LT1215 Linear Technology, LT1215 Datasheet - Page 13

• Manufacturer Part Number: LT1215
• Description: 23MHz/ 50V/us/ Single Supply Dual and Quad Precision Op Amps
• Manufacturer: Linear Technology

Supply Voltage
The LT1215/LT1216 op amps are fully functional and all
internal bias circuits are in regulation with 2.2V of supply.
The amplifiers will continue to function with as little as
1.5V, although the input common mode range and the
phase margin are about gone. The minimum operating
supply voltage is guaranteed by the PSRR tests which are
done with the input common mode equal to 500mV and a
minimum supply voltage of 2.5V. The LT1215/LT1216 are
guaranteed over the full – 55 C to 125 C range with a
minimum supply voltage of 2.7V.
The positive supply pin of the LT1215/LT1216 should be
bypassed with a small capacitor (about 0.01 F) within an
inch of the pin. When driving heavy loads and for good
settling time, an additional 4.7 F capacitor should be
used. When using split supplies, the same is true for the
negative supply pin.
Power Dissipation
The LT1215/LT1216 amplifiers combine high speed and
large output current drive into very small packages. Be-
cause these amplifiers work over a very wide supply range,
it is possible to exceed the maximum junction temperature
under certain conditions. To insure that the LT1215/
LT1216 are used properly, calculate the worst case power
dissipation, define the maximum ambient temperature,
select the appropriate package and then calculate the
maximum junction temperature.
The worst case amplifier power dissipation is the total of
the quiescent current times the total power supply voltage
plus the power in the IC due to the load. The quiescent
supply current of the LT1215/LT1216 has a positive tem-
perature coefficient. The maximum supply current of each
amplifier at 125 C is given by the following formula:
The power in the IC due to the load is a function of the
output voltage, the supply voltage and load resistance. The
worst case occurs when the output voltage is at half
supply, if it can go that far, or its maximum value if it
cannot reach half supply.
A
PPLICATI
I
V
SMAX
S
is the total supply voltage.
= 8.4 + 0.076 • (V
O
U
S
I FOR ATIO
U
S
– 5) in mA
W
U
For example, calculate the worst case power dissipation
while operating on 15V supplies and driving a 500 load.
If this is the dual LT1215, the total power in the package is
twice that, or 0.844W. Now calculate how much the die
temperature will rise above the ambient. The total power
dissipation times the thermal resistance of the package
gives the amount of temperature rise. For this example, in
the SO-8 surface mount package, the thermal resistance is
150 C/W junction-to-ambient in still air.
The maximum junction temperature allowed in the plastic
package is 150 C. Therefore the maximum ambient al-
lowed is the maximum junction temperature less the
temperature rise.
That means the SO-8 dual can only be operated at or below
room temperature on 15V supplies with a 500 load.
Obviously this is not recommended. Lowering the supply
voltage is recommended, or use the DIP packaged part.
As a guideline to help in the selection of the LT1215/
LT1216, the following table describes the maximum sup-
ply voltage that can be used with each part based on the
following assumptions:
PART
LT1215MJ8
LT1215CN8
LT1215CS8
LT1216CN
LT1216CS
I
P
P
Temperature Rise = P
Maximum Ambient = 150 C – 126.6 C = 23.4 C
1. The maximum ambient is 70 C or 125 C depending
2. The load is 500 , includes the feedback resistors.
3. The output can be anywhere between the supplies.
SMAX
DMAX
DMAX
on the part rating.
= 8.4 + 0.076 • (30 – 5) = 10.3mA
= 2 • V
= 2 • 15V • 10.3mA + (15V – 7.5V) • 7.5V/500
= 0.309 + 0.113 = 0.422 Watt per Amp
20.3V or 14.5V
15.7V or 10.8V
16.4V or 11.4V
13.0V or 8.7V
MAX SUPPLIES
15.0V or 10.3V
S
• I
SMAX
= 126.6 C
DMAX
+ (V
•
S
LT1215/LT1216
– V
JA
MAX POWER AT MAX T
= 0.844W • 150 C/W
OMAX
1143mW
) • V
500mW
800mW
533mW
800mW
OMAX
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A