ADT14

–6–

REV. 0

APPLICATIONS INFORMATION

Programming the ADT14

To program any of the four temperature trip points, simply set

the voltage at the setpoint pin equal to the voltage expected at

the VPTAT output at the desired trip temperature. The on-

board 2.5 V precision reference provides a temperature stable

output that is used to establish the setpoint voltages. Figure 14

illustrates the basic temperature setpoint configuration. This

parallel resistor ladder configuration uses six resistors to set the

four setpoint voltages.

R4

R1

R2

R5

R3

R6

SET 4

SET 3

SET 2

SET 1

GND

ADT14

HYS

Figure 14. ADT14 Setpoint Programming

For SET4,

T4 = 100

°C

V(SET4) = (T4 + 273.15)(5 mV/K)

For SET1,

T1 = 75

°C

V(SET1) = (T1 + 273.15)(5 mV/K)

µA,

For SET3,

T3 = 50

°C

V(SET3) = (T3 + 273.15)(5 mV/K)

For SET2,

T2 = –10

°C

V(SET2) = (T2 + 273.15)(5 mV/K)

For the example shown in Figure 14 and the related equations,

Setpoint 4 was chosen as highest temperature trip point, fol-

lowed in order by Setpoint 1, Setpoint 3 and Setpoint 2. The

user may choose to alter this order at will as all the setpoint

inputs and trip point outputs are identical in operation. The

minimum recommended parallel ladder resistance is 12.5 k

Ω.

errors, choose 50

µA < I

µA.

For those applications where setpoints do not need to be

changed, a single ladder of five resistors can be used. Figure 15

illustrates a single resistor ladder configuration.

50

µA < I

µA

R1

R2

R3

R4

R5

SET4

SET1

SET3

SET2

T4 > T1 > T3 > T2

Figure 15. Single Resistor Ladder

Temperature Hysteresis

Temperature hysteresis is the number of degrees below the

original setpoint temperature that must be sensed by the

ADT14 before the setpoint comparator will be reset and the

open-collector output disabled. Figure 16 shows the hysteresis

profile. Hysteresis is programmed by the user by setting a speci-

fied voltage at the hysteresis pin (See Table I).

HYSTERESIS

HI

LO

TEMPERATURE

Figure 16. ADT14 Hysteresis Profile

Table I. Common Hysteresis Values and Voltages

Hysteresis

Connect Pin 11 to

0.65

°C

+2.5 V Reference

1.5

°C

Leave Open

5

°C

Ground

The voltage on Pin 11 programs the internal hysteresis current,

which is mirrored and fed to a buffer controlled by an analog

switch. After a temperature setpoint has been exceeded and a

comparator tripped, the buffer is enabled, allowing hysteresis

current to flow. This current generates a hysteresis offset voltage