ADT14GP AD [Analog Devices], ADT14GP Datasheet - Page 6

• Manufacturer Part Number: ADT14GP
• Description: Quad Setpoint, Programmable Temperature Monitor and Controller
• Manufacturer: AD [Analog Devices]

ADT14
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.
Choose I
For SET3,
For SET2,
Since I
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 .
This maintains a V
errors, choose 50 A < I
For SET4,
For SET1,
T4 = 100 C
V(SET4) = (T4 + 273.15)(5 mV/K)
T1 = 75 C
V(SET1) = (T1 + 273.15)(5 mV/K)
R1 = (V
R2 = (V[SET4] – V[SET1])/I
R3 = V(SET1)/I
T3 = 50 C
V(SET3) = (T3 + 273.15)(5 mV/K)
T2 = –10 C
V(SET2) = (T2 + 273.15)(5 mV/K)
R4 = (V
R5 = (V[SET3] – V[SET2])/I
R6 = V(SET2)/I
L1
L1
= I
Figure 14. ADT14 Setpoint Programming
REF
REF
R1
R2
R3
= I
L2
– V[SET4])/I
– V[SET3])/I
L2
= 25 A,
I
L1
= 25 A,
L1
L2
REF
R4
R5
R6
load current less than 200 A. To avoid
L
I
L2
I
< 200 A.
L
L1
L2
L1
L2
V
SET 4
SET 3
SET 2
SET 1
GND
REF
ADT14
HYS
–6–
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.
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).
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
R1 = (V
R2 = (V[SET4] – V[SET1])/I
R3 = (V[SET1] – V[SET3])/I
R4 = (V[SET3] – V[SET2])/I
R5 = V(SET2)/I
Table I. Common Hysteresis Values and Voltages
LO
HI
Hysteresis
0.65 C
1.5 C
5 C
REF
Figure 16. ADT14 Hysteresis Profile
Figure 15. Single Resistor Ladder
– V[SET4])/I
T
SET2
L
R4
R5
R2
R1
R3
50 A < I
V
REF
T
I
L
SET3
L
HYSTERESIS
TEMPERATURE
SET2
SET4
SET1
SET3
L
50 A < I
T4 > T1 > T3 > T2
L
L
L
< 200 A
Connect Pin 11 to
+2.5 V Reference
Leave Open
Ground
T
SET1
L
< 200 A
T
SET4
REV. 0