TLV2780 Datasheet, PDF (15/32 Pages) Texas Instruments – FAMILY OF 1.8 V HIGH-SPEED RAIL-TO-RAIL INPUT/OUTPUT OPERATIONAL AMPLIFIERS WITH SHUTDOWN

TLV2780, TLV2781, TLV2782, TLV2783, TLV2784, TLV2785, TLV278xA
FAMILY OF 1.8 V HIGHĆSPEED RAILĆTOĆRAIL INPUT/OUTPUT
OPERATIONAL AMPLIFIERS WITH SHUTDOWN
SLOS245E − MARCH 2000 − REVISED JANUARY 2005
APPLICATION INFORMATION
circuit layout considerations
To achieve the levels of high performance of the TLV278x, follow proper printed-circuit board design techniques.
A general set of guidelines is given in the following.
D Ground planes − It is highly recommended that a ground plane be used on the board to provide all
components with a low inductive ground connection. However, in the areas of the amplifier inputs and
output, the ground plane can be removed to minimize the stray capacitance.
D Proper power supply decoupling − Use a 6.8-µF tantalum capacitor in parallel with a 0.1-µF ceramic
capacitor on each supply terminal. It may be possible to share the tantalum among several amplifiers
depending on the application, but a 0.1-µF ceramic capacitor should always be used on the supply terminal
of every amplifier. In addition, the 0.1-µF capacitor should be placed as close as possible to the supply
terminal. As this distance increases, the inductance in the connecting trace makes the capacitor less
effective. The designer should strive for distances of less than 0.1 inches between the device power
terminals and the ceramic capacitors.
D Sockets − Sockets can be used but are not recommended. The additional lead inductance in the socket pins
will often lead to stability problems. Surface-mount packages soldered directly to the printed-circuit board
is the best implementation.
D Short trace runs/compact part placements − Optimum high performance is achieved when stray series
inductance has been minimized. To realize this, the circuit layout should be made as compact as possible,
thereby minimizing the length of all trace runs. Particular attention should be paid to the inverting input of
the amplifier. Its length should be kept as short as possible. This will help to minimize stray capacitance at
the input of the amplifier.
D Surface-mount passive components − Using surface-mount passive components is recommended for high
performance amplifier circuits for several reasons. First, because of the extremely low lead inductance of
surface-mount components, the problem with stray series inductance is greatly reduced. Second, the small
size of surface-mount components naturally leads to a more compact layout, thereby minimizing both stray
inductance and capacitance. If leaded components are used, it is recommended that the lead lengths be
kept as short as possible.
shutdown function
Three members of the TLV278x family (TLV2780/3/5) have a shutdown terminal for conserving battery life in
portable applications. When the shutdown terminal is tied low, the supply current is reduced to 900 nA/channel,
the amplifier is disabled, and the outputs are placed in a high impedance mode. To enable the amplifier, the
shutdown terminal can either be left floating or pulled high. When the shutdown terminal is left floating, care
should be taken to ensure that parasitic leakage current at the shutdown terminal does not inadvertently place
the operational amplifier into shutdown.
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