BD37511FS_15 Datasheet, PDF (23/30 Pages) Rohm – Sound Processor with Built-in 2-band Equalizer

BD37511FS
Operational Notes – continued
12. Regarding the 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 the P layers with the N layers of other elements, creating a
parasitic diode or transistor. For example (refer to figure below):
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 inevitably occur in the structure of the IC. The operation of parasitic diodes can result in mutual
interference among circuits, operational faults, or physical damage. Therefore, 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.
Resistor
Transistor (NPN)
Pin A
Pin A
Pin B
C
B
E
Pin B
P⁺
N
N
Parasitic
Elements
P
P⁺
N
N
P Substrate
GND
Parasitic
Elements
N ^P+
N _{P N P}⁺ _N
P Substrate
Parasitic
GND GND
Elements
Figure 19. Example of monolithic IC structure
B
N Region
close-by
C
E
Parasitic
Elements
GND
13. About a Signal Input Part
(a) About Input Coupling Capacitor Constant Value
In the input signal terminal, please decide the constant value of the input coupling capacitor C(F) that would be
sufficient to form an RC characterized HPF with input impedance RIN(Ω) inside the IC.
G〔dB〕
C〔F〕
0
RIN
〔Ω〕
A(f)
SSH
INPUT
f〔Hz〕
(b) About the Input Selector SHORT
Af  
2 fCR_IN ²
1 2 fCR_IN ²
SHORT mode is the command which makes switch SSH =ON of input selector part so that the input impedance
RIN of all terminals becomes small. Switch SSH is OFF when SHORT command is not selected.
The constant time brought about by the small resistance inside and the capacitor outside the LSI becomes
small when this command is used. The charge time of the capacitor becomes short. Since SHORT mode turns
ON the switch of SSH and makes it low impedance, please use it at no signal condition.
14. About Mute Terminal(Pin 16) when power supply is OFF
There should be no applied voltage across the Mute terminal (Pin 16) when power-supply is OFF.
A resistor (about 2.2kΩ) should be connected in series to Mute terminal in case a voltage is supplied to Mute terminal.
(Please refer Application Circuit Diagram.)
15. About TEST Pin
TEST Pin, should be OPEN.
Pin 9, 8, 7 are TEST Pins.
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TSZ22111・15・001
23/26
TSZ02201-0C2C0E100410-1-2
16.Dec.2015 Rev.001