ADCMP604 datasheet(30/34 Pages) AD

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LTC6563

Rev. 0

For more information www.analog.com

APPLICATIONS INFORMATION

Avoiding Zero-Input Signal Clipping when Using TILT

along with Clamp

Clamp operation is meant to mainly safeguard against

transient overload conditions. Under normal operation,

ensure that the clamps are not engaged with nominal

signal levels and/or zero input current signal! To do this,

set the HI input above the expected output voltage, or

alternatively, tie HI input to VCCI to disable clamp opera-

tion. When the TILT input is used to maximize the output

swing, the voltage applied to the TILT input should be

just enough to provide the required differential full-scale

voltage without running the output(s) to the clamp region.

Referring to Figure 15 for this particular operating point

example:

• ADJ =11, RL = 50Ω to ground on each output pin, VCM

pin tied to 1.5V to match actual output CM voltage

since CM servo loop is not used here

If clamps are used, set TILT to 1.3V, which is just above

the Tilt voltage needed to ensure the maximum output

swing can be achieved without running into the clamp(s).

In this example, the HI pin should be tied to approximately

2V or higher. If clamps are disabled (HI pin tied to VCCI),

TILT input can simply be tied to VCCI since running into

the clamps is not an issue.

Limitations of Output Clamp Architecture

The out clamps will only prevent overload scenarios that

originate from the LTC6563’s signal chain itself. Overloads

caused by external stimuli at the LTC6563’s may not

be clamped, e.g. injecting current into the LTC6563’s

output(s).

Figure 15. Tilt Input Transfer Function Example

(ADJ11) with no TIA Input Current

Output Tilt Control

RL = 50Ω TO GROUND

ON EACH OUTPUT

|| 100Ω DIFF

TERM AND TERMBAR

DISCONNECTED

ADJ = 11

OUT VOLTAGE

OUTBAR VOLTAGE

OUT CURRENT

OUTBAR CURRENT

TILT PIN VOLTAGE (V)

0.7

1.3

2.0

2.6

3.3

0.5

1.0

1.5

2.0

2.5

6563 F15

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