4 POWER SUPPLY
S1C33L26 TECHNICAL MANUAL
Seiko Epson Corporation
4-3
Precautions on Power Supply
4.7
Power-on sequence
To ensure that the device will operate normally, observe the timing requirements given below when turning the
power on.
HV
DD
, AV
DD
LV
DD
, PLLV
DD
, RTCV
DD
#RESET
LV
DD
min.
t
LVDD
t
PR
7.1 Power-On Sequence
Figure 4.
(1)
t
LVDD
: Elapsed time until the power supply stabilizes after power-on
Supply power in the following sequence.
Power-on: 1. LV
DD
, PLLV
DD
, (and RTCV
DD
)
2. HV
DD
, AV
DD
(May be applied with 1 above at the same time.)
3. Apply the input signal
*
The RTCV
DD
can be always supplied to the chip to operate the RTC and BBRAM.
(2)
t
PR
: Power-on-reset time
Keep the #RESET signal low for this period. See the “#RESET Pin” section in the “Reset and NMI”
chapter for the power-on-reset time.
Power-off sequence
Shut off the power supply in the following sequence.
Power-off: 1. Turn off the input signal
2. HV
DD
, AV
DD
3. LV
DD
, PLLV
DD
(and RTCV
DD
) (May be turned off with 2 above at the same time.)
Note: Be sure to avoid applying HV
DD
or AV
DD
for a duration of one second or more when the LV
DD
power is off, as a breakdown may occur in the device or the characteristics may be degraded due
to flow-through current of the HV
DD
or AV
DD
.
Latch-up
The CMOS device may be in the latch-up condition. This is the phenomenon caused by conduction of the para-
sitic PNPN junction (thyristor) contained in the CMOS IC, resulting in a large current between LV
DD
and V
SS
and leading to breakage.
Latch-up occurs when the voltage applied to the input/output exceeds the rated value and a large current flows
into the internal element, or when the voltage at the LV
DD
pin exceeds the rated value and the internal element
is in the breakdown condition. In the latter case, even if the application of a voltage exceeding the rated value is
instantaneous, the current remains high between LV
DD
and V
SS
once the device is in the latch-up condition. As
this may result in heat generation or smoking, the following points must be taken into consideration:
(1) The voltage level at the input/output must not exceed the range specified in the electrical characteristics. In
other words, it must be below the power-supply voltage and above V
SS
. The power-on timing should also be
taken into consideration.
(2) Abnormal noise must not be applied to the device.
(3) The potential at the unused input should be fixed at LV
DD
, HV
DD
, AV
DD
, or V
SS
.
(4) No outputs should be shorted.