Datasheet

MAX6305–MAX6313
open-drain, N-channel output. The MAX6308/MAX6309/
MAX6310 feature an active-low, complementary output
structure that both sinks and sources current, and the
MAX6311/MAX6312/MAX6313 have an active-high com-
plementary reset output.
The MAX6305/MAX6308/MAX6311 switch from under-
voltage lockout operation to normal operation between
1.5V < V
CC
< 2.5V. Below 1.5V, V
CC
undervoltage-
lockout mode asserts RESET. Above 2.5V, V
CC
normal-
operation mode asserts reset if RST IN_ falls below the
RST IN_ threshold.
Manual-Reset Input
(MAX6306/MAX6309/MAX6312)
Many µP-based products require manual-reset capability,
allowing an operator or external logic circuitry to initiate a
reset. A logic low on MR asserts reset. Reset remains
asserted while MR is low, and for a reset active timeout
period (t
RP
) after MR returns high. This input has an inter-
nal 63.5kΩ pull-up resistor, so it can be left open if it is not
used. MR can be driven with TTL-logic levels in 5V sys-
tems, with CMOS-logic levels in 3V systems, or with open-
drain/collector output devices. Connect a normally open
momentary switch from MR to GND to create a manual-
reset function; external debounce circuitry is not required.
If MR is driven from long cables or if the device is used in
a noisy environment, connecting a 0.1µF capacitor from
MR to ground provides additional noise immunity.
The MR pin has internal ESD-protection circuitry that may
be forward biased under certain conditions, drawing
excessive current. For example, assume the circuitry driv-
ing MR uses a +5V supply other than V
CC
. If V
CC
drops or
browns out lower than +4.7V, MR’s absolute maximum rat-
ing is violated (-0.3V to (V
CC
+ 0.3V)), and undesirable
current flows through the ESD structure from MR to V
CC
.
To avoid this, it is recommended that the supply for the MR
pin be the same as the supply monitored by V
CC
. In this
way, the voltage at MR will not exceed V
CC
.
Adjustable Reset Inputs
The MAX6305–MAX6313 each have one or more reset
inputs (RST IN_ /OVRST IN). These inputs are com-
pared to the internal reference voltage (Figure 1).
Connect a resistor voltage divider to RST IN_ such that
V
RST IN_
falls below V
RSTH
(1.23V) when the monitored
voltage (V
IN
) falls below the desired reset threshold
(V
TH
) (Figure 2). Calculate the desired reset voltage
with the following formula:
R1 + R2
V
TH
=
________
x V
RSTH
R2
5-Pin, Multiple-Input,
Programmable Reset ICs
6
RST IN1
*
††
†
†††
+1.23V
+1.23V
+1.23V
+1.23V
RST IN2
RESET
GENERATOR
RESET***
OVRST IN
GND
V
CC
V
CC
MR
RESET**
MAX6306/MAX6307/MAX6309/MAX6310/MAX6312/MAX6313 ONLY
MAX6305–MAX6310 ONLY
MAX6311/MAX6312/MAX6313 ONLY
MAX6307/MAX6310/MAX6313 ONLY
MAX6305/MAX6308/MAX6311 ONLY
MAX6306/MAX6309/MAX6312 ONLY
MAX6305–MAX6313
*
**
***
†
††
†††
Figure 1. Functional Diagram