Getting Started; Switches And Potentiometers - Analog Devices ADN8831 Application Note

Application Note

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.
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 R3
V
REF
R2
R
TH
TEMPOUT
V
REF
2
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
S1 CD
S2 RD
S3 RI
S4 RP
S5 CI
S6 Standby/shutdown
CD CI
RD RP
CF
RI
OUT2
TEMPSET
Default
1 uF
24.9 kΩ
249 kΩ
249 kΩ
470 nF
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
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.
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
R1
R2
R3
W1
W2
W3
W4
Rev. C | Page 3 of 12
and SYNCO outputs of
REF
10µF 4.7µF 2.2µF 1µF 470µF
Figure 4. Switch Position for Switch S1
Function
Temperature compensation network
Temperature compensation network
Temperature compensation network
TEMPSET
V
LIM
V , V
ILIMC ILIMH
V , V
ILIMC ILIMH
AN-695
Default
17.5 kΩ
7.5 kΩ
81.3 kΩ
20 kΩ
20 kΩ
20 kΩ
20 kΩ