Quad Setpoint, Programmable
Temperature Monitor and Controller
a
ADT14
FEATURES
FUNCTIONAL BLOCK DIAGRAM
Four Programmable Temperature Setpoints
Programmable Thermal Hysteresis
Accuracy ؎3؇C Typ from –40؇C to +125؇C
Temperature Output Scale Factor = 5 mV/K
Resistor Programmable Temperature Setpoints
5 mA Open-Collector Setpoint Outputs
Internal 2.5 V Reference
2.5V
HYSTERESIS
V
REF
SETPOINT
OUTPUT 1
SET 1
CURRENT
MIRROR
SETPOINT
OUTPUT 2
600 A Max Quiescent Current at +5 V
SET 2
APPLICATIONS
Power Supply Monitor and Control System
Multiple Fan Controller System
Workstation Thermal Management System
SETPOINT
OUTPUT 3
SET 3
WINDOW
COMPARATORS
SETPOINT
OUTPUT 4
SET 4
GENERAL DESCRIPTION
The ADT14 is a temperature sensor and controller that generates
an output voltage proportional to temperature and provides four
temperature trip points. The four trip points, or temperature
setpoints, and their hysteresis are determined by voltage levels set
by the user. An on-chip voltage reference provides an easy method
for setting the temperature trip points.
HYSTERESIS
VOLTAGE
VOLTAGE
REFERENCE
AND
V+
VPTAT
SENSOR
TEMPERATURE
OUTPUT
ADT14
GND
The ADT14 consists of a bandgap voltage reference combined
with four matched comparators. The reference provides both a
temperature-stable 2.5 V output, and a voltage proportional to
absolute temperature (VPTAT) which has a precise temperature
coefficient of 5 mV/K = 5 mV/(°C +273.15). The VPTAT out-
put is nominally 1.49 V at +25°C. The comparators determine
whether the VPTAT output is above the voltages set up by
external resistive dividers (temperature trip points) and generate
an open-collector output signal when one of their respective
thresholds has been exceeded.
PIN CONFIGURATIONS
DIP & SO
OUTPUT 1
SETPOINT 1
NC
OUTPUT 4
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
SETPOINT 4
2.5V REFERENCE
V+
ADT14
NC
TOP VIEW
(Not to Scale)
GROUND
VPTAT
NC
Hysteresis is programmed by a user-selected voltage at the hys-
teresis pin. This voltage adjusts the hysteresis current which is
used to generate a hysteresis offset voltage. The comparator’s
noninverting inputs are connected in parallel, which guarantees
that there is no hysteresis overlap and eliminates erratic transi-
tions between adjacent trip zones.
HYSTERESIS
SETPOINT 3
OUTPUT 3
SETPOINT 2
OUTPUT 2
NC = NO CONNECT
Using a proprietary thin-film resistor process in conjunction
with production laser trimming, a temperature accuracy of ±3°C
at 25°C is guaranteed. The open-collector outputs are capable
of sinking 5 mA, and provide TTL/CMOS logic compatibility
with an external pull-up resistor. Operating from a single 5 V
supply, the quiescent current is 600 µA max.
The ADT14 is available in the 16-lead epoxy DIP and SO
(small outline) packages.
REV. 0
Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 617/329-4700
Fax: 617/326-8703
World Wide Web Site: http://www.analog.com
© Analog Devices, Inc., 1997
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