ISL24021_15 Datasheet, PDF (10/13 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--_Θ---–-_J---_A^T---^A----^M-----^A---^X-
(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
FN6637.1
October 18, 2011