HI5630 查看數據表（PDF） - Intersil

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HI5630

Triple 8-Bit, 80MSPS A/D Converter with Internal Voltage Reference

Intersil 

HI5630

DC Voltage Source, VDC

An internal band-gap reference voltage followed by an

amplifier/buffer generates the precision +2.0V DC voltage

source to the user to help simplify circuit design. The

characteristics of the DC source is equivalent to the internal

reference.

Analog Input, Differential Connection

The analog input to the HI5630 is a differential input that can

be configured in various ways depending on the signal

source and the required level of performance. A fully

differential connection (Figures 4 and 5) will deliver the best

performance from the converter.

coupled inputs as well. Note, however, that the value of

capacitor C chosen must take into account the highest

frequency component of the analog input signal.

VIN+

VDC

VIN-

VDC

VIN+

R

C

HI5630

VDC

R

VIN-

FIGURE 5. DC COUPLED DIFFERENTIAL INPUT

VIN+

VIN-

VIN+

R

HI5630

VDC

R

VIN-

FIGURE 4. AC COUPLED DIFFERENTIAL INPUT

Since the HI5630 is powered by a single +5V analog supply,

the analog input is limited to be between ground and +5V.

For the differential input connection this implies the analog

input common mode voltage can range from 0.25V to 4.75V.

The performance of the ADC does not change significantly

with the value of the analog input common mode voltage.

A DC voltage source, VDC, equal to 2.0V (typical), is made

available to the user to help simplify circuit design when using

an AC coupled differential input. This low output impedance

voltage source is not designed to be a reference but makes

an excellent DC bias source and stays well within the analog

input common mode voltage range over temperature.

For the AC coupled differential input (Figure 4) and with

VRIN connected to VROUT, full scale is achieved when the

VIN and VIN- input signals are 0.5VP-P, with -VIN being

180 degrees out of phase with VIN . The converter will be at

positive full scale when the VIN+ input is at VDC + 0.25V

and the VIN- input is at VDC - 0.25V (VIN+ - VIN- = +0.5V).

Conversely, the converter will be at negative full scale when

the VIN+ input is equal to VDC - 0.25V and VIN- is equal to

VDC + 0.25V (VIN+ - VIN- = -0.5V).

The analog input can be DC coupled (Figure 5) as long as

the inputs are within the analog input common mode voltage

range (0.25V ≤ VDC ≤ 4.75V).

The resistors, R, in Figure 5 are not absolutely necessary

but may be used as load setting resistors. A capacitor, C,

connected from VIN+ to VIN- will help filter any high

frequency noise on the inputs, also improving performance.

Values around 20pF are sufficient and can be used on AC

Analog Input, Single-Ended Connection

The configuration shown in Figure 6 may be used with a

single ended AC coupled input.

VIN

VDC

VIN+

R

HI5630

VIN-

FIGURE 6. AC COUPLED SINGLE ENDED INPUT

Again, with VRIN connected to VROUT, if VIN is a 1VP-P

sinewave, then VIN+ is a 1.0VP-P sinewave riding on a

positive voltage equal to VDC. The converter will be at

positive full scale when VIN+ is at VDC + 0.5V (VIN+ - VIN- =

+0.5V) and will be at negative full scale when VIN+ is equal

to VDC - 0.5V (VIN+ - VIN- = -0.5V). Sufficient headroom

must be provided such that the input voltage never goes

above +5V or below AGND. In this case, VDC could range

between 0.5V and 4.5V without a significant change in ADC

performance. The simplest way to produce VDC is to use the

DC bias source, VDC, output of the HI5630.

The single ended analog input can be DC coupled (Figure 1)

as long as the input is within the analog input common mode

voltage range.

The resistor, R, in Figure 7 is not absolutely necessary but

may be used as a load setting resistor. A capacitor, C,

connected from VIN+ to VIN- will help filter any high

frequency noise on the inputs, also improving performance.

Values around 20pF are sufficient and can be used on AC

coupled inputs as well. Note, however, that the value of

capacitor C chosen must take into account the highest

frequency component of the analog input signal.

A single ended source may give better overall system

performance if it is first converted to differential before

driving the HI5630.

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