Technical Note

11/13

BD7844AEFV

www.rohm.com

2011.07 - Rev.A

© 2011 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.

Power supply and ground line

Design PCB pattern to provide low impedance for the wiring between the power supply and the ground lines. Pay

attention to the interference by common impedance of layout pattern when there are plural power supplies and ground

lines. Especially, when there are ground pattern for small signal and ground pattern for large current included the

external circuits, please separate each ground pattern. Furthermore, for all power supply pins to ICs, mount a capacitor

between the power supply and the ground pin. At the same time, in order to use a 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.

3.

Ground voltage

Make setting of the potential of the ground pin so that it will be maintained at the minimum in any operating state.

Furthermore, check to be sure no pins are at a potential lower than the ground voltage including an actual electric

transient.

4.

Short circuit between pins 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 pins or between

the pin and the power supply or the ground pin, the ICs can break down.

5.

Operation in strong electromagnetic field

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

6.

Input pins

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 pin. Therefore, pay thorough attention not to handle the input pins, such as to apply to the input pins a voltage

lower than the ground respectively, so that any parasitic element will operate. Furthermore, do not apply a voltage to the

input pins when no power supply voltage is applied to the IC. In addition, even if the power supply voltage is applied,

apply to the input pins a voltage lower than the power supply voltage or within the guaranteed value of electrical

characteristics.

7.

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.

8.

Thermal shutdown circuit (TSD)

This LSI builds in a thermal shutdown (TSD) circuit. When junction temperatures become detection temperature or

higher, the thermal shutdown circuit operates and turns a switch OFF. The thermal shutdown circuit, which is aimed at

isolating the LSI from thermal runaway as much as possible, is not aimed at the protection or guarantee of the LSI.

Therefore, do not continuously use the LSI with this circuit operating or use the LSI assuming its operation.

9.

Thermal design

Perform thermal design in which there are adequate margins by taking into account the permissible dissipation (Pd) in

actual states of use.

10. About the pin for the test, the un-use pin

Prevent a problem from being in the pin for the test and the un-use pin under the state of actual use. Please refer to a

function manual and an application notebook. And, as for the pin that doesn't specially have an explanation, ask our

company person in charge.

11. About the rush current

For ICs with more than one power supply, it is possible that rush current may flow instantaneously due to the internal

powering sequence and delays. Therefore, give special consideration to power coupling capacitance, power wiring,

width of ground wiring, and routing of wiring.

12. About the function description or application note or more.

The function description and the application notebook are the design materials to design a set. So, the contents of the

materials aren't always guaranteed. Please design application by having fully examination and evaluation include the

external elements.