Application Note
AN-695
Rev. C | Page 3 of 12
GETTING STARTED
The ADN8831-EVALZ, shown in Figure 2, is set by factory
default to deliver about 2 A bidirectional TEC current while
working with a 10 kΩ thermistor at 25°C.
04592-
002
Figure 2.
Top View of the Evaluation Board
The factory default setting determines the on-board component
values of the temperature-to-voltage converter circuit and the
PID circuit shown in Figure 3. With the on-board switches and
potentiometers, the circuits in Figure 3 can be adapted to work
with most TEC and thermistors used in telecommunications.
R1
R2
R
TH
R3
CD
RD
CI
TEMPOUT
TEMPSET
OUT2
V
REF
RP
V
REF
2
04592-
004
CF
RI
Figure 3. Temperature and Compensation Network Circuits
Referring to Figure 3, note that TEMPOUT refers to voltage signal
outputs from Pin 4 (OUT1) and TEMPSET, a voltage signal,
applied to Pin 5 (IN2P). These terms are used throughout this
application note.
SWITCHES AND POTENTIOMETERS
Table 1. Switch Settings
Switch
Function
Default
S1
CD
1 uF
S2
RD
24.9 k
Ω
S3
RI
249 k
Ω
S4
RP
249 k
Ω
S5
CI
470 nF
S6
Standby/shutdown
Up/up
Switch S6, Left Hand Side: Standby Control
The ADN8831 is placed in standby mode when Switch S6 (the
left hand side knob) is down. When the knob is up (default), the
ADN8831 is released from standby mode. In standby mode, all
circuits, with the exception of the V
REF
and SYNCO outputs of
the ADN8831, are powered off.
Switch S6, Right Hand Side: Shutdown Control
The ADN8831 is in shutdown mode when Switch S6 (the right
hand side knob) is down. When the knob is up (default), the
ADN8831 is released from shutdown mode. In shutdown mode,
the ADN8831 is powered off.
Switches S1, S2, S3, S4, and S5: Adjustable Components
for an Optimal PID Compensation Network
Switches S1, S2, S3, S4, and S5 provide PID network component
adjustability for CD, RD, RI, RP, and CI as shown in Figure 3.
After connecting one TEC to an ADN8831-EVALZ, a thermal
oscillation may occur. To squelch the oscillation, optimize the
system settling time, and to control the TEC temperature
precisely, PID network component tuning is necessary.
10µF
4.7µF
2.2µF
1µF
470µF
04592-
003
Figure 4. Switch Position for Switch S1
When a switch knob is in the up position, the value listed below
the switch knob is an increment to the component. For example,
Switch S1 determines the CD value in Figure 3 and Figure 9.
Switch S1 shows the up knobs for the 4.7 μF and the 1 μF (note
that these knobs are set to the upper position). In this example,
the value of CD is
4.7 μF + 1 μF = 5.7 μF
The same principle applies to Switches S1, S2, S3, S4, and S5.
On-Board Potentiometers
The ADN8831-EVALZ has the following on-board potentio-
meters to adjust the component values (shown in Figure 3) and
to configure the TEC current limitation at both cooling and
heating modes.
The default settings are shown in Table 2.
Table 2. Potentiometer Settings
Potentiometer Function
Default
R1
Temperature compensation network 17.5 kΩ
R2
Temperature compensation network 7.5 kΩ
R3
Temperature compensation network 81.3 kΩ
W1
TEMPSET
20 kΩ
W2
V
LIM
20 kΩ
W3
V
ILIMC
, V
ILIMH
20 kΩ
W4
V
ILIMC
, V
ILIMH
20 kΩ
