LT1206C Linear Technology, LT1206C Datasheet - Page 12

• Manufacturer Part Number: LT1206C
• Description: 250mA/60MHz Current Feedback Amplifier
• Manufacturer: Linear Technology

LT1206
A
power plane layer either inside or on the opposite side of
the board. Although the actual thermal resistance of the
PCB material is high, the length/area ratio of the thermal
resistance between the layer is small. Copper board stiff-
eners and plated through holes can also be used to spread
the heat generated by the device.
Tables 1 and 2 list thermal resistance for each package. For
the TO-220 package, thermal resistance is given for junc-
tion-to-case only since this package is usually mounted to
a heat sink. Measured values of thermal resistance for
several different board sizes and copper areas are listed for
each surface mount package. All measurements were
taken in still air on 3/32" FR-4 board with 1oz copper. This
data can be used as a rough guideline in estimating
thermal resistance. The thermal resistance for each appli-
cation will be affected by thermal interactions with other
components as well as board size and shape.
Table 1. R Package, 7-Lead DD
TOPSIDE*
2500 sq. mm 2500 sq. mm
1000 sq. mm 2500 sq. mm
125 sq. mm
*Tab of device attached to topside copper
Table 2. S8 Package, 8-Lead Plastic SOIC
TOPSIDE*
2500 sq. mm
1000 sq. mm
225 sq. mm
100 sq. mm
100 sq. mm
100 sq. mm
100 sq. mm
*Pins 1 and 8 attached to topside copper
Y Package, 7-Lead TO-220
Thermal Resistance (Junction-to-Case) = 5 C/W
N8 Package, 8-Lead DIP
Thermal Resistance (Junction-to-Ambient) = 100 C/W
12
PPLICATI
COPPER AREA
COPPER AREA
2500 sq. mm
2500 sq. mm 2500 sq. mm
2500 sq. mm 2500 sq. mm
2500 sq. mm 2500 sq. mm
2500 sq. mm 2500 sq. mm
1000 sq. mm 2500 sq. mm
BACKSIDE
225 sq. mm
100 sq. mm
BACKSIDE
O
U
S
BOARD AREA (JUNCTION-TO-AMBIENT)
2500 sq. mm
2500 sq. mm
2500 sq. mm
BOARD AREA (JUNCTION-TO-AMBIENT)
2500 sq. mm
2500 sq. mm
I FOR ATIO
U
W
THERMAL RESISTANCE
THERMAL RESISTANCE
25 C/W
27 C/W
35 C/W
60 C/W
62 C/W
65 C/W
69 C/W
73 C/W
80 C/W
83 C/W
U
Calculating Junction Temperature
The junction temperature can be calculated from the
equation:
where:
As an example, calculate the junction temperature for the
circuit in Figure 7 for the N8, S8, and R packages assuming
a 70 C ambient temperature.
The device dissipation can be found by measuring the
supply currents, calculating the total dissipation, and
then subtracting the dissipation in the load and feedback
network.
Then:
Since the Maximum Junction Temperature is 150 C, the
N8 package is clearly unacceptable. Both the S8 and R
packages are usable.
330
T
T
T
P
P
T
for the N8 package
T
T
J
J
A
JA
J
J
J
D
D
= (1.03W 100 C/W) + 70 C = 173 C
= (1.03W 65 C/W) + 70 C = 137 C
for the S8 with 225 sq. mm topside heat sinking
= (1.03W 35 C/W) + 70 C = 106 C
for the R package with 100 sq. mm topside
heat sinking
= (P
= Junction Temperature
= Ambient Temperature
= Device Dissipation
= (39mA 30V) – (12V)
= Thermal Resistance (Junction-to Ambient)
D
Figure 7. Thermal Calculation Example
+
–
–15V
15V
LT1206
I
JA
S/D
) + T
39mA
0.01 F
A
2k
2
2k
/(2k||2k) = 1.03W
300pF
f = 2MHz
LT1206 • F07
12V
–12V