AN8049 Panasonic Semiconductor, AN8049 Datasheet - Page 16

• Manufacturer Part Number: AN8049
• Description: 1.8-volt 3-channel step-up/ step-down/ and polarity inverting DC-DC converter control IC
• Manufacturer: Panasonic Semiconductor

AN8049FHN
16
[4] Function descriptions (continued)
R1
R2
4. Error amplifier 2
5. Error amplifier 3
V
6. Timer latch short-circuit protection circuit
Application Notes (continued)
REF
V
amplifier that detects and amplifies the DC-DC
converter output voltage, and inputs that signal to
a PWM comparator. The 1.26 V internal reference
voltage is applied to the noninverting input. Arbi-
trary gain and phase compensation can be set up
by inserting a resistor and capacitor in series be-
tween the FB2 pin (pin 20) and the IN 2 pin (pin
19). The output voltage V
circuit shown in the figure.
voltage and inputs that signal to a PWM comparator. Arbitrary gain and phase compensation can be set up by
inserting a resistor and capacitor in series between the FB3 pin (pin 18) and the IN 3 pin (pin 17). The output voltage
V
against degradation or destruction if an excessive load or a short circuit of the power supply output continues for
longer than a certain fixed period.
output voltage drops and an FB pin (pins 18, 20, or 22) voltage exceeds 0.9 V, the S.C.P. comparator outputs a low
level and the timer circuit starts. This starts charging the external protection circuit delay time capacitor.
the latch circuit latches, the output drive transistors are turned off, and the dead-time is set to 100%.
OUT3
R3
R4
V
OUT3
OUT3
This circuit is an npn-transistor input error
This circuit is a pnp-transistor input error amplifier that detects and amplifies the DC-DC converter output
This circuit protects the external main switching elements, flywheel diodes, choke coils, and other components
The timer latch short-circuit protection circuit detects the output of the error amplifiers. If the DC-DC converter
If the error amplifier output does not return to the normal voltage range before that capacitor reaches 1.26 V,
can be set using the circuit shown in the figure.
R
1
R
+R
2
Step-down output
IN 3
FB3
2
IN 3
R
18
16
17
3
Error
amplifier 3
R
R
4
4
OUT2
V
Figure 4. Connection method of error amplifier 3
REF
can be set using the
To the PWM
comparator input
Figure 3. Connection method of error amplifier 2 (Step-up output)
R1
R2
V
OUT2
R1
R2
V
V
OUT3
REF
V
OUT2
FB2
IN 2
V
OUT3
FB3
Inverting output
20
19
IN 3
IN 3
1.26
Error
amplifier 2
18
16
17
V
Error
amplifier 3
REF
1.26 V
R
Voltage Regulators
1
R
2
R
R
R
2
1
2
To the PWN
comparator input
To the PWM
comparator input