CS8101 Cherry Semiconductor Corporation, CS8101 Datasheet - Page 4

• Manufacturer Part Number: CS8101
• Description: Micropower 5V/ 100mA Low Dropout Linear Regulator with RESET and ENABLE
• Manufacturer: Cherry Semiconductor Corporation

Figure 3. RC Network for
An external RC network on the
vides a sufficiently long delay for most microprocessor
The circuit depicted in Figure 4 lets the microprocessor
control its power source, the CS8101 regulator. An I/O
port on the µP and the SWITCH port are used to drive the
base of Q1. When Q1 is driven into saturation, the voltage
on the
regulatorÕs output is enabled . When the drive current is
removed, the voltage on the
put is switched off and the IC moves into Sleep mode
where it draws 50µA (max).
Figure 4. Microprocessor Control of CS8101 using external switching transistor Q
ENABLE
V
CS8101
BAT
RESET
lead falls below its lower threshold. The
V
OUT
RESET
SWITCH
Delay
ENABLE
R
RST
C
RESET
RST
0.1mF
lead rises, the out-
500kW
lead (Figure 3) pro-
Q
C
1
OUT
Circuit Description: continued
500kW
to mP
RESET
Port
5V to mP
and
System
Power
V
ENABLE
Applications Notes
IN
CS8101
Gnd
4
based applications. RC values can be chosen using the
following formula:
where:
100kW
By coupling these two controls with the
system has added flexibility. Once the system is running,
the state of the SWITCH is irrelevant as long as the I/O
port continues to drive Q1. The microprocessor can turn
off its own power by withdrawing drive current, once the
SWITCH is open. This software control at the I/O port
allows the microprocessor to finish key housekeeping
functions before power is removed.
The logic options are summarized in Table 1.
RESET
R
1
V
.
TOT
OUT
C
R
R
R
C
t
V
V
RST
Delay
RST
IN
TOT
RST
RST
T
=
= µP port impedance
= R
=
= desired delay time
= V
=
R
[
=
RST
ln
RESET
RESET
RESET
C
RST
RST
SAT
(
in parallel with R
V
of
100kW
V
RST
Delay capacitor
threshold
Delay resistor
RESET
T
Ðt
Ð V
Delay
Ð V
OUT
C
OUT
OUT
lead (0.7V @ turn - ON)
)
RESET
V
CC
]
ENABLE
IN
I/O Port
mP
lead, the