Datasheet

AMP OUT

390 nH

3 pF

41 pF

27 nH

200

ADC IN

200:

3 pF

100:

UP/DN

PULSE TIMING

RESET TIMING

LMH6517

www.ti.com

SNOSB19K –NOVEMBER 2008–REVISED MARCH 2013

Figure 56. Pulse Mode Timing

EXPOSED PAD WQFN PACKAGE

The LMH6517 is packaged in a thermally enhanced package. The exposed pad is connected to the GND pins. It

is recommended, but not necessary, that the exposed pad be connected to the supply ground plane. In any

case, the thermal dissipation of the device is largely dependent on the attachment of this pad. The exposed pad

should be attached to as much copper on the circuit board as possible, preferably external copper. However, it is

also very important to maintain good high speed layout practices when designing a system board. Please refer to

the LMH6517 evaluation board for suggested layout techniques.

Package information is available on the Texas Instruments web site.

http://www.ti.com/packaging/

INTERFACING TO ADC

The LMH6517 was designed to be used with high speed ADCs such as the ADC16DV160. As shown in

Figure 40, AC coupling provides the best flexibility especially for IF sub-sampling applications. For DC coupled

applications the use of a level shifting amplifier or a resistive biasing network may be possible.

The inputs of the LMH6517 will self bias to the optimum voltage for normal operation. The internal bias voltage

for the inputs is approximately mid rail which is 2.5V with the typical 5V power supply condition. In most

applications the LMH6517 input will need to be AC coupled.

The output common mode voltage is also self biasing to mid supply. This means that for driving most ADCs AC

coupling is required. Since most often a band pass filter is desired between the amplifier and ADC the bandpass

filter can be configured to block the DC voltage of the amplifier output from the ADC input.

Figure 57. Bandpass Filter

A. Center Frequency is 140 MHz with a 20 MHz Bandwidth. Designed for 200Ω Impedance

Product Folder Links: LMH6517