AN79L07 Datasheet, PDF (10/12 Pages) Panasonic Semiconductor – 3-pin negative output voltage regulator (100 mA type)

AN79Lxx/AN79LxxM Series
I Usage Notes
1. Cautions for a basic circuit
C_I: When a wiring from a smoothing circuit to a three-pin regulator
Di
is long, it is likely to oscillate at output. A capacitor of 0.1µF to
0.47µF should be connected near an input pin.
C_O: Deadly needed to prevent from oscillation (0.33µF to 1.0µF). It
VI
VO
is recommended to use a capacitor of a small internal imped-
1
3
ance (ex. tantalum capacitor) when using it under a low tem-
CI
2
perature.
CO
When any sudden change of load current is likely to occur, con-
nect an electrolytic capacitor of 10µF to 100µF to improve a
transitional response of output voltage.
Figure 1
D_i: Normally unnecessary. But add it in the case that there is a
residual voltage at the output capacitor Co even after switching
off the supply power because a current is likely to flow into an
output pin of the IC and damage the IC.
2. Other caution items
1) Short-circuit between the input pin and GND pin
If the input pin is short-circuitted to GND or is cut
off when a large capacitance capacitor has been con-
nected to the IC's load, a voltage of a capacitor con-
nected to an output pin is applied between input/out-
put of the IC and this likely results in damage of the
IC. It is necessary, therefore, to connect a diode, as
shown in figure 2, to counter the reverse bias between
input/output pins.
2) Floating of GND pin
1
In
2
GND
3
Out
−
+
Output
CO
Figure 2
If a GND pin is made floating in an operating mode, an unstabilized input voltage is outputted. In this case, a
thermal protection circuit inside the IC does not normally operate. In this state, if the load is short-circuited or
overloaded, it is likely to damage the IC.
I Application Circuit Example
−VI Input ₃
1 ^Output
AN79Lxx
2
−
Common
+ ^2µF
IBias
VO' R2
−
+
R1
−VO
1µF
|VO | = VO'
1+
R1
R2
+ IQR1
Note) VO varies due to sample to sample variation of IBias .
Never fail to adjust individually with R1 .
10
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