MAX6303CSA ,+5V, Low-Power uP Supervisory Circuits with Adjustable Reset/WatchdogFeaturesThe MAX6301/MAX6302/MAX6303/MAX6304* low- ' Adjustable Reset Thresholdpower microprocessor ..
MAX6303CSA ,+5V, Low-Power uP Supervisory Circuits with Adjustable Reset/WatchdogFeaturesThe MAX6301/MAX6302/MAX6303/MAX6304* low- ' Adjustable Reset Thresholdpower microprocessor ..
MAX6303CSA ,+5V, Low-Power uP Supervisory Circuits with Adjustable Reset/WatchdogMAX6301–MAX6304 19-1078; Rev 0; 6/96+5V, Low-Power µP Supervisory Circuits with Adjustable Reset/Wa ..
MAX6303CSA+ ,+5V, Low-Power, µP Supervisory Circuits with Adjustable Reset/WatchdogGeneral Description ________
MAX6303CSA+T ,+5V, Low-Power, µP Supervisory Circuits with Adjustable Reset/WatchdogFeaturesThe MAX6301–MAX6304* low-power microprocessor♦ Adjustable Reset Threshold(µP) supervisory c ..
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MAX6301CSA-MAX6301CUA-MAX6301EPA-MAX6301ESA-MAX6302CPA-MAX6302CSA-MAX6302ESA-MAX6303CPA-MAX6303CSA-MAX6303CUA-MAX6303EPA-MAX6303ESA-MAX6304CPA-MAX6304CSA
+5V, Low-Power uP Supervisory Circuits with Adjustable Reset/Watchdog
_______________General DescriptionThe MAX6301/MAX6302/MAX6303/MAX6304* low-
power microprocessor (µP) supervisory circuits provide
maximum adjustability for reset and watchdog functions.
The reset threshold can be adjusted to any voltage
above 1.22V, using external resistors. In addition, the
reset and watchdog timeout periods are adjustable
using external capacitors. A watchdog select pin
extends the watchdog timeout period to 500x. The reset
function features immunity to power-supply transients.
These four devices differ only in the structure of their reset
outputs (see Selector Guide). The MAX6301–MAX6304
are available in the space-saving 8-pin µMAX package,
as well as 8-pin DIP/SO.
________________________ApplicationsMedical EquipmentEmbedded Controllers
Intelligent InstrumentsCritical µP Monitoring
Portable EquipmentSet-Top Boxes
Battery-Powered Computers
Computers/Controllers
____________________________FeaturesAdjustable Reset ThresholdAdjustable Reset TimeoutAdjustable Watchdog Timeout500x Watchdog Timeout Multiplier4µA Supply CurrentRESET or RESET
Output OptionsPush/Pull or Open-Drain Output OptionsGuaranteed RESETAsserted At or Above
VCC= 1V (MAX6301/MAX6303)Power-Supply Transient ImmunityWatchdog Function Can Be DisabledDIP/SO/µMAX Packages Available
MAX6301–MAX6304
+5V, Low-Power µP Supervisory Circuits
with Adjustable Reset/Watchdog
__________________Pin Configuration
__________Typical Operating Circuit19-1078; Rev 0; 6/96
_____________________Selector Guide* Patents pending
MAX6301–MAX6304
+5V, Low-Power µP Supervisory Circuits
with Adjustable Reset/Watchdog
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS(VCC= +2V to +5.5V, TA= TMINto TMAX, unless otherwise noted. Typical values are at VCC= +5V and 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 +7.0V
RESET IN, SWT, SRT..................................-0.3V to (VCC+ 0.3V)
WDI, WDS..............................................................-0.3V to +7.0V
RESET, RESET
MAX6301...........................................................-0.3V to +7.0V
MAX6302/6303/6304..............................-0.3V to (VCC+ 0.3V)
Input Current
VCC...............................................................................±20mA
GND..............................................................................±20mA
Output Current
RESET, RESET..............................................................±20mA
Continuous Power Dissipation (TA= +70°C)
Plastic DIP (derate 9.09mW/°C above +70°C)............727mW
SO (derate 5.88mW/°C above +70°C).........................471mW
µMAX (derate 4.10mW/°C above +70°C)....................330mW
Operating Temperature Ranges
MAX630_C_A......................................................0°C to +70°C
MAX630_E_A...................................................-40°C to +85°C
Storage Temperature Range.............................-65°C to +160°C
Lead Temperature (soldering, 10sec).............................+300°C
MAX6301–MAX6304
+5V, Low-Power µP Supervisory Circuits
with Adjustable Reset/Watchdog10,000
RESET TIMEOUT PERIOD
vs. CSRT
6301-4 TOC-01
CSRT (nF)
RESET TIMEOUT PERIOD (ms)
10,000
EXTENDED-MODE
WATCHDOG TIMEOUT PERIOD vs. CSWT
(WDS = VCC)
6301-4 TOC-02
CSWT (nF)
WATCHDOG TIMEOUT PERIOD (sec)
100010,000
NORMAL-MODE
WATCHDOG TIMEOUT PERIOD vs. CSWT
(WDS = GND)
6301-4 TOC-03
CSWT (nF)
WATCHDOG TIMEOUT PERIOD (ms)
ELECTRICAL CHARACTERISTICS (continued)
(VCC= +2V to +5.5V, TA= TMINto TMAX, unless otherwise noted. Typical values are at VCC= +5V and TA= +25°C.)
Note 1:Reset is guaranteed valid from the selected reset threshold voltage down to the minimum VCC.
Note 2:VDS = VCC, WDI unconnected.
Note 3:Precision timing currents of 500nA are present at both the SRT and SWT pins. Timing capacitors connected to these nodes
must have low leakage consistent with these currents to prevent timing errors.
Note 4:The sink/source is supplied through a resistor, and is proportional to VCC(Figure 8). At VCC= 2V, it is typically ±24µA.
__________________________________________Typical Operating Characteristics(CSWT= CSRT= 1500pF, TA= +25°C, unless otherwise noted.)
MAX6301–MAX6304
+5V, Low-Power µP Supervisory Circuits
with Adjustable Reset/Watchdog
____________________________Typical Operating Characteristics (continued)(CSWT= CSRT= 1500pF, TA= +25°C, unless otherwise noted.)
SUPPLY CURRENT
vs. TEMPERATURE
6301-4 TOC-07
TEMPERATURE (°C)
SUPPLY CURRENT (
RESET IN THRESHOLD VOLTAGE
vs. TEMPERATURE
6301-4 TOC-08
TEMPERATURE (°C)
RESET REFERENCE VOLTAGE (V)
VCC TO RESET DELAY
vs. TEMPERATURE (VCC FALLING)
6301-4 TOC-09
TEMPERATURE (°C)
PROPAGATION DELAY (
RESET AND WATCHDOG
TIMEOUT vs. VCC
6301-4 TOC-10
SUPPLY VOLTAGE (V)
tRP
(ms)23546
SUPPLY CURRENT vs.
SUPPLY VOLTAGE
6301-4 TOC-04
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (
RESET AND NORMAL-MODE
WATCHDOG TIMEOUT PERIOD
vs. TEMPERATURE
6301-4 TOC-05
TEMPERATURE (°C)
tRP
(ms)
6301-4 TOC-06
RESET THRESHOLD OVERDRIVE (mV)
TRANSIENT DURATION (
MAXIMUM TRANSIENT DURATION vs.
RESET THRESHOLD OVERDRIVE (VRST)
MAX6301–MAX6304
+5V, Low-Power µP Supervisory Circuits
with Adjustable Reset/Watchdog
______________________________________________________________Pin Description
_______________Detailed Description
Reset Function/OutputThe reset output is typically connected to the reset
input of a microprocessor (µP). A µP’s reset input starts
or restarts the µP in a known state. The MAX6301–
MAX6304 µP supervisory circuits provide the reset
logic to prevent code-execution errors during power-
up, power-down, and brownout conditions (see Typical
Operating Circuit).
For the MAX6301/MAX6303, RESETchanges from high
to low whenever the monitored voltage (VIN) drops
below the reset threshold voltage (VRST). RESET
remains low as long as VINis below VRST. Once VIN
exceeds VRST, RESETremains low for the reset timeout
period, then goes high. When a reset is asserted due to
a watchdog timeout condition, RESETstays low for the
reset timeout period. Anytime reset asserts, the watch-
dog timer clears. At the end of the reset timeout period,
RESETgoes high and the watchdog timer is restarted
from zero. If the watchdog timeout period is exceeded
again, then RESETgoes low again. This cycle contin-
ues unless WDI receives a transition.
On power-up, once VCCreaches 1V, RESETis guaran-
teed to be a logic low. For information about applica-
tions where VCCis less than 1V, see the section
Ensuring a Valid RESET/RESET Output Down to VCC=
0V (MAX6303/MAX6304). As VCCrises, RESETremains
low. When VINrises above VRST, the reset timer starts
and RESETremains low. When the reset timeout period
ends, RESETgoes high.
On power-down, once VINgoes below VRST, RESET
goes low and is guaranteed to be low until VCCdroops
below 1V. For information about applications where
VCCis less than 1V, see the section Ensuring a Valid
RESET/RESET Output Down to VCC= 0V (MAX6303/
MAX6304).
The MAX6302/MAX6304 active-high RESET output is
the inverse of the MAX6301/MAX6303 active-low
RESEToutput, and is guaranteed valid for VCC>1.31V.
Reset ThresholdThese supervisors monitor the voltage on RESET IN.
The MAX6301–MAX6304 have an adjustable reset
threshold voltage (VRST) set with an external resistor
voltage divider (Figure 1). Use the following formula to
calculate VRST(the point at which the monitored volt-
age triggers a reset):
where VRSTis the desired reset threshold voltage and
VTHis the reset input threshold (1.22V). Resistors R1 and
R2 can have very high values to minimize current con-
sumption. Set R2 to some conveniently high value (1MΩ,
for example) and calculate R1 based on the desired
reset threshold voltage, using the following formula:
Watchdog TimerThe watchdog circuit monitors the µP’s activity. If the µP
does not toggle the watchdog input (WDI) within tWD
(user selected), reset asserts. The internal watchdog
timer is cleared by reset, by a transition at WDI (which
can detect pulses as short as 30ns), or by a transition
at WDS. The watchdog timer remains cleared while
reset is asserted; as soon as reset is released, the timer
starts counting (Figure 2).
The MAX6301–MAX6304 feature two modes of watch-
dog timer operation: normal mode and extended mode.
In normal mode (WDS = GND), the watchdog timeout
period is determined by the value of the capacitor con-
nected between SWT and ground (see the section
Selecting the Reset and Watchdog Timeout Capacitor).
In extended mode (WDS = VCC), the watchdog timeout
period is multiplied by 500. For example, in the extend-
ed mode, a 1µF capacitor gives a watchdog timeout
period of 22 minutes (see the graph Extended-Mode
Watchdog Timeout Period vs. CSWTin the Typical
Operating Characteristics).
In extended mode, the watchdog function can be dis-
abled by leaving WDI unconnected or by three-stating
the driver connected to WDI. In this mode, the watch-
dog input is internally driven low during the watchdogR2V1RST−() ΩVR1R2 VRST=()()
MAX6301–MAX6304
+5V, Low-Power µP Supervisory Circuits
with Adjustable Reset/Watchdog
