upd64a Renesas Electronics Corporation., upd64a Datasheet - Page 28

• Manufacturer Part Number: upd64a
• 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 a low power supply voltage (the oscillation start voltage of the resonator being even lower than
the POC detection 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 detection 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 detection voltage, the growing oscillation of the X
pin can be confirmed within several ms after 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, an oscillation stabilization wait time must elapse before the circuit is switched to operating
A reliable reset operation can be expected from 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 (when 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 detection voltage (V
DD
V
: Power supply voltage, V
DD
Reset
mode. The oscillation stabilization wait time is about 246/f
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.
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 is lower than the POC detection voltage. Therefore, no malfunction occurs 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
< approx. 1.7 V), the X
Note 1
POC
POC
Operating mode
: POC detection voltage.
= 1.85 V (TYP.)), the voltage of the X
OUT
POC
Data Sheet U14380EJ3V0DS00
DD
DD
) varies between approximately 1.7 to 2.0 V; thus, the reset may
pin is 0 V regardless of the V
DD
> V
OUT
has reached V
POC
V
pin so that the oscillation status can be measured.
POC
.
DD
.
> 3.6 V).
Note 2
Reset
POC
.
Operating ambient temperature T
Clock frequency f
POC detection voltage V
X
to 694/f
DD
. However, at the point when V
X
POC
OUT
(about 70 to 190 s, at f
OUT
X
= 2.4 to 8 MHz
for a period of 1 ms or more.
DD
pin jumps to about 0.5V
pin. If, by any chance, the
= 2.0 to 3.6 V). However,
POC
t
= 1.85 V (TYP.)
A
= –40 to +85 C
PD64A, 65
X
= 3.64
Note 3
OUT
DD
DD
.