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AS273D1D13

Over-Temperature Detector

Astec Semiconductor => Silicon Link 

Over-Temperature Detector

Adjustable Hysteresis Temperature

Detector

The hysteresis of the AS273 can be increased by

reprogramming the device to a lower tempera-

ture set point upon over-temp. A higher tempera-

ture is set by R1. When the temperature exceeds

the high-temp set point, the open collector output

is turned on and allows R2 to rob current from the

reference pin and resets the AS273 to the low-

temp set point. As a result, the hysteresis esca-

lates by the difference between the high-temp

and the low-temp set points.

AS273

VCC

R1

R2

VOUT

REF

OUT

AS273

GND

Figure 15.

Three-State Temperature Sensor

In the Three-State Temperature Sensor shown in

Figure 16, a low-temp trip point is selected by R1

and a high-temp trip point is selected by the two-

transistor latch. When the temperature is below

the low-temp set point, VOUT is in the high state

(VOUT = 5.0 V). When the temperature exceeds

the low-temp set point, the two-transistor latch is

set and VOUT is pulled low (VOUT = 2.5 V). The

latch also supplies extra current to the reference

pin to reset the IC to sense a higher temperature.

Once the high-temp is reached, the output will

turn ÒonÓ (VOUT = 0.2 V). This circuit is highly use-

ful in applications where a stand-by, a warning

and a shut-down state are required.

VCC

+5 V

R1

2.4 kΩ

R2

R3

1 kΩ

1.5 kΩ

R4

470 Ω

R5

2 kΩ

R6

500 Ω

REF

OUT

AS273

VO

+ C1

1 µF

GND

Stand-by State:

Warning State:

Shut-down State:

T < T1, T2

T1 < T < T2

T1, T2 < T

Figure 16.

VO = 5.0 V

VO = 2.5 V

VO = 0.2 V

ASTEC Semiconductor

11

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