UPD62A NEC, UPD62A Datasheet - Page 28

• Manufacturer Part Number: UPD62A
• Description: 4-BIT SINGLE-CHIP MICROCONTROLLER FOR INFRARED REMOTE CONTROL TRANSMISSION
• Manufacturer: NEC

1.7 V (approx.)
7.1 Functions of POC Circuit
7.2 Oscillation Check at Low Supply Voltage
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 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
Internal reset signal
The POC circuit has the following functions:
• Generating an internal reset signal when V
• Canceling an internal reset signal when V
Here, V
Notes 1. In reality, oscillation stabilization wait time must elapse before the circuit is switched to operating
A reliable reset operation can be expected of the POC circuit if it satisfies the condition that the clock can oscillate
<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
Reset
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
Therefore, in reality, there is a time lag of up to 1 ms until the reset takes effect.
at a power supply voltage smaller than the assured range (V
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).
DD
DD
from 0 V (making sure to avoid V
< 1.7 V (approx.)), the X
Note 1
POC
POC
Operating mode
: POC-detected voltage.
= 1.85 V (TYP.)), the voltage of the X
POC
Data Sheet U14474EJ1V0DS00
OUT
) varies between about 1.7 to 2.0 V; thus, the reset may be canceled
DD
DD
OUT
pin is 0 V regardless of the V
> V
DD
pin so that the oscillation status can be measured.
V
POC
has reached the V
POC
DD
.
> 3.6 V).
.
Note 2
Reset
Operating ambient temperature T
Clock frequency f
POC-detected voltage V
POC
X
DD
to 700/f
.
= 2.0 to 3.6 V). However, as long as
DD
. However, at the point that V
OUT
POC
OUT
X
(about 70 to 190 s: when f
pin jumps to about 0.5 V
X
for a period of 1 ms or more.
pin. If, by any chance, the
= 2.4 to 8 MHz
POC
t
= 1.85 V (TYP.)
A
= –40 to +85 C
PD62A
Note 3
OUT
DD
DD
X
.