Microchip Technology AC164127-7 Data Sheet
2011 Microchip Technology Inc.
DS01368A-page 9
AN1368
POWER SEQUENCING IN DISPLAY
PANELS
PANELS
Different display panels will have different power supply
requirements and timing to enable each of the power
signals of the panel. In some display panels, the
following power signals can be found:
• Digital Power Signal
• Analog Power Signal
• LCD Power Signal
• Backlight Power Signal
The digital power signal is used to power-up the digital
logic on the panel. The analog power signal is used to
power the analog portion of the panel. The LCD power
signal, also known as the gate voltage, along with the
digital data signals are primarily used to control the
pixel illumination. In some cases, the LCD power signal
is composed of two power signals: the positive LCD
power signal and the negative LCD power signal. In
some cases, only one signal is available. The backlight
illumination is controlled by the backlight power signal.
requirements and timing to enable each of the power
signals of the panel. In some display panels, the
following power signals can be found:
• Digital Power Signal
• Analog Power Signal
• LCD Power Signal
• Backlight Power Signal
The digital power signal is used to power-up the digital
logic on the panel. The analog power signal is used to
power the analog portion of the panel. The LCD power
signal, also known as the gate voltage, along with the
digital data signals are primarily used to control the
pixel illumination. In some cases, the LCD power signal
is composed of two power signals: the positive LCD
power signal and the negative LCD power signal. In
some cases, only one signal is available. The backlight
illumination is controlled by the backlight power signal.
Depending on the design of the display panel, all four
types of the power signals can be found in the panel
data sheet. In some cases, only the digital power and
backlight signals appear. This means that the panel
has integrated an internal circuitry to generate the
analog and LCD power signals. This is usually true for
small displays (2'' to 4''). For larger displays, the analog
and LCD power signals tend to be higher in voltage
requirements. In these cases, it is not practical for the
display panel to integrate such circuitry; therefore,
those two power signals, that are specified as inputs,
must be externally provided.
The different power signals of the display panel must
follow the power sequencing recommended by the
manufacturer. If the proper sequence is not followed,
the display panel’s life cycle can be reduced
significantly. The typical power sequence of a panel is
shown in
types of the power signals can be found in the panel
data sheet. In some cases, only the digital power and
backlight signals appear. This means that the panel
has integrated an internal circuitry to generate the
analog and LCD power signals. This is usually true for
small displays (2'' to 4''). For larger displays, the analog
and LCD power signals tend to be higher in voltage
requirements. In these cases, it is not practical for the
display panel to integrate such circuitry; therefore,
those two power signals, that are specified as inputs,
must be externally provided.
The different power signals of the display panel must
follow the power sequencing recommended by the
manufacturer. If the proper sequence is not followed,
the display panel’s life cycle can be reduced
significantly. The typical power sequence of a panel is
shown in
.
Timing requirements are represented by t1, t2, t3, t4, t5
and t6. In most cases, the requirements are
represented as t1 = t4, t2 = t3 and t5 = t6.
and t6. In most cases, the requirements are
represented as t1 = t4, t2 = t3 and t5 = t6.
FIGURE 9:
POWER SEQUENCE OF A PANEL
Voltage
Time
V
D
V
A
V
LCD
t1
t2
t3
t4
Time
Data
V
BK
t5
t6
V
D
= Digital Supply
V
LCD
= LCD Supply
Data = Digital Signal from Controller
V
BK
= Backlight Supply
V
A
= Analog Supply