MP6400 -- LOW QUIESCENT CURRENT PROGRAMMABLE-DELAY SUPERVISORY CIRCUIT
MP6400 Rev. 1.1 www.MonolithicPower.com 10
12/27/2013 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2013 MPS. All Rights Reserved.
TM
RESET
MR
GND
3.3V
SENSE
VCC
MP6400DJ-33
Figure 6—Minimizing I
CC
When
R
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).
RESET
GND
3.3V
C
DELAY
C
DELAY
C
DELAY
C
DELAY
50k
SENSE
VCC
MP6400DJ-33
RESET
GND
3.3V
(a)
(b)
(c)
380ms Delay
24ms Delay
SENSE
VCC
MP6400DJ-33
RESET
GND
3.3V
SENSE
VCC
MP6400DJ-33
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:
107s4.99stnFC
DDELAY
××−=
−
)](10)([)(
4
The reset delay time is determined by the charge
time of external capacitor. While SENSE is above
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
capacitor voltage rises to 1.13V, the
is de-
asserted. The capacitor will be discharged when
the
is again asserted. Stray capacitance
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
negative transient can not assert the
output. The effective duration is relative to the
threshold overdrive, as shown in Figure 8.
01020304050
Maximum SENSE Transient
Duration vs.SENSE Threshold
Overdrive Voltage
1
10
100
SENSE THRESHOLD OVERDRIVE(%)
MAXIMUM SENSE TRANSIENT
DURATION(us)
Figure 8—Maximum Transient Duration vs.
Sense Threshold Overdrive Voltage
