Datasheet HT16D35A/HT16D35B (Holtek) - 8

HT16D35A/HT16D35B Functional Description Address Pointer Power-on Reset
The addressing mechanism for the display RAM is implemented using the address pointer. This allows After power is applied the device will be initialised by the loading of an individual display data byte, or a an internal power-on reset circuit. The internal circuit series of display data bytes, into any location of the status after initialisation is as follows: display RAM. The sequence commences with the initialisation of the address pointer using the Address • All registers are set to their default value but the pointer command. contents of the DDRAM are not affected • System Oscillator will be off
Over Temperature Protection
• All COM outputs will be high impedance The devices include thermal protection circuitry. • All ROW outputs will be high impedance When the junction temperatures exceed a certain • The LED display will be in an off state temperature the temperature protection circuit is Data transfers on the I2C-bus or SPI 3-wire serial bus activated. The TSD flag bit will be set to “1”, the should be avoided for 1ms following a power-on to display will be off and the direct pins will be turned allow the reset initialisation operation to complete. off. When the chip junction temperature exceeds 150°C,
LED Driver
the entire IC display is turned off and the direct pins The HT16D35A/HT16D35B is a 224 (28×8) pattern will be turned off along with the TSD flag bit being LED driver which can be configured to have 1 set to “1”. The device will resume operation and turn or 8 commons using the Number of COM output on the direct pins and the TSD flag bit will be cleared Command configuration. This feature makes the to “0” when the chip junction temperatures falls HT16D35A/HT16D35B suitable for multiple LED below 125°C. applications. The temperature protection function detect temperature has a value of about 150°C but as the
System Oscillator
detect temperature function includes hysteresis, its release temperature is about 125°C. The internal logic and the LED drive signals of the HT16D35A/HT16D35B are timed by the integrated RC oscillator.
Constant Current Output
The System Clock frequency determines the LED The constant onstant current current output output of of each each row row output output chan- chan- frame frequency. A clock signal must always be nel is setup using an external resistor connected supplied to the device; removing the clock may freeze between the R_EXT pin and GND. The current scale the device if the standby mode command is executed. range can be adjusted by changing the resistor value. At initial system power on, the System Oscillator is in The maximum current variation between channels the stop state. is less than ±3%. The characteristic curve of the output stage in the saturation region is flat for which
ROW Driver Outputs
users can refer to the charts below. The output cur- rent remains constant regardless of the LED forward The LED drive section includes 28 ROW outputs. voltage (VF) variations. The constant current can be ROW0 to ROW27 which should be connected directly calculated using the following formula: to the LED panel. The ROW output signals are V generated in accordance with the multiplexed column R_EXT=1.25V, IROW=(VR_EXT/R_EXT)×12=15/R_EXT for current range signals and with the data resident in the display latch. When less than 28 ROW outputs are required the unused ROW outputs should be left open-circuit.
Column Driver Outputs
The LED drive section includes eight column outputs, COM0 to COM7, which should be connected directly to the LED panel. The column output signals are generated in accordance with the selected LED drive mode. When less than 8 column outputs are required the unused column outputs should be left open-circuit Rev. 1.00 8 July 12, 2017 Document Outline Features Applications General Description Selection Table Block Diagram Pin Assignment Pin Description Absolute Maximum Ratings D.C. Characteristics A.C. Characteristics A.C. Characteristics – SPI 3-wire Serial Bus A.C. Characteristics – I2C Serial Bus Timing Diagrams SPI 3-Wire Serial Bus Timing I2C Bus Timing Power on Reset Timing Functional Description Power-on Reset LED Driver System Oscillator ROW Driver Outputs Column Driver Outputs Address Pointer Over Temperature Protection Constant Current Output Setting the Output Current Load Supply Voltage – LED_V Display Data RAM – DDRAM LED Driver Output Waveform Output Signal Timing Fade Data RAM Universal COM (UCOM) RAM Data Universal SEG (USEG) RAM Data Matrix Masking RAM Data Command Description – Command Table Software Reset Binary/Gray Select Number of COM Outputs Global Blinking Cascade Mode System Control Constant Current Ratio Global Brightness Mode Control Scrolling Control Scrolling Speed COM Pin Control ROW Pin Control Direct Pin Control Read Flag Read Status Write Display Data Write Fade Data Write UCOM Data Write USEG Data Write Matrix Masking Data SPI 3-wire Serial Interface I2C Serial Interface Power Supply Sequence Operation Flow Chart Application Circuits LED Matrix Circuit Single LED IC Application Cascade Function Cascade Control Flow Package Information 48-pin LQFP (7mm×7mm) Outline Dimensions (Exposed Pad)