RHD5940 Datasheet, PDF (2/6 Pages) Aeroflex Circuit Technology – RadHard-by-Design RHD5940 14-Bit Analog to Digital Converter

The analog input impedance is primary capacitance (20pF). The input voltage charges a track-and-hold hold
capacitor through transmission gates. The input bandwidth is determined by the slew rate of the hold amplifier
and is adequate to allow input sampling in three clock periods (3uS nominal). The ultimate bandwidth is
determined by the aperture uncertainty associated with the closing of the sample gate (approximately 5nS). The
converter bandwidth is then determined by the sampling Nyquist frequency rather than the input signal; change
rate (dv/dt) and the LSB weight in volts as would be the case if there were no sample and hold.
Start-Convert (STCNV_H), Busy (BUSY_L) and End-Of-Convert (EOC_H) status and control line are provided.
The converter will operate in either continuous or single conversion modes. The digital output register changes at
the end of a conversion and is available until the next End-Of-Convert. Digital input and output circuits operate
from a voltage independent of the remainder of the chip such that I/O is compatible with digital systems from less
than 3.3 to 5 volts.
The converter divides the reference voltage into 16 segments with a linear weighted resistor network. The voltage
on any segment is passed to a linear 10-bit DAC for interpolation. The architecture is inherently capable of
monotonic operation. INL is ±10 LSBs. DNL is ±1/2 LSB. The sampled input voltage is compared to the output
of the two stage DAC for a 14-bit successive approximation conversion.
All inputs are protected to both power supply rails by semiconductor diodes. Inputs should be constrained to Vcc
+0.4 and Vee-0.4 to avoid forward biasing protection paths.
The devices will not latch with SEU events to above 100 MeV-cm²/mg. Total dose degradation is minimal to
above 1Mrad(Si). Displacement damage environments to neutron fluence equivalents in the mid 10¹² neutrons
per cm² range are readily tolerated. There is no sensitivity to low-dose rate (ELDRS) effects. SEU effects are
application dependant.
SCD5940 Rev A Advanced 1/10/12
FIGURE 1: BLOCK DIAGRAM
2
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