AD10465AZ View Datasheet(PDF) - Analog Devices

Part Name

Description

Manufacturer

AD10465AZ

Dual Channel, 14-Bit, 65 MSPS A/D Converter with Analog Input Signal Conditioning

Analog Devices 

AD10465

Power Supplies

Care should be taken when selecting a power source. Linear

supplies are strongly recommended. Switching supplies tend

to have radiated components that may be “received” by the

AD10465. Each of the power supply pins should be decoupled as

closely to the package as possible using 0.1 µF chip capacitors.

The AD10465 has separate digital and analog power supply

pins. The analog supplies are denoted AVCC and the digital

supply pins are denoted DVCC. AVCC and DVCC should be

separate power supplies. This is because the fast digital output

swings can couple switching current back into the analog sup-

plies. Note that AVCC must be held within 5% of 5 V. The

AD10465 is specified for DVCC = 3.3 V as this is a common

supply for digital ASICs.

Output Loading

Care must be taken when designing the data receivers for the

AD10465. The digital outputs drive an internal series resistor

(e.g., 100 Ω) followed by a gate like 75LCX574. To minimize

capacitive loading, there should only be one gate on each output

pin. An example of this is shown in the evaluation board sche-

matic shown in Figure 10. The digital outputs of the AD10465

have a constant output slew rate of 1 V/ns. A typical CMOS

gate combined with a PCB trace will have a load of approxi-

mately 10 pF. Therefore, as each bit switches, 10 mA (10 pF ×

1 V, ÷ 1 ns) of dynamic current per bit will flow in or out of the

device. A full-scale transition can cause up to 140 mA (14 bits ×

10 mA/bit) of current flow through the output stages. These

switching currents are confined between ground and the DVCC

pin. Standard TTL gates should be avoided since they can

appreciably add to the dynamic switching currents of the AD10465.

It should also be noted that extra capacitive loading will increase

output timing and invalidate timing specifications. Digital out-

put timing is guaranteed with 10 pF loads.

LAYOUT INFORMATION

The schematic of the evaluation board (Figure 10) represents a

typical implementation of the AD10465. The pinout of the

AD10465 is very straightforward and facilitates ease of use and

the implementation of high frequency/high resolution design

practices. It is recommended that high quality ceramic chip

capacitors be used to decouple each supply pin to ground directly

at the device. All capacitors can be standard high quality ceramic

chip capacitors.

Care should be taken when placing the digital output runs.

Because the digital outputs have such a high slew rate, the

capacitive loading on the digital outputs should be minimized.

Circuit traces for the digital outputs should be kept short and

connect directly to the receiving gate. Internal circuitry buffers

the outputs of the ADC through a resistor network to eliminate

the need to externally isolate the device from the receiving gate.

EVALUATION BOARD

The AD10465 evaluation board (Figure 9) is designed to pro-

vide optimal performance for evaluation of the AD10465 analog-

to-digital converter. The board encompasses everything needed

to insure the highest level of performance for evaluating the

AD10465. The board requires an analog input signal, encode

clock and power supply inputs. The clock is buffered on-board

to provide clocks for the latches. The digital outputs and clocks

are available at the standard 40-pin connectors J1 and J2.

Power to the analog supply pins is connected via banana jacks. The

analog supply powers the associated components and the analog

section of the AD10465. The digital outputs of the AD10465

are powered via banana jacks with 3.3 V. Contact the factory if

additional layout or applications assistance is required.

REV. 0

Figure 9a. Evaluation Board Mechanical Layout

–11–

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