ISL28288 Datasheet, PDF (11/12 Pages) Intersil Corporation – Dual Micropower Single Supply Rail-to-Rail Input and Output (RRIO) Precision Op-Amp

ISL28288
currents, components can be mounted to the PC board
using Teflon standoff insulators.
HIGH IMPEDANCE INPUT
IN
V+
1/2 ISL28288
FIGURE 38. GUARD RING EXAMPLE FOR UNITY GAIN
AMPLIFIER
Example Application
Thermocouples are the most popular temperature-sensing
device because of their low cost, interchangeability, and
ability to measure a wide range of temperatures. The
ISL28288 (Figure 39) is used to convert the differential
thermocouple voltage into single-ended signal with 10X gain.
The ISL28288's rail-to-rail input characteristic allows the
thermocouple to be biased at ground and the amplifier to run
from a single 5V supply.
R₄
R₃ 10kΩ
R₂
K TYPE
THERMOCOUPLE
10kΩ
100kΩ
+ ^V+
ISL28288
-
V-
+
5V
410µV/°C
R₁
100kΩ
FIGURE 39. THERMOCOUPLE AMPLIFIER
Current Limiting
The ISL28288 has no internal current-limiting circuitry. If the
output is shorted, it is possible to exceed the Absolute
Maximum Rating for output current or power dissipation,
potentially resulting in the destruction of the device.
Power Dissipation
It is possible to exceed the +150°C maximum junction
temperatures under certain load and power-supply
conditions. It is therefore important to calculate the
maximum junction temperature (T_JMAX) for all applications
to determine if power supply voltages, load conditions, or
package type need to be modified to remain in the safe
operating area. These parameters are related as follows:
T_JMAX = T_MAX + (θ_JAxPD_MAXTOTAL)
(EQ. 1)
where:
• P_DMAXTOTAL is the sum of the maximum power
dissipation of each amplifier in the package (PD_MAX)
• PD_MAX for each amplifier can be calculated as follows:
PD_MAX
=
2*V_S × I_SMAX + (V_S
-
V_OUTMAX
)
×
V_{-----O----U----T----M-----A----X--}
R_L
(EQ. 2)
where:
• T_MAX = Maximum ambient temperature
• θ_JA = Thermal resistance of the package
• PD_MAX = Maximum power dissipation of 1 amplifier
• V_S = Supply voltage
• I_MAX = Maximum supply current of 1 amplifier
• V_OUTMAX = Maximum output voltage swing of the
application
• R_L = Load resistance
11
FN6339.0
September 20, 2006