1.0 Functional Description

1.1 PIN DESCRIPTIONS

V

+

This is the positive supply voltage pin, which has

a range of 2.8 to 3.8 volts. This pin should be

bypassed with a 0.1µF capacitor to ground.

GND

This is the ground pin.

D0+, D1+ These pins connect to the positive terminal of the

diodes (e.g. a 2N3904 collector base shorted or a

Pentium thermal diode anode) and provide the

source current for forward biasing the diodes for

the temperature measurement. During a tem-

perature conversion, the current source switches

between 120µA and 12µA. The diodes are

sampled sequentially.

D−

This pin should be connected to the negative pin

of each diode (e.g. a 2N3904 emitter or a Pen-

tium thermal diode cathode). A star connection is

recommended. Separate traces should be routed

from this pin to each diode cathode. This pin

biases the negative diode terminals to approxi-

mately 0.7V.

O_CRIT

This is an active-low open-drain digital output. It

goes LOW when a comparison of either diode

temperature reading to the setpoint T_CRIT is

true. It returns to HIGH when the comparison of

the diode temperature, that caused the true con-

parator can be factory programmed to make a

greater than or less than comparison. (See Sec-

tion 1.3 LM88 OPTIONS)

O_SP1

This is an active-low open-drain digital output. It

goes LOW when the comparison of the tempera-

ture reading of diode one to the value of T_SP1 is

true. The SP1 comparator has a built in hyster-

esis of 1˚C. Therefore, O_SP1 returns to HIGH

when diode one’s temperature comparison to the

tor can be factory programmed to make a greater

than or less than comparison.(See Section 1.3

LM88 OPTIONS)

O_SP0

This is an active-low open-drain digital output. It

goes LOW when the comparison of the tempera-

ture reading of diode one to the value of T_SP0 is

true. The SP0 comparator has a built in hyster-

esis of 1˚C. Therefore, O_SP0 returns to HIGH

when diode one’s temperature comparison to the

tor can be factory programmed to make a greater

than or less than comparison.(See Section 1.3

LM88 OPTIONS)

10132611

a) When programmed for a greater than comparison

10132612

b) When programmed for a less than comparison

FIGURE 2. Comparator output temperature response diagrams

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