AS4040
AS4040 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.
Figure 1. AS4040 Fixed
Shunt Regulator Application
SOT-23
The AS4040 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.
VS
Conventional Shunt Regulator
RS
VR
IO + IL
IL
In a conventional shunt regulator application (see Figure 1),
an external series resister (RS) is connected between the
supply voltage and the AS4040. 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
AS4040 is less than 15mA
VO
IQ
AS4040
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)
Rev. 10/11/00
SIPEX [ SIPEX CORPORATION ]
