LM97600CIUTSLASHNOPB datasheet(40/58 Pages) TI1

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LM97600

SNAS600A – JULY 2012 – REVISED MARCH 2013

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Power Down Feature

The Power Down pin (PD) allows the LM97600 to be entirely powered down. See Power Down Feature for

details on the power down feature.

The digital data (+/-) output pins are put into a high impedance state when the PD pin is high. Upon return to

normal operation, the pipeline will contain meaningless information and must be flushed.

If the PD input is brought high while a calibration is running, the device will not go into power down until the

calibration sequence is complete. However, if power is applied and PD is concurrently high, the device will not

begin the calibration sequence until the PD input goes low. If a manual calibration is requested while the device

is powered down, the calibration will not begin at all. That is, the manual calibration input is completely ignored in

the power down state.

THE DIGITAL OUTPUTS

The LM97600 output data is transmitted on 10 high speed serial data lanes. The output data from the four

internal converters is formatted to the 10 lanes, 8b10b encoded, and serialized. Examining the resulting data

rates, we have: 5 Gigasamples/sec x 8 bits = 40 Gigabits/second.

8b10b encoding adds a 10/8 overhead, resulting in a net data rate of 50 Gigabits/second.

The serial output data clock rate is therefore the same as the total aggregate ADC sampling rate (5

Gigasamples/sec gives 5 Gigabits/sec on each of the 10 lanes).

The ADC data is encoded in Offset Binary. Accordingly, a full-scale input level with VIN+ positive with respect to

VIN− will produce an output code of all ones, a full-scale input level with VIN− positive with respect to VIN+ will

produce an output code of all zeros and when VIN+ and VIN− are equal, the output code will be 128.

POWER CONSIDERATIONS

A/D converters draw sufficient transient current to corrupt their own power supplies if not adequately bypassed. A

33 µF capacitor should be placed within an inch (2.5 cm) of the A/D converter power pins for each supply

voltage. A 0.1 µF capacitor should be placed as close as possible to each supply pin, preferably within one-half

centimeter. Leadless chip capacitors are preferred because they have low lead inductance.

As is the case with all high speed converters, the LM97600 should be assumed to have little power supply noise

rejection. Any power supply used for digital circuitry in a system where a lot of digital power is being consumed

should not be used to supply power to the LM97600. The ADC supplies should be the same supply used for

other analog circuitry, if not a dedicated supply.

Supply Voltage

The LM97600 is specified to operate with nominal supply voltages of 1.2V (VA, VTH, VC) and 2.5V (V25, VO). For

detailed information regarding the operating voltage minimums and maximums, refer to the Operating Ratings

section. It is very important to note that, while this device will function with slightly higher supply voltages, these

higher supply voltages may reduce product lifetime.

During Power-up, the voltage on all 2.5V supplies should always be equal to, or greater than the voltage on the

1.2V supplies. Similarly, during Power-down, the voltage on the 1.2V supplies should always be equal to or lower

than that of the 2.5V supplies. In general, it is simplest to supply all 2.5V buses from a single regulator, and all

1.2V buses from a single regulator. If the 1.2V buses are generated from separate regulators, they should all rise

and fall together, or the user should ensure that the VC≥VA≥VTH during power up.

No pin should ever have a voltage on it that is in excess of the supply voltage or below ground by more than 150

mV, not even on a transient basis. This can be a problem upon application of power and power shut-down. Be

sure that the supplies to circuits driving any of the input pins, analog or digital, do not come up any faster than

does the voltage at the LM97600 power pins.

The Absolute Maximum Ratings should be strictly observed, even during power up and power down. A power

supply that produces a voltage spike at turn-on and/or turn-off of power can destroy the LM97600. Please refer

to the documentation provided with the LM97600RB reference board for specific guidance on voltage regulators

and power sequencing.

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