MAX6895–MAX6899
Ultra-Small, Adjustable
Sequencing/Supervisory Circuits
10 ______________________________________________________________________________________
Enable Input (ENABLE or
ENABLE
)
The MAX6895/MAX6897 offer an active-high enable
input (ENABLE), while the MAX6896/MAX6898/MAX6899
offer an active-low enable input (ENABLE). With V
IN
above
V
TH
, drive ENABLE high (ENABLE low) to force OUT high
(OUT low) after the adjustable delay time (A versions). For
P version devices, when V
IN
> 0.5V and enable is assert-
ed, the output asserts after typically 150ns.
The enable input has logic-high and logic-low voltage
thresholds of 1.4V and 0.4V, respectively. For both ver-
sions, when V
IN
> 0.5V, drive ENABLE low (ENABLE
high) to force OUT low (OUT high) within 150ns typ.
Output (OUT or
OUT
)
The MAX6895/MAX6899 offer an active-high, push-pull
output (OUT), and the MAX6896 offers an active-low
push-pull output (OUT). The MAX6897 offers an active-
high open-drain output (OUT), and the MAX6898 offers
an active-low open-drain output (OUT).
Push-pull output devices are referenced to V
CC
. Open-
drain outputs can be pulled up to 28V.
Applications Information
Input Threshold
The MAX6895–MAX6899 monitor the voltage on IN with
an external resistive divider (see R1 and R2 in the
Typical Operating Circuit
). Connect R1 and R2 as close
to IN as possible. R1 and R2 can have very high values
to minimize current consumption due to low IN leakage
currents (±15nA max). Set R2 to some conveniently
high value (1M, for example) and calculate R1 based
on the desired monitored voltage using the following
formula:
where V
MONITOR
is the desired monitored voltage and
V
IN
is the detector input threshold (0.5V).
RR
V
V
MONITOR
IN
12 1
Figure 7. MAX6899P Timing Diagram
V
CC
V
UVLO
t
PROPP
t
DL
t
OFF
t
DELAY
t > t
PW
t
PROPP
IN
ENABLE
OUT
MAX6895–MAX6899
Pullup Resistor Values
(MAX6897/MAX6898)
The exact value of the pullup resistors for the open-
drain outputs is not critical, but some consideration
should be made to ensure the proper logic levels when
the device is sinking current. For example, if V
CC
=
2.25V and the pullup voltage is 28V, you would try to
keep the sink current less than 0.5mA as shown in the
Electrical Characteristics
table. As a result, the pullup
resistor should be greater than 56k. For a 12V pullup,
the resistor should be larger than 24k. It should be
noted that the ability to sink current is dependent on the
V
CC
supply voltage.
Typical Application Circuits
Figures 8, 9, 10 show typical applications for the
MAX6895–MAX6899. Figure 8 shows the MAX6895
used with a p-channel MOSFET in an overvoltage pro-
tection circuit. Figure 9 shows the MAX6895 in a low-
voltage sequencing application using an n-channel
MOSFET. Figure 10 shows the MAX6895 used in a mul-
tiple-output sequencing application.
Using an n-Channel Device for Sequencing
In higher power applications, using an n-channel device
reduces the loss across the MOSFETs as it offers a
lower drain-to-source on-resistance. However, an n-
channel MOSFET requires a sufficient V
GS
voltage to
fully enhance it for a low R
DS_ON
. The application in
Figure 9 shows the MAX6895 in a switch sequencing
application using an n-channel MOSFET.
Similarly, if a higher voltage is present in the system, the
open-drain version can be used in the same manner.
Figure 8. Overvoltage Protection
MAX6897
ENABLE
GND
V
CC
P
3.3V ALWAYS ON
OUT
R1
0 TO 28V
R
PULLUP
R2
IN
CDELAY
MAX6895
ENABLE
GND
V
CC
5V BUS
OUT
R1
R2
IN
CDELAY
C
CDELAY
1.2V INPUT
1.2V OUTPUT
N
MONITORED
3.3V
Figure 9. Low-Voltage Sequencing Using an n-Channel MOSFET
Ultra-Small, Adjustable
Sequencing/Supervisory Circuits
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MAX6895–MAX6899
Ultra-Small, Adjustable
Sequencing/Supervisory Circuits
12 ______________________________________________________________________________________
Figure 10. Multiple-Output Sequencing
C
CDELAY
C
CDELAY
GND GND
GND GND
OUT
OUT
OUT
OUT
IN IN
IN IN
V
CC
V
CC
V
CC
V
CC
ENABLE ENABLE ENABLE
ENABLE
EN
EN
EN
EN
DC-DC
3.3V
5V BUS
SYSTEM
ENABLE
2.5V
1.8V
1.2V
DC-DC
DC-DC
DC-DC
C
CDELAY
C
CDELAY
MAX6895 MAX6895 MAX6895 MAX6895

MAX6895AAZT+T

Mfr. #:
Manufacturer:
Maxim Integrated
Description:
Supervisory Circuits Adjustable Sequencer/Supervisor
Lifecycle:
New from this manufacturer.
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