Holtek HT45FH3T Guide

Using the HT45FH3T in the Active 3D Glasses
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Using the HT45FH3T for Active 3D Glasses
D/N: AN0315E
Introduction
With the continuous development of people’s living standards, the requirements for
audio-visual entertainment is increasing, thus more and more 3D videos, movies and
games are being produced and along with this is the rising demand for 3D glasses. A new
3D technology, a combination of active shutter 3D technology and active shutter 3D glasses,
is widely used in TV and projector applications and provides good imaging effects.
The Holtek HT45FH3T is especially designed for active 3D glasses development and this
application sets out to show how it is used in such applications.
3D Glasses Functions
The main function of 3D glasses is to receive and decode the IR signals from the TV for
3D glasses control. Due to the high voltage driving requirement, a boost circuit is needed
to increase the battery voltage to 10V~12V for 3D glasses driving. A pair of 3D glasses
contains two lenses each for the left eye and right eye. As each lens needs two high
driving voltages, thus four high driving voltages are needed. So each 3D glasses circuit
contains four level shift circuits, which are used to increase the 3V MCU I/O output
voltage to 10V~12V for the 3D glasses on/off control. In addition, each pair of 3D glasses
needs an IR receiver circuit to receive external IR signals.
3D glasses normally use a battery power supply, which can be divided into two types. The
first type is a chargeable lithium battery and the second type is a non-chargeable button
battery. An additional lithium battery charging circuit is required when using the lithium
battery.

Using the HT45FH3T in the Active 3D Glasses
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3D Glasses Block Diagram
5V
USB I/P
Charger IC
+
Booster
LCD Panel
x 2
IR Receiver
10~12V
HT45FH3T
ANx VCC1
TP0_1
PWM
AX
BX
CX
DX
V12
HT45FH3T 3D Glasses Block Diagram
Flash ROM
2K x 16
RAM
128 x 8
PTM
ADC
HIRC
4MHz
LDO PTM
I/O Level
Shift
CTM x 2
HT45FH3T Active 3D Glasses Main Features
HT45FH3T Basic Features
• Operating Voltage : 2.2V ~ 5.5V @4MHz
• System Clock : HIRC 4MHz
• Multi-mode operation : NORMAL, SLOW, IDLE and SLEEP
• Flash Program Memory : 2K×16
• RAM Data Memory : 128 bytes
• 4-channel 12-bit ADC
• 10-bit CTM×2
• 10-bit PTM×1 -- provides PWM outputs
• 16-bit PTM×1 -- decodes IR input signals
• Over Voltage Protection function
• Level shift×4
• 3V LDO×1
Note: 1. The HT45FH3T system clock can be up to 4MHz.
2. The HT45FH3T-1 system clock can be up to 8MHz.

Using the HT45FH3T in the Active 3D Glasses
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HT45FH3T 3D Glasses Main Features
• Uses lithium battery : 100mAh
• Charging
−Charging stand : USB Mini-B type ; input voltage : 5V
−Use 100mA constant current for charging
• Use 3-Line controlled LCD lenses
• Provides a battery charging indicator LED (Y) and a low voltage indicator LED (R)
• Provides a button for glasses on/off control
• Operating current: about 680µA
• Three-stage power saving mode
−First stage power saving mode average current: 280µA
−Second stage power saving mode average current: 180µA
−Third stage power saving mode: self-power off
• Use nVIDIA 3D VISION Protocol for IR
Hardware Block Diagram
Hardware Block Diagram

Using the HT45FH3T in the Active 3D Glasses
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Hardware Block Diagram Functional Description
• Main control IC : HT45FH3T-1 -- system clock : 8MHz
• Main USB charging port
This port can be connected to a computer USB interface or an external power adapter
for lithium battery charging.
• Charging IC
Use 100mA constant current for lithium battery charging, during which the yellow LED
lights up.
• Inductor
Used to boost the battery voltage to the LCD lenses switch voltage.
• N-MOS
Used for inductor booster control.
• Lithium battery
A lithium battery with a capacity of 100mAh.
• Battery control circuit
Used for the third stage power saving mode: self-power off.
• Button
For user manual power on/off.
• LED indicator
Used for low voltage indicating.
• Resistance divider
Used for booster feedback control.
• IR receiver
Receives the IR signals and converts them into digital signals.
• LCD lenses
Works along with the IR signal for left and right lens on/off control.
Hardware Circuit and Description
Main Board Circuit

Using the HT45FH3T in the Active 3D Glasses
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IR Receiver Circuit
The schematic is shown below:
-
+
OPA
-
+
OPA
-
+
CMP TO MCU
15pF
200k
15pF
4.7nF
2k
2k
7.15k
VDD
3M
330pF
Amplify and filter the
tiny current generated
by the IR Photodiode
Filter the amplified signal
with a negative half cycle
and add a base level
Two signals input to the
CMP - a digital signal
is
output to the MCU

Using the HT45FH3T in the Active 3D Glasses
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Circuit Description
Battery Control Circuit
The MCU can use PA1 to control the battery. When powered off, the user can press the
button to turn on the power. When powered on, the MCU must keep PA1 high to ensure
Q3 remains on. After the power is turned on, when the user press the button, the MCU
will generate an external interrupt via INT1(PA6) and turn off the power via PA1.
Charging IC Circuit
Use an IN4054 for lithium battery charging. Setup R13 to be 10K so that a 100mA
constant current can be used.
OVP Function Settings
Connect the OVP pin to the voltage dividing circuit which is output from the boost circuit.
Setup the internal D/A reference voltage to come from VDD. Write a proper value to
OVOREF[5:0] bits. When the boost circuit outputs a low voltage, the OUTH pin will
automatically output a PWM signal to increase the boost voltage.

Using the HT45FH3T in the Active 3D Glasses
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Boost Circuit
Use the BOOST_ON (MCU Pin 8, OUTH) PWM signal to control the Q1 on/off state. The
energy stored in L1 is transferred and stored in C1 and C2, which together can generate
a 10V boost voltage. A divided voltage generated using R6 and R7 is fed back to the
MCU OVP function to maintain the boost out voltage at the correct level.
LCD Lens Control
The 3D glasses LCD lenses have 3-Line and 4-Line types. In this application, 3-Line
controlled lenses are used. For the level shift circuits, whose power is supplied by the
boost circuit, increase the LCD control voltage to 10V for the lens on/off control.
Battery Voltage Detect Circuit
Use the ADC to check the MCU internal band gap voltage, and select the ADC reference
voltage to come from VDD. If the battery voltage falls below 3V, the VDD voltage will also
fall below 3V. The band gap value detected at this moment will be higher than before, this
indicating a VDD low voltage condition.
LED used as a Low Voltage Indicator
Main control MCU
The main control MCU is the HT45FH3T-1, which has both integrated PWM and OVP
circuits.
IR Receiver Circuit
In this circuit, tiny signals received by the IR photodiode will be filtered, amplified and
integrated to generate the digital signals that can be processed by the MCU.

Using the HT45FH3T in the Active 3D Glasses
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IR Signals and LCD Lens Control Description
Different 3D videos may generate different control signals, some IR signals have carrier
signals while some signals are carrier-free. This application uses an nVIDIA protocol
working together with IR signals with no carrier to implement decode operation and
control the LCD lenses.
Note that LCD lenses must be properly controlled to avoid the liquid crystals remaining at
the same voltage level for too long to avoid damage.
Basically, during a COM cycle, the positive level time and the negative level time are
same for the same lens. This demo board uses 3-Line control mode, the liquid crystal
level control and left/right lens control is shown below.

Using the HT45FH3T in the Active 3D Glasses
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PCB Layout
Main Board
Front
Back

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Receiver Board

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HT45FH3T 3D Glasses Demo Board – BOM Table
Main Board
Type Symbol Value Package Number Note
MCU U1 HT45FH3T-1 SSOP16 1
Charging IC U2 IN4054 SOT23-5 1
LDO U3 HT7830 SOT89 1
Capacitor C9,C8 0.1uF 0603 2
C6 10uF 0805 1
C1,C2,C3,C4,C5 1uF 0603 5
Resistor R12 1K 0603 1
R14 1M 0603 1
R6 3.3M 0603 1
R13 10K 0603 1
R1 100 0603 1
R4,R2 100K 0603 2
R3 NC 0603 1
R7 360K 0603 1
R9,R10 470 0603 2
R11 470K 0603 1
LED D4,D5 Red, Yellow 0603 2
Inductor L1 100uH SMD 1
N-MOSFET Q1,Q2 AO3400 SOT23 2
P-MOSFE Q3 AO3401 SOT23 1
Diode D1,D2,D3 BAT54 SOD232 3
Button SW1 SMD 1
Connector J5 FPC-0.5mm-10pin 1
USB
connector J6 MINI USB 1
TVS D3 SOD323 1
IR Receiver Board
Type Symbol Value Package Number Note
OPA U1 OPA2348 SOT23-8 1
Comparator U2 LM7239 SOT23-5 1
C4 4.7nF 0402 1
C5,C6 0.1uF 0402 2
Capacitor
C3 330pF 0402 1
R4,R2 2K 0402 2
R6 3M 0402 1
R5 7.15K 0402 1
Resistor
R1 200K 0402 1
Diode D2 BAT54 SOD523 1
Photodiode D1 BPW 34 1
summary 50

Using the HT45FH3T in the Active 3D Glasses
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Software Flowchart
Main Architecture Flowchart

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LCD Lenses Flowchart

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Demo Board Pictures
Conclusions
As the demand for 3D glasses products is increasing, the HT45FH3T can be used to
reduce additional circuit requirements and PCB area, thus reducing production costs.