Data Sheet

ADA4830-1/ADA4830-2

Rev. C | Page 13 of 22

THEORY OF OPERATION

CORE AMPLIFIER

At the core of the ADA4830-1 and ADA4830-2 are high speed,

rail-to-rail op amps that are built on a 0.35 µm CMOS process.

Together with the core amplifier, the ADA4830-1 and ADA4830-2

combine four highly matched on-chip resistors into a difference

amplifier function. Common-mode range extension at its inputs

is achieved by employing a resistive attenuator. The closed-loop

differential to single-ended gain of the video channel is internally

fixed at 0.50 V/V (−6 dB) to ensure compatibility with video

decoders whose input range is constrained to 1 V p-p or less.

The transfer function of the ADA4830-1 and ADA4830-2 is

REF

INN

INP

OUT

V

V

V

V

+

−

=

2

where:

respectively.

OVERVOLTAGE (SHORT-TO-BATTERY)

PROTECTION

Robust inputs guarantee that sensitive internal circuitry is not

subjected to extreme voltages or currents during a stressful event. A

short-to-battery condition usually consists of a voltage on either

input (or both inputs) that is significantly higher than the power

supply voltage of the amplifier. Duration may vary from a short

transient to a continuous fault.

The ADA4830-1 and ADA4830-2 can withstand voltages of up

to 18 V on the inputs. Critical internal nodes are protected from

exposure to high voltages by circuitry that clamps the inputs at a

safe level and limits internal currents. This protection is available

whether the device is enabled or disabled, even when the supply

voltage is removed.

SHORT-TO-BATTERY OUTPUT FLAG

The short-to-battery output flag (STB pin) is functionally

independent of the short-to-battery protection. Its purpose is

to indicate an overvoltage condition on either input. Because

protection is provided passively, it is always available; the flag

merely indicates the presence or absence of a fault condition.

ESD PROTECTION

All pins on the ADA4830-1 and ADA4830-2 are protected with

internal ESD protection structures connected to the power supply

pins (+VS and GND). These structures provide protection during

the handling and manufacturing process.

The inputs (INN and INP) of the ADA4830-1 and ADA4830-2

can be exposed to dc voltages well above the supply voltage;

therefore, conventional ESD structure protection cannot be used.

The ADA4830-1 and ADA4830-2 employ Analog Devices, Inc.,

proprietary ESD devices at the input pins (INN, INP) to allow

for a wide common-mode voltage range and ESD protection

well beyond the handling and manufacturing requirements.

The inputs of the ADA4830-1 and ADA4830-2 are ESD protected

to survive ±8 kV human body model (HBM)

POWER SUPPLY PINS (ADA4830-2)

As indicated in the Absolute Maximum Ratings section, the voltage

difference between the +VS1 and +VS2 pins of the ADA4830-2

cannot exceed 0.5 V. To ensure compliance with the Absolute

Maximum Ratings, it is recommended that these supply pins be

connected together to the same power supply source.