MAX8211ESA ,Microprocessor Voltage Monitors with Programmable Voltage DetectionELECTRICAL CHARACTERISTICS(V = 2.65V to 5.5V, T = T to T , unless otherwise noted.)CC A MIN MAXPARA ..
MAX8211ESA ,Microprocessor Voltage Monitors with Programmable Voltage DetectionApplicationsL 4.62ComputersM 4.37T 3.06ControllersS 2.91Intelligent InstrumentsR 2.61Critical µP Po ..
MAX8211ESA ,Microprocessor Voltage Monitors with Programmable Voltage Detectionfeatures include the following:' On-Board Gating of Chip-Enable Signals1) µP reset: Assertion of RE ..
MAX8211ESA ,Microprocessor Voltage Monitors with Programmable Voltage DetectionApplicationsL 4.62ComputersM 4.37T 3.06ControllersS 2.91Intelligent InstrumentsR 2.61Critical µP Po ..
MAX8211ESA+ ,Microprocessor Voltage Monitors with Programmable Voltage DetectionApplicationsMAX8211EJA -40°C to +85°C 8 CERDIPµP Voltage MonitoringMAX8211ETY -40°C to +85°C 8 TO-9 ..
MAX8211ESA+T ,Microprocessor Voltage Monitors with Programmable Voltage Detectionapplications.The use of CMOS technology has several advantages.Figure 1. MAX8211
MB81464- ,MOS 262144 Bit DRAMfeatures page mode which allows high speed
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..
MB81C81A-35 ,CMOS 256K-BIT HIGH-SPEED SRAMMay 1990 00
Edition1.0 FUJITSU
M38 1 C8 1A-25/-35
CMOS 256K-BI T HIGH-SPEED SRAM
256K Words ..
MB81F643242C-10FN ,4 x 512K x 32 bit synchronous dynamic RAMFUJITSU SEMICONDUCTORADVANCED INFO. AE0.1EDATA SHEETMEMORYCMOS4 · 512 K · 32 BITSYNCHRONOUS DYNAMIC ..
MB81F643242C-10FN ,4 x 512K x 32 bit synchronous dynamic RAMfeatures a fully synchronous operation referenced to a positive edge clock whereby all operations a ..
MB81N643289-60FN ,8 x 256K x 32 bit double data rate FCRAMapplications where large memory density and high effective bandwidth arerequired and where a simple ..
MB8264A-10 , MOS 65536-BIT DYNAMIC RANDOM ACCESS MEMORY
MAX8211CUA-MAX8211EPA-MAX8211ESA
Microprocessor Voltage Monitors with Programmable Voltage Detection
MAX792/MAX820
Microprocessor and Non-Volatile
Memory Supervisory Circuits19-0147; Rev. 2; 6/98
General DescriptionThe MAX792/MAX820 microprocessor (µP) supervisory
circuits provide the most functions for power-supply
and watchdog monitoring in systems without battery
backup. Built-in features include the following:µP reset: Assertion of RESET and RESEToutputs dur-
ing power-up, power-down, and brownout condi-
tions. RESETis guaranteed valid for VCCdown to 1V.Manual-reset input.Two-stage power-fail warning: A separate low-line
comparator compares VCCto a preset threshold
120mV above the reset threshold; the low-line and
reset thresholds can be programmed externally.Watchdog fault output: Assertion of WDOif the watch-
dog input is not toggled within a preset timeout
period.Pulsed watchdog output: Advance warning of
impending WDOassertion from watchdog timeout
that causes hardware shutdown.Write protection of CMOS RAM, EEPROM, or other
memory devices.
The MAX792 and MAX820 are identical, except the
MAX820 guarantees higher low-line and reset threshold
accuracy (±2%).
ApplicationsComputers
Controllers
Intelligent Instruments
Critical µP Power Monitoring
FeaturesManual-Reset Input200ms Power-OK/Reset Time DelayIndependent Watchdog Timer—Preset or AdjustableOn-Board Gating of Chip-Enable SignalsMemory Write-Cycle Completion10ns (max) Chip-Enable Gate Propagation DelayVoltage Monitor for Overvoltage Warning±2% Reset and Low-Line Threshold Accuracy
(MAX820, external programming mode)
Ordering Information continued at end of data sheet.* Dice are tested at TA= +25°C, DC parameters only.
**These parts offer a choice of five different reset threshold volt-
ages. Select the letter corresponding to the desired nominal
reset threshold voltage and insert it into the blank to complete the
part number.
ypical Operating Circuit
Ordering Information
MAX792/MAX820Input Voltage (with respect to GND)
VCC.......................................................................-0.3V to +6V
All Other Inputs.......................................-0.3V to (VCC+ 0.3V)
Input Current
GND................................................................................25mA
All Other Outputs............................................................25mA
Continuous Power Dissipation (TA= +70°C)
Plastic DIP (derate 10.53mW/°C above +70°C)..........842mW
Narrow SO (derate 9.52mW/°C above +70°C)............762mW
CERDIP (derate 10.00mW/°C above +70°C)...............800mW
Operating Temperature Ranges:
MAX792_C__/MAX820_C__................................0°C to +70°C
MAX792_E__/MAX820_E__.............................-40°C to +85°C
MAX792_MJE__/MAX820_MJE__..................-55°C to +125°C
Storage Temperature Range.............................-65°C to +160°C
Lead Temperature (soldering, 10sec).............................+300°C
Microprocessor and Non-Volatile
Memory Supervisory Circuits
ELECTRICAL CHARACTERISTICS(VCC= 2.65V to 5.5V, TA= TMINto TMAX, unless otherwise noted.)
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.
ABSOLUTE MAXIMUM RATINGS
MAX792/MAX820
Microprocessor and Non-Volatile
Memory Supervisory Circuits
ELECTRICAL CHARACTERISTICS (continued)(VCC= 2.65V to 5.5V, TA= TMINto TMAX, unless otherwise noted.)
MAX792/MAX820
Microprocessor and Non-Volatile
Memory Supervisory Circuits
Note 1:The minimum operating voltage is 2.65V; however, the device is guaranteed to operate down to its preset reset threshold.
Note 2:Pulling RESET IN/INTbelow 60mV selects internal threshold mode and connects the internal voltage divider to the reset
and low-line comparators. External programming mode allows an external resistor divider to set the low-line and reset
thresholds (see Figure 4).
Note 3:The Chip-Enable Propagation delay is measured from the 50% point at CEIN to the 50% point at CEOUT.
ELECTRICAL CHARACTERISTICS (continued)(VCC= 2.65V to 5.5V, TA= TMINto TMAX, unless otherwise noted.)
MAX792/MAX820
Microprocessor and Non-Volatile
Memory Supervisory Circuits
__________________________________________Typical Operating Characteristics(TA = +25°C, unless otherwise noted.)
MAX792/MAX820
Microprocessor and Non-Volatile
Memory Supervisory Circuits
____________________________Typical Operating Characteristics (continued)(TA = +25°C, unless otherwise noted.)
MAX792/MAX820
Microprocessor and Non-Volatile
Memory Supervisory Circuits
______________________________________________________________Pin Description
MAX792/MAX820
Microprocessor and Non-Volatile
Memory Supervisory Circuits
Detailed Description
Manual-Reset InputMany µP-based products require manual-reset capabil-
ity, allowing the operator to initiate a reset. The manu-
al/external-reset input (MR)can connect directly to a
switch without an external pull-up resistor or debounc-
ing network. MRinternally connects to a 1.30V com-
parator, and has a high-impedance pull-up to VCC, as
shown in Figure 1. The propagation delay from assert-
ing MRto reset asserted is typically 12µs. Pulsing MR
low for a minimum of 25µs asserts the reset function
(see Reset Functionsection). The reset output remains
active as long as MRis held low, and the reset timeout
period begins after MRreturns high (Figure 2). To pro-
vide extra noise immunity in high-noise environments,
pull MRup to VCCwith a 100kΩresistor.
Use MRas either a digital logic input or as a second low-
line comparator. Normal TTL/CMOS levels can be
wire-OR connected via pull-down diodes (Figure 3),
and open-drain/collector outputs can be wire-ORed
directly.
Monitoring the Regulated SupplyThe MAX792/MAX820 offer two modes for monitoring
the regulated supply and providing reset and non-
maskable interrupt (NMI) signals to the µP: internal
threshold mode uses the factory preset low-line and
reset thresholds, and external programming mode
allows the low-line and reset thresholds to be pro-
grammed externally using a resistor voltage divider
(Figure 4).
Internal Threshold ModeConnecting the reset-input/internal-mode select pin
(RESET IN/INT) to ground selects internal threshold
mode (Figure 4a). In this mode, the low-line and reset
thresholds are factory preset by an internal voltage
divider (Figure 1) to the threshold voltages specified in
the Electrical Characteristics(Reset Threshold Voltage
and Low-Line Threshold Voltage). Connect the low-line
output (LOWLINE) to the µP NMI pin, and connect the
active-high reset output (RESET) or active-low reset
output (RESET) to the µP reset input pin.
Additionally, the low-line input/reference-output pin
(LLIN/REFOUT) connects to the internal 1.30V refer-
ence in internal threshold mode. Buffer LLIN/REFOUT
with a high-impedance buffer to use it with external
circuitry. In this mode, when VCCis falling, LOWLINEis
guaranteed to be asserted prior to reset assertion.
External Programming ModeConnecting RESET IN/INTto a voltage above 600mV
selects external programming mode. In this mode, the
low-line and reset comparators disconnect from the inter-
nal voltage divider and connect to LLIN/REFOUT and
RESET IN/INT, respectively (Figure 1). This mode allows
flexibility in determining where in the operating voltage
range the NMI and reset are generated. Set the low-line
and reset thresholds with an external resistor divider, as in
Figure 4b or Figure 4c. RESET typically remains valid for
VCCdown to 2.5V; RESETis guaranteed to be valid with
VCCdown to 1V.
Calculate the values for the resistor voltage divider in
Figure 4b using the following equations:
1) R3 = (1.30 x VCCMAX)/(VLOW LINEx IMAX)
2) R2 = [(1.30 x VCCMAX)/(VRESETx IMAX)] - R3
3) R1 = (VCCMAX/IMAX) - (R2 + R3).
First choose the desired maximum current through the
voltage divider (IMAX) when VCCis at its highest (VCC
MAX). There are two things to consider here. First, IMAX
contributes to the overall supply current for the circuit, so
you would generally make it as small as possible.
Second, IMAXcannot be too small or leakage currents will
adversely affect the programmed threshold voltages; 5µA
is often appropriate. Determine R3 after you have chosen
IMAX. Use the value for R3 to determine R2, then use both
R2 and R3 to determine R1.
For example, to program a 4.75V low-line threshold and a
4.4V reset threshold, first choose IMAXto be 5µA when
VCC= 5.5V and substitute into equation 1.
R3 = (1.30 x 5.5)/(4.75 x 5E-6) = 301.05kΩ.
301kΩis the nearest standard 0.1% value. Substitute
into equation 2:
R2 = [(1.30 x 5.5)/(4.4 x 5E-6)] - 301kΩ= 23.95kΩ.
The nearest 0.1% resistor value is 23.7kΩ. Finally, sub-
stitute into equation 3:
R1 = (5.5/5E-6) - (23.7kΩ+ 301kΩ) = 775kΩ.
The nearest 0.1% value resistor is 787kΩ. Determine the
actual low-line threshold by rearranging equation 1 and
plugging in the standard resistor values. The actual low-
line threshold is 4.75V and the actual reset threshold is
4.40V. An additional resistor allows the MAX792/MAX820
to monitor the unregulated supply and provide an NMI
before the regulated supply begins to fall (Figure 4c).
Both of these thresholds will vary from circuit to circuit
with resistor tolerance, reference variation, and compara-
tor offset variation. The initial thresholds for each circuit
will also vary with temperature due to reference and off-
set drift. For highest accuracy, use the MAX820.
