UPD65MC NEC, UPD65MC Datasheet - Page 28

• Manufacturer Part Number: UPD65MC
• Description: 4-BIT SINGLE-CHIP MICROCONTROLLER FOR INFRARED REMOTE CONTROL TRANSMISSION
• Manufacturer: NEC

7.1 Functions of POC Circuit
7.2 Oscillation Check at Low Supply Voltage
oscillate even at low power supply voltage (the oscillation start voltage of the resonator being even lower than the
POC-detected voltage). Whether this condition is being met or not can be checked by measuring the oscillation
status on a product which actually contains a POC circuit, as follows.
reaches the POC-detected voltage (V
Maintain this power supply voltage for a while to measure the waveform of the X
oscillation start voltage of the resonator is lower than the POC-detected voltage, the growing oscillation of the X
pin can be confirmed within several ms after the V
28
Approx. 1.7 V
Internal reset signal
The POC circuit has the following functions:
• Generates an internal reset signal when V
• Cancels an internal reset signal when V
Here, V
Notes 1. In reality, there is the oscillation stabilization wait time until the circuit is switched to OPERATING
A reliable resetting operation can be expected of the POC circuit if it satisfies the condition that the clock can
<1> Connect a storage oscilloscope to the X
<2> Connect a power supply whose output voltage can be varied and then gradually raise the power supply
At first (during V
3.6 V
2.0 V
voltage V
V
0 V
POC
2. For the POC circuit to generate an internal reset signal when the power supply voltage has fallen,
3. The POC-detected voltage (V
DD
V
: power supply voltage, V
DD
mode. The oscillation stabilization wait time is about 252/f
= 3.64 MHz).
it is necessary for the power supply voltage to be kept less than the V
more. Therefore, in reality, there is the time lag of up to 1 ms until the reset takes effect.
be canceled at a power supply voltage smaller than the assured range (V
as long as the conditions for operating the POC circuit are met, the actual lowest operating power
supply voltage becomes lower than the POC-detected voltage. Therefore, there is no malfunction
occurring due to the shortage of power supply voltage. However, malfunction for such reasons as
the clock not oscillating due to low power supply voltage may occur (refer to Cautions 3. in 7. POC
CIRCUIT).
Reset
DD
DD
from 0 V (making sure to avoid V
< approx. 1.7 V), the X
Note 1
POC
OPERATING mode
POC
: POC-detected voltage.
= 1.85 V (TYP.)), the voltage of the X
POC
Data Sheet U14380EJ2V0DS00
OUT
DD
) varies between approximately 1.7 to 2.0 V; thus, the resetting may
DD
> V
pin is 0 V regardless of the V
OUT
DD
POC
V
pin so that the oscillation status can be measured.
has reached the V
POC
.
DD
.
> 3.6V).
Note 2
Reset
Operating ambient temperature T
Clock frequency f
POC-detected voltage V
POC
X
to 700/f
.
DD
. However, at the point that V
OUT
OUT
X
(when about 70 to 190 s; f
POC
pin jumps to about 0.5 V
DD
X
pin. If, by any chance, the
= 2.4 to 8 MHz
= 2.0 to 3.6 V). However,
for the period of 1 ms or
POC
t
= 1.85 V (TYP.)
A
= – 40 to + 85 C
PD64A, 65
Note 3
OUT
DD
DD
X
.