SCD5028-2 Rev G

FEATURES

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Enhanced version of the ACT5028B

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Radiation performance

- Total dose: 1 Mrad(Si), Dose rate = 50 - 300 rads(Si)/s

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Programmable: By using a few non critical external resistors and capacitors

- Resolution: 10, 12, 14 or 16 bit resolution

- Bandwidth

- Tracking rate

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Low power: +5V @ 20 mA typ

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45 to 30,000 Hz carrier frequency range

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Accuracy:

- 10.0 Arc Minutes if not compensated by INL correction factors.

- 5.3 Arc Minutes using INL correction factors.

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Differential instrument amplifiers resolver input

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-55° to +125°C operating temperature

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Digital interface logic voltage of 3.3V to 5V

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Designed for aerospace and high reliability space applications

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Packaging – Hermetic

- 52 Pin Ceramic QUAD flat package (CQFP), .956" SQ x .100"Ht

- Weight: 5.0g max

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Evaluation board available for test and evaluation. See Aeroflex Application note AN5028-1

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Aeroflex Plainview’s Radiation Hardness Assurance Plan is DLA Certified to MIL-PRF-38534, Appendix G.

RDC5028C 16-Bit Monolithic Tracking

Standard Products

Rad Tolerant Resolver-To-Digital Converter

APPLICATIONS

This single chip Resolver-to-Digital Converter (RDC) is used in shaft angle control systems, and is suitable for space

or other radiation environments that require > 1 Mrad(Si) total dose tolerance. The part is latchup free in heavy ion

environments (e.g., geosynchronous orbits) and is estimated to experience SEU induced errors of less than 15 minutes

of arc at a rate of 1 per device per 2 years when operating dynamically.

THEORY OF OPERATION

The RDC5028 converter is a single CMOS Type II tracking resolver to digital converter monolithic chip. It is

implemented using precision analog circuitry and digital logic. For flexibility, the converter bandwidth, dynamics and

velocity scaling are externally set with passive components. Refer to Figure 1, RDC5028 Block Diagram.

The converter consists of three main sections; the Analog Control Transformer (CT), the Analog Error Processor (EP)

and the Digital Logic Interface.

The CT has two analog resolver inputs (Sin and Cos) that are buffered by high impedance input instrumentation type

amplifiers and the 16 bit digital word which represents the output digital angle. The CT performs the ratiometric

trigonometric computation of:

SIN(A) sin(wt) COS(B) – COS(A) sin(wt) SIN(B) = SIN(A-B) sin(wt)

Utilizing amplifiers, switches, logic and resistors in precision ratios. “A” represents the resolver angle, “B“ represents

the digital angle and sin(wt) represents the resolver reference carrier frequency.

The Error Processor is configured as a critically damped Type II loop. The AC error, SIN (A-B) sin (wt) is full wave

demodulated using the reference squared off as its drive. This DC error is integrated in an analog integrator yielding a

velocity voltage which in turn drives a Voltage Controlled Oscillator (VCO). Note in the block diagram, hysterisis is

added to prevent dithering and disables counting when the error is less than 1 LSB. This VCO is an incremental

integrator (constant voltage input to position rate output) which, together with the velocity integrator, forms a Type II

loop. A lead is inserted to stabilize the loop and a lag is inserted at a higher frequency to attenuate the carrier

frequency ripple. The error processor drives the 16 bit digital output until it nulls out. Then angle “A” = “B”. The

digital output equals angle input to the accuracy of the precision control transformer. The various error processor

settings are done with external resistors and capacitors so that the converter loop dynamics can be easily controlled by

anywhere from +3V to the +5V power supply.

May 7, 2014

www.aeroflex.com/RDC

Datasheet