BD95513MUV_10 Datasheet, PDF (16/18 Pages) Rohm – Switching Regulator with MOS FET for DDR-SDRAM Cores

BD95513MUV
Technical Note
(11) Regarding IC input pins
This monolithic IC contains P+ isolation and P substrate layers between adjacent elements in order to keep them isolated.
PN junctions are formed at the intersection of these P layers with the N layers of other elements, creating parasitic diodes
and/or transistors. For example (refer to the figure below):
When GND > Pin A and GND > Pin B, the PN junction operates as a parasitic diode
When GND > Pin B, the PN junction operates as a parasitic transistor
Parasitic diodes occur inevitably in the structure of the IC, and the operation of these parasitic diodes can result in mutual
interference among circuits, operational faults, or physical damage. Accordingly, conditions that cause these diodes to
operate, such as applying a voltage lower than the GND voltage to an input pin (and thus to the P substrate) should be
avoided.
Pin A
N ^{P+ N}
Parasitic Element
Resistance
P
P⁺ _N
P Substrate
GND
Pin A
Transistor (NPN)
Pin B
C
B
E
Pin B
N _P+ N
NP
P⁺ _N
Parasitic Element
Parasitic Elements
Example of IC Structure
P Substrate
GND
GND
B
C
E
Parasitic Elements
GND
Other Adjacent Elements
(12) Ground wiring traces
When using both small-signal and large-current GND traces, the two ground traces should be routed separately but
connected to a single ground potential within the application in order to avoid variations in the small-signal ground caused
by large currents. Also ensure that the GND traces of external components do not cause variations on GND voltage.
●Power Dissipation
5.5
5.0
④4.56W
4.5
4.0
3.5
3.0
2.5
③2.06W
2.0
1.5
1.0 ^②0.88W
0.5 ^①0.38W
0.0
0
25
50
75
100
125
Ambient Temperature: Ta(℃)
① IC Only
Θ_j-a = 328.9 ℃/W
② IC mounted on 1-layer board
(with 20.2 mm² copper thermal pad)
Θ_j-a = 142.0 ℃/W
③ IC mounted on 4-layer board
(with 20.2 mm² pad on top layer, 5502 mm² pad on layers 2,3)
Θ_j-a = 60.7 ℃/W
④ IC mounted on 4-layer board (with 5505mm² pad on all layers)
Θ_j-a = 27.4 ℃/W
150
VQFN032V5050
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2010.10- Rev.A