●
Other Points of Caution
1)Protection Circuits
Over-current Protection Circuit
A built-in over-current protection circuit corresponding to the current capacity prevents the destruction of the IC when there
are load shorts. This protection circuit is a “7”-shaped current control circuit that is designed such that the current is restricted
and does not latch even when a large current momentarily flows through the system with a high-capacitance capacitor.
However, while this protection circuit is effective for the prevention of destruction due to unexpected accidents, it is not
suitable for continuous operation or transient use. Please be aware when creating thermal designs that the overcurrent
protection circuit has negative current capacity characteristics with regard to temperature (Refer to Figs.4 and 16).
Thermal Shutdown Circuit (Thermal Protection)
This system has a built-in temperature protection circuit for the purpose of protecting the IC from thermal damage. As shown
above, this must be used within the range of acceptable loss, but if the acceptable loss happens to be continuously exceeded,
the chip temperature Tj increases, causing the temperature protection circuit to operate.
When the thermal shutdown circuit operates, the operation of the circuit is suspended. The circuit resumes operation
immediately after the chip temperature Tj decreases, so the output repeats the ON and OFF states (Please refer to Figs.12
and 24 for the temperatures at which the temperature protection circuit operates).
There are cases in which the IC is destroyed due to thermal runaway when it is left in the overloaded state. Be sure to avoid
leaving the IC in the overloaded state.
Reverse Current
In order to prevent the destruction of the IC when a reverse current flows through the IC, it is recommended that a diode
be placed between the Vcc and Vo and a pathway be created so that the current can escape (Refer to Fig.35).
2) This IC is bipolar IC that has a P-board (substrate) and P+ isolation layer
between each devise, as shown in Fig.36. A P-N junction is formed between
Reverse current
this P-layer and the N-layer of each device, and the P-N junction operates as a
parasitic diode when the electric potential relationship is GND> Terminal A,
OUT
Vcc
GND> Terminal B, while it operates as a parasitic transistor when the electric
potential relationship is Terminal B GND> Terminal A. Parasitic devices are
structurally inevitable in the IC. The operation of parasitic devices induces
mutual interference between circuits, causing malfunctions and eventually the
destruction of the IC. It is necessary to be careful not to use the IC in ways that
would cause parasitic elements to operate. For example, applying a voltage
that is lower than the GND (P-board) to the input terminal.
CTL
GND
Fig. 36:Bypass diode
Transistor (NPN)
B
Resistor
(Pin A)
(Pin B)
O
(Pin B)
E
C
B
GND
E
N
P+
P+
P
N
GND
P
P+
Parasitic element
or transistor
N
P
N
P+
N
N
N
Parasitic element
GND
P
(Pin A)
Parasitic element
GND
Parasitic element
or transistor
GND
Fig. 37: Example of the basic structure of a bipolar IC
●Part Number Selection
H P
0
F
B A
D D
W
2
33
E
Output
voltage
Current capacity
CC0 : 1A
DD0 : 2A
ROHM
model name
Shutdown switch Package
Package specification
W : With switch
None : Without
switch
T : TO220-3,5
F P : TO252-3,5
HFP : HRP5
TR : Embossed taping(HRP5)
E2 : Embossed taping(TO252-3,5)
None : Tube container
V5 :Foaming(V5 only)
(Unit:mm)
(Unit:mm)
(Unit:mm)
TO252-3
TO252-5
7/8
HRP5