LT1630 Linear Technology, LT1630 Datasheet - Page 12

• Manufacturer Part Number: LT1630
• Description: 30MHz/ 10V/us/ Dual/Quad Rail-to-Rail Input and Output Precision Op Amps
• Manufacturer: Linear Technology

APPLICATIONS
LT1630/LT1631
Power Dissipation
The LT1630/LT1631 amplifiers combine high speed and
large output current drive in a small package. Because the
amplifiers operate over a very wide supply range, it is
possible to exceed the maximum junction temperature of
150 C in plastic packages under certain conditions. Junc-
tion temperature T
perature T
The power dissipation in the IC is the function of the supply
voltage, output voltage and load resistance. For a given
supply voltage, the worst-case power dissipation P
occurs at the maximum supply current and when the
output voltage is at half of either supply voltage (or the
maximum swing if less than 1/2 supply voltage). There-
fore P
12
LT1630CN8: T
LT1630CS8: T
LT1631CS: T
P
DMAX
DMAX
+ IN
– IN
= (V
A
225
225
is given by:
and power dissipation P
R6
R7
S
J
• I
J
J
= T
SMAX
D5
= T
J
= T
U
is calculated from the ambient tem-
A
A
A
+ (P
) + (V
D6
+ (P
+ (P
INFORMATION
U
V
V
D
+
–
D
D
• 150 C/W)
S
Q4
• 190 C/W)
• 130 C/W)
/2)
Q7
D1
D2
2
Q3
/R
W
L
D
Figure 1. LT1630 Simplified Schematic Diagram
as follows:
Q5
Q6
U
V
BIAS
Q1
DMAX
D3
D4
+
Q2
I
1
To ensure that the LT1630/LT1631 are used properly,
calculate the worst-case power dissipation, get the ther-
mal resistance for a chosen package and its maximum
junction temperature to derive the maximum ambient
temperature.
Example: An LT1630CS8 operating on 15V supplies and
driving a 500 , the worst-case power dissipation per
amplifier is given by:
If both amplifiers are loaded simultaneously, then the total
power dissipation is 0.512W. The SO-8 package has a
junction-to-ambient thermal resistance of 190 C/W in still
air. Therefore, the maximum ambient temperature that the
part is allowed to operate is:
For a higher operating temperature, lower the supply
voltage or use the DIP package part.
P
= 0.143 + 0.113 = 0.256W
T
T
Q11
A
A
DMAX
= T
= 150 C – (0.512W • 190 C/W) = 53 C
Q9
R3
R1
J
Q12
= (30V • 4.75mA) + (15V – 7.5V)(7.5/500)
– (P
Q8
R4
R2
DMAX
V
Q13
–
+
R5
• 190 C/W)
I
2
OUTPUT BIAS
C
C
BUFFER
AND
C2
C1
Q15
Q14
1630/31 F01
OUT