BD9997FVT 查看數據表（PDF） - ROHM Semiconductor
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BD9997FVT Datasheet PDF : 5 Pages
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○Operation Notes
1．About grand potential
Set PGND and GND to equal potential.The ground line is where the lowest potential and transient voltages are connected to
the IC.
2．About starting
Keep light Load at VOUT output while start-up.
3．About board pattern
Use separates ground lines for small control signals and high current outputs. Because these high current outputs that
flows to the wire impedance changes the GND voltage for control signal. Therefore each ground of IC must be connected at
one point on the set circuit board. As for GND of external parts, it’s similar to the above-mentioned. The characteristics of
DC/DC converter might influenced by surrounding components and board pattern. Consider the effects from surroundings
while design. Make VCC,PGND and GND impedance sufficiently low Solder RESERVE to GND on set circuit board.
4．About peripheral circuit
Bypass capacitor between power supply and ground should be use low ESR ceramic capacitor and placed close to
the IC pin as possible. External components such as L and C is necessary to be placed as near to the IC as
possible with shortest distance. Monitor the output voltage at both end of capacitor connected to VOUT.PMOS
over current limit must not be built into, and the over current must not flow to PMOS. please have safe
countermeasure such as adding POLY SWITCH and fuse to avoid from over stressing.
5．About absolute maximum rating
Exceeding supply voltage and operating Temp. over Absolute Maximum Ratings may cause degradation of IC and
even may destroy the IC. If special mode such that exceeding Absolute Maximum Ratings is expected, please have
safe countermeasure such as adding POLY SWITCH and fuse to avoid from over stressing.
6．About heat design
Do not exceed the power dissipation (PD) of the package specification rating under actual operation.
7．About Short between terminals and the mis-installation
While mounting IC on the board, check direction and position of the IC. If inadequately mounted, the IC may destroy.
Moreover this IC might be destroyed when dust short the terminals between pins or pin and ground.
8．About operation in strong electromagnetic field
Strong electromagnetic radiation can cause operation failures.
9．About heat interception circuit (TSD)
The TSD is activated when the junction temperature (Tj) reaches 175℃ and the output terminal is switched to Hi-Z. The
TSD circuit aims to intercept IC from high temperature. The guarantee and protection of IC are not purpose. Therefore,
please do not use this IC after TSD circuit operates, nor use it for assumption that operates the TSD circuit.
10．About inspection by set substrate
The stress might hang to IC by connecting the capacitor to the terminal with low impedance. Then, please discharge
electricity in each and all process. Moreover, in the inspection process, please turn off the power before mounting the IC, and
turn on after mounting the IC. In addition, please take into consideration the countermeasures for electrostatic damage, such
as giving the earth in assembly process, transportation or preservation.
11．About each input terminal
This IC is a monolithic IC, and has P+ isolation and P substrate for the element separation. Therefore, a parasitic PN junction
is firmed in this P-layer and N-layer of each element. When the GND voltage potential is greater than the voltage potential at
Terminals A or B, the PN junction operates as a parasitic diode. In addition, the parasitic NPN transistor is formed in said
parasitic diode and the N layer of surrounding elements close to said parasitic diode. These parasitic elements are formed in
the IC because of the voltage relation. The parasitic element operating causes the wrong operation and destruction.
Therefore, please be careful so as not to operate the parasitic elements by impressing to input terminals lower voltage than
GND (P substrate). Please do not apply the voltage to the input terminal when the power –supply voltage is not impressed.
Moreover, please impress each input terminal lower than the power-supply voltage or equal to the specified range in the
guaranteed voltage when the power-supply voltage is impressing..
REV. B
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