AN8018 Panasonic Semiconductor, AN8018 Datasheet - Page 14

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

AN8018SA
14
[4] Function descriptions (continued)
10. Output 2 block
9. Output 1 block
4. Error amplifier 2 block (continued)
5. Timer latch short-circuit protection circuit
6. Low input voltage malfunction prevention circuit (U.V.L.O.)
7. PWM comparator block
8. Unlatch block
Application Notes (continued)
and the phase compensation arbitrarily by con-
necting a resistor and a capacitor from the FB2
terminal (pin 13) to GND in series.
ing connection as shown in figure 3.
destruction or deterioration if overload or short-circuit condition of power supply output lasts for a certain time.
voltage of DC-DC converter drops and the FB1 terminal (pin 5) becomes 0.9 V or more, or the FB2 terminal
(pin 13) becomes 0.22 V or less, the low-level output is given and the timer circuit is actuated to start the charge
of the external protection-enable capacitor.
this capacitor reaches 1.19 V, it sets the latch circuit, and cuts off the output drive transistor, and sets the dead-time
to 100%.
voltage is low in the transient state of power on/off.
according to the supply voltage level. Until the supply voltage reaches 1.67 V during its rise time, it cuts off the
output drive transistor, and sets the dead-time to 100%. At the same time, it holds the S.C.P. terminal (pin 2) and
DT1 terminal (pin 6) to low-level, and the OSC terminal (pin 1) and DT2 terminal (pin 12) to high-level.
and PWM2 block are set in an opposite logic relation of each other and on-period of each output is staggered.
(pin 1) is lower than any lower one of the FB1 (pin 5) terminal voltage and the DT1 (pin 6) terminal voltage.
(pin 1) is higher than any higher one of the FB2 (pin 13) terminal voltage and the DT2 (pin 12) terminal voltage.
tor in parallel with the resistor-dividing for the maximum duty ratio setting.
less. The unlatch circuit 2 block fixes the FB2 terminal (pin 13) at high-level at the DT2 terminal (pin 12) is 0.9
V or more. Consequently, by controlling the DT1 and the DT2 terminal voltages, it is possible to operate only one
channel or to start and stop each channel in any required sequence.
of output terminal is 15 V.
it is possible to arbitrarily set a constant-current source-output having a small fluctuation with the supply voltage.
Also, it is possible to perform the gain setting
The output voltage V
This circuit protects the external main switching devices, flywheel diodes, and choke coils, etc. from
The timer latch short-circuit protection circuit detects the output level of the error amplifier. When the output
If the output of the error amplifier does not return to a normal voltage range by the time when the voltage of
This circuit protects the system from destruction or deterioration due to control malfunction when the supply
The low input voltage malfunction prevention circuit detects the internal reference voltage which changes
The PWM comparator controls the on-period of the output pulse according to the input voltage. The PWM1
The PWM1 block turns on the output transistor during the period when the triangular wave of OSC terminal
The PWM2 block turns on the output transistor during the period when the triangular wave of OSC terminal
The maximum duty ratio is variable from the outside.
Also, the soft start which gradually extends on-period of the output pulse is activated by connecting a capaci-
The unlatch circuit 1 block fixes the FB1 terminal (pin 5) at low level at the DT1 terminal (pin 6) is 0.20 V or
This output circuit is open-collector type. The available output current is up to 50 mA. The breakdown voltage
This block uses a totem pole type output circuit. By connecting the current setting resistor to the RB2 terminal,
The available constant-current source-output is up to 50 mA.
OUT2
can be set by mak-
R1
R2
Figure 3. Connection method of error amplifier 2 block
V
OUT2
IN 2
FB2
V
OUT2
13
14
(step-up output)
Error amplifier 2
block
1.19
1.19 V
Voltage Regulators
R
1
R
2
R
2
To PWM
comparator input