SPX4040 datasheet(4/8 Pages) SIPEX

4 / 8 page

Rev. 10/25/00

SPX4040

SPX4040 Applications Hints

This device is designed for stable operation and has no need

of an external capacitor between pin 4 and 8. The reference

remains stable if a bypass capacitor is used.

SOT-23

The SPX4040 in the SOT-23 package has a parasitic

Schottky diode between pin 3 and pin 1. Pin 1 of SOT-23

must float or be connected to pin 3.

Conventional Shunt Regulator

In a conventional shunt regulator application (see Figure 1),

an external series resister (RS) is connected between the

supply voltage and the SPX4040. RS determines the current

that flows through the load (IL) and the reference(IQ). Since

load current and supply voltage may vary, RS should be small

enough to supply at least the minimum acceptable IQ to the

reference even when the supply voltage is at its minimum and

the load current is at its maximum value. When the supply

voltage is at its maximum and IL is at its minimum, RS should

be large enough so that the current flowing through the

SPX4040 is less than 15mA

RS is determined by the supply voltage (VS), the load and

operating current (IL and IQ), reference’s reverse breakdown

voltage (VR).

RS = (VS - VR)/(IL+IQ)

Figure 1. SPX4040 Fixed

Shunt Regulator Application

O + IL

SPX4040

SPX4040 Datasheet(PDF) 4 Page - Sipex Corporation