Technical Note

9/11

BU9796FS

www.rohm.com

2009.05 - Rev.A

© 2009 ROHM Co., Ltd. All rights reserved.

●Notes for use

(1) Absolute Maximum Ratings

An excess in the absolute maximum ratings, such as supply voltage, temperature range of operating conditions, etc., can break down devices,

thus making impossible to identify breaking mode such as a short circuit or an open circuit. If any special mode exceeding the absolute

maximum ratings

is assumed, consideration should be given to take physical safety measures including the use of fuses, etc.

(2)

Operating conditions

These conditions represent a range within which characteristics can be provided approximately as expected. The electrical

characteristics are guaranteed under the conditions of each parameter.

(3)

Reverse connection of power supply connector

The reverse connection of power supply connector can break down ICs. Take protective measures against the breakdown due to the reverse

connection,

such as mounting an external diode between the power supply and the IC’s power supply terminal.

(4)

Power supply line

Design PCB pattern to provide low impedance for the wiring between the power supply and the GND lines. In this regard, or the digital block

power

supply and the analog block power supply, even though these power supplies has the same level of potential, separate the power supply

pattern for

the digital block from that for the analog block, thus suppressing the diffraction of digital noises to the analog block power supply resulting from

impedance common to the wiring patterns. For the GND line, give consideration to design the patterns in a similar manner.

Furthermore, for all power supply terminals to ICs, mount a capacitor between the power supply and the GND terminal. At the same time, in

order to use

an electrolytic capacitor, thoroughly check to be sure the characteristics of the capacitor to be used present no problem including the

occurrence of

capacity dropout at a low temperature, thus determining the constant.

(5)

GND voltage

Make setting of the potential of the GND terminal so that it will be maintained at the minimum in any operating state. Furthermore, check to be

sure

no terminals are at a potential lower than the GND voltage including an actual electric transient.

(6)

Short circuit between terminals and erroneous mounting

In order to mount ICs on a set PCB, pay thorough attention to the direction and offset of the ICs. Erroneous mounting can break down the ICs.

Furthermore,

if a short circuit occurs due to foreign matters entering between terminals or between the terminal and the power supply or the GND terminal,

the ICs can break down.

(7)

Operation in strong electromagnetic field

Be noted that using ICs in the strong electromagnetic field can malfunction them.

(8)

Inspection with set PCB

On the inspection with the set PCB, if a capacitor is connected to a low-impedance IC terminal, the IC can suffer stress. Therefore, be sure to

discharge

from the set PCB by each process. Furthermore, in order to mount or dismount the set PCB to/from the jig for the inspection process, be sure

to turn OFF

the power supply and then mount the set PCB to the jig. After the completion of the inspection, be sure to turn OFF the power supply and then

dismount

it from the jig. In addition, for protection against static electricity, establish a ground for the assembly process and pay thorough attention to the

transportation and the storage of the set PCB.

(9)

Input terminals

In terms of the construction of IC, parasitic elements are inevitably formed in relation to potential. The operation of the parasitic element can

cause interference with circuit operation, thus resulting in a malfunction and then breakdown of the input terminal. Therefore, pay thorough

attention

not to handle the input terminals, such as to apply to the input terminals a voltage lower than the GND respectively, so that any parasitic

element will

operate. Furthermore, do not apply a voltage to the input terminals when no power supply voltage is applied to the IC. In addition, even if the

power

supply voltage is applied, apply to the input terminals a voltage lower than the power supply voltage or within the guaranteed value of

electrical characteristics.

(10) Ground wiring pattern

If small-signal GND and large-current GND are provided, It will be recommended to separate the large-current GND pattern from the

small-signal

GND pattern and establish a single ground at the reference point of the set PCB so that resistance to the wiring pattern and voltage fluctuations

due to

a large current will cause no fluctuations in voltages of the small-signal GND. Pay attention not to cause fluctuations in the GND wiring pattern

of

external parts as well.

(11) External capacitor

In order to use a ceramic capacitor as the external capacitor, determine the constant with consideration given to a degradation in the nominal

capacitance

due to DC bias and changes in the capacitance due to temperature, etc.