TM
MP6400 -- LOW QUIESCENT CURRENT PROGRAMMABLE-DELAY SUPERVISORY CIRCUIT
3.3V
VCC
SENSE
MR
RESET
MP6400DJ-33
GND
Figure 6—Minimizing I
CC
When
MR
Signal isn’t
over V
CC
by External MOSFET
Programmable Reset Delay Time
The reset delay time can be programmed by
C
DELAY
configure. When C
DELAY
is connected to
VCC through a resistor between 50kΩ and
200kΩ, the delay time is 380ms. When C
DELAY
floated, the delay time is 24ms. In addition, a
capacitor connected C
DELAY
to GND could be
used to get the user’s programmable delay time
from 2.1ms to 10s. The three configures can be
found in Figure 7(a)(b)(c).
3.3V
SENSE
VCC
3.3V
SENSE
VCC
The reset delay time is determined by the charge
time of external capacitor. While SENSE is above
M R
V
IT
and
is a logic high, the internal 140nA
current source is enabled and starts to charge
the capacitor to set the delay time. When the
R E S E T
capacitor voltage rises to 1.13V, the
is de-
asserted. The capacitor will be discharged when
R E S E T
is again asserted. Stray capacitance
the
may cause errors of the delay time. A ceramic
capacitor with low leakage is strongly
recommended.
SENSE Voltage Transients Immunity
The MP6400 can be immune to SENSE pin short
negative transient. The maximum immune
duration is 17us while overdrive is 5%. A shorter
R E S E T
negative transient can not assert the
output. The effective duration is relative to the
threshold overdrive, as shown in Figure 8.
Maximum SENSE Transient
Duration vs.SENSE Threshold
Overdrive Voltage
MAXIMUM SENSE TRANSIENT
DURATION(us)
100
MP6400DJ-33
50k
C
DELAY
GND
RESET
MP6400DJ-33
RESET
C
DELAY
GND
10
380ms Delay
(a)
3.3V
SENSE
VCC
24ms Delay
(b)
1
0
10
20
30
40
50
SENSE THRESHOLD OVERDRIVE(%)
Figure 8
—Maximum Transient Duration vs.
Sense Threshold Overdrive Voltage
MP6400DJ-33
RESET
C
DELAY
C
DELAY
GND
(c)
Figure 7—Programmable Configurations to
the Reset Delay Time
The external capacitor C
DELAY
must be larger than
150pF. For a given delay time, the capacitor
value can be calculated using the following
equation:
C
DELAY
(
nF
)
=
[
t
D
(
s
)
−
4.99
×
10
−
4
(
s
)]
×
107
MP6400 Rev. 1.0
9/7/2012
www.MonolithicPower.com
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2012 MPS. All Rights Reserved.
10
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