The information contained in this section has been developed through characterization by Intersil Semiconductor and is for use as applica-

tion and design information only. No guarantee is implied.

DESIGN INFORMATION

August 1999

7-15

Semiconductor

HA5340

High Speed, Low Distortion, Precision

Monolithic Sample and Hold Amplifier

Applying the HA-5340

The HA-5340 has the uncommitted differential inputs of an

op amp, allowing the Sample and Hold function to be com-

bined with many conventional op amp circuits. See the Inter-

sil Application Note 517 for a collection of circuit ideas.

Layout

A printed circuit board with ground plane is recommended

for best performance. Bypass capacitors (0.01 to 0.1

µF,

ceramic) should be provided from each power supply termi-

nal to the Supply Ground terminal on pin 13.

The ideal ground connections are pin 6 (SIG. Ground)

directly to the system Signal Ground, and pin 13 (Supply

Ground) directly to the system Supply Common.

Hold Capacitor

The HA-5340 includes a 135pF MOS hold capacitor, suffi-

cient for most high speed applications (the Electrical Specifi-

cations section is based on this internal capacitor).

Additional capacitance may be added between pins 7 and

11. This external hold capacitance will reduce droop rate at

the expense of acquisition time, and provide other trade-offs

as shown in the Performance Curves.

The hold capacitor CH should have high insulation resis-

tance and low dielectric absorption, to minimize droop

errors. Teflon

®, polystyrene and polypropylene dielectric

capacitor types offer good performance over the specified

operating temperature range.

The hold capacitor terminal (pin 11) remains at virtual

ground potential. Any PC connection to this terminal should

be kept short and ‘‘guarded’’ by the ground plane, since

nearby signal lines or power supply voltages will introduce

errors due to drift current.

®Teflon is a registered Trademark of Dupont Corporation.

Applications

Figure 1 shows the HA-5340 connected as a unity gain non-

inverting amplifier – its most widely used configuration. As

an input device for a fast successive – approximation A/D

converter, it offers very high throughput rate for a monolithic

IC sample/hold amplifier. Also, the HA-5340’s hold step error

is adjustable to zero using the Offset Adjust potentiometer,

to deliver a 12-bit accurate output from the converter.

The HA-5340 output circuit does not include short circuit

protection, and consequently its output impedance remains

low at high frequencies. Thus, the step changes in load cur-

rent which occur during an A/D conversion are absorbed at

the S/H output with minimum voltage error. A momentary

short circuit to ground is permissible, but the output is not

designed to tolerate a short of indefinite duration.

FIGURE 1. TYPICAL HA-5340 CONNECTIONS; NONINVERTING UNITY GAIN MODE

NOTE: Pin Numbers Refer to DIP Package Only.

+15V

VIN

C H

50K

Ω

34

9

5

7

1

2

14

135pF

13

6

SYSTEM

POWER

GROUND

SYSTEM

SIGNAL

GROUND

5

9

CONVERT

13

INPUT

DIGITAL

OUTPUT

H

S

S/H CONTROL

11

-15V

HA 5340

-

HI-774

OFFSET

ADJUST

ANALOG

COMMON

R/C

Spec Number

511117-883