Texas Instruments ATL431, User Manual

Page: 6 / 12

2.5 NŸ
I
K
GND
OUTPUT
10 NŸ
10 NŸ
10µF
5.0V
+
-
I
off
V
KA
Input
I
ref
I
KA
V
KA
Input
V
ref
R1
R2
KA ref ref
R1
V = V 1 + + I × R1
R2
æ ö
ç ÷
è ø
V
ref
Input V
KA
I
KA
EVM Theory and Operation
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When setting V
KA
, be sure to not exceed the absolute maximum rating of 40 V for the cathode voltage.
Along with maximum voltage, stability must be taken in to account as there are operating regions that are
susceptible to oscillations
3.3 Checking Stability and Transient Response
One of the issues that many designers face designing with shunt regulators is stability and
response/clamp time. The ATL431EVM allows users to measure this by setting the load capacitance (C
L
).
As shown in Figure 2 , this portion is on the right side of the PCB and is indicated as "Load Cap Selection".
Each jumper is denoted with its respective capacitance value.
These capacitors are all ceramic and have very low ESR.
4 Test Modes
The ATL431EVM can be configured to measure practically every parameter shown in the typical
characteristics of the datasheet.
Figure 4 through Figure 10 show the configurations that can be used to
take these measurements.
Figure 4. Test Circuit for V
KA
= V
ref
Figure 5. Test Circuit for V
KA
> V
ref
Figure 6. Test Circuit for I
off
Figure 7. Test Circuit for Phase and Gain Measurement
6 ATL431 Adjustable Shunt Regulator EVM SLVUAE7 – April 2015
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