MAX1979ETM Maxim Integrated Products, MAX1979ETM Datasheet - Page 16

• Manufacturer Part Number: MAX1979ETM
• Description: Other Power Management
• Manufacturer: Maxim Integrated Products

Specifications of MAX1979ETM

• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

The MAX1979 controls the TEC current in only one
direction (unipolar). Set the maximum unipolar TEC cur-
rent by applying a voltage to MAXIP. Connect MAXIN to
MAXIP when using the MAX1979. The equation for set-
ting MAXIP is the same for the MAX1978 and
MAX1979. Do not exceed the positive or negative cur-
rent-limit specifications on the TEC. Refer to the TEC
manufacturer’s data sheet for these limits.
Apply a voltage to MAXV to control the maximum differ-
ential TEC voltage. MAXV can vary from 0 to REF. The
voltage across the TEC is four times V
positive or negative.
Use resistors from 10kΩ to 100kΩ to form a voltage-
divider to set V
The MAX1978/MAX1979 provide all the necessary
amplifiers needed to create a thermal-control loop.
Typically, the chopper-stabilized instrumentation ampli-
fier generates an error signal and the integrator amplifi-
er is used to create a PID controller. Figure 4 shows an
example of a simple PID implementation. The error sig-
nal needed to control the loop is generated from the
difference between the set point and the thermistor
voltage. The desired set-point voltage can be derived
from a potentiometer, DAC, or other voltage source.
Figure 5 details the required connections. Connect the
output of the PID controller to CTLI. For details, see the
Applications Information section.
Integrated Temperature
Controllers for Peltier Modules
Figure 4. Proportional Integral Derivative Controller
16
DIFOUT
______________________________________________________________________________________
C1
|V
MAXV
R1
R2
OS1
.
- V
OS2
REF
INT-
| = 4
Setting Max TEC Voltage
R3
Thermal-Control Loop
C3

V
MAXV
C2
MAXV
and can be
INTOUT
The voltage at CTLI directly sets the TEC current. CTLI
typically is driven from the output of a temperature-con-
trol circuit C
equations, it is assumed that positive TEC current is
heating.
The transfer function relating current through the TEC
(I
where V
and I
V
V
ing. Current flow is from OS2 to OS1. The voltages are:
when V
Figure 5. The Set Point can be Derived from a Potentiometer
or a DAC
TEC
CTLI
CTLI
MAX1978
MAX1979
MAX1978
MAX1979
) and V
TEC
= 1.50V. When V
is centered around REF (1.50V). I
CTLI
REF
I
= (V
TEC
REF
FB+
REF
FB+
FB-
FB-
< 1.50V, current flows from OS1 to OS2:
CTLI
is 1.50V
INTOUT
OS1
= (V
V
is given by:
SETPOINT
- V
V
V
CTLI
C
C
OS2
OS2
. For the purposes of the following
REF
REF
V
CS
SETPOINT
CTLI
- V
) / R
> V
< V
REF
Control Inputs/Outputs
> 1.50V, the MAX1978 is heat-
OS1
OS1
SENSE
DAC
) / (10
> V
< V
TEC Current Control
CS
CS
DIGITAL
INPUT

R
TEC
SENSE
V
THERMISTOR
is zero when
)
V
THERMISTOR