CXA1166 查看數據表（PDF） - Sony Semiconductor

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CXA1166

8-bit 250 MSPS Flash A/D Converter

Sony Semiconductor 

CXA1166K

Notes on Operation

• The CXA1166K is an ultra-high speed A/D converter featuring ECL level of input/output for the logic block. In

order to derive the most from its high-speed performance, the characteristic impedance should be matched

properly.

• The outputs are designed to drive a load terminated to –2V at 50Ω. An excellent transmission characteristic

can be yielded by designing the printed circuit board with a 50Ω characteristic impedance.

Yielding its top performance is difficult on the printed circuit board with a characteristic impedance of 100Ω or

more.

• The power supply and ground pattern greatly affect the characteristics of the converter. The higher the

frequency, the more important these connections become. The general precautions are as follows.

– Make the pattern of the power supply and ground as wide as possible. Using a ground plane inner layer by

using a multilayer printed circuit board is recommended.

– lsolate the AGND, DGND pins and the AVEE, DVEE from one another on the pattern in order to safeguard

against interaction. Connect the AGND and DGND pins at one place using a ferrite-bead filter to prevent

DC offset. The same processing is requited for the AVEE and DVEE pins.

• When mounting the A/D converter on the socket, use the one of shortest leads. The QFP socket, the type

name IC61-0684-048, manufactured by YAMAICHI ELECTRONICS CO., LTD. is recommended.

• The VIN analog input pins have somewhat large input capacitance (approximately 18pF) for high-frequency

circuits. In order to drive them with an excellent frequency response, it is necessary to safeguard against any

deterioration in performance resulting from parasitic capacitance and parasitic inductance by using a high-

capacity drive circuit, keeping the wiring as short as possible, and using chip parts as resistors and

capacitors, for instance. The drive circuit shown in the Application Circuit has a virtually flat frequency

response up to approximately 170MHz. C89, R11 and C15 have been inserted mainly to expand the

bandwidth, while R10 has been inserted mainly to suppress operational amplifier oscillation and block

peaking of the frequency response. Since the optimal values of these elements differ depending on the

printed circuit board pattern and mounting condition of the A/D converter socket used, they must be

determined on the basis of experimentation.

• Connect all four VIN pins directly and as short as possible. Unlike the CXA1176, it is not necessary to insert

resistance of several ohms for each pin.

• The voltage at the VRT and VRB reference voltage pins and the reference voltage inside these pins differ

slightly due to residual resistance. VRTS and VRBS are provided to detect the reference voltage inside the pins.

The overrange reference voltage is 1/2 LSB down from VRTS; the lowest input voltage at which the output

code changes is 1/2 LSB up from VRBS.

• Provide adequate by-pass capacitors for VRT and VRB to protect them from high-frequency noise. Normally,

VRT is connected to AGND of an inner layer of the printed circuit board. Using a chip capacitor (approximately

0.1µF), make the by-pass from VRB to AGND as short as possible. C22 (1µF), in the Application Circuit is for

suppressing the oscillation of the reference voltage generation circuit.

– 10 –

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