LTC1050 datasheet(15/28 Pages) LINER

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LTC6258/LTC6259/LTC6260

6258960fa

For more information www.linear.com/LTC6258

ESD

The LTC6258 family has reverse-biased ESD protection

diodes on all inputs and output as shown in Figure 1.

Supply Voltage Ramping

Fast ramping of the supply voltage can cause a current

glitch in the internal ESD protection circuits. Depending on

the supply inductance, this could result in a supply volt-

age transient that exceeds the maximum rating. A supply

voltage ramp time of greater than 1ms is recommended.

Feedback Components

Care must be taken to ensure that the pole formed by the

feedback resistors and the parasitic capacitance at the

inverting input does not degrade stability. For example, in

a gain of +2 configuration with gain and feedback resis-

tors of 100k, a poorly designed circuit board layout with

parasitic capacitance of 5pF (part +PC board) at the ampli-

fier’s inverting input will cause the amplifier to oscillate

due to a pole formed at 640kHz. An additional capacitor of

4.7pF across the feedback resistor as shown in Figure 2

will eliminate any ringing or oscillation.

Shutdown

The single and dual versions have package options with

SHDN pins that can shut down the amplifier to less than

7µA supply current. The SHDN pin voltage needs to be

within 0.6V of V– for the amplifier to shut down. During

shutdown, the output is in a high output impedance state.

When left floating, the SHDN pin is internally pulled up

to the positive supply and the amplifier remains enabled.

100k

4.7pF

CPAR

VOUT

VIN

6258960 F02

–

LTC6258

Figure 2.

Figure 3a. 10kHz Bandpass Filter

Figure 3b. Frequency Response of

10kHz Bandpass Filter of Figure 3a

APPLICATIONS INFORMATION

V+

4.7nF

21k

4.7nF

562

RA1

499k

6258 F03a

RA2

499k

CD1

1µF

10k

OUT

CD2

0.1µF

LT6259

–

5dB/DIV

5dB

–45dB

6258 F03b

Active Filter

The bandpass filter Figure 3a is AC-coupled to an input.

As a result, LTC6259 input does not place a burden on

the previous stage to develop an absolute common mode

voltage. A simple resistor divider with RA1 and RA2

provides biasing for the LTC6259 inputs. Pegging the op

amp inputs to a fixed voltage helps to reduce distortion

that might arise with moving common mode. This filter is

centered at 10kHz. The exact resistance and capacitance

values can be tweaked upwards or downwards, depending

on whether lowest resistor noise or lowest total supply

current is more important.

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