MAX120CAG 查看數據表（PDF） - Maxim Integrated

零件编号

产品描述 (功能)

生产厂家

MAX120CAG

500ksps, 12-Bit ADCs with Track/Hold and Reference

Maxim Integrated 

MAX120/MAX122

500ksps, 12-Bit ADCs with Track/Hold

and Reference

Figure 13. Using MAX120 with FIFO Memory

Digital-Bus Noise

If the ADC’s data bus is active during a conversion,

coupling from the data pins to the ADC comparator can

cause errors. Using slow-memory mode (mode 3) avoids

this problem by placing the µP in a wait state during the

conversion. If the data bus is active during the conversion

in either mode 1 or 4, use three-state drivers to isolate the

bus from the ADC.

In ROM mode (mode 4), considerable digital noise is

generated in the ADC when RD or CS go high, disabling

the output buffers after a conversion is started. This noise

can cause errors if it occurs at the same instant the SAR

latches a comparator decision. To avoid this problem, RD

and CS should be active for less than 1 clock cycle. If

this is not possible, RD or CS should go high coinciding

with CLKIN’s falling edge, since the comparator output is

always latched at CLKIN’s rising edge

Layout, Grounding, and Bypassing

For best system performance, use PCBs with separate

analog and digital ground planes. Wire­wrap boards are

not recommended. The two ground planes should be tied

together at the low-impedance power-supply source, as

shown in Figure 14.

The board layout should ensure that digital and analog

signal lines are kept separate from each other as much as

possible. Do not run analog and digital (especially clock)

lines parallel to one another.

The ADC’s high-speed comparator is sensitive to high­

frequency noise in the VDD and VSS power supplies.

Bypass these supplies to the analog ground plane with

0.1µF and 10µF bypass capacitors. Minimize capacitor

lead lengths for best noise rejection. If the +5V power

supply is very noisy, connect a 5Ω resistor, as shown in

Figure 14. Figure 15 shows the negative power-supply

(VSS) rejection vs. frequency. Figure 16 shows the posi-

tive power-supply (VDD) rejection vs. frequency, with and

without the optional 5Ω resistor.

www.maximintegrated.com

Maxim Integrated │  10

Share Link: