AD8509/AD8511

Rev. B | Page 7 of 8

APPLICATIONS

The AD8509 and AD8511 are CMOS buffers with A/B inputs,

which are used to select between two different reference voltages

set up by an external resistor ladder. Input bias currents are

orders of magnitude less than competitive parts. This allows

very large resistor ladders to be used to save supply current. A

guaranteed value of 50 nA is much higher than actual values

and is limited by leakage in the test system.

Buffer outputs are designed to drive resistive loads. They are

also stable with capacitive loads, so no resistors should be used

in series with these outputs to attain the best display perform-

ance. Outputs have high slew rates and 6 µs settling times. Each

output can deliver a minimum of 120 mA, assuring fast response

to varying loads.

The AD8509 is a 9-channel buffer and is similar to the LMC6009

in functionality. The AD8511 is an 11-channel buffer similar to

the CL-FP6131. However, the control to select either 9- or

11-channel operation, the EN_11 pin of the CL-FP6131, is not

available on the AD8511. If 9-channel operation is desired, use

the AD8509.

Power supply pins on the AD8509 and AD8511 have multiple

that these buffers can deliver, it is strongly recommended that

pins be suitably bypassed.