Rainbow-electronics MAX106 Manual do Utilizador descarregar pdf (Página 24)

MAX106

±5V, 600Msps, 8-Bit ADC with On-Chip

2.2GHz Bandwidth Track/Hold Amplifier

24 ______________________________________________________________________________________

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

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

°= ⋅

TEMP

CONST PTAT

−

=+ +1

T 300

273

DIE

PTAT

CONST













−

CONST

TEMP

7.5k

15k

3.32k

7.5k

6.65k

6.05k

12.1k

JU1

10-TURN

PTAT

CONST

1/4 MAX479

Figure 20. Die Temperature-Acquisition Circuit with the MAX479

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