Q-Tech QT488 - Manual (Page 5)

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Q-TECH Corporation - 10150 W. Jefferson Boulevard, Culver City 90232 - Tel: 310-836-7900 - Fax: 310-836-2157 - www.q-tech.com
QT481 AND QT488 SERIES
ULTRA-LOW CURRENT REAL TIME CLOCK OSCILLATORS
2.5Vdc and 3.3Vdc - 32.768kHz
Q-TECH
CORPORATION
QPDS-0008 (Revision A, June 2013) (ECO # 10907)
Output Waveform (Typical)
Frequency vs. Temperature Curve
Test Circuit
-
-
Output
Ground
4 3
2
0.1µF
15pF
1
Tristate Function
Power
supply 10k
mA
Vdc
+
+
+
(*)
or
0.01µF
QT88
(*) CL includes probe and jig capacitance
Typical test circuit for CMOS logic
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.
-250
-200
-150
-100
-50
0
50
100
150
200
250
0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200
Frequency Stability (PPM)
Temperature (°C)
Type: QT88LD8M Vcc Input:3.3 Out Freq:32.768Khz +/-250ppm@ 0 to 200 deg.C
Start up Time
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 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