Datasheet

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
INNINP
OUT
V
VV
V +
=
2
where:
V
OUT
is the voltage at the output pin, VOUT.
V
INP
and V
INN
are the input voltages at the INP and INN pins,
respectively.
V
REF
is the voltage at the VREF pin.
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.