TM
MP6400 -- LOW QUIESCENT CURRENT PROGRAMMABLE-DELAY SUPERVISORY CIRCUIT
3.3V
The reset delay time is determined by the charge
time of external capacitor. While SENSE is above
MR
VCC
SENSE
RESET
VIT 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
RESET
MR
capacitor voltage rises to 1.13V, the
is de-
asserted. The capacitor will be discharged when
RESET
MP6400DJ-33
the
is again asserted. Stray capacitance
GND
may cause errors of the delay time. A ceramic
capacitor with low leakage is strongly
recommended.
Figure 6—Minimizing ICC When
Signal isn’t
MR
over VCC by External MOSFET
SENSE Voltage Transients Immunity
The MP6400 can be immune to SENSE pin short
negative transient. The maximum immune
Programmable Reset Delay Time
The reset delay time can be programmed by
CDELAY configure. When CDELAY is connected to
VCC through a resistor between 50kΩ and
200kΩ, the delay time is 380ms. When CDELAY
floated, the delay time is 24ms. In addition, a
capacitor connected CDELAY 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).
duration is 17us while overdrive is 5%. A shorter
RESET
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
100
3.3V
3.3V
SENSE
SENSE
VCC
VCC
MP6400DJ-33
MP6400DJ-33
50k
RESET
RESET
10
CDELAY
GND
CDELAY
GND
24ms Delay
(b)
380ms Delay
(a)
1
0
10
20
30
40
50
3.3V
SENSE THRESHOLD OVERDRIVE(%)
Figure 8—Maximum Transient Duration vs.
Sense Threshold Overdrive Voltage
SENSE
VCC
MP6400DJ-33
RESET
CDELAY
GND
CDELAY
(c)
Figure 7—Programmable Configurations to
the Reset Delay Time
The external capacitor CDELAY must be larger than
150pF. For a given delay time, the capacitor
value can be calculated using the following
equation:
C
DELAY (nF) = [tD (s) − 4.99×10−4 (s)]×107
MP6400 Rev. 1.0
9/7/2012
www.MonolithicPower.com
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© 2012 MPS. All Rights Reserved.
10
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