BA3259HFP(2009) Просмотр технического описания (PDF) - ROHM Semiconductor

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производитель

BA3259HFP
(Rev.:2009)

Dual-output Secondary Fixed/Variable Output LDO Regulators for Local Power Supplies

ROHM Semiconductor 

BA3259HFP,BA30E00WHFP

Technical Note

 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 the devices, thus making impossible to identify breaking mode, such as a short circuit or an open circuit. If any

over rated values will expect to exceed the absolute maximum ratings, consider adding circuit protection devices, such as

fuses.

2) GND voltage

The potential of GND pin must be minimum potential in all operating conditions.

3) Thermal design

Use a thermal design that allows for a sufficient margin in light of the power dissipation (Pd) in actual operating conditions.

4) Inter-pin shorts and mounting errors

Use caution when positioning the IC for mounting on printed circuit boards. The IC may be damaged if there is any

connection error or if pins are shorted together.

5) Actions in strong electromagnetic field

Use caution when using the IC in the presence of a strong electromagnetic field as doing so may cause the IC to

malfunction.

6) Testing on application boards

When testing the IC on an application board, connecting a capacitor to a pin with low impedance subjects the IC to stress.

Always discharge capacitors after each process or step. Always turn the IC's power supply off before connecting it to or

removing it from a jig or fixture during the inspection process. Ground the IC during assembly steps as an antistatic

measure. Use similar precaution when transporting or storing the IC.

7) Regarding input pin of the IC

This monolithic IC contains P+ isolation and P substrate layers between adjacent elements in order to keep them isolated.

P-N junctions are formed at the intersection of these P layers with the N layers of other elements, creating a parasitic diode

or transistor. For example, the relation between each potential is as follows:

When GND > Pin A and GND > Pin B, the P-N junction operates as a parasitic diode.

When GND > Pin B, the P-N junction operates as a parasitic transistor.

Parasitic diodes can occur inevitable in the structure of the IC. The operation of parasitic diodes can result in mutual

interference among circuits, operational faults, or physical damage. Accordingly, methods by which parasitic diodes

operate, such as applying a voltage that is lower than the GND (P substrate) voltage to an input pin, should not be used.

8) Ground wiring patterns

When using both small signal and large current GND patterns, it is recommended to isolate the two ground patterns,

placing a single ground point at the ground potential of application so that the pattern wiring resistance and voltage

variations caused by large currents do not cause variations in the small signal ground voltage. Be careful not to change the

GND wiring pattern of any external components, either.

9) Thermal Shutdown Circuit (TSD)

This IC incorporates a built-in thermal shutdown circuit for protection against thermal destruction. Should the junction

temperature (Tj) reach the thermal shutdown ON temperature threshold, the TSD will be activated, turning off all output

power elements. The circuit will automatically reset once the chip's temperature Tj drops below the threshold temperature.

Operation of the thermal shutdown circuit presumes that the IC's absolute maximum ratings have been exceeded.

Application designs should never make use of the thermal shutdown circuit.

10) Overcurrent protection circuit

An overcurrent protection circuit is incorporated in order to prevention destruction due to short-time overload currents.

Continued use of the protection circuits should be avoided. Please note that current increases negatively impact the

temperature.

11) Damage to the internal circuit or element may occur when the polarity of the Vcc pin is opposite to that of the other pins

inapplications. (I.e. Vcc is shorted with the GND pin while an external capacitor is charged.)

Use a maximum capacitance of 1000 mF for the output pins. Inserting a diode to prevent back-current flow in series with

Vcc or bypass diodes between Vcc and each pin is recommended.

Bypass diode

Diode for preventing back current flow

VCC

Output pin

Fig. 32 Bypass diode

（( P端IN子AA) ）

P＋

N

PP基su板bstr ate

R e抵s抗isto r

（(端P子IN BB)）

Trトanラsiンstoジrス(NタP(NN)PN)

B

C

E

(PINB)

C

B

E

P

N

P＋

N

Para寄s生iti c素e子lem ent

P＋

N

N

PＰ

ＮN

GND

P＋

ＮN

(PINA)

P sPub基st板rate

GND

Other adjacent elements

Parasitic element

GND

G ND

GND

Parasitic element

Fig. 33 Example of Simple Bipolar IC Architecture

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

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2009.04 - Rev.A

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