Rainbow Electronics MAX106 User Manual
Page 24
MAX106
±5V, 600Msps, 8-Bit ADC with On-Chip
2.2GHz Bandwidth Track/Hold Amplifier
24
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determining the die temperature is to measure each
current with an ammeter (which shuts off the internal
catch diodes) referenced to GNDI. The die temperature
in °C is then calculated by the expression:
Another method of determining the die temperature
uses the operational amplifier circuit shown in Figure
20. The circuit produces a voltage that is proportional
to the die temperature. A possible application for this
signal is speed control for a cooling fan to maintain
constant MAX106 die temperature. The circuit operates
by converting the I
CONST
and I
PTAT
currents to volt-
ages V
CONST
and V
PTAT
, with appropriate scaling to
account for their equal values at +27°C. This voltage
difference is then amplified by two amplifiers in an
instrumentation-amplifier configuration with adjustable
gain. The nominal value of the circuit gain is 4.5092V/V.
The gain of the instrumentation amplifier is given by the
expression:
To calibrate the circuit, first connect pins 2-3 on JU1 to
zero the input of the PTAT path. With the MAX106 pow-
ered up, adjust potentiometer R3 until the voltage at the
V
TEMP
output is -2.728V. Connecting pins 1-2 on JU1
restores normal operation to the circuit after the calibra-
tion is complete. The voltage at the V
TEMP
node will
then be proportional to the actual MAX106 die tempera-
ture according to the equation:
The overall accuracy of the die temperature measure-
ment using the operational-amplifier scaling circuitry is
limited mainly by the accuracy and matching of the
resistors in the circuit.
Thermal Management
Depending on the application environment for the
ESBGA-packaged MAX106, the customer may have to
apply an external heatsink to the package after board
assembly. Existing open-tooled heatsinks are available
from standard heatsink suppliers (listed in Heatsink
Manufacturers). The heatsinks are available with preap-
plied adhesive for easy package mounting.
T
( C)
100 V
DIE
TEMP
°
=
⋅
A
V
V
V
A
R
R
R
R
V
TEMP
CONST
PTAT
V
=
−
=
+
+
1
1
2
2
1
3
T
300
I
I
273
DIE
PTAT
CONST
=
−
V
CONST
V
TEMP
R1
7.5k
R2
15k
R2
15k
3.32k
5k
R1
7.5k
6.65k
6.65k
6.05k
12.1k
12.1k
1
2
3
JU1
10-TURN
I
PTAT
V
PTAT
I
CONST
1/4 MAX479
1/4 MAX479
1/4 MAX479
1/4 MAX479
Figure 20. Die Temperature-Acquisition Circuit with the MAX479