Dual Trip SOT Temperature Switches

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_______________Detailed Description

The MAX6505–MAX6508 fully integrated temperature

switches incorporate two temperature-dependent refer-

ences and a comparator. One reference exhibits a pos-

itive temperature coefficient and the other a negative

temperature coefficient. The temperature at which the

two reference voltages are equal determines the tem-

perature trip point. There are two versions, each of

which has two logic outputs.

temperature rises above these trip points, the ALARM

and WARN outputs are asserted (Figure 1). The differ-

ence between the two trip points (

table to +5°C, +10°C, +20°C, or +30°C by connecting

the two control pins (S0 and S1) high or low (Table 1).

MAX6505 has open-drain active-low outputs; MAX6506

has push-pull active-high outputs.

The MAX6507/MAX6508 have two factory-programmed

outputs (OK and OVER). One output (OK) asserts

The other output (OVER) asserts when the temperature

mine the part numbers associated with specific values

number MAX6508UTA04B (Table 4 and Figure 2).

MAX6507 has open-drain outputs; MAX6508 has push-

pull outputs.

Hysteresis Selection

The temperature threshold hysteresis for the ALARM

output of the MAX6505/MAX6506 is 2°C. The hysteresis

for the WARN output depends on the value of

teresis is 5°C. If

sis is 10°C. MAX6507 and MAX6508 have pin-selectable

hysteresis of 2°C or 10°C for both OVER and OK out-

puts (Table 2).

Applications Information

Thermal Considerations

The MAX6505–MAX6508 supply current is typically

30µA. When used to drive high-impedance loads, the

devices dissipate negligible power. Therefore, the die

temperature is essentially the same as the package

temperature. The key to accurate temperature monitor-

ing is good thermal contact between the MAX6505–

MAX6508 package and the device being monitored. In

some applications, the SOT23 packages may be small

enough to fit underneath a socketed microprocessor

(µP), allowing the device to monitor the µP’s tempera-

ture directly. Use the monitor’s output to reset the µP,

assert an interrupt, or trigger an external alarm.

Accurate temperature monitoring depends on the ther-

mal resistance between the device being monitored

and the MAX6505–MAX6508 die.

The rise in die temperature due to self-heating is given

by the following formula:

MAX6505–MAX6508, and

resistance. The typical thermal resistance is 115°C/W for

the SOT23 package. To limit the effects of self-heating,

minimize the output currents. For example, if the

MAX6505 sinks 5mA, the output voltage is guaranteed to

be less than 0.5V. Therefore, an additional 2.5mW of

Figure 1. Temperature Response—MAX6505UTP065 Outputs,

HYSTERESIS

≈ 2°C

HYSTERESIS

≈ 5°C

65°C

55°C

WARN

ALARM

Selection Table

CONTROL PINS

DESCRIPTION

S1

S0

(

°C)

GND

GND

5

GND

10

GND

20

30