ISL24021 Datasheet, PDF (10/12 Pages) Intersil Corporation – 1A Rail-to-Rail Input-Output Operational Amplifier

ISL24021
.
INN
INP
ISL24021
0.1µF
VDD
4.7µF
VSS
4.7µF
0.1µF
THERMAL PAD
CONNECTED TO VSS
RSNUBBER
OUT
ZL
CSNUBBER
FIGURE 25. OUTPUT SNUBBER CIRCUIT
.
INN
INP
ISL24021
0.1µF
VDD
4.7µF
VSS
4.7µF
0.1µF
THERMAL PAD
CONNECTED TO V_SS
RSERIES
OUT
ZL
FIGURE 26. OUTPUT SERIES RESISTOR CIRCUIT
Typical Application Circuit
A typical application of the ISL24021 is as a TFT-LCD V_COM
driver (see Figure 27). A V_COM driver maintains the
backplane common voltage of a TFT-LCD panel. Maintaining
the V_COM voltage at a steady level is critical to panel
performance. The ability of the ISL24021 to source/sink
large peak short circuit currents make it ideal as a V_COM
driver. The ±1A short circuit current capability combined with
a large bandwidth and fast settling time give the ISL24021
ideal V_COM driver characteristics, and make it a great choice
for TFT-LCD applications.
VCOM
CALIBRA TOR /
RESISTOR
LADDER
INN
INP
ISL24021
-
+
VDD = 15V
0.1µF _4.7µF
TFT-LCD
0.1µF
OUT
+
PANEL
VSS
CSTORAGE
CAPACITANCE
THERMAL PAD CONNECTED
TO VSS
NOTE: CSTORAGE WILL VARY
DEPENDING ON THE
APPLICATION
FIGURE 27. TYPICAL APPLICATION CIRCUIT: TFT-LCD V_COM
Power Dissipation
With a 300mA maximum continuous output drive capability, it
is possible to exceed the rated +150°C maximum junction
temperature. It is important to calculate the maximum power
dissipation of the ISL24021 for the application. Proper load
conditions will ensure that the ISL24021 junction temperature
stays within a safe operating region.
The ISL24021 has a built-in thermal protection, which
automatically shuts the output OFF (high impedance) when
the die temperature reaches +165°C. This ensures safe
operation and prevents internal damage to the device. When
the die cools by +15°C the output will automatically turn ON.
The maximum power dissipation allowed in a package is
determined according to Equation 1:
P_DMAX
=
T_{----J---M-----A----X-----–-----}T_{----A---M-----A----X--}
Θ_JA
(EQ. 1)
where:
• T_JMAX = Maximum junction temperature
• T_AMAX = Maximum ambient temperature
• θ_JA = Thermal resistance of the package
• P_DMAX = Maximum power dissipation in the package
The actual maximum power dissipation of the IC is the total
quiescent supply current, times the total power supply
voltage, plus the power dissipation in the IC caused by the
loading condition.
Sourcing:
P_DMAX = V_S × I_S + [V_DD – V_OUT ) × I_LOAD]
(EQ. 2)
Sinking:
P_DMAX = V_S × I_S + [V_OUT – V_SS ) × I_LOAD]
(EQ. 3)
• V_S = Total supply voltage range (V_DD - V_SS)
• I_S = Device supply current
• V_DD = Positive supply voltage
• V_SS = Negative supply voltage
• V_OUT = Output voltage
• I_LOAD = Load current
Device overheating can be avoided by calculating the
minimum resistive load condition, R_LOAD, resulting in the
highest power dissipation. To find R_LOAD, set the two
P_DMAX equations equal to each other and solve for
V_OUT/I_LOAD. Reference the package power dissipation
curve, Figure 28, for further information.
10
FN6637.0
June 3, 2009