LT1016IS8 datasheet(8/20 Pages) LINER

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LT1016

APPLICATIO S I FOR ATIO

Other common problems include different measurement

results using various pieces of test equipment, inability to

make measurement connections to the circuit without

inducing spurious responses and dissimilar operation

between two “identical” circuits. If the components used

in the circuit are good and the design is sound, all of the

above problems can usually be traced to failure to provide

a proper circuit “environment.” To learn how to do this

requires studying the causes of the aforementioned

difficulties.

By far the most common error involves power supply

bypassing. Bypassing is necessary to maintain low supply

impedance. DC resistance and inductance in supply wires

and PC traces can quickly build up to unacceptable levels.

This allows the supply line to move as internal current

levels of the devices connected to it change. This will

almost always cause unruly operation. In addition, several

devices connected to an unbypassed supply can “commu-

nicate” through the finite supply impedances, causing

erratic modes. Bypass capacitors furnish a simple way to

eliminate this problem by providing a local reservoir of

energy at the device. The bypass capacitor acts like an

electrical flywheel to keep supply impedance low at high

frequencies. The choice of what type of capacitors to use

for bypassing is a critical issue and should be approached

carefully. An unbypassed LT1016 is shown responding to

a pulse input in Figure 3. The power supply the LT1016

sees at its terminals has high impedance at high fre-

quency. This impedance forms a voltage divider with the

LT1016, allowing the supply to move as internal condi-

tions in the comparator change. This causes local feed-

back and oscillation occurs. Although the LT1016

responds to the input pulse, its output is a blur of 100MHz

oscillation.

Always use bypass capacitors.

Figure 2. LT1016 vs a TTL Gate

Figure 3. Unbypassed LT1016 Response

TRACE A

5V/DIV

TRACE B

5V/DIV

TRACE C

5V/DIV

10ns/DIV

–

OUTPUTS

PULSE

GENERATOR

Ω

VREF

1016 F02

LT1016

TEST CIRCUIT

7404

2V/DIV

100ns/DIV

1016 F03

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