CA3306CE Intersil, CA3306CE Datasheet - Page 13

• Manufacturer Part Number: CA3306CE
• Description: IC CONV A/D FLASH 6BIT 18-DIP
• Manufacturer: Intersil

Specifications of CA3306CE

• Rohs Status: RoHS non-compliant
• Other names: CA3306

frequency domain with a 4096 point FFT and analyzed to
Doubled Sampling Speed
The phase control and both positive and negative true chip
enables allow the parallel connection of two CA3306s to
double the sampling speed. Figure 18 shows this configura-
tion. One converter samples on the positive phase of the
clock, and the second on the negative. The outputs are also
alternately enabled. Care should be taken to provide a near
square-wave clock it operating at close to the maximum
clock speed for the devices.
8-Bit to 12-Bit Conversion Techniques
To obtain 8-bit to 12-bit resolution and accuracy, use a feed-
forward conversion technique. Two A/D converters will be
needed to convert up to 11 bits; three A/D converters to con-
vert 12 bits. The high speed of the CA3306 allows 12-bit
conversions in the 500ns to 900ns range.
The circuit diagram of a high-speed 12-bit A/D converter is
shown in Figure 19. In the feed-forward conversion method
two sequential conversions are made. Converter A first does
a coarse conversion to 6 bits. The output is applied to a 6-bit
D/A converter whose accuracy level is good to 12 bits. The
D/A converter output is then subtracted from the input volt-
age, multiplied by 32, and then converted by a second flash
A/D converter, which is connected in a 7-bit configuration.
The answers from the first and second conversions are
added together with bit 1 of the first conversion overlapping
bit 7 of the second conversion.
When using this method, take care that:
• The linearity of the first converter is better than
• An offset bias of 1 LSB (1/64) Is subtracted from the first
• The D/A converter and its reference are accurate to the
The first converter can be offset-biased by adding a 20Ω
resistor at the bottom of the ladder and increasing the refer-
ence voltage by 1 LSB. If a 6.4V reference is used in the
system, for example, then the first CA3306 will require a
6.5V reference.
Definitions
Dynamic Performance Definitions
Fast Fourier Transform (FFT) techniques are used to evaluate
the dynamic performance of the converter. A low distortion
sine wave is applied to the input, it is sampled, and the output
is stored in RAM. The data is then transformed into the
evaluate the dynamic performance of the A/D. The sine wave
input to the part is -0.5dB down from full scale for all these
tests.
conversion since the second converter is unipolar.
total number of bits desired for the final conversion (the A/D
converter need only be accurate to 6 bits).
CA3306, CA3306A, CA3306C
1
/
2
LSB.
13
Signal-to-Noise (SNR)
SNR is the measured RMS signal to RMS noise at a
specified input and sampling frequency. The noise is the
RMS sum of all of the spectral components except the
fundamental and the first five harmonics.
Signal-to-Noise + Distortion Ratio (SINAD)
SINAD is the measured RMS signal to RMS sum of all other
spectral components below the Nyquist frequency excluding DC.
Effective Number of Bits (ENOB)
The effective number of bits (ENOB) is derived from the
SINAD data. ENOB is calculated from:
ENOB = (SINAD - 1.76 + V
where: V
Total Harmonic Distortion (THD)
THD is the ratio of the RMS sum of the first 5 harmonic
components to the RMS value of the measured input signal.
Operating and Handling Considerations
HANDLING
All inputs and outputs of Intersil CMOS devices have a
network for electrostatic protection during handling. Recom-
mended handling practices for CMOS devices are described
in AN6525. “Guide to Better Handling and Operation of
CMOS Integrated Circuits.”
OPERATING
Operating Voltage
During operation near the maximum supply voltage limit,
care should be taken to avoid or suppress power supply
turn-on and turn-off transients, power supply ripple, or
ground noise; any of these conditions must not cause
V
Input Signals
To prevent damage to the input protection circuit, input
signals should never be greater than V
Input currents must not exceed 20mA even when the power
supply is off. The zener (pin 4) is the only terminal allowed to
exceed V
Unused Inputs
A connection must be provided at every input terminal. All
unused input terminals must be connected to either V
V
Output Short Circuits
Shorting of outputs to V
devices by exceeding the maximum device dissipation.
DD
SS
, whichever is appropriate.
- V
SS
DD
CORR
to exceed the absolute maximum rating.
.
= 0.5dB.
DD
CORR
or V
)/6.02,
SS
DD
may damage CMOS
nor less than V
DD
SS
or
.