Datasheet AS273H5LPT, AS273H5LPB, AS273H5LPA, AS273H5LP13, AS273H1LPA Datasheet (ASTEC)

1

ASTEC Semiconductor

AS273

Over-Temperature Detector

Features

¥

Programmable to three different
over-temperature thresholds

¥

2.5 V temperature compensated
bandgap reference trimmed to 1%

¥

Open collector output goes low
on over-temp condition

¥

±3¡C temperature accuracy

¥

Reference shunt current serves to
program over-temp threshold

¥

Available with 5¡C or 10¡C of
temperature hysteresis

¥

Available in a wide range of over­temp thresholds to fit most
temperature monitoring
applications

¥

Now available in the SOT-223 for
improved substrate temperature
sensing

Description

The AS273 is a series of programmable over-temperature
detectors. Each is internally composed of a precision 2.5 V
shunt reference, a proportional-to-absolute temperature
thermal sensor, a comparator with controlled hysteresis, and
an open collector output that indicates an over-temp condi­tion. The threshold for the over-temp signal can be set to any
of three values on a given part by controlling the magnitude
of the reference shunt current.

The AS273 has an excellent absolute temperature accuracy
of ±3¡C for each of the three over-temp thresholds. The low
power dissipation minimizes any temperature sensing errors
due to self-heating. There is either 5¡C or 10¡C of tempera­ture hysteresis to prevent bouncing when an over-temp con­dition is removed.

The packaging options available with the AS273 make it
appealing to a wide variety of temperature-sensing applica­tions. The TO-92 package can be mechanically clamped to a
heat sink to monitor the temperature of power devices. The
8L-SOIC and SOT-223 surface mount packages allow for
temperature sensing in high component density applications.

SEMICONDUCTOR

Pin Configuration Ñ Top view

OUT

TO-92 (LP) SOT-223 (G)

GROUND

V

REF

OUT

GROUND

V

REF

SOIC (D)

VREF

DO NOT USE

DO NOT USE

GROUND

OUT

N/C

N/C

N/C

1

2

3

4

8

7

6

5

2

ASTEC Semiconductor

AS273 Over-Temperature Detector

Ordering Information

Functional Block Diagram

Pin Function Description

Pin Number Function Description

1 V

REF

2.5 V shunt reference; current into V

REF

pin also programs

over-temperature trip point to one of three TOTvalues

2 GND Circuit ground and silicon substrate

3 OUT Open collector output. Output low when die temperature exceeds

programmed trip point

Circuit Type:
Over-Temperature Detector

Temperature Option:
(Refer to Table A)

Packaging Option:
A
B
T
13

Package Style:
D
G
LP

Hysteresis Option:
1
5

= Ammo Pack
= Bulk
= Tube
= Tape and Reel (13" Reel Dia)

= SOIC
= SOT-223
= TO-92

= 10°C
= 5°C

AS273 D 1 D A

Ð

+

CURRENT

PROGRAMMING

1

3

2

V

REF

2.5 V

+
Ð

GND

OUT

4 mV/K

Table A – Temperature Options

Code T

OT1

T

OT2

T

OT3

D 40 45 50
F 75 80 85
G 90 95 100
H 105 110 115

3

ASTEC Semiconductor

AS273Over-Temperature Detector

Absolute Maximum Ratings

Parameter Symbol Rating Unit

Reference Current V

REF

±10 mA

Output Current I

OUT

±10 mA

Output Voltage V

OUT

18 V

Continuous Power Dissipation at 25¡C

TO-92 P

D

775 mW

8-SOIC P

D

750 mW

SOT-223 P

D

1000 mW

Junction Temperature T

J

150 ¡C

Storage Temperature T

STG

Ð65 to 150 ¡C

Lead Temp, Soldering 10 Seconds T

L

300 ¡C

Stresses greater than those listed under ABSOLUTE MAXIMUM RATINGS may cause permanent damage to the device. This is a
stress rating only and functional operation of the device at these or any other conditions above those indicated in the operational sec­tions of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect reliability.

Typical Thermal Resistances

Package θ

JA

θ

JC

Typical Derating

SOT-223 115¡C/W 8¡C/W 8.7 mW/¡C

TO-92 160¡C/W 80¡C/W 6.3 mW/¡C

8L SOIC 175¡C/W 45¡C/W 5.7 mW/¡C

4

ASTEC Semiconductor

AS273 Over-Temperature Detector

Electrical Characteristics

Electrical Characteristics are guaranteed over the full junction temperature range (0 to 125¡C). Ambient temperature must be derated
based upon power dissipation and package thermal characteristics.

Parameter Symbol Test Condition Min. Typ. Max. Unit

Reference

Reference Voltage V

REF

I

REF

= 2 mA, TJ= 25¡C 2.500 2.525 2.550 V

Load Regulation V

Id

0.65 mA ≤ I

REF

≤ 5.5 mA 5 10 mV

Average Temperature Coefficient ∆V

REG

/∆T 0.65 mA ≤ I

REF

≤ 5.5 mA 75 ppm/¡C

Output

Saturation Voltage V

OL

I

OUT

= 4 mA; TJ> T

OT

200 400 mV

Breakdown Voltage BV I

OUT

= 100 µA; T

J

< T

OT

18 30 V

Leakage Current I

OH

V

OUT

= 18 V; TJ< T

OT

1 1000 nA

Over-Temp Sensing

Temperature Accuracy T

OT(1)

0.7 mA ≤ I

REF

≤ 1.3 mA Ð3 +3 ¡C

T

OT(2)

1.55 mA ≤ I

REF

≤ 2.6 mA Ð3 +3 ¡C

T

OT(3)

3.0 mA ≤ I

REF

≤ 5.0 mA Ð3 +3 ¡C

Hysteresis H

OT

Percentage Error in Nominal Hysteresis

Ð30 +30 %

+5V

I

REF

OUTV

REF

GND

AS273

R

LOAD

2 kΩ

Test Circuit

Figure 1. Test Circuit for Output Hysteresis Curve

5

ASTEC Semiconductor

AS273Over-Temperature Detector

Typical Performance Curves

Figure 2

Figure 4

Figure 3

Figure 5

0 25 50 75 100 125 150

300

275

250

225

200

175

150

125

100

Minimum Reference Current for Regulation

Junction Temperature, TJ (°C)

Turn-on Current, I

REF

(µA)

0 200 400 600 800 1000

3

2

1

0

Turn-on Characteristic of Reference

Reference Current, I

REF

(µA)

Reference Voltage, V

REF

(V)

0 25 50 75

Junction Temperature, T

J

(°C)

100 125 150

2.55

2.54

2.53

2.52

2.51

2.50

Temperature Regulation of Reference

Reference Voltage, V

REF

(V)

0 25 50 75

Junction Temperature, T

J

(°C)

100 125 150

10

9
8
7
6
5

4
3

2

1
0

Load Regulation of Reference Over-temperature

Load Regulation (mV)

6

ASTEC Semiconductor

AS273 Over-Temperature Detector

Typical Performance Curves

Figure 6

Figure 8

Figure 7

0.001 0.01 0.1 1 10

900

800

700

600

500

400

300

200

100

Output Saturation Characteristic

Output Voltage, V

OUT

(mV)

125°C

100°C

75°C

50°C

25°C

0°C

Saturation Current, I

OUT

(mA)

88 90 92 94

Over-temperature Threshold (°C)

96 98 100 102

0

10

20

30

40

50

I

REF

= 1 mA I

REF

= 2 mA I

REF

= 4 mA

Typical Over-temperature Threshold Distribution – Option G

Distribution of Population (%)

0 2 4 6 8 10 12

120

100

80

60

40

20

0

8L SOIC

TO-92

SOT-223

Time (s)

Percent of Thermal Equilibrium (%)

Thermal Response by Package in a Stirred Oil Bath

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ASTEC Semiconductor

Theory of Operation

The AS273 is an over-temperature detector that
gives an over-temp signal when the device
junction temperature exceeds a programmed
over-temp threshold. Over-temp threshold pro­gramming is accomplished by controlling the
magnitude of the reference shunt current.

Over-temperature Condition

Internal to the AS273 is a temperature sensor
which creates a voltage proportional to the
absolute temperature (PTAT) of the die. This
PTAT voltage is compared with a fraction of the

reference voltage corresponding to the over­temperature threshold. When the PTAT voltage
exceeds the reference voltage, the comparator is
tripped and an over-temp signal is given to the
output. The output consists of an open collector
transistor that pulls low on an over-temp condi­tion. Built into the comparator is temperature hys­teresis, which keeps the over-temp signal until
the junction temperature has fallen 5¡C (or 10¡C)
below the over-temp threshold. Figure 9 shows
the output of the AS273 (with 10¡C of hysteresis)
over a range of junction temperature.

AS273Over-Temperature Detector

Figure 9. Temperature Characteristic of Output with 10¡C of Hysteresis

5

0

I

REF

= 4 mA

5

0

I

REF

= 2 mA

5

0

I

REF

= 1 mA

OT1 OT2 OT3OT1-5OT1-10

Output Voltage, V

Junction Temperature, TJ (°C)

8

ASTEC Semiconductor

Current Programming

There are three different over-temp thresholds
for each AS273. The detector senses the amount
of current being shunted through the 2.5 V refer­ence of pin 1 and programs an over-temp thresh-

old based on the magnitude of that current. Fig­ure 10 illustrates the ranges of reference shunt
current, I

REF

, associated with each of the three

over-temp thresholds, OT1, OT2 and OT3.

AS273 Over-Temperature Detector

Figure 10. Reference Shunt Current Programming Ranges of Over-temperature Thresholds

OT3

OT2

OT1

0 1 2 3 4 5

Over-temperature Thresholds (°C)

Reference Shunt Current, I

REF

(mA)

Output Disabled

Transition Regions

9

ASTEC Semiconductor

Typical Detector Applications

Over-Temperature Detector

The AS273 senses the ambient temperature and
turns on its open collector output to indicate an
over-temp condition. Each AS273 can be pro­grammed to any one of its three over-temp
thresholds by forcing a different range of current
into the reference pin.

Dual Speed Fan Control

The diagram of Figure 12 shows an easy way to
implement smart fan control. When the tempera­ture is below the over-temp trip point set by R1,
the detectorÕs open collector output is off. There­fore, the fan speed is controlled by the ratio
between R2 and R3. When the temperature
exceeds the over-temp set point, the open col­lector is turned on, and fan motor runs at its full
speed.

AS273Over-Temperature Detector

Figure 11.

Figure 12.

V

CC

R2R1

V

OUT

REF OUT

GND

AS273

+12 V

R1

9.1 kΩ

REF OUT

GND

AS273

R2
10 kΩ

R3
10 kΩ

Q1

M

10

ASTEC Semiconductor

AS273 Over-Temperature Detector

Over-Temperature Protection with
Latch (Low Current)

The diagram of Figure 13 illustrates how a power
supply can be shut down with a simple two­transistor latch. When the programmed over­temp is reached, the open collector output of the
AS273 enables the latch and pulls V

CC

below the
under-voltage threshold of the AS3842, shutting
off the AS3842. The latch can be disabled only
with a power reset.

Over-Temperature Protection with
Hysteresis

In this over-temperature circuit, the hysteresis of
the AS273 is used to automatically restart the
power supply after the temperature drops below
the hysteresis temperature window. R1 supplies
the current to power the AS273 after the AS3842
and the power supply are shut down. R2 and
the external zener set the over-temperature trip
point.

Figure 13.

Figure 14.

V

CC

ICC = 400 mA
MAX.

REF OUT

GND

AS273

COMP V

REG

V

FB

V

CC

SENSE OUT

RT/CT GND

AS3842

R1
1 k

R3
350 Ω

+

R2
350 Ω

V BULK

R1

REF OUT

GND

AS273

R2

COMP V

REG

V

FB

V

CC

SENSE OUT

RT/CT GND

AS3842

11

ASTEC Semiconductor

AS273Over-Temperature Detector

Adjustable Hysteresis Temperature
Detector

The hysteresis of the AS273 can be increased by
reprogramming the device to a lower tempera­ture set point upon over-temp. A higher tempera­ture 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 low­temp set point. As a result, the hysteresis esca­lates by the difference between the high-temp
and the low-temp set points.

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 two­transistor latch. When the temperature is below
the low-temp set point, V

OUT

is in the high state

(V

OUT

= 5.0 V). When the temperature exceeds
the low-temp set point, the two-transistor latch is
set and V

OUT

is pulled low (V

OUT

= 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 (V

OUT

= 0.2 V). This circuit is highly use­ful in applications where a stand-by, a warning
and a shut-down state are required.

Figure 15.

Figure 16.

V

CC

R2

R1

V

OUT

REF OUT

GND

AS273

V

CC

+5 V

R1

2.4 kΩ

REF OUT

GND

AS273

R2
1 kΩ

R3

1.5 kΩ

R5
2 kΩ

R4
470 Ω

R6

500 Ω

+

V

O

C1
1 µF

Stand-by State:
Warning State:
Shut-down State:

T < T1, T2
T1 < T < T2
T1, T2 < T

V

O

= 5.0 V

V

O

= 2.5 V

V

O

= 0.2 V

12

ASTEC Semiconductor

AS273 Over-Temperature Detector

Notes