BD6941FM_09 Datasheet, PDF (7/9 Pages) Rohm – Power Management IC Series for Automotive Body Control Motor Driver

BD6941FM
Technical Note
7) IC terminal input voltage
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 to create a variety of
parasitic elements. For example, when the resistors and transistors are connected to the pins as shown in the following
figure,
The P/N junction functions as a parasitic diode when GND > Pin A for the resistor or GND > Pin B for the transistor(NPN).
Similarly, when GND > Pin B for the transistor (NPN), the parasitic diode described above combines with the N layer of
other adjacent elements to operate as a parasitic NPN transistor.
The formation of parasitic elements as a result of the relationships of the potentials of different pins is an inevitable result of
the IC's architecture. The operation of parasitic elements can cause interference with circuit operation as well as IC
malfunction and damage. For these reasons, it is necessary to use caution so that the IC is not used in a way that will trigger
the operation of parasitic elements, such as by the application of voltages lower than the GND (P substrate) voltage to input
pins.
(Pin A)
Resistor
(Pin B)
Transistor (NPN)
B
C
E
(Pin B)
BC
P+
N
P
P
N
P+
N
Parasitic elements
P+
N
N
P
N
P+
N
P substrate
GND
Parasitic elements
or Transistors
GND
(Pin A)
GND
Parasitic elements or
Parasitic elements
8) Input terminals
Do not apply the voltage to input pin when the Vcc is not applied. And when the Vcc is applied, the voltage of input pin
must not exceed Vcc. It is feared that output get malfunction, as input voltage is sweeped slowly near the H, L threshold
voltage. Please pay attention to input slew rate.
9) Back electro motive force (BEMF)
There is a possibility that the BEMF is changed by use of the operating condition, environment and the individual
characteristics of motor. Please make sure there is no problem of operating the IC although the BEMF is occurred.
10) The note of pattern design at printed circuit
This IC flows large current between power supply for motor division and GND. So, it is feared that get undesirable result
malfunction, oscillation and so on, as input lines is affected by large output current. Please consider pattern design at
printed circuit doesn’t have common impedance on output large current lines-input lines. Please consider to keep low
impedance of power supply for fear of oscillation from power supply high impedance, also.
11) Rash current
This IC doesn’t have current limit circuit for rash current. Therefore physical security countermeasure, like current limit
resistor is to be given.
12) Thermal shutdown circuit
This IC incorporates a built-in TSD circuit for the protection from thermal destruction. The IC should be used within the
specified power dissipation range. However, in the event that the IC continues to be operated in excess of its power
dissipation limits , the attendant rise in the junction temperature (Tj) will trigger the TSD circuit to turn off all output power
elements. The circuit automatically resets once the junction temperature (Tj) drops. Operation of the TSD circuit presumes
that the IC's absolute maximum ratings have been exceeded. Application designs should never make use of the TSD circuit.
13) Over voltage lock out function
This IC has the function of turning off the output when detecting the over voltage. More than 30V(typ.) triggers this
function. But in the standby mode, this function does not work. Although this IC has over voltage lockout function, the
voltage that exceeds absolute maximum ratings might destroy the IC. Please do not exceed the absolute maximum
ratings.
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2009.06 - Rev.A