an8041s Panasonic Corporation of North America, an8041s Datasheet - Page 12

• Manufacturer Part Number: an8041s
• Description: Liquid Crystal Backlight Control Ic
• Manufacturer: Panasonic Corporation of North America

AN8041S
12
[3] Function descriptions (continued)
6. Remote circuit
7. PWM comparator block
Application Notes (continued)
16) is set under approximately 0.8 V, the internal reference voltage falls to stop the IC control function, and decrease
the circuit current to a value under 5 A, When the voltage of Off terminal is set at a value higher than approximately
2.0 V, the internal reference voltage rises, and starts the control operation.
voltage of triangular wave of the CT terminal (pin 3) is lower than any one of the output of the error amplifier 1
and 2 block (pin 8 and pin 9) and the voltage of the DTC terminal (pin 4), it sets the Out terminal (pin 13) to high-
level so that the switching device (n-channel MOSFET) turns on .
connecting the external resistor R
and 100% when V
overshoot and undershoot amount differ depending on the oscillation frequency.
Example)
oscillation value may cause the deviation of the actual measurements value from the theoretical value. So, regu-
lation on IC-mounted PCB should be required.
gradually broadens the on-period of the output pulse at the time of the power supply operation start. The soft start
operation prevents the overshoot of DC-DC comparator output.
The IC control function can be turned on or off by the external control. When the voltage of Off terminal (pin
The PWM comparator controls the on-period of the output pulse according to the input voltage. While the
The dead-time is set by regulating the DTC terminal voltage V
The DTC terminal is of a constant current output using the resistor R
At the oscillation frequency f
However, pay attention to the peak value V
The output duty ratio Du and the DTC terminal voltage V
In addition, the operation delay of the PWM comparator, the deviation of the peak and trough triangular
By adding the external resistor R
CT waveform
DTC waveform
Out waveform
Du
V
V
t
ON
DTC
CTH
t
ON
When f
V
Therefore I
t
CTH
DTC
OFF
V
V
CTL
CTL
OSC
1.32 [V], V
1.32 V typical.
100 [%]
t
Off
OFF
100 [%]
V
Du
DTC
200 [kHz] (R
DTC
OSC
DTC
t
On
ON
55.1 [%]
12.3 [ A]
CTL
of 200 kHz, the output duty ratio becomes 0% when V
0.925 [V]
between the DTC terminal and GND terminal.
DTC
Figure 5. Setting the dead-time
Off
0.44 [V], V
and capacitor C
T
CTH
15 k , C
I
V
DTC
and the trough value V
DTC
DTC
T
V
I
V
R
V
V
V
DTC
RT
T
RT
DTC
CTH
DTC
CTL
0.37 [V]
150 pF), R
DTC
, the soft start function can be installed, which
R
R
DTC
R
are given in the following equation:
1
2
DTC
DTC
T
[A]
as shown in figure 5.
DTC
CTL
V
1
2
T
REF
of the triangular wave because their
I
, so that the V
75 [k ]
R
DTC
[A]
DTC
Voltage Regulators
CT
FB
DTC
DTC
C
DTC
is regulated by
0.44 V typical,
PWM