MAX12555ETL 查看數據表（PDF） - Maxim Integrated

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MAX12555ETL

14-Bit, 95Msps, 3.3V ADC

Maxim Integrated 

14-Bit, 95Msps, 3.3V ADC

CLKP

CLKN

tAD

ANALOG

INPUT

tAJ

SAMPLED

DATA

T/H

TRACK

HOLD

TRACK

HOLD

TRACK

HOLD

TRACK

HOLD

Figure 4. T/H Aperture Timing

REFOUT sources up to 1.0mA and sinks up to 0.1mA

for external circuits with a load regulation of 35mV/mA.

Short-circuit protection limits IREFOUT to a 2.1mA

source current when shorted to GND and a 0.24mA

sink current when shorted to VDD.

Analog Inputs and Reference

Configurations

The MAX12555 full-scale analog input range is

adjustable from ±0.35V to ±1.10V with a VDD / 2 ±0.5V

common-mode input range. The MAX12555 provides

three modes of reference operation. The voltage at

REFIN (VREFIN) sets the reference operation mode

(Table 1).

To operate the MAX12555 with the internal reference,

connect REFOUT to REFIN either with a direct short or

through a resistive divider. In this mode, COM, REFP,

and REFN are low-impedance outputs with VCOM =

VDD / 2, VREFP = VDD / 2 + VREFIN x 3/8, and VREFN =

VDD / 2 - VREFIN x 3/8. The REFIN input impedance is

very large (>50MΩ). When driving REFIN through a

resistive divider, use resistances ≥10kΩ to avoid load-

ing REFOUT.

Buffered external reference mode is virtually identical to

internal reference mode except that the reference

source is derived from an external reference and not

the MAX12555 REFOUT. In buffered external reference

mode, apply a stable 0.7V to 2.2V source at REFIN. In

this mode, COM, REFP, and REFN are low-impedance

outputs with VCOM = VDD / 2, VREFP = VDD / 2 + VREFIN

x 3/8, and VREFN = VDD / 2 - VREFIN x 3/8.

To operate the MAX12555 in unbuffered external refer-

ence mode, connect REFIN to GND. Connecting REFIN

to GND deactivates the on-chip reference buffers for

COM, REFP, and REFN. With the respective buffers

deactivated, COM, REFP, and REFN become high-

impedance inputs and must be driven through sepa-

rate, external reference sources. Drive VCOM to VDD / 2

±5%, and drive REFP and REFN so VCOM = (VREFP +

VREFN) / 2. The full-scale analog input range is ±(VREFP

- VREFN) x 2/3.

Table 1. Reference Modes

VREFIN

REFERENCE MODE

35% VREFOUT to 100%

VREFOUT

Internal Reference Mode. Drive REFIN with REFOUT either through a direct short or a resistive divider.

The full-scale analog input range is ±VREFIN / 2:

VCOM = VDD / 2

VREFP = VDD / 2 + VREFIN x 3/8

VREFN = VDD / 2 - VREFIN x 3/8

0.7V to 2.2V

Buffered External Reference Mode. Apply an external 0.7V to 2.2V reference voltage to REFIN.

The full-scale analog input range is ±VREFIN / 2:

VCOM = VDD / 2

VREFP = VDD / 2 + VREFIN x 3/8

VREFN = VDD / 2 - VREFIN x 3/8

<0.4V

Unbuffered External Reference Mode. Drive REFP, REFN, and COM with external reference sources.

The full-scale analog input range is ±(VREFP - VREFN) x 2/3.

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