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LTC1164-7 Datasheet(PDF) 9 Page - Linear Technology |
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LTC1164-7 Datasheet(HTML) 9 Page - Linear Technology |
9 / 16 page 9 LTC1164-7 11647fb PI FU CTIO S External Connection (Pins 7, 14): Pins 7 and 14 should be connected together. In a printed circuit board the connec- tion should be done under the IC package through a short trace surrounded by the analog ground plane. Ratio Input (Pin 10): The DC level at this pin determines the ratio of the clock frequency to the cutoff frequency of the filter. Pin 10 at V + gives a 50:1 ratio and pin 10 at V– gives a 100:1 ratio. For single supply operation the ratio is 50:1 when Pin 10 is at V + and 100:1 when Pin 10 is at ground. When Pin 10 is not tied to ground, it should be bypassed to analog ground with a 0.1 µF capacitor. If the DC level at Pin 10 is switched mechanically or electrically at slew rates greater than 1V/ µs while the device is operating, a 10k resistor should be connected between pin 10 and the DC source. Clock Input (Pin 11): Any TTL or CMOS clock source with a square-wave output and 50% duty cycle ( ±10%) is an adequate clock source for the device. The power supply for the clock source should not be the filter’s power supply. The analog ground for the filter should be connected to clock’s ground at a single point only. Table 7 shows the clock’s low and high level threshold values for dual or single supply operation. A pulse generator can be used as a clock source provided the high level ON time is greater than 0.5 µs. Sine waves are not recommended for clock input frequencies less than 100kHz, since excessively slow clock rise or fall times generate internal clock jitter (maximum clock rise or fall time ≤ 1µs). The clock signal should be routed from the right side of the IC package and perpendicular to it to avoid coupling to any input or output analog signal path. A 1k resistor between clock source and Pin 11 will slow down the rise and fall times of the clock to further reduce charge coupling (Figures 2 and 3). NC (Pins 1, 8, 13): Pins 1, 8 and 13 are not connected to any internal circuit point on the device and should be preferably tied to analog ground. Filter Input (Pin 2): The input pin is connected internally through a 50k resistor tied to the inverting input of an op amp. Analog GND (Pins 3, 5): The filter performance depends on the quality of the analog signal ground. For either dual or single supply operation, an analog ground plane sur- rounding the package is recommended. The analog ground plane should be connected to any digital ground at a single point. For dual supply operation, Pins 3 and 5 should be connected to the analog ground plane. For single supply operation, Pins 3 and 5 should be biased at 1/2 supply and should be bypassed to the analog ground plane with at least a 1 µF capacitor (Figure 3). For single 5V operation at the highest fCLK of 2MHz, Pins 3 and 5 should be biased at 2V. This minimizes passband gain and phase variations. Power Supply (Pins 4, 12): The V + (pin 4) and the V – (Pin 12) should each be bypassed with a 0.1 µF capacitor to an adequate analog ground. The filter’s power supplies should be isolated from other digital or high voltage analog supplies. A low noise linear supply is recommended. Using a switching power supply will lower the signal-to- noise ratio of the filter. The supply during power-up should have a slew rate less than 1V/ µs.WhenV+isappliedbefore V – and V– is allowed to go above ground, a signal diode should clamp V – to prevent latch-up. Figures 2 and 3 show typical connections for dual and single supply operation. Filter Output (Pins 6, 9): Pin 6 is an intermediate filter output providing an unspecified 6th order lowpass filter. Pin 6 should not be loaded. Pin 9 is the specified output of the filter; it can typically source/sink 1mA. Driving coaxial cables or resistive loads less than 20k will degrade the total harmonic distortion of the filter. When evaluating the device’s distortion an output buffer is required. A noninverting buffer, Figure 4, can be used provided that its input common-mode range is well within the filter’s output swing. Table 7. Clock Source High and Low Threshold Levels POWER SUPPLY HIGH LEVEL LOW LEVEL Dual Supply = ±7.5V ≥ 2.18V ≤ 0.5V Dual Supply = ±5V ≥ 1.45V ≤ 0.5V Dual Supply = ±2.5V ≥ 0.73V ≤ – 2.0V Single Supply = 12V ≥ 7.80V ≤ 6.5V Single Supply = 5V ≥ 1.45V ≤ 0.5V |
Similar Part No. - LTC1164-7_15 |
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Similar Description - LTC1164-7_15 |
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