an8041s Panasonic Corporation of North America, an8041s Datasheet - Page 9

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

Voltage Regulators
[3] Function descriptions
1. Reference voltage block
2. Triangular wave oscillation block (OSC)
3. Error amplifier 1 block and error amplifier 2 block
Application Notes (continued)
voltage to the V
and used as the operating power supply for the IC inside. It is possible to take out a load current of up to 1 mA.
value V
the C
by the value of timing capacitor C
by the following calculations:
frequency. In addition, when the oscillation frequency becomes high, overshoot and undershoot are generated due
to the operation delay of the triangular oscillation comparator. Care should be taken because the actual measure-
ment values deviate from the above calculation values.
R
ICs are synchronously operating in parallel.
type error amplifier, and the amplified signal are inputted to PWM comparator.
the connection of error amplifier 1 block or 2 block arbitrarily.
voltage is given to the noninverted input. Also, any desired gain setting and phase compensation can be obtained
by connecting the feedback resistor and capacitor from the error amplifier output terminals (pin 8 and pin 9) to the
inverted input terminals (pin 7 and pin 10).
current (110 A) and the large output sink current (8 mA).
calculation:
T
externally attached to RT terminal. For this reason, the AN8041S can not be used as a slave IC when multiple
This block is composed of the band gap circuit, and outputs the temperature-compensated 2.57 V reference
The triangular wave which swings from the upper limit value V
It is possible to use the circuit in the recommended operating range of 5 kHz to 500 kHz of the oscillation
In the case of this IC, the output source current of S.C.P. terminal and DTC terminal are set by the timing resistor
DC-DC output voltage and a detected lamp current of back-light are amplified through the PNP transistor input
Figure 2 shows the connection method of the error amplifier when the backlight inverter is controlled. Select
The common-mode input range is from 0.1 V to 0.8 V. The voltage which is resistor-dividing of the reference
The overshoot at operation start due to feedback delay can be suppressed by providing the large output source
The output voltage V
T
f
I
Since
therefore
Example) When C
V
V
V
OSC
O
terminal (pin 2) and R
IN
OUT
C1
OSCL
1.7
of approximately 0.44 V will be generated by connecting a timing capacitor C
t
V
V
V
R
1
REF
T
REF
IN 1
IN+2
+ t
1
V
V
f
f
RT
OSC
OSC
2
terminal (pin 16). The reference voltage is stabilized when the supply voltage is 3.6 V or higher,
CTH
R
R
R
1.7
238 [kHz].
3
1
5
2 C
V
R
R
T
R
OUT
2.80
CTL
4
2
5
R
R
R
V
T
100 [pF], R
T
0.37
4
2
R
and the detection voltage of the lamp current V
T
terminal (pin 3) respectively. The oscillation frequency can be arbitrarily decided
V
R
T
0.88 V,
1
C
R
(V
and resistor R
T
6
I
O
CTH
R
T
T
V
CHL
15 [k ],
[Hz]
T
)
connected externally. The oscillation frequency f
Figure 1. Triangular wave oscillation waveform
OSCH
Charging
of approximately 1.32 V to the lowest limit
t
1
T
Discharging
t
2
C1
are given from the following
T
V
V
and a resistor R
CTH
CTL
OSC
AN8041S
0.44 V typ.
1.32 V typ.
is obtained
T
to
9