HCPL-7800-500E Datasheet, PDF(18/18 Page) AVAGO TECHNOLOGIES LIMITED – 15 kV/μs Common-Mode Rejection at VCM = 1000 V

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HCPL-7800-500E Datasheet, PDF (18/18 Pages) AVAGO TECHNOLOGIES LIMITED – 15 kV/μs Common-Mode Rejection at VCM = 1000 V

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4.2: Does the gain change if the internal LED light output

degrades with time?

No. The LED is used only to transmit a digital pattern.

Avago Technologies has accounted for LED degradation

in the design of the product to ensure long life.

5. POWER SUPPLIES AND START-UP

5.1: What are the output voltages before the input side

power supply is turned on?

VO+ is close to 1.29 V and VO- is close to 3.80 V. This is

equivalent to the output response at the condition that

LED is completely off.

5.2: How long does the HCPL-7800(A) take to begin work-

ing properly after power-up?

Within 1 ms after VDD1 and VDD2 powered the device

starts to work. But it takes longer time for output to settle

down completely. In case of the offset measurement

while both inputs are tied to ground there is initially VOS

adjustment (about 60 ms). The output completely settles

down in 100 ms after device powering up.

6. MISCELLANEOUS

6.1: How does the HCPL-7800(A) measure negative signals

with only a +5 V supply?

The inputs have a series resistor for protection against

large negative inputs. Normal signals are no more than

200 mV in amplitude. Such signals do not forward bias

any junctions sufficiently to interfere with accurate

operation of the switched capacitor input circuit.

For product information and a complete list of distributors, please go to our web site: www.avagotech.com

Avago, Avago Technologies, and the A logo are trademarks of Avago Technologies Limited in the United States and other countries.

AV02-0410EN - May 26, 2008