AD537 Analog Devices, Inc., AD537 Datasheet
AD537
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AD537 Summary of contents
Page 1
... AD537S is specified for operation over the extended temperature range, –55°C to +125°C. PRODUCT HIGHLIGHTS 1. The AD537 is a complete V-F converter requiring only an external RC timing network to set the desired full-scale fre- quency and a selectable pull-up resistor for the open collec- tor output stage ...
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... Temperature reference output performance is specified from 0°C to +70°C for “J” and “K” devices, –55°C to +125°C for “S” model Ceramic DIP Hermetic Metal Can. For outline information see Package Information section. 7 For AD537/883B specifications, refer to Analog Devices Military Products Databook. Specifications subject to change without notice. (typical @ +25 C with V (total unless otherwise noted) ...
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... CIRCUIT OPERATION Block diagrams of the AD537 are shown above. A versatile operational amplifier (BUF) serves as the input stage; its pur- pose is to convert and scale the input voltage signal to a drive current in the NPN follower. Optimum performance is achieved when, at the full-scale input voltage drive current is delivered to the current-to-frequency converter ...
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... The most sensitive nodes (besides the inputs) are the capacitor terminals and the SYNC pin. The timing capacitor should be located as close as possible to the AD537 to minimize signal pickup in the leads. In some cases, guard rings or shield- ing may be required. The SYNC pin should be decoupled through a 0.005 µ ...
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... The stage limits the output current at 25 mA; it can handle this limit indefinitely without damaging the device. REV. C Figure 5 shows the AD537 with a standard 0 to +10 volt input connection and the output stage connections. The values for the logic common voltage, pull-up resistor, positive logic level, and – ...
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... AD537 F-V CONVERTERS The AD537 can be used as a high linearity VCO in a phase- locked loop to accomplish frequency-to-voltage conversion. By operating the loop without a low-pass filter in the feedback path (first-order system), it can lock to any frequency from zero to an upper limit determined by the design, responding in three or four cycles to a step change of input frequency ...
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... Figure 13 which shows the response to an input rms 1 kHz sinusoid plus 1 V rms Gaussian noise. The positive supply to the AD537 is reduced by about order to keep the voltages at Pins 11 and 12 within the common-mode range of the AD534. Since this is also a first-order loop the circuit possesses a very wide capture range ...
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... This small amount of voltage can be introduced without an additional calibration step using the +1.00 V output of the AD537. To adjust the scale, the thermocouple should be raised to a known reference tempera- ture near 500°C and the frequency adjusted to value using R1. ...