PT6553_10 Datasheet, PDF (21/41 Pages) Princeton Technology Corp – LCD Driver IC with Key Input Function

LCD Driver IC with Key Input Function
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PT6553
VOLTAGE DETECTION TYPE RESET CIRCUIT (VDET)
The Voltage Detection Type Reset Circuit (V_DET) generates an output signal and resets the system
when the power is first applied as well as when the voltage drops (i.e., when the power supply voltage
is less than or equal to the power down detection voltage, V_DET [3.0v typ.]). To insure proper operation
of this function, a capacitor must be connected to the power supply line so that the power supply
voltage (V_DD) rise time (when the power is first applied) and the power supply voltage (V_DD) fall time
(when the voltage drops) are at least 1ms. Please refer to the diagram below.
SYSTEM RESET
RESET METHOD
If the Supply voltage V_DD rise time is at least 1 ms when power is applied, a system reset will be
initialized by the V_DET output signal when the supply voltage is increased. If the supply voltage V_DD fall
time is at least 1ms when the power drops, a system reset will be initialized by the V_DET output signal
when the supply voltage is decreased. When all the serial data (including display data, D1 to D126 and
the control data) has been transferred, reset function is cleared.
This means that if for example, on the falling edge of the last direction data transfer's CE signal, (that is
after all the direction data have been transferred), the reset function is cleared. Please refer to the
diagram below.
VDD
VDET
t1
CE
INTERNAL
DATA
Display and control data transfer
Undefined
System reset period
Defined
VDET
t2
Power Supply Voltage (V_DD) Rise Time: t1 ≥ 1ms
Power Supply Voltage (V_DD) Fall Time: t2 ≥ 1ms
PT6553 V1.7
- 21 -
November, 2007