© 2023
20
WHY5640 TEMPERATURE CONTROLLER
SAFE OPERATING AREA
The Safe Operating Area of the WHY5640 controller is
determined by the amount of power that can be dissipated
within the output stage of the controller. If that power limit is
exceeded permanent damage can result.
!
Do not exceed the Safe Operating Area
(SOA). Exceeding the SOA voids the
warranty.
Refer to the Wavelength Electronics website for the most
up-to-date SOA calculator for our products. The online tool
is fast and easy to use, and also takes into consideration
operating temperature.
www.teamwavelength.com/support/design-tools/soa-tc-calculator/
SOA charts are included in this datasheet for quick reference,
however we recommend you use the online tools instead.
See our SOA video:
How to use the Safe Operating Area
An example SOA calculation for the WHY5640 with heatsink
and fan is shown in
where:
V
S
= 12 Volts (Point C) V
LOAD
= 5 Volts
I
LOAD
= 1 Amp (Point B) V
DROP
= 12 - 5 = 7 Volts (Point A)
!
1: No heatsink required (P
WHY
< 1.2 W)
!
2: WHS heatsink required (P
WHY
< 2 W)
!
3: Heatsink and 3.5CFM fan required
(2 W < P
WHY
< 9 W)
!
4: Unsafe Operating Area
P
WHY
=Power internally dissipated in the WHY5640
1
2
3
4
5
10
15
20
25
0
0
0.5
1.0
1.5
2.0
Voltage Drop Across WHY (VS - V
LOAD
) (
V
)
M
aximum Supply C
ur
ren
t fr
om
V
S
(
A
)
25ºC Ambient
75ºC Case
B
BB
A
C
Follow these steps to determine if the controller will be
operating within the SOA.
•
Refer to the thermoelectric datasheet to find the maximum
voltage (V
LOAD
) and current (I
LOAD
) specifications
•
Calculate the voltage drop across the controller:
V
DROP
= V
S
- V
LOAD
(V
S
is the power supply voltage)
• Mark V
DROP
on the X-axis, and extend a line upward
• Mark I
LOAD
on the Y-axis, and extend a line (Line BB) to
the right until it intersects the V
DROP
line
•
On the X-axis, mark the value of V
S
•
Extend a diagonal line from V
S
to the intersection of the
V
DROP
and I
LOAD
lines; this is the Load Line
•
If the Load Line crosses the Safe Operating Area line at
any point, the configuration is not safe
If the SOA Calculator indicates the WHY5640 will be outside
of the Safe Operating Area, the system must be changed
so that less power is dissipated within the controller. See
Wavelength Electronics Application Note
Principle of the Safe Operating Area
for information on
shifting the Load Line.
Figure 23. WHY5640 SOA
