ST10R272L - POWER REDUCTION MODES
300/320
.
17.2.4 Selecting R and C values
Select an external capacitor C which will produce a sufficient discharge time (in conjunction
with internal weak pulldown device on the Vpp/RPD pin) for the internal clock signal to
stabilize.
First, determine the worst-case clock signal stabilization time, then use the following formula
to calculate the C value: where:
Examples:
Figure 119 Simplified Powerdown Exit Circuitry
C
is the external capacitor on Vpp/RPD, in µF
T
DIS
is the worst-case discharge time, in s
I
is the discharge current, in µA
V
TH
is the Vpp/RPD threshold voltage, in V
D
Q
Q
enter
cd
external
interrupt
reset
stop pll
stop oscillator
V
DD
D
Q
Q
cd
System clock
CPU and Peripherals clocks
V
PP
/RPD
V
DD
exit_pwrd
en_clk_n
PULLUP
WEAK PULLDOWN
(~ 200
µ
A)
PowerDown
Q1
Q2
C
T
DIS
1
×
5
V
TH
–
(
)
⁄
=
