AN8018 Panasonic Semiconductor, AN8018 Datasheet - Page 9

• Manufacturer Part Number: AN8018
• Description: 1.8-volt 2-channel step-up/ step-down/ or inverting DC-DC converter control IC
• Manufacturer: Panasonic Semiconductor

Voltage Regulators
[1] The loss P of this IC increases in proportion to the supply voltage. Use the IC so as not to exceed the allowable
[2] Since the output 2 of the AN8018SA is assuming the bipolar transistor driving, it is necessary to pay attention to
[3] In order to realize a low noise and high efficiency, a care should be taken in the following points in designing the
[4] There is a case in which this IC does not start charging to the S.C.P. capacitor when the output is short-circuited
1. Select an n-channel MOSFET having a low input
2. Select an n-channel MOSFET having a low gate
1. The wiring for ground line should be taken as wide as possible and grounded separately from the power system.
2. The input filter capacitor should be arranged in a place as close to V
3. The wiring between the Out terminal and switching device (transistor or MOSFET) should be as short as possible
4. In wiring the detection resistor of the output voltage, the wiring for the low impedance side should be longer.
Usage Notes
power dissipation of package P
Reference formula:
P
the following points when directly driving n-channel MOSFET.
due to the malfunction of U.V.L.O. circuit biased by V
switching transistor. The allowable range of the V
by inserting a capacitor near the V
range. However, this allowable range is design reference value and not the guaranteed value.
capacitance
maximum) output source-current type circuit assum-
ing the bipolar transistor driving. Also, its sink cur-
rent capability is around 80 mA maximum. For those
reason, it is necessary to pay attention to the increase
of loss due to the extension of the output rise time and
the output fall time.
by amplifying with inverters as shown in figure 1.
threshold value
AN8018SA is V
necessary to select a low V
ciently low on-state resistance in accordance with the
using operating supply voltage.
the double-voltage of the input to the IC's V
using the transformer as shown in figure 2.
board layout.
allow switching noise to enter into the IC inside.
to obtain a clean switching waveform.
V
V
I
Du
V
I
Du
I
The AN8018SA is of the constant-current (50 mA
If any problem arises, there is a method to solve it
The output high-level voltage of Out2 pin of the
If a larger V
OUT1
SO(OUT)
CC
O(SAT)1
O(SAT)1
BEQ2
1
2
: Out1 terminal saturation voltage (0.5 V maximum at I
: Out1 terminal output current ( {V
: Output1 duty ratio
: Base-emitter voltage of NPN transistor Q2
: Out2 terminal output source current
: Output2 duty ratio
: V
I
(set by RB, I
OUT1
GS
CC
CC
is desired, there is a method to apply
terminal current (8.0 mA maximum but at V
Du
1.0 V minimum, so that it is
1
T
SO(OUT)
MOSFET having a suffi-
(V
D
CC
.
CC
terminal and GND terminal of this IC so that the V
V
40 mA maximum at RB2
BEQ2
)
CC
I
pin by
SO(OUT)
CC
CC
ripple is as shown in the following figure. Reduce the V
CC
V
Du
BEQ1
that has ripples generated by turning on and off of the
2
+ V
Out2
Out2
Figure 2. Gate drive voltage increasing method
V
V
V
V
CC
10
10
O(SAT)1
9
CC
CC
820 )
IN
IN
Figure 1. Output boost circuit example
OUT1
CC
2.4 V)
I
CC
} / R
and GND pin as possible so as not to
V
30 mA)
P
CC
O1
SBD
D
)
2 V
CC
IN
ripple is in this allowable
SBD
V
D
SBD
AN8018SA
CC
V
V
OUT
ripple
OUT
9