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

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

source current when shorted to GND and a 0.24mA

Analog Inputs and Reference

Configurations

The MAX1209 full-scale analog input range is

adjustable from ±0.35V to ±1.15V with a common-

vides three modes of reference operation. The voltage

(Table 1).

To operate the MAX1209 with the internal reference,

connect REFOUT to REFIN either with a direct short or

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

large (>50M

Ω). When driving REFIN through a resistive

divider, use resistances

≥10kΩ to avoid loading

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

MAX1209 REFOUT. In buffered external reference mode,

apply a stable 0.7V to 2.3V source at REFIN. In this

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

To operate the MAX1209 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-

12-Bit, 80Msps, 3.3V IF-Sampling ADC

______________________________________________________________________________________

15

T/H

CLKN

CLKP

TRACK

HOLD

TRACK

HOLD

TRACK

HOLD

TRACK

HOLD

ANALOG

INPUT

SAMPLED

DATA

Figure 4. T/H Aperture Timing

REFERENCE MODE

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

0.7V to 2.3V

Buffered External Reference Mode. Apply an external 0.7V to 2.3V reference voltage to REFIN.

<0.4V

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

Table 1. Reference Modes