The CH451 is a versatile peripheral chip that integrates digital tube display driver and keyboard scan control with μP monitoring.CH451 has built-in RC oscillator circuit, which can dynamically drive 8-digit digital tube or 64 LED tube, with BCD decoding, flickering, shifting, etc. It can also perform 64-key keyboard scanning; The CH451 exchanges data with a single chip microcomputer via a serial interface that can be cascaded; it also provides monitoring functions such as power-on reset and watchdog.
2.1. Display driver
- Built-in high current drive stage, segment current is not less than 25mA, word current is not less than 150mA.
- Dynamic display scan control, direct drive 8-digit digital tube or 64 LED Luminous tubes.
- The segment of the digital tube and data bit can be chosen as no decoding mode or BCD decoding mode.
- Left shift, right shift, left loop, right loop of the digital tube word data.
- Each digital tube is digitally flashed independently.
- Arbitrary segment addressing, independently controlling the on and off of each LED or each segment of each digital tube.
- 16 levels of brightness control are provided by the duty cycle setting.
- The segment current upper limit adjustment is supported, and the limited current resistance can be omitted.
- Scanning limit control, supports 1 to 8 digital tubes, and only allocates scan time for valid digital tubes.
2.2. keyboard control
- Built-in 64-key keyboard controller based on 8×8 matrix keyboard scan.
- Built-in debounce circuit with pull-down resistor for built-in button status input.
- Keyboard interrupt, active low output.
- A button release flag is provided for querying the button to be pressed and released.
- High-speed 4-wire serial interface that supports multi-chip cascading with clock speeds from 0 to 10MHz.
- The DIN and DCLK signal lines in the serial interface can be shared with other interface circuits, saving pins.
- Fully built-in clock oscillating circuit, no need for external crystal or RC oscillation.
- Built-in power-on reset and watchdog Watch-Dog and provide active-high and active-low reset outputs.
- Supports low-power sleep, saves power, can be woken up by a button or wake up by a command operation.
- Support 3V~5V voltage.
- Available in SOP28 and DIP24S lead-free packages, compatible with RoHS
- The pin and function are basically compatible with the CH452 chip of the 4-wire interface mode.