MAX6305UK00D1-T ,5-Pin / Multiple-Input / Programmable Reset ICsMAX6305–MAX631319-1145; Rev 1; 8/985-Pin, Multiple-Input,Programmable Reset ICs
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MAX6305UK00D1-T-MAX6306UK29D2-T-MAX6306UK29D3-T-MAX6306UK46D3-T-MAX6307UK31D3-T-MAX6308UK00D3-T-MAX6309UK26D2-T-MAX6309UK26D3-T-MAX6309UK32D1-T-MAX6309UK39D4-T-MAX6310UK33D4-T-MAX6310UK43D1-T-MAX6310UK47D4-T-MAX6310UK48D1-T
5-Pin / Multiple-Input / Programmable Reset ICs
General DescriptionThe MAX6305–MAX6313 CMOS microprocessor (µP)
supervisory circuits are designed to monitor more than
one power supply. Ideal for monitoring both 5V and
3.3V in personal computer systems, these devices
assert a system reset if any of the monitored supplies
falls outside the programmed threshold. Low supply
current (15µA) and a small package suit them for
portable applications. The MAX6305–MAX6313 are
specifically designed to ignore fast transients on
any monitored supply.
These devices are available in a SOT23-5 package,
have factory-programmed reset thresholds from 2.5V to
5.0V (in 100mV increments), and feature four power-on
reset timeout periods.
ApplicationsPortable Computers
Computers
Controllers
Intelligent Instruments
Portable/Battery-Powered Equipment
Multivoltage Systems: 3V/5V, 5V/12V, 5V/24V
Embedded Control Systems
FeaturesSmall 5-Pin SOT23 PackagePrecision Factory-Set VCCReset Thresholds;
Available in 0.1V Increments from 2.5V to 5VImmune to Short VCCTransientsGuaranteed RESETValid to VCC= 1VGuaranteed Over Temperature8µA Supply CurrentFactory-Set Reset Timeout Delay from
1ms (min) to 1120ms (min)No External ComponentsManual Reset InputUnder/Overvoltage Supply Monitoring
MAX6305–MAX6313
5-Pin, Multiple-Input,
Programmable Reset ICs19-1145; Rev 1; 8/98
Pin Configurations and Typical Operating Circuit appear at
end of data sheet.
_______________________________________________________________Selector Table
MAX6305–MAX6313
5-Pin, Multiple-Input,
Programmable Reset ICs
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICSVCC= +2.5V to +5.5V for the MAX6305/MAX6308/MAX6311, VCC = (VTH+ 2.5%) to +5.5V for the MAX6306/MAX6307/MAX6309/
MAX6310/MAX6312/MAX6313; TA = 0°C to +70°C; unless otherwise noted. Typical values are at TA= +25°C.)
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
VCC...........................................................................-0.3V to +6V
All Other Pins..............................................-0.3V to (VCC+ 0.3V)
Input/Output Current, All Pins.............................................20mA
Rate of Rise, VCC............................................................100V/µs
Continuous Power Dissipation (TA= +70°C)
SOT23-5 (derate 7.1mW/°C above +70°C).................571mW
Operating Temperature Range...............................0°C to +70°C
Storage Temperature Range.............................-65°C to +160°C
Lead Temperature (soldering, 10sec).............................+300°C
MAX6305–MAX6313
5-Pin, Multiple-Input,
Programmable Reset ICs
ELECTRICAL CHARACTERISTICS (continued)(VCC= +2.5V to +5.5V for the MAX6305/MAX6308/MAX6311, VCC = (VTH+ 2.5%) to +5.5V for the MAX6306/MAX6307/MAX6309/
MAX6310/MAX6312/MAX6313; TA = 0°C to +70°C; unless otherwise noted. Typical values are at TA= +25°C.)
Note 1: The MAX6305/MAX6308/MAX6311 switch from undervoltage reset to normal operation between 1.5V < VCC< 2.5V.
Note 2: The MAX6306/MAX6307/MAX6309/MAX6310/MAX6312/MAX6313 monitor VCCthrough an internal factory-trimmed voltage
divider, which programs the nominal reset threshold. Factory-trimmed reset thresholds are available in approximately
100mV increments from 2.5V to 5V (Table 1).
MAX6305–MAX6313
5-Pin, Multiple-Input,
Programmable Reset ICs
__________________________________________Typical Operating Characteristics(VCC= +5V, TA = +25°C, unless otherwise noted.)
_______________Detailed DescriptionThe MAX6305–MAX6313 CMOS microprocessor (µP)
supervisory circuits are designed to monitor more than
one power supply and issue a system reset when any
monitored supply falls out of regulation. The MAX6305/
MAX6308/MAX6311 have two adjustable undervoltage
reset inputs (RST IN1 and RST IN2). The MAX6306/
MAX6307/MAX6309/MAX6310/MAX6312/MAX6313 mon-
itor VCCthrough an internal, factory-trimmed voltage
divider. The MAX6306/MAX6309/MAX6312 have, in
addition, an adjustable undervoltage reset input and a
manual-reset input. The internal voltage divider sets the
reset threshold as specified in the device part number
(Table 1). The MAX6307/MAX6310/ MAX6313 feature an
adjustable undervoltage reset input (RST IN) and an
adjustable overvoltage reset input (OVRST IN) in addition
to the factory-trimmed reset threshold on the VCCmoni-
tor. Program the adjustable reset inputs with an external
resistor divider (see Adjustable Reset Inputs section).
Reset OutputsA µP’s reset input starts the µP in a known state. These
µP supervisory circuits assert reset to prevent code-
execution errors during power-up, power-down, or
brownout conditions.
RESET(MAX6305–MAX6310) and RESET (MAX6311/
MAX6312/MAX6313) are guaranteed to be asserted at
a valid logic level for VCC> 1V (see Electrical
Characteristics). Once all monitored voltages exceed
their programmed reset thresholds, an internal timer
keeps reset asserted for the reset timeout period (tRP);
after this interval, reset deasserts.
If a brownout condition occurs (any or all monitored volt-
ages dip outside their programmed reset threshold),
reset asserts (RESET goes high; RESETgoes low). Any
time any of the monitored voltages dip below their reset
threshold, the internal timer resets to zero and reset
asserts. The internal timer starts when all of the moni-
tored voltages return above their reset thresholds, and
reset remains asserted for a reset timeout period. The
MAX6305/MAX6306/MAX6307 feature an active-low,
MAX6305–MAX6313
5-Pin, Multiple-Input,
Programmable Reset ICs
______________________________________________________________Pin Description
MAX6305–MAX6313open-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 < VCC< 2.5V. Below 1.5V, VCCundervoltage-
lockout mode asserts RESET. Above 2.5V, VCCnormal-
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 MRasserts reset. Reset remains
asserted while MRis low, and for a reset active timeout
period (tRP) after MRreturns high. This input has an inter-
nal 63.5kΩpull-up resistor, so it can be left open if it is not
used. MRcan 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 MRto GND to create a manual-
reset function; external debounce circuitry is not required.
If MRis driven from long cables or if the device is used in
a noisy environment, connecting a 0.1µF capacitor fromto ground provides additional noise immunity.
The MRpin has internal ESD-protection circuitry that may
be forward biased under certain conditions, drawing
excessive current. For example, assume the circuitry driv-
ing MRuses a +5V supply other than VCC. If VCCdrops or
browns out lower than +4.7V, MR’s absolute maximum rat-
ing is violated (-0.3V to (VCC+ 0.3V)), and undesirable
current flows through the ESD structure from MRto VCC.
To avoid this, it is recommended that the supply for the MR
pin be the same as the supply monitored by VCC. In this
way, the voltage at MRwill not exceed VCC.
Adjustable Reset InputsThe 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
VRST IN_falls below VRSTH(1.23V) when the monitored
voltage (VIN) falls below the desired reset threshold
(VTH) (Figure 2). Calculate the desired reset voltage
with the following formula:
R1 + R2VTH= ________x VRSTHR2
5-Pin, Multiple-Input,
Programmable Reset ICs
MAX6305–MAX6313
5-Pin, Multiple-Input,
Programmable Reset ICsThe ±25nA max input leakage current allows resistors on
the order of megohms. Choose the pull-up resistor in the
divider to minimize the error due to the input leakage cur-
rent. The error term in the calculated threshold is simply:
±25nA x R1
If you choose R1 to be 1MΩ, the resulting error is
±25 x 10-9x 1 x 106= ±25mV.
Like the VCCvoltage monitors on the MAX6306/MAX6307/
MAX6309/MAX6310/MAX6312/MAX6313, the RST IN_
inputs (when used with a voltage divider) are designed to
ignore fast voltage transients. Increase the noise immunity
by connecting a capacitor on the order of 0.1µF between
RST IN and GND (Figure 2). This creates a single-pole
lowpass filter with a corner frequency given by:
f = (1/2π) / (R1 + R2)(R1 x R2 x C)
For example, if R1 = 1MΩand R2 = 1.6MΩ, adding a
0.1µF capacitor from RST IN_ to ground results in a
lowpass corner frequency of f = 2.59Hz. Note that
adding capacitance to RST IN slows the circuit’s overall
response time.
__________Applications Information
Interfacing to µPs with
Bidirectional Reset PinsSince the RESEToutput on the MAX6305/MAX6306/
MAX6307 is open drain, these devices interface easily
with µPs that have bidirectional reset pins, such as the
Motorola 68HC11. Connecting the µP supervisor’s
RESEToutput directly to the microcontroller’s RESET
pin with a single pull-up resistor allows either device to
assert reset (Figure 3).
Negative-Going VCCTransientsIn addition to issuing a reset to the µP during power-up,
power-down, and brownout conditions, these devices
are relatively immune to short-duration, negative-going
VCCtransients (glitches).
The Typical Operating Characteristics show the
Maximum Transient Duration vs. VCCReset Threshold
Overdrive, for which reset pulses are not generated.
The graph was produced using negative-going pulses,
starting at VTHmax, and ending below the pro-
grammed reset threshold by the magnitude indicated
(reset threshold overdrive). The graph shows the maxi-
mum pulse width that a negative-going VCCtransient
may typically have without causing a reset pulse to be
issued. As the amplitude of the transient increases (i.e.,
goes farther below the reset threshold), the maximum
allowable pulse width decreases.
RST IN_/OVRST IN are also immune to negative/positive-
going transients (see Typical Operating Characteristics).
A 0.1µF bypass capacitor mounted close to the RST IN_,
OVRST IN, and/or the VCCpin provides additional tran-
sient immunity.
Ensuring a Valid RESET/RESET
Output Down to VCC= 0VWhen VCCfalls below 1V, push/pull structured RESET/
RESET current sinking (or sourcing) capabilities
decrease drastically. High-impedance CMOS-logic
inputs connected to RESETcan drift to undetermined
voltages. This presents no problem in most applica-
tions, since most µPs and other circuitry do not operate
with VCCbelow 1V. In those applications where RESET
must be valid down to 0V, adding a pull-down resistor
between RESETand ground sinks any stray leakage
currents, holding RESETlow (Figure 4). The pull-down
resistor’s value is not critical; 100kΩis large enough not
to load RESETand small enough to pull RESETto
ground. For applications where RESET must be valid to
VCC, a 100kΩpull-up resistor between RESET and VCC
will hold RESET high when VCCfalls below 1V (Figure 5).
Since the MAX6305/MAX6306/MAX6307 have open-
drain, active-low outputs, they typically use a pull-up
resistor. With these devices and under these conditions
(VCC< 1V), RESETwill most likely not maintain an
active condition, but will drift toward a nonactive level
due to the pull-up resistor and the RESEToutput’s
reduction in sinking capability. These devices are not
recommended for applications that require a validRESEToutput below 1V.
* Factory-trimmed reset thresholds are available in approximately
100mV increments with a ±1.5% room-temperature variance.
MAX6305–MAX6313
5-Pin, Multiple-Input,
Programmable Reset ICsFigure 4. Ensuring RESETValid to VCC= 0V
Figure 5. Ensuring RESET Valid to VCC= 0V
Table 1. Factory-Trimmed Reset
Thresholds*
