.footprint(
@@ -337,7 +337,7 @@ def generate(self):
     assert suitable_parts, "no regulator with compatible output"
     part_output_voltage_nominal, part_number, part_dropout, lcsc_part = suitable_parts[0]
 
-    self.assign(self.actual_target_voltage, part_output_voltage_nominal * Volt(tol=TOLERANCE))
+    self.assign(self.pwr_out.voltage_out, part_output_voltage_nominal * Volt(tol=TOLERANCE))
     self.assign(self.actual_dropout, part_dropout * Volt)
     self.footprint(
       'U', 'Package_TO_SOT_SMD:SOT-23-5',
@@ -408,7 +408,7 @@ def generate(self):
     assert suitable_parts, "no regulator with compatible output"
     part_output_voltage_nominal, part_number, jlc_number = suitable_parts[0]
 
-    self.assign(self.actual_target_voltage, part_output_voltage_nominal * Volt(tol=TOLERANCE))
+    self.assign(self.pwr_out.voltage_out, part_output_voltage_nominal * Volt(tol=TOLERANCE))
     self.footprint(
       'U', 'Package_TO_SOT_SMD:SOT-23-5',
       {
@@ -496,7 +496,7 @@ def generate(self):
     assert suitable_parts, "no regulator with compatible output"
     part_output_voltage, part_number, footprint, jlc_number = suitable_parts[0]
 
-    self.assign(self.actual_target_voltage, part_output_voltage)
+    self.assign(self.pwr_out.voltage_out, part_output_voltage)
     if footprint == 'Package_TO_SOT_SMD:SOT-23-5':
       pinning: Dict[str, CircuitPort] = {
         '1': self.pwr_in,
@@ -591,7 +591,7 @@ def generate(self):
     assert suitable_parts, "no regulator with compatible output"
     part_output_voltage, part_number, part_dropout, lcsc = suitable_parts[0]
 
-    self.assign(self.actual_target_voltage, part_output_voltage)
+    self.assign(self.pwr_out.voltage_out, part_output_voltage)
     self.assign(self.actual_dropout, (0, part_dropout)*Volt)
 
     self.footprint(
@@ -659,7 +659,7 @@ def generate(self):
                       if part[0] in self.get(self.output_voltage)]
     assert suitable_parts, "no regulator with compatible output"
 
-    self.assign(self.actual_target_voltage, suitable_parts[0][0])
+    self.assign(self.pwr_out.voltage_out, suitable_parts[0][0])
     self.assign(self.pwr_in.voltage_limits, suitable_parts[0][1])
     self.assign(self.pwr_out.current_limits, (0, 100)*mAmp)
     self.assign(self.actual_quiescent_current, suitable_parts[0][2])

edg/parts/VoltageReferences.py

@@ -30,7 +30,7 @@ def generate(self):
     assert suitable_parts, "no regulator with compatible output"
     part_output_voltage, part_number, lcsc_part = suitable_parts[0]
 
-    self.assign(self.actual_target_voltage, part_output_voltage)
+    self.assign(self.pwr_out.voltage_out, part_output_voltage)
     self.assign(self.lcsc_part, lcsc_part)
     self.assign(self.actual_basic_part, False)
     self.footprint(

examples/test_pcbbot.py

@@ -208,6 +208,7 @@ def refinements(self) -> Refinements:
         ]),
 
         (['prot_batt', 'diode', 'footprint_spec'], 'Diode_SMD:D_SMA'),  # big diodes to dissipate more power
+        (['reg_3v3', 'ic', 'actual_dropout'], Range(0.0, 0.3))  # tighter dropout from lower current draw
       ],
       class_refinements=[
         (PassiveConnector, JstPhKVertical),  # default connector series unless otherwise specified