AN8018 Panasonic Semiconductor, AN8018 Datasheet - Page 13

• 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
[4] Function descriptions
1. Reference voltage block
2. Triangular wave oscillation block
3. Error amplifier 1 block
4. Error amplifier 2 block
Application Notes (continued)
R1
R2
voltage. The reference voltage is stabilized when the supply voltage is 1.8 V or more. The reference voltage is also
used as the reference voltage for the error amplifier 2 block.
a peak of approximately 0.7 V and a trough of approxi-
mately 0.2 V can be generated by connecting the timing
capacitor C
The oscillation frequency can be freely set by the value of
C
tion frequency is from 20 kHz to the maximum 1 MHz.
The triangular wave is connected with the inverting input
of PWM comparator for channel 1 side and the
noninverting input of PWM comparator for channel 2 side
within the IC inside. Rough calculation of oscillation fre-
quency can be calculated by the following equation.
And refer to the experimentally determined graph of the frequency characteristics provided in the main
characteristics section.
amplified signal is input to the PWM comparator.
and a capacitor from the FB1 terminal (pin 5) to GND in series.
amplified signal is input to the PWM comparator. The internal reference voltage 1.19 V is given to the noninverting
input.
V
T
REF
and R
This block is composed of the band gap circuit, and outputs the temperature compensated 1.19 V reference
The sawtooth-waveform-like triangular wave having
f
However, boosting charge time, over-shoot and under shoot quantities are not considered in the above equation.
The output voltage of DC-DC converter is detected by the PNP-transistor-input type error-amplifier and the
Also, it is possible to perform the gain setting and the phase compensation arbitrarily by connecting a resistor
The output voltage V
The output voltage of DC-DC converter is detected by the NPN-transistor-input type error-amplifier and the
OSC
R3
R4
V
OUT1
T
V
to be connected externally. The usable oscilla-
Case of step-up output
T
OUT1
and resistor R
C
T
IN 1 3
IN 1 4
FB2
R
R1 R2
T
R2
1
5
ln V
OUT1
Error amplifier 1
block
T
V
Figure 2. Connection method of error amplifier 1 block
to the OSC terminal (pin 1).
·
OSCL
OSCH
R3 R4
can be set by making connection as shown in figure 2.
R4
To PWM
comparator input
0.8
·
V
REF
C
T
1
R
T
[Hz]
R1
R2
V
V
REF
OUT1
Boosting
charge
Figure 1. Triangular wave oscillation waveform
R3
R4
V
V
t
Case of inverting output
1
OUT1
IN 1
IN 1 3
IN 1 4
FB2
V
Discharging
REF
(V
t
T
2
REF
5
·
R3 R4
Error amplifier 1
block
R4
V
IN 1
)
To PWM
comparator input
·
R1 R2
AN8018SA
V
V
OSCH
OSCL
R1
0.2 V
0.7 V
V
REF
13