LC78622NE Datasheet, PDF (29/31 Pages) Sanyo Semicon Device – Compact Disc Player DSP

LC78622NE
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• In general, latch-up can be prevented by tying any unused pins to either V_DD or VSS. However, be sure to follow any
special instructions provided with this IC for unused pin handling.
• Do not short the outputs.
Interface
When the inputs and outputs of devices of different types are connected, incorrect operation may occur due to
discrepancies between the input V_IL/V_IH and output V_OL/V_OH values. Insert level shifters between devices that have
different supply voltages to prevent device destruction in systems that use dual power-supply systems.
Load Capacitance and Output Current
• When a load with a large capacitance is connected, since a load short that lasts for an extended period, fused output
lines can be caused. Also, high charge and discharge currents can result in noise which can degrade end product
performance or result in incorrect operation. Always use the recommended load capacitances.
• Large output sink or source currents can also cause the same types of problems described in the previous item. Use the
recommended currents, while taking the maximum allowable power dissipation into account.
Notes on Power Application and Reset
• There are points that require care that are related to power application, the period during which a reset is applied, and
the period after a reset is cleared. Refer to the specific notes provided in the specification sheets for the individual
products, and design end products with these points in mind.
• The pin output states, the pin I/O settings, the contents of registers, and other aspects of this IC are not guaranteed
when power is first applied. Aspects that are defined by the reset operation or by settings are only guaranteed once the
reset or setting has been performed. Applications that use this IC should apply a reset immediately after power is
applied. Pin states and register values that are undefined may differ between samples, and may change between lots
over time. Applications should not depend on undefined states and values.
• The general-purpose I/O ports are set to the input state during a reset. For pins that must be fixed at high or low due to
fail-safe design considerations, pulling up to V_DD or pulling down to V_SS through an individual resistor can be an
effective design.
• When the 4.2MHz output is used as the microcontroller master clock, the reset circuit will be shared with the
microcontroller. Since the microcontroller will not be reset unless a clock signal is applied, do not control the reset
input to this IC from a microcontroller output port. If this IC has not been reset, the 4.2-MHz output is not guaranteed,
and the microcontroller may not be reset. This can result in incorrect application system operation.
Notes on Thermal Design
The failure rate of semiconductor devices is significantly accelerated by increases in ambient temperature and power
dissipation. To assure high reliability, designs must include adequate margins to take possible changes in ambient
conditions into account.
Notes on Printed Circuit Board Patterns
• If possible, the influence of common impedances should be reduced by separating the V_DD and ground lines for each
system.
• The V_DD and ground lines should be as wide and as short as possible to lower their high-frequency impedance. Ideally,
decoupling capacitors (0.01 to 1 µF) should be inserted between each V_DD and ground pair. These capacitors should be
located extremely close to their corresponding power supply system pins. Additionally, it is appropriate to insert a
capacitor of about 100 to 220 µF between V_DD and ground as a low-frequency filter. However, note that using
excessively large capacitors here can result in latch-up.
— In servo systems, the V_REF lines should be handled in the same manner as the V_CC and ground lines. Driver ground
lines should be particularly wide, and the recommended driver pattern should be used direct under the power
devices taking heat radiation effect into consideration.
— If a current output type pickup is used, locate the optical sensor connector and the ASP RF input as close together
as possible. If a voltage output type pickup is used, locate the I/V conversion resistor as close to the ASP RF input
side as possible.
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