Shunt reference in an 8-TSSOP — what the ±2.2% tolerance buys you
The TL431CPWE4 is a three-terminal adjustable shunt regulator from the TL431 family, delivering a 2.495 V reference that can be set to any value up to 36 V with two external resistors. The ±2.2% tolerance on the reference voltage is tighter than the standard ±1% grade found in many TL431 variants, which matters when the output voltage accuracy of a switching power supply or linear regulator feedback loop depends on that initial tolerance.
Output current and cathode current — the drive and bias budget
Rated for 100 mA continuous output current, the TL431CPWE4 can sink enough current to drive the optocoupler LED in an isolated flyback supply or the bias network of a linear post-regulator. The minimum cathode current is 1 mA — below that the device drops out of regulation, so the external resistor from cathode to the supply rail must be sized to keep at least 1 mA flowing even at no load.
Package and temperature grade — board-fit constraints
Housed in an 8-TSSOP (0.173", 4.40 mm width) surface-mount package, the TL431CPWE4 is a compact option for space-constrained boards.
Lifecycle reality — obsolete, sourced to order
TI lists the TL431CPWE4 as obsolete.