LT6350IMS8#TRPBF Linear Technology, LT6350IMS8#TRPBF Datasheet - Page 15

• Manufacturer Part Number: LT6350IMS8#TRPBF
• Description: IC DIFF CONVERT/ADC DRIVER 8MSOP
• Manufacturer: Linear Technology
• Type: ADC Driverr

Specifications of LT6350IMS8#TRPBF

• Applications: Data Acquisition
• Mounting Type: Surface Mount
• Package / Case: 8-MSOP, Micro8™, 8-uMAX, 8-uSOP,
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

APPLICATIONS INFORMATION
as the total –IN1 parasitic capacitance will eliminate
any ringing or oscillation. Special care should be taken
during layout, including using the shortest possible trace
lengths and stripping the ground plane under the –IN1
pin, to minimize the parasitic capacitance introduced at
that pin.
Input bias current induced DC voltage offsets in the input
op amp can be minimized by matching the parallel imped-
ance of R
+IN1. For example, in the typical gain-of-two application,
when the input op amp is confi gured as a unity-gain buffer,
choosing R
output. Since nonzero values of R
total output noise, R
to reduce the noise bandwidth.
INVERTING AMPLIFIER (OP AMP 2) CHARACTERISTICS
The operational amplifi er at pins OUT1, +IN2 and OUT2 is
internally confi gured as a unity-gain inverter and provides
on pin OUT2 an inverted copy of the voltage at pin OUT1.
The voltage applied to pin +IN2 sets the output common
mode voltage in accordance with Equation (3). The range
of useful output common mode voltages is limited by the
full-scale input range of A/D converters; values of output
common mode near mid-rail are most useful. The op amp
used for the inverting buffer therefore differs from the
input op amp primarily in that its input common mode
range is not rail-to-rail: the inverting op amp has an input
stage that functions over the input range from V
to V
The inverting op amp uses tightly matched, 1k on-chip re-
sistors to set the gain of –1. Note that during output swings,
current fl ows through these resistors, increasing the total
power dissipation of the LT6350. The worst-case increase
over quiescent power dissipation can be found by assuming
that the full power supply voltage appears between OUT1
and OUT2. In this case the extra power dissipated in the
internal feedback network will be V
+
– 0.1V.
F
and R
F
= R
G
S
to the impedance of the source that drives
will minimize the differential offset at the
F
may be bypassed with a capacitor
F
S
will contribute to the
2
/2kΩ.
–
+ 1.5V
Since the inverting op amp is permanently confi gured
with a noise gain of two, the internal frequency compen-
sation has been adjusted such that the GBW product
of the inverting op amp is higher than that of the input
op amp. This allows the closed-loop bandwidths of the
two op amps to match more closely when the LT6350 is
used in the typical differential gain of two confi guration
and increases the closed-loop differential bandwidth in
that application.
The input referred voltage offset of the inverting op amp,
which is equivalent to output common mode voltage
offset, and which could contribute to differential voltage
offset in accordance with Equation (2), is trimmed during
manufacture to within ±125μV. To minimize the offset
contribution of the input bias current into pin +IN2, an
external 499Ω resistor should be installed at pin +IN2
for all applications. For more information, see the Setting
The Output Common Mode and Offset Considerations
sections.
INPUT PROTECTION
There are back-to-back diodes across the + and – inputs
of both LT6350 op amps. The inputs of the LT6350 do not
have internal resistors in series with the input transistors,
a technique often used to protect the input transistors
from excessive current fl ow during a differential overdrive
condition. Adding series input resistors would signifi -
cantly degrade the low noise performance. Therefore, if
the voltage across the op amp input stages is allowed to
exceed ±0.7V, steady-state current conducted though the
protection diodes should be externally limited to ±20mA.
The input diodes are rugged enough to handle transient
currents due to amplifi er slew rate overdrive or momentary
clipping without protection resistors.
LT6350
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