Low-Cost, +2.7V to +5.5V, Micropower

Temperature Switches in SOT23 and TO-220

4

_______________________________________________________________________________________

Pin Description

1, 2

1, 2

Ground. Not internally connected. Tie both ground pins togeth-

er close to the chip. Pin 2 provides the lowest thermal resis-

tance to the die.

1, 2

PIN

1, 2

GND

3

3

Hysteresis Input. Connect HYST to GND for +2°C hysteresis, or

3

3

HYST

4

4

Supply Input (+2.7V to +5.5V)

5

—

Open-Drain, Active-Low Output. TOVER goes low when the die

temperature exceeds the factory-programmed temperature

threshold. Connect to a 100k

Ω pull-up resistor. May be pulled

—

—

TOVER

4

4

—

5

Push-Pull Active-High Output. TOVER goes high when the die tem-

perature exceeds the factory-programmed temperature threshold.

—

—

Open-Drain, Active-Low Output. TUNDER goes low when the

die temperature goes below the factory-programmed tempera-

ture threshold. Connect to a 100k

Ω pull-up resistor. May be

5

—

TUNDER

—

—

Push-Pull Active-High Output. TUNDER goes high when the die tem-

perature falls below the factory-programmed temperature threshold.

—

5

TUNDER

—

—

TOVER

MAX6502

MAX6501

MAX6503

MAX6504

NAME

FUNCTION

________________General Description

The MAX6501–MAX6504 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 (Figure 1). The temperature at

which the two reference voltages are equal determines

the temperature trip point. Pin-selectable +2°C or

+10°C hysteresis keeps the output from oscillating

when the die temperature approaches the threshold

temperature. The MAX6501/MAX6503 have an active-

low, open-drain output structure that can only sink cur-

rent. The MAX6502/MAX6504 have an active-high,

push-pull output structure that can sink or source cur-

rent. The internal power-on reset circuit guarantees the

The MAX6501–MAX6504 are available with factory-

preset temperature thresholds from -45°C to +115°C in

10°C increments. Table 1 lists the available temperature

threshold ranges. The MAX6501/MAX6503 outputs are

intended to interface with a microprocessor (µP) reset

input (Figure 2). The MAX6502/MAX6504 outputs are

intended for applications such as driving a fan control

(Figure 3).

Hysteresis Input

The HYST pin is a CMOS-compatible input that selects

or a low level (+2°C for HYST = GND). Hysteresis pre-

vents the output from oscillating when the temperature

approaches the trip point. The HYST pin should not

voltages cause increased supply current. The actual

amount of hysteresis depends on the part’s pro-

grammed trip threshold. (See the Typical Operating

Characteristics graphs.)

Table 1. Factory-Programmed Threshold

Range

MAX6503

MAX6504

MAX6501

MAX6502

PART