EM65570
68COM/ 98SEG 65K Color STN LCD Driver
7.25 Safety Measures when Switching Power ON and OFF
The high current that may occur when a voltage is supplied to the LCD driver power
supply while the system power supply is floating, could permanently damage the LSI.
Hence, the precautionary actions as detailed below should be taken into
considerations seriously when switching power on and off.
7.25.1 When Using the External Power Supply
Power ON Proper Sequence:
1) Logic system (VDD) power ON, perform a reset operation
2) Supply the external LCD drive voltage to the corresponding pins (V0, V1, V2, V3
and V4)
Power OFF Proper Sequence:
1) Set the HALT register to “1” or perform a reset operation
2) Cut off external LCD drive voltage
3) Logic system (VDD) power OFF
NOTE
Connect the serial resistor (50 to 100Ω) or fuse to the LCD drive power V0 or VOUT
(when using the internal voltage conversion circuit) of the system as a current limiter.
In addition, set a suitable resister value of the resistor depending on the quality of the
LCD display.
7.25.2 When Using the Built-in Power Supply
Power ON Proper Sequence:
1) Logic system (VDD) power ON
2) Booster circuit system (VEE) power ON
3) Perform a reset operation and enable the booster and voltage conversion circuit.
NOTE
If the VDD and VEE voltages do NOT have the same potential, the logic system
(VDD) is automatically powered on first.
Power OFF Proper Sequence:
1) Set the HALT register to “1” or perform a reset operation
2) Booster circuit system (VEE) power OFF
3) Logic system (VDD) power OFF
If VDD and VEE do NOT have the same potential, cut off VEE first. After the VEE,
VOUT, V0, V1, V2, V3, and V4 voltages are below the LCD ON voltage (threshold
voltage when the Liquid Crystal is turned on), power off the logic system (VDD).
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Product Specification (V1.0) 09.05.2005
(This specification is subject to change without further notice)
ELAN [ ELAN MICROELECTRONICS CORP ]
