Detailed Description

The MAX6516–MAX6519 fully integrated temperature

switches incorporate a fixed reference, an analog tem-

perature sensor, and a comparator. The temperature at

which the two reference voltages are equal determines

the temperature trip point. OUT is an analog voltage

that varies with the die’s temperature. Pin-selectable

2°C or 10°C hysteresis keeps the digital output from

oscillating when the die temperature approaches the

threshold temperature. The MAX6516 and MAX6518

have an active-high, push-pull output structure that can

sink or source current. The MAX6517 and MAX6519

have an active-low, open-drain output structure that

can only sink current. The internal power-on reset cir-

cuit guarantees the logic output is at its +25°C state for

at least 50µs.

Analog Output

OUT is an analog output that is proportional to the die

temperature. OUT voltage range is between 0.77V to

2.59V, within the temperature range of -45°C to

+125°C. For applications with a switching threshold of

-45°C, the supply voltage must be greater than 4.5V.

The temperature-to-voltage transfer function is approxi-

mately linear and can be described by the quadratic

equation:

2

where T = temperature in °C.

In most cases, a linear approximation can be applied:

Therefore,

Hysteresis Input

The HYST input selects the devices’ temperature hys-

teresis and prevents the output from oscillating when the

temperature approaches the trip point. Connect HYST to

Logic Temperature Indicators

Overtemperature Indicator (Hot Thresholds)

TOVER and TOVER designations apply to thresholds

+85°C, +95°C, +105°C, +115°C). All “hot” thresholds are

positive temperatures.

The overtemperature indicator output is open-drain

active low (TOVER) or push-pull active high (TOVER).

TOVER goes low when the die temperature exceeds

the factory-programmed temperature threshold. TOVER

should be pulled up to a voltage no greater than 5.5V

with a 100k

Ω pullup resistor. TOVER is a push-pull

active-high CMOS output that goes high when the die

temperature exceeds the factory-programmed temper-

ature threshold.

Undertemperature Indicator (Cold Thresholds)

TUNDER and TUNDER designations apply to thresholds

-35°C, -45°C). The undertemperature indicator output is

open drain, active low (TUNDER), or push-pull active

high (TUNDER). TUNDER goes low when the die tem-

perature goes below the factory-programmed tempera-

ture threshold. TUNDER should be pulled up to a

voltage no greater than 5.5V with a 100k

Ω pullup resis-

tor. TUNDER is a push-pull active-high CMOS output

that goes high when the die temperature falls below the

factory-programmed temperature threshold.

Applications Information

Temperature-Window Alarm

The MAX6516/MAX6518 logic outputs assert when the

die temperature is outside the factory-programmed

range. Combining the outputs of two devices creates

an over/undertemperature alarm. Two MAX6516s or

two MAX6518s are used to form two complementary

pairs, containing one cold trip-point output and one hot

trip-point output. The assertion of either output alerts

the system to an out-of-range temperature. The

MAX6516 push-pull output stages can be ORed to

produce a thermal out-of-range alarm (Figure 1).

More favorably, two MAX6517s or two MAX6519s can

be directly wire-ORed with a single external resistor to

accomplish the same task. The temperature window

alarms shown in Figure 2 can be used to accurately

determine when a device’s temperature falls out of the

-5°C to +75°C range. The thermal overrange signal can

be used to assert a thermal shutdown, power-up,

recalibration, or other temperature-dependent function.

T

V

C

OUT

=+

°

−

1 8015

0 01062

30

.

.

Low-Cost, 2.7V to 5.5V, Analog Temperature

Sensor Switches in a SOT23

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