BU97950FUV Datasheet, PDF (18/25 Pages) Rohm – Standard LCD Segment Drivers

BU97950FUV MAX 280 segments (SEG35×COM8)
●Operational Notes
(1) Absolute maximum ratings
Operating the IC over the absolute maximum ratings may damage the IC. The damage can either be a short circuit
between pins or an open circuit between pins. Therefore, it is important to consider circuit protection measures, such as
adding a fuse, in case the IC is operated over the absolute maximum ratings.
(2) Recommended operating conditions
These conditions represent a range within which the expected characteristics of the IC can be approximately obtained.
The electrical characteristics are guaranteed under the conditions of each parameter.
(3) Reverse connection of power supply
Connecting the power supply in reverse polarity can damage the IC. Take precautions against reverse polarity when
connecting the power supply, such as mounting an external diode between the power supply and the IC‟s power supply
terminals.
(4) Power supply lines
Design the PCB layout pattern to provide low impedance ground and supply lines. Separate the ground and supply lines
of the digital and analog blocks to prevent noise in the ground and supply lines of the digital block from affecting the
analog block. Furthermore, connect a capacitor to ground at all power supply pins. Consider the effect of temperature
and aging on the capacitance value when using electrolytic capacitors.
(5) Ground Voltage
The voltage of the ground pin must be the lowest voltage of all pins of the IC at all operating conditions. Ensure that no
pins are at a voltage below the ground pin at any time, even during transient condition.
(6) Short between pins and mounting errors
Be careful when mounting the IC on printed circuit boards. The IC may be damaged if it is mounted in a wrong orientation
or if pins are shorted together. Short circuit may be caused by conductive particles caught between the pins.
(7) Operation under strong electromagnetic field
Operating the IC in the presence of a strong electromagnetic field may cause the IC to malfunction.
(8) Testing on application boards
When testing the IC on an application board, connecting a capacitor directly to a low-impedance output pin may subject
the IC to stress. Always discharge capacitors completely after each process or step. The IC‟s power supply should
always be turned off completely before connecting or removing it from the test setup during the inspection process. To
prevent damage from static discharge, ground the IC during assembly and use similar precautions during transport and
storage.
(9) Regarding input pins of the IC
In the construction of this IC, P-N junctions are inevitably formed creating parasitic diodes or transistors. The operation of
these parasitic elements can result in mutual interference among circuits, operational faults, or physical damage.
Therefore, conditions which cause these parasitic elements to operate, such as applying a voltage to an input pin lower
than the GND voltage should be avoided. Furthermore, do not apply a voltage to the input terminals when no power
supply voltage is applied to the IC. Even if the power supply voltage is applied, make sure that the input terminals have
voltages within the values specified in the electrical characteristics of this IC.
(10) GND wiring pattern
When using both small-signal and large-current GND traces, the two ground traces should be routed separately but
connected to a single ground at the reference point of the application board to avoid fluctuations in the small-signal
ground caused by large currents. Also ensure that the GND traces of external components do not cause variations on the
GND voltage. The power supply and ground lines must be as short and thick as possible to reduce line impedance.
(11) External Capacitor
When using a ceramic capacitor, determine the dielectric constant considering the change of capacitance with
temperature and the decrease in nominal capacitance due to DC bias and others.
(12) Unused input terminals
Input terminals of an IC are often connected to the gate of a CMOS transistor. The gate has extremely high impedance
and extremely low capacitance. If left unconnected, the electric field from the outside can easily charge it. The small
charge acquired in this way is enough to produce a significant effect on the conduction through the transistor and cause
unexpected operation of IC. So unless otherwise specified, input terminals not being used should be connected to the
power supply or ground line.
(13) Rush current
When power is first supplied to the IC, rush current may flow instantaneously. It is possible that the charge current to the
parasitic capacitance of internal photo diode or the internal logic may be unstable. Therefore, give special consideration
to power coupling capacitance, power wiring, width of GND wiring, and routing of connections.
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