7

Applications Information

Power Supplies and Circuit Layout

The EL5185 comparator operates with single and dual

side of the comparator is supplied by a single supply from

2.7V to 5V. The rail to rail output swing enables direct

connection of the comparator to both CMOS and TTL logic

circuits. As with many high speed devices, the supplies must

be well bypassed. Elantec recommends a 4.7µF tantalum in

parallel with a 0.1µF ceramic. These should be placed as

close as possible to the supply pins. Keep all leads short to

reduce stray capacitance and lead inductance. This will also

minimize unwanted parasitic feedback around the

comparator. The device should be soldered directly to the

PC board instead of using a socket. Use a PC board with a

good, unbroken low inductance ground plane. Good ground

plane construction techniques enhance stability of the

comparators.

Input Voltage Considerations

output still responds correctly to a small differential input

signal. The differential input stage is a pair of PNP

transistors, therefore, the input bias current flows out of the

device. When either input signal falls below the negative

input voltage limit, the parasitic PN junction formed by the

substrate and the base of the PNP will turn on, resulting in a

significant increase of input bias current. If one of the inputs

goes above the positive input voltage limit, the output will still

maintain the correct logic level as long as the other input

stays within the input range. However, the propagation delay

will increase. When both inputs are outside the input voltage

range, the output becomes unpredictable. Large differential

voltages greater than the supply voltage should be avoided

to prevent damages to the input stage.

Pin Descriptions

PIN NUMBER

PIN NAME

FUNCTION

EQUIVALENT CIRCUIT

1

Positive supply voltage

2

IN+

Positive input

Circuit 1

3

IN-

Negative input

(Reference Circuit 1)

4

Negative supply voltage

5

LATCH

Latch input

Circuit 2

6

GND

Digital ground

7

OUT

Output

Circuit 3

8

Digital Supply

IN+

IN-

LATCH

OUT

EL5185