Product Main Title:
LS028T22-S-V1: 2.8-Inch TN TFT LCD Module, 240x320 Resolution, 262K Colors, 4-Line SPI Interface
Product Subtitle / Keywords:
2.8 Inch Display, QVGA 240x320 Resolution, Transmissive a-Si TN TFT, 4-line SPI Interface, COG+FPC+B/L, 262K Colors, Standard Viewing Direction, 4-Chip White LED Parallel Backlight
Comprehensive Technical Specification & Application Guide
1. Executive Summary & Product Positioning
The LS028T22-S-V1, developed by LESSON (Wan'an) Zhixian Technology Co., Ltd., is a 2.8-inch transmissive amorphous Silicon TFT-LCD module. This product specification book is the definitive technical document, detailing its structural composition (COG+FPC+B/L), mechanical dimensions, absolute maximum ratings, detailed electrical characteristics, 4-line SPI (Serial Peripheral Interface) pinout and timing, and comprehensive electro-optical performance. It delivers a QVGA resolution of 240(RGB)×320 with 262K-color display capability. The document provides the core parameters necessary for system integration into embedded display applications. The unequivocal recommendation is to follow the mechanical tolerances, temperature ranges, and backlight driving conditions given in the document during enclosure design and system integration to ensure compatibility and reliability.
2. Detailed Product Overview & Architecture
- Core Technology: Transmissive-type a-Si TFT-LCD (amorphous silicon thin film transistor liquid crystal display).
- Display Mode: TN (Twisted Nematic).
- Display Characteristics: Capable of displaying up to 262 thousand colors.
- Module Construction: COG (Chip-On-Glass) + FPC (Flexible Printed Circuit) + B/L (Backlight Unit). Composed of a TFT-LCD panel, a driver circuit, and a backlight unit.
- Interface: 4-line SPI (Serial Peripheral Interface).
- Viewing Direction: 12 o'clock (as per drawing notes).
- Backlight: 4 Chip-White LEDs in parallel.
- Approval Status: Approved Product Specification only.
3. Exhaustive Technical Specifications
3.1 Mechanical & Physical Specifications
| Item | Specification | Unit |
|---|---|---|
| Module size (H×V×D) | 50.0 × 69.2 × 2.32 | mm |
| Active area (H×V) | 43.2 × 57.6 | mm |
| Number of dots / Resolution | 240(RGB) × 320 | pixel |
| Panel Size (Diagonal) | 2.8 | inch |
Critical Mechanical Design Notes (from document):
- Display Type: Main LCD: TN.
- Operating Temperature: -20°C ~ +70°C.
- Storage Temperature: -30°C ~ +80°C.
- ROHS Compliance: Yes.
- Backlight: 4 Chip-White LED Parallel.
- Bezel Opening: It is recommended that the housing's visible area be at least 0.3mm smaller per side than the module's active area (AA).
- Foam Gasket Cutout: Should be at least 0.6mm larger per side than the module's viewing area (VA).
- Metal Contact: The TP (Touch Panel, if applicable) edges must not contact metal conductors.
- Segment to Glass Edge Tolerance: ±0.2 mm.
- Total Module Thickness: 2.32 ±0.2 mm (excluding adhesive thickness).
3.2 Electrical & Interface Specifications
3.2.1 Absolute Maximum Ratings
| Item | Symbol | Min | Max | Unit | Remark |
|---|---|---|---|---|---|
| Supply voltage | VCC | -0.3 | 4.6 | V | Note1, Note2 |
| Operating temperature | TOPR | -20 | 70 | °C | Note1, Note2 |
| Storage temperature | TSTR | -30 | 80 | °C | Note1, Note2 |
Notes (interpreted):
- Note1/Note2: Stress beyond these ratings may cause permanent damage; functional operation is not implied under these conditions.
3.2.2 Electrical Characteristics (DC)
| Item | Symbol | Min | Typ | Max | Unit |
|---|---|---|---|---|---|
| Supply voltage (Main) | VCC | 2.4 | 2.75 | 3.3 | V |
| Input Voltage (Low level) | VIL | 0 | -- | 0.3 * IOVCC | V |
| Input Voltage (High level) | VIH | 0.7 * IOVCC | -- | IOVCC | V |
(Note: The parameter IOVCC is referenced in the VIL/VIH formulas but its value range is not explicitly defined in the provided DC table. It is typically 1.8V or 3.3V for such interfaces.)
3.2.3 Pin Description (10-pin FPC)
| PIN NO. | Symbol | I/O | Description |
|---|---|---|---|
| 1 | GND | P | Ground |
| 2 | RS | I | Command and Data select pin (also called D/CX). |
| 3 | CS | I | Chip select pin. |
| 4 | SCL | I | Serial clock pin. |
| 5 | SDA | I/O | Serial data input/output pin. |
| 6 | RESET | I | Reset pin. |
| 7 | VCC | P | Main power supply. |
| 8 | GND | P | Ground. |
| 9 | LEDA | P | Power for LED backlight anode. |
| 10 | LEDK | P | Power for LED backlight cathode. |
3.2.4 SPI Interface Timing Characteristics (4-line serial)
Conditions: VDDI=1.65 to 3.3V, VDD=2.4 to 3.3V, AGND=DGND=0V, Ta=25°C. Input signal rise/fall time (Tr, Tf) ≤ 15 ns.
A. Write Operation Timing:
| Signal | Symbol | Parameter | MIN | MAX | Unit | Description |
|---|---|---|---|---|---|---|
| CSX | T_CSS | Chip select setup time (write) | TBD | - | ns | |
| CSX | T_CSH | Chip select hold time (write) | TBD | - | ns | |
| CSX | T_CHW | Chip select "H" pulse width | TBD | - | ns | |
| SCL | T_SCYCW | Serial clock cycle (Write) | TBD | - | ns | For write command & data RAM |
| SCL | T_SHW | SCL "H" pulse width (Write) | TBD | - | ns | For write command & data RAM |
| SCL | T_SLW | SCL "L" pulse width (Write) | TBD | - | ns | For write command & data RAM |
B. Read Operation Timing:
| Signal | Symbol | Parameter | MIN | MAX | Unit | Description |
|---|---|---|---|---|---|---|
| CSX | T_CSS | Chip select setup time (read) | TBD | - | ns | |
| CSX | T_SCC | Chip select hold time (read) | TBD | - | ns | |
| SCL | T_SCYCR | Serial clock cycle (Read) | TBD | - | ns | For read command & data RAM |
| SCL | T_SHR | SCL "H" pulse width (Read) | TBD | - | ns | For read command & data RAM |
| SCL | T_SLR | SCL "L" pulse width (Read) | TBD | - | ns | For read command & data RAM |
| D/CX | T_DCS | D/CX setup time | TBD | - | ns | |
| D/CX | T_DCH | D/CX hold time | TBD | - | ns | |
| SDA (DIN) | T_SDS | Data setup time | TBD | - | ns | |
| SDA (DIN) | T_SDH | Data hold time | TBD | - | ns | |
| DOUT | T_ACC | Access time | TBD | TBD | ns | For CL=30pF(max)/8pF(min) |
(Note: All timing parameters are listed as "TBD" (To Be Determined) in the provided revision. The final production specification or a later revision would define concrete values. The presence of separate read/write timing indicates a bidirectional SDA line.)
3.2.5 Reset Timing
| Related Pins | Symbol | Parameter | MIN | MAX | Unit |
|---|---|---|---|---|---|
| RESX | T_RW | Reset pulse duration | 10 | - | µs |
| RESX | T_RT | Reset cancel time | - | 5 (Note 1, 5) | ms |
| RESX | T_RT | Reset cancel time | - | 120 (Note 1, 6, 7) | ms |
Key Reset Notes:
- A reset pulse shorter than 5µs is rejected; longer than 9µs causes a reset.
- The reset cancel time (
T_RT) includes time for loading initial settings from non-volatile memory. AT_RTwithin 5ms after RESX rising edge triggers this load. - During reset, the display blanks and returns to the hardware default condition.
3.2.6 Backlight Unit
- Configuration: 4 Chip-White LEDs in parallel.
- Drive Condition (Typical): Forward Current (I_F) = 80 mA; Forward Voltage (V_f) = 3 V.
3.3 Optical & Electro-Optical Characteristics
| Item | Symbol | Condition | Min. | Typ. | Max. | Unit | Remark |
|---|---|---|---|---|---|---|---|
| Response Time | Tr + Tf | θx = θy = 0 | -- | 16 | -- | ms | Note 1 |
| Contrast Ratio | CR | θx = θy = 0 | -- | 500 | -- | -- | Note 2 |
| Transmittance | T% | θx = θy = 0 | -- | 6.4 | -- | % | |
| Color Chromaticity (White) | W x | θx = θy = 0 | -- | 0.301 | -- | -- | CIE1931 |
| Color Chromaticity (White) | W y | θx = θy = 0 | -- | 0.337 | -- | -- | CIE1931 |
| Viewing Angle (Top, CR>10) | θT | -- | -- | 50 | -- | Deg. | Note 3 |
| Viewing Angle (Bottom, CR>10) | θB | -- | -- | 20 | -- | Deg. | Note 3 |
| Viewing Angle (Left, CR>10) | θL | -- | -- | 45 | -- | Deg. | Note 3 |
| Viewing Angle (Right, CR>10) | θR | -- | -- | 45 | -- | Deg. | Note 3 |
Notes (from document):
- Response time is the sum of rise (Tr) and fall (Tf) time.
- Contrast Ratio (CR) = (Luminance of "white" state) / (Luminance of "black" state).
- Viewing angles are asymmetric (typical for TN panels), with better horizontal (Left/Right: 45°) than vertical (Top: 50°, Bottom: 20°) viewing.
4. Application Guidelines & Critical Notes
- Intended Use: Embedded systems, industrial controls, consumer devices, instrumentation—applications requiring a standard 2.8-inch color display with a simple SPI interface.
- Critical Design Considerations:
- Mechanical Integration: Strictly follow the housing design rules: Bezel opening should be 0.3mm smaller per side than AA; foam cutout should be 0.6mm larger per side than VA. This prevents pressure-induced defects and ensures proper visibility.
- SPI Interface: The host MCU's SPI peripheral must be configured to meet the timing parameters (once defined). Note the bidirectional SDA (pin 5) for read operations.
- Reset Circuit: Ensure the RESET pin receives a low pulse of at least 10µs during power-up. Follow the reset timing notes regarding cancellation and blanking periods.
- Backlight Drive: The backlight uses 4 LEDs in parallel, each requiring ~3V at 80mA total. Design a constant-current driver capable of sourcing 80mA at ~3V. Do not connect LEDA directly to VCC without current limiting.
- Power Supply: Provide a stable VCC between 2.4V and 3.3V (2.75V typical). Decouple the power pins closely.
- Temperature Limits: Operate within -20°C to +70°C and store within -30°C to +80°C.
- Viewing Angle Consideration: This is a TN panel with limited and asymmetric viewing angles (especially bottom). Ensure the intended user viewing position aligns with the 12 o'clock direction for best performance.
- Handling & Compliance: The module is ROHS compliant. Handle with care to avoid damaging the FPC or glass. Observe ESD precautions.
5. Conclusion & Design-In Support
The LS028T22-S-V1 specification details a classic 2.8-inch TN SPI display module. Its key defined parameters are the precise mechanical dimensions, absolute maximum ratings, simple 10-pin SPI interface, and standard electro-optical characteristics. The main design focus should be on precise mechanical housing design (following the clear guidelines), providing a stable 2.75V power supply, and implementing a suitable 80mA constant-current LED driver for the parallel backlight. While the AC timing parameters are TBD in the provided revision, the core electrical and optical specs provide a solid foundation for integration. This module is a reliable and straightforward choice for cost-sensitive embedded applications where wide viewing angles are not a primary requirement.
