TM1668 SMD IC Digital display Keypad driver 7 SEGMENT SOP24 TM1668

Product Overview:The TM1668 is a specialized LED driver and keyboard scanning control circuit designed for appliances such as VCRs, VCDs, DVDs, and home theater systems. It integrates an MCU digital interface, data latch, high-voltage LED drive, and keyboard scanning circuitry into a single package.

Core Specifications

• Manufacturer: Titan Micro Electronics

• Technology: Power CMOS

• Package Types: SOP24, SSOP24, SKDIP24, SDIP24

• Display Modes: Supports configurations from 10 segments × 7 digits to 13 segments × 4 digits.

• Keyboard Scanning: 10 × 2 bit matrix.

• Control Interface: 3-wire serial interface (CLK, STB, DIO).

• Brightness Control: 8-level duty cycle adjustment.

• Oscillator: Built-in RC oscillator (450KHz ± 5%).

• Operating Voltage: 5V ± 10%.

Key Functional Details

• Interface Operations: Data is input/output via the serial interface on the rising edge of the clock (CLK). The STB pin initiates the interface; when STB is low, the first byte received is treated as an instruction.

• Keyboard Scanning: The chip automatically performs keyboard scanning every two display cycles. To read the key values, the host must issue a read command and read back up to 5 bytes (BYTE1–BYTE5).

• Data Readout: When reading data (e.g., key values), there is a required wait time ($T_{wait}$) of at least 1µs between the command and data readout. A 10kΩ pull-up resistor is recommended for the DIO pin when performing read operations.

• Display Addressing: The display register consists of 14 bytes (00H–0DH) corresponding to the SEG and GRID pins.

Important Design Considerations

• Component Placement: Filter capacitors between $V_{DD}$ and GND should be placed as close to the chip as possible to enhance filtering effects.

• Communication Stability: Adding 100pF capacitors to the DIO, CLK, and STB communication lines is recommended to reduce signal interference.

• Ghosting Prevention: To prevent display interference when multiple keys are pressed, you can use diodes in series with the keys or place 510Ω resistors in series on the SEG lines.

• Operating Temperature: The device is designed to operate between -20°C and +70°C.