Lcd Reset Function - Holtek HT67F2350 Manual

C Type Biasing – 1/3 Bias Only
For C type biasing the LCD voltage source can be supplied on the external pin PLCD, V1 or V2 or
derived from the internal voltage source to generate the required biasing voltages. The C type bias
voltage source is selected using the LCDP1 and LCDP0 bits in the LCDC0 register. The C type
biasing scheme uses an internal charge pump circuit and can generate voltages higher than what is
supplied on PLCD or V2. This feature is useful in applications where the microcontroller supply
voltage is less than the supply voltage required by the LCD. Additional charge pump capacitors must
also be connected between pins C1 and C2 to generate the necessary voltage levels.
For C type 1/3 bias external power supply scheme, the LCD power can be supplied on PLCD, V1
or V2 pin. However, the LCD power is internally supplied on VA, VB or VC for C type 1/3 bias
internal power supply scheme. Four internally generated voltage levels, V
utilised. These bias voltages have different levels depending upon different LCD power supply
schemes.
LCD Power Supply
External Power
Supply
Internal
Power Supply
The connection to the VMAX pin depends upon the LCD power supply scheme. It is extremely
important to ensure that these charge pump generated internal voltages do not exceed the maximum
V voltage of 5.5V.
DD

LCD Reset Function

The LCD has an internal reset function that is an OR function of the inverted LCDEN bit in the
LCDC0 register and the SLEEP function. When the LCDEN bit is set to 1 to enable the LCD driver
function before the device enters the SLEEP mode, the LCD function will be reset after the device
enters the SLEEP mode. Clearing the LCDEN bit to zero will also reset the LCD function.
MCU Reset
No
No
No
Yes
Note: 1. The watchdog time-out reset in the IDLE or SLEEP Mode is excluded from the MCU Reset
conditions.
2. "x": Don't care.
Rev. 1.60
Advanced A/D Flash MCU with LCD & EEPROM
VA voltage
V on V1 V
IN IN
V on PLCD 3/2 × V
IN IN
V on V2 3 × V
IN IN
V on VA V
DD DD
V on VB 3/2 × V
DD DD
V on VC 3 × V
REFIN REFIN
C Type Bias Power Supply Scheme
Condition
V > V × 1.5 Connect VMAX to VDD
DD IN
Otherwise Connect VMAX to V1
C Type Bias VMAX Pin Connection
SLEEP Mode LCDEN
Off 1
Off 0
On x
x x
LCD Reset Function
228
HT67F2350/HT67F2360
HT67F2370/HT67F2390
, V , V
SS A
VB voltage VC voltage
2/3 × V
IN
V
IN
2 × V
IN
2/3 × V 1/3 × V
DD
V 1/2 × V
DD
2 × V
REFIN
VMAX Connection
COM & SEG
LCD Reset
Voltage Level
No Normal Operation
Yes
Yes
Yes Floating
May 16, 2019
and V , are
B C
1/3 × V
IN
1/2 × V
IN
V
IN
DD
DD
V
REFIN
Low
Low