Q-tech, Class b+ products, Thermal characteristics – Q-Tech CLASS B+ User Manual
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Q-TECH
CORPORATION
QPDS-0001, Rev L, June 2013 (ECO #10851)
CLASS B+ PRODUCTS
HIGH RELIABILITY HYBRID CRYSTAL CLOCK OSCILLATORS
2.5 to 5.0Vdc - 15kHz to 350MHz
Differential Output of a
QT93NW10M-312.500MHz
Frequency vs. Temperature Curve
15-Day Aging of a QT122L10S-200MHz
Test Circuit
-
-
Output
Ground
0.1µF
15pF
Tristate Function
Power
supply
10k
mA
Vdc
+
+
+
(*)
or
0.01µF
(*) CL includes probe and jig capacitance
Typical test circuit for CMOS logic
4
3
2
1
QT178
-5
-4
-3
-2
-1
0
1
2
3
4
5
-50
-40
-30
-20
-10
0
10
20
30
40
50
-55
-45
-35
-25
-15
-5
5
15
25
35
45
55
65
75
85
95
105
115
125
Frequency Stability (PPM)
Temperature (°C)
Frequency-Temperature Curve
QTX88LD9M-48.21MHz
45º
45º
Hybrid Case
Substrate
Die
D/A epoxy
D/A epoxy
Heat
Die
R1
D/A epoxy
Substrate
D/A epoxy
Hybrid Case
R2
R3
R4
R5
Thermal Characteristics
JA
JC
CA
Die
T
T
T
C
A
J
CA
JC
(Figure 1)
(Figure 2)
The Tristate function on pin 1 has a built-in pull-up resistor typical 50kΩ, so it can
be left floating or tied to Vdd without deteriorating the electrical performance.
The heat transfer model in a hybrid package is described in figure 1.
Heat spreading occurs when heat flows into a material layer of
increased cross-sectional area. It is adequate to assume that spreading
occurs at a 45° angle.
The total thermal resistance is calculated by summing the thermal
resistances of each material in the thermal path between the device
and hybrid case.
RT = R1 + R2 + R3 + R4 + R5
The total thermal resistance RT (see figure 2) between the heat source
(die) to the hybrid case is the Theta Junction to Case (Theta JC)
in°C/W.
• Theta junction to case (Theta JC) for this product is 30°C/W.
• Theta case to ambient (Theta CA) for this part is 100°C/W.
• Theta Junction to ambient (Theta JA) is 130°C/W.
Maximum power dissipation PD for this package at 25°C is:
• PD(max) = (TJ (max) – TA)/Theta JA
• With TJ = 175°C (Maximum junction temperature of die)
• PD(max) = (175 – 25)/130 = 1.15W