MAX104 Maxim, MAX104 Datasheet - Page 24

• Manufacturer Part Number: MAX104
• Description: 5V / 1Gsps / 8-Bit ADC with On-Chip 2.2GHz Track/Hold Amplifier
• Manufacturer: Maxim

of 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 sig-
nal is speed control for a cooling fan, to maintain con-
stant MAX104 die temperature. The circuit operates by
converting the I
V
for their equal values at +27°C. This voltage difference
is then amplified by two amplifiers in an instrumenta-
tion-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 expres-
sion:
±5V, 1Gsps, 8-Bit ADC with
On-Chip 2.2GHz Track/Hold Amplifier
24
Figure 20. Die Temperature Acquisition Circuit with the MAX479
CONST
______________________________________________________________________________________
I
CONST
and V
I
PTAT
T
6.65k
DIE
PTAT
A
A
V
V
CONST
, with appropriate scaling to account
300
1
V
CONST
and I
6.65k
1/4 MAX479
R
R
I
CONST
I
V
1
2
PTAT
PTAT
TEMP
6.05k
2
V
currents to voltages
PTAT
R
R
1
3
273
12.1k
12.1k
1/4 MAX479
2
JU1
1
3
V
PTAT
To calibrate the circuit, first connect pins 2-3 on JU1 to
zero the input of the PTAT path. With the MAX104 pow-
ered up, adjust potentiometer R3 until the voltage at the
V
restores normal operation to the circuit after the calibra-
tion is complete. The voltage at the V
then be proportional to the actual MAX104 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.
Depending on the application environment for the
ESBGA-packaged MAX104, 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 (see Heatsink
Manufacturers ). The heatsinks are available with pre-
applied adhesive for easy package mounting.
TEMP
7.5k
R1
V
CONST
output is -2.728V. Connecting pins 1-2 on JU1
3.32k
15k
R2
1/4 MAX479
T
DIE
(°C) = 100 · V
5k
15k
R2
10-TURN
Thermal Management
TEMP
7.5k
R1
1/4 MAX479
TEMP
node will
V
TEMP