Datasheet
INA330
8
SBOS260
www.ti.com
INA330 PIN 5
Pin 5 of the INA330 should be connected to V+ to ensure
proper operation.
COMPLETE TEMPERATURE CONTROLLER
See Figure 6 for a complete temperature control loop with a
TEC (thermoelectric cooler) for cooling and heating. PID
(proportional, integral, differential) control circuitry is shown
for loop compensation and stability.
The loop controls temperature to an adjustable set-point of
22.5°C to 27.5°C. The nominal 10kΩ at 25°C thermistor
ranges from approximately 11.4kΩ to 8.7kΩ over this range.
A 1V excitation voltage is applied to V
1
and V
2
, producing a
nominal 100µA current in the 10kΩ R
SET
resistor. The ther-
The INA330 is designed and tested for amplifying 10kΩ
thermistor signals used in the control of thermoelectric
coolers for optical networking applications. The simplified
schematic in Figure 5 shows the basic function of the
INA330. An excitation voltage is applied as V
1
and V
2
.
Typically, these voltages are equal. They generate cur-
rents I
1
and I
2
in the thermistor and R
SET
resistor.
Auto-corrected current mirror circuitry around A
1
and A
2
produce an output current, I
O
, equal to the difference
A1
V+ Enable
Current Mirror
Current Mirror
I
2
I
2
I
2
R
SET
R
THERM
R
G
C
FILTER
V
O
V
2
V
1
I
2
I
O
I
1
–
I
2
I
O
=
I
1
–
I
2
I
O
A3
A2
V
ADJUST
Current Mirror
Current Mirror
956
8
74
3
10
1
2
INA330
I
1
current I
1
– I
2
. The gain is set by the value of R
G
. The
output voltage, V
O
, is the voltage resulting from I
O
flowing
through R
G.
The INA330 uses internal charge pumps to create volt-
ages beyond the power-supply rails. As a result, the
voltage on R
G
can actually swing 20mV below the nega-
tive power-supply rail, and 100mV beyond the positive
supply rail. An internal oscillator has a frequency of
90kHz and accuracy of ±20%.
INSIDE THE INA330
FIGURE 5. INA330 Simplified Schematic.
mistor current is approximately 100µA at 25°C, but will vary
above or below this value over the ±2.5°C set-point tempera-
ture range. The difference of these two currents flows in the
gain-set resistor, R
G
. This produces a voltage output of
approximately 0.9V/°C.
The set-point temperature is adjusted with V
ADJ
. Thus, the
voltage at V
O
is the sum of (I
O
)(R
G
) + V
ADJ
. V
ADJ
can be
manually adjusted or set with a Digital-to-Analog (D/A) con-
verter. Optionally, set-point temperature can be adjusted by
choosing a different fixed value resistor more closely ap-
proximating the value of R
THERM
at the desired temperature.
The noninverting input of the integrator in the PID compen-
sation is connected to V
BIAS
. Thus, the feedback loop will
drive the heating or cooling of the TEC to force V
O
to equal
V
BIAS
. V
ADJ
= 2.5V will produce a set-point temperature of