External Power Supplies; Vddh And Vdd - Horizontal And Vertical Analog Voltages - Epson S1D13706 Technical Manual

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2 External Power Supplies

2.1 VDDH and VDD - Horizontal and Vertical Analog Voltages

VCC = 3.3V
1
YSCL
S1D13706
X31B-G-012-03
The S1D13706 provides all necessary data and control signals to connect to the Epson
LF37SQT and LF26SCT D-TFD panels. However, it does not provide any of the vertical
and horizontal logic voltages, contrast or brightness voltages, or the horizontal and vertical
liquid crystal driving voltages. Therefore, external supplies must be designed for any
device utilizing these D-TFD panels.
VDDH and VDD control the horizontal and vertical drivers that activate the liquid crystals
in the D-TFD display. The range of VDDH is from 4.5V to 5.5V and VDD is from 4.0V to
5.0V. These voltages should be set to 4.5V.
VDDH and VDD must be activated after all D-TFD control signals are active, and should
be deactivated after the control signals are inactive.
Figure 2-1: "VDDH and VDD Voltage Generation" shows an example implementation
which generates VDDH and VDD from 3.3V.
VCC = 3.3V
1 2 Q2
2SJ285
3
U2A
7
3
7W14F
1 2 Q1
2SK1848
Figure 2-1: VDDH and VDD Voltage Generation
The circuit in Figure 2-1: "VDDH and VDD Voltage Generation" uses the Vertical Shift
Clock control signal, YSCL, to control a pair of ultrahigh-speed P and N-channel MOSFET
transistors. These transistors are used to generate a 3.3V square wave which is passed
through C1. This blocks any DC component in the signal. The 3.3V square wave is then
added to 3.0V from diode D1 (VF = 0.3V) and passed through diode D2 (VF = 0.3V) to
produce a 6.0V DC input voltage to the linear regulator (Toko part TK11245BM). This
regulator provides the high precision output of 4.5V required for VDDH and VDD.
An alternative method would be to use a switching regulator IC to generate 4.5V from
3.3V. If 5.0V is available, a low dropout linear regulator may also be used.
VCC = 3.3V
D1
1SS388
C1
1uF 16V D2
1SS388
C2
1uF 16V
Epson Research and Development
Vancouver Design Center
VDDH / VDD = 4.5V
U1
4 3
VOUT C
5 2
GND GND
6 1
VIN CONT
TK11245BM
Connecting to the Epson D-TFD Panels
Issue Date: 01/02/23
C3
4,7uF 16V
C4
0.1uF 16V