upd63a Renesas Electronics Corporation., upd63a Datasheet - Page 28

• Manufacturer Part Number: upd63a
• Description: 4-bit Single-chip Microcontroller For Infrared Remote Control Transmission
• Manufacturer: Renesas Electronics Corporation.

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.
the POC-detected voltage (voltage somewhere between V
about 0.5 V
chance, the oscillation start voltage of the resonator is lower than the POC-detected voltage, the growing oscillation
of the X
28
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
2.2 V
0.9 V
V
0 V
voltage V
POC
OUT
V
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
DD
DD
pin can be confirmed within several ms after the V
Reset
: power supply voltage, V
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.
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).
. Maintain this power supply voltage for a while to measure the waveform of the X
DD
DD
from 0 V (making sure to avoid V
< 0.9 V), the X
Note 1
OPERATING mode
OUT
POC
pin is 0 V regardless of the V
: POC-detected voltage.
POC
DD
) varies between 0.9 to 2.2 V; thus, the resetting may be canceled
DD
> V
OUT
POC
V
pin so that the oscillation status can be measured.
POC
.
DD
.
> 3.6V).
POC
Note 2
= 0.9 to 2.2 V), the voltage of the X
DD
Reset
has reached the V
Operating ambient temperature T
Clock frequency f
DD
POC-detected voltage V
. However, at the point that V
X
DD
to 700/f
= 1.8 to 3.6 V). However, as long as
X
X
(when about 70 to 190 s; f
POC
POC
= 2.4 to 4 MHz
.
for the period of 1 ms or
POC
t
= 0.9 to 2.2 V
OUT
PD63, 63A, 64
OUT
A
= – 20 to + 70°C
pin. If, by any
pin jumps to
DD
reaches
Note 3
X