12.1 Layout Guidelines
To achieve the levels of high performance of the TLV237x , follow proper printed-circuit board design techniques. A general set of guidelines is shown in the following list:
- Ground planes: TI highly recommends using a ground plane 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.
- Proper power supply decoupling: Use a 6.8-μF tantalum capacitor in parallel with a 0.1-μF ceramic capacitor on each supply pin. It may be possible to share the tantalum among several amplifiers depending on the application. Always use a 0.1-µF ceramic capacitor on the supply pin of every amplifier. In addition, the 0.1-μF capacitor must be placed as close to the supply pin as possible. As this distance increases, the inductance in the connecting trace makes the capacitor less effective. The designer must strive for distances of less than 0.1 inches between the device power pins and the ceramic capacitors.
- Sockets: Sockets can be used but are not recommended. The additional lead inductance in the socket pins often lead to stability problems. For best results, solder the surface mount packages directly to the printed circuit board.
- Short trace runs and compact part placements: Optimum high performance is achieved when stray series inductance are minimized. To realize this, the circuit layout must be made as compact as possible, which minimizes the length of all trace runs. Pay particular attention to the inverting input of the amplifier. The length of the inverting input must be kept as short as possible. This helps to minimize stray capacitance at the input of the amplifier.
- Surface-mount passive components: Using surface-mount passive components is recommended for high performance amplifier circuits for several reasons. First, because of the low lead inductance of surface-mount components, the problem with stray series inductance is reduced. Second, the small size of surface-mount components naturally leads to a more compact layout, which minimizes stray inductance and capacitance. TI recommends that lead lengths are kept as short as possible if leaded components are used.