Holtek HT16H25, Application Manuallines, Page: 13 / 22

HT16H25 Treadmill Display Application Guideline
AN0505E V1.00 13 / 22 January 8, 2019
LCD Bias Function Command
The LCD Bias can be selected to come from the Charge Pump or from the Resistor
Divider using a control command.
When the LCD Bias selects the Charge Pump, the Charge Pump coefficient selection
depends on the Bias setting. The relationship between the LCD Bias and the Charge
Pump coefficient is shown in the table below. Here, all the capacitors used with the
Charge Pump should have a value of
0.1μF . The Charge Pump output requires about
20ms to stabilise after being enabled.
LCD Bias Charge Pump Ratio Setting
Static Charge Pump Input Voltage
1/2 X2
1/3 X3
1/4 X4
1/5 X5
When the LCD Bias chooses the resistor divider, there are 3 resistor values to choose: 4K,
8K or 16K. For this option, V
LCD
can only be provided by an external power supply.
●
LCD Bias Circuit Select Command
Command R/W Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 Def.
LCD Bias
Circuit select
W 1 1 0 1 0 0 0 0 D0h
W X X X BV X X BC1 BC0 00h
Note: "BV" bit: VLCD Select Control
BV VLCD Select
0 VLCD is supplied from Charge Pump (default)
1 VLCD is supplied from external power
BC[1:0]: LCD Bias Circuit Select
BC1 BC0 LCD Bias Circuit Select
0 0 disable (default)
0 1 Charge Pump
1 0 Invalid
1 1 Resistor divider
●
Contrast Adjustment Command
Command R/W Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 Def.
Contrast
Adjustment
W 1 1 0 1 0 0 1 0 D2h
W X X X X CA3 CA2 CA1 CA0 00h
Note: When the LCD Bias selects the Charge Pump this instruction has no effect.
CA[3:0]: Contrast adjustment bit, LCD Bias circuit select Resistor Divider.