MAX809SEUR+T ,3-Pin Microprocessor Reset CircuitsMAX803/MAX809/ 3-Pin Microprocessor Reset CircuitsMAX810
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MAX803LEXR-MAX803LEXR+-MAX803LEXR+T-MAX803MEXR-MAX803MEXR+T-MAX803REXR+-MAX803REXR+T-MAX803SEXR-MAX803SEXR+-MAX803SEXR+T-MAX803TEXR+-MAX803TEXR+T-MAX803ZEXR+-MAX809JEUR-MAX809JEUR+T-MAX809LEUR-MAX809LEUR+T-MAX809LEUR-TG05-MAX809LEXR+-MAX809MEUR-MAX809MEUR+-M
3-Pin Microprocessor Reset Circuits
General DescriptionThe MAX803/MAX809/MAX810 are microprocessor (μP)
supervisory circuits used to monitor the power supplies in μP and digital systems. They provide excellent circuit reliability and low cost by eliminating external components and adjustments when used with +5V, +3.3V, +3.0V, or +2.5V powered circuits.
These circuits perform a single function: they assert a reset signal whenever the VCC supply voltage declines below a preset threshold, keeping it asserted for at least
140ms after VCC has risen above the reset threshold.
Reset thresholds suitable for operation with a variety of supply voltages are available.
The MAX803 has an open-drain output stage, while the MAX809/MAX810 have push-pull outputs. The MAX803’s
open-drain RESET output requires a pullup resistor that can be connected to a voltage higher than VCC. The
MAX803/MAX809 have an active-low RESET output, while the MAX810 has an active-high RESET output. The reset comparator is designed to ignore fast transients on
VCC, and the outputs are guaranteed to be in the correct logic state for VCC down to 1V.
Low supply current makes the MAX803/MAX809/MAX810 ideal for use in portable equipment. The MAX803 is available in a 3-pin SC70 package, and the MAX809/MAX810 are available in 3-pin SC70 or SOT23 packages.
Applications●Computers●Controllers●Intelligent Instruments●Critical μP and μC Power Monitoring●Portable/Battery-Powered Equipment●Automotive
Beneits and Features●Precision Monitoring of +2.5V, +3V, +3.3V, and +5V Power-Supply Voltages●Fully Specified Over Temperature●Available in Three Output Configurations • Open-Drain RESET Output (MAX803) • Push-Pull RESET Output (MAX809) • Push-Pull RESET Output (MAX810)●140ms (min) Power-On-Reset Pulse Width●12μA Supply Current●Guaranteed Reset Valid to VCC = +1V●Power Supply Transient Immunity●No External Components●3-Pin SC70 and SOT23 Packages
MAX803
MAX809VCC
VCC
RPULLUP*
RESETRESET
INPUT
GND
VCC
GND
*MAX803 ONLY
Selector Guide and Ordering Information appear at end of data sheet.
MAX803/MAX809/
MAX810
3-Pin Microprocessor Reset Circuits
Typical Operating Circuit
Terminal Voltage (with respect to GND)
VCC ...................................................................-0.3V to +6.0V RESET, RESET (push-pull) ..................-0.3V to (VCC + 0.3V)
RESET (open drain) .........................................-0.3V to +6.0V
Input Current, VCC .............................................................20mAOutput Current, RESET, RESET ........................................20mA
Rate of Rise, VCC ..........................................................100V/μs
Continuous Power Dissipation (TA = +70°C) 3-Pin SC70 (derate 2.17mW/°C above +70°C) ...........174mW 3-Pin SOT23 (derate 4mW/°C above +70°C) .............320mWOperating Temperature Range 3-Pin SC70 ...................................................-40°C to +125°C 3-Pin SOT23 .................................................-40°C to +105°CStorage Temperature Range .............................-65°C to +150°CLead Temperature (soldering, 10s) .................................+300°CSoldering Temperature (reflow) .......................................+260°C
(VCC = full range, TA = -40°C to +105°C (SOT23) or TA = -40°C to +125°C (SC70), unless otherwise noted. Typical values are at TA = +25°C, VCC = 5V for L/M/J versions, VCC = 3.3V for T/S versions, VCC = 3V for R version, and VCC = 2.5V for Z version.) (Note 1)
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITSVCC Range
TA = 0°C to +70°C1.05.5TA = -40°C to +105°C (MAX8_ _ _EUR)1.25.5
TA = -40°C to +125°C (MAX8_ _ _EXR)1.25.5
Supply Current (SOT23)ICC
TA = -40°C to +85°C
VCC < 5.5V, MAX8_ _L/M2460
VCC < 3.6V, MAX8_ _R/S/T/Z1750
TA = +85°C to +105°C
VCC < 5.5V, MAX8_ _L/M100
VCC < 3.6V, MAX8_ _R/S/T/Z100
Supply Current (SC70)ICC
TA = -40°C to +85°C
VCC < 5.5V, MAX8_ _L/M2435
VCC < 3.6V, MAX8_ _R/S/T/Z1730
TA = +85°C to +125°C
VCC < 5.5V, MAX8_ _L/M60
VCC < 3.6V, MAX8_ _R/S/T/Z60
Reset Threshold(SOT only)VTH
MAX8_ _L
TA = +25°C4.564.634.70
TA = -40°C to +85°C4.504.75
TA = -40°C to +125°C4.404.86
MAX8_ _M
TA = +25°C4.314.384.45
TA = -40°C to +85°C4.254.50
TA = -40°C to +125°C4.164.56
MAX809J(SOT only)
TA = +25°C3.934.004.06
TA = -40°C to +85°C3.894.10
TA = -40°C to +125°C3.804.20
MAX8_ _T
TA = +25°C3.043.083.11
TA = -40°C to +85°C3.003.15
TA = -40°C to +125°C2.923.23
MAX8_ _S
TA = +25°C2.892.932.96
TA = -40°C to +85°C2.853.00
TA = -40°C to +125°C2.783.08
MAX8_ _R
TA = +25°C2.592.632.66
TA = -40°C to +85°C2.552.70
MAX803/MAX809/
MAX810
3-Pin Microprocessor Reset Circuits
Absolute Maximum RatingsStresses 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.
Electrical Characteristics
(VCC = full range, TA = -40°C to +105°C (SOT23) or TA = -40°C to +125°C (SC70), unless otherwise noted. Typical values are at TA = +25°C, VCC = 5V for L/M/J versions, VCC = 3.3V for T/S versions, VCC = 3V for R version, and VCC = 2.5V for Z version.) (Note 1)
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITSReset Threshold(SC70 only)VTH
MAX8_ _L
TA = +25°C4.564.634.70
TA = -40°C to +85°C4.504.75
TA = -40°C to +125°C4.444.82
MAX8_ _M
TA = +25°C4.314.384.45
TA = -40°C to +85°C4.254.50
TA = -40°C to +125°C4.204.56
MAX8_ _T
TA = +25°C3.043.083.11
TA = -40°C to +85°C3.003.15
TA = -40°C to +125°C2.953.21
MAX8_ _S
TA = +25°C2.892.932.96
TA = -40°C to +85°C2.853.00
TA = -40°C to +125°C2.813.05
MAX8_ _R
TA = +25°C2.592.632.66
TA = -40°C to +85°C2.552.70
TA = -40°C to +125°C2.522.74
MAX8_ _Z(SC70 only)
TA = +25°C2.282.322.35
TA = -40°C to +85°C2.252.38
TA = -40°C to +125°C2.222.42
Reset Threshold Tempco30ppm/°C
VCC to Reset Delay (Note 2)VCC = VTH to (VTH - 100mV)20µs
Reset Active Timeout Period (SOT23)
TA = -40°C to +85°C140240560msTA = +85°C to +105°C100840
Reset Active Timeout Period (SC70)
TA = -40°C to +85°C140240460msTA = +85°C to +125°C100840
RESET Output Voltage Low
(push-pull active low and open-
drain active low, MAX803 and MAX809)
VOL
VCC = VTH (min), ISINK = 1.2mA, MAX803R/S/T/Z, MAX809R/S/T/Z0.3VCC = VTH (min), ISINK = 3.2mA,
MAX803L/M, MAX809J/L/M0.4
VCC > 1.0V, ISINK = 50µA0.3
RESET Output Voltage High (push-pull active low MAX809)VOH
VCC > VTH (max), ISOURCE = 500µA, MAX803R/S/T/Z, MAX809R/S/T/Z0.8VCCVCC > VTH (max), ISOURCE = 800µA,
MAX803L/M, MAX809J/L/MVCC - 1.5
RESET Output Voltage Low (push-pull active high, MAX810)VOL
VCC = VTH (max), ISINK = 1.2mA, MAX810R/S/T/Z0.3VCC = VTH (max), ISINK = 3.2mA,
MAX810L/M0.4
MAX803/MAX809/
MAX810
3-Pin Microprocessor Reset Circuits
Electrical Characteristics (continued)
(VCC = full range, TA = -40°C to +105°C (SOT23) or TA = -40°C to +125°C (SC70), unless otherwise noted. Typical values are at TA = +25°C, VCC = 5V for L/M/J versions, VCC = 3.3V for T/S versions, VCC = 3V for R version, and VCC = 2.5V for Z version.) (Note 1)
Note 1: Production testing done at TA = +25°C; limits over temperature guaranteed by design only.
Note 2: RESET output for MAX803/MAX809; RESET output for MAX810.
Note 3: Guaranteed by design, not production tested.
(VCC = full range, TA = -40°C to +105°C, unless otherwise noted. Typical values are at TA = +25°C, VCC = +5V for L/M/J versions,
VCC = +3.3V for T/S versions, VCC = +3V for R version, and VCC = +2.5V for Z version.)
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITSRESET Output Voltage High (push-pull active high, MAX810)VOH1.8V < VCC < VTH (min), ISOURCE = 150µA0.8VCCV
RESET Open-Drain Output Leakage Current (MAX803)(Note 3)
VCC > VTH, RESET deasserted1µA
POWER-DOWN RESET DELAY vs.
TEMPERATURE (MAX8_ _R/S/T/Z)MAX803-TOC3
TEMPERATURE (°C)
POWER-DOWN RESET DELAY (µs)
VOD = VTH - VCC
VOD = 20mV
VOD = 10mV
VOD = 200mV
VOD = 100mV
POWER-DOWN RESET DELAY vs.
TEMPERATURE (MAX8_ _J/L/M)MAX803-TOC4
TEMPERATURE (°C)
POWER-DOWN RESET DELAY (µs)
VOD = VTH - VCC
VOD = 10mV
VOD = 100mV
VOD = 200mV
VOD = 20mV
POWER-UP RESET TIMEOUT
vs. TEMPERATURE
MAX803-TOC5
POWER-UP RESET TIMEOUT (µs)
MAX8_ _R/S/T/Z
MAX8_ _J/L/M
NORMALIZED RESET THRESHOLD
vs. TEMPERATURE
MAX803-TOC6
NORMALIZED THRESHOLD
SUPPLY CURRENT vs. TEMPERATURE
(SC70 PACKAGE, NO LOAD)
MAX803 toc01
TEMPERATURE (°C)
SUPPLY CURRENT (µA)
MAX8_ _R/S/T, VCC = 3.3V
MAX8_ _L/M/R/S/T/Z, VCC = 1V
MAX8_ _Z, VCC = 2.5V
MAX8_ _L/M, VCC = 5V
MAX803/MAX809/
MAX810
3-Pin Microprocessor Reset Circuits
Electrical Characteristics (continued)
Typical Operating Characteristics
Detailed DescriptionA microprocessor’s (μP’s) reset input starts the μP in a known state. The MAX803/MAX809/MAX810 assert reset to prevent code-execution errors during power-up, power-down, or brownout conditions. They assert a reset signal
whenever the VCC supply voltage declines below a preset threshold, keeping it asserted for at least 140ms after VCC has risen above the reset threshold. The MAX803 uses
an open-drain output, and the MAX809/MAX810 have a push-pull output stage. Connect a pullup resistor on the MAX803’s RESET output to any supply between 0 and 6V.
Applications Information
Negative-Going VCC TransientsIn addition to issuing a reset to the μP during power-up,
power-down, and brownout conditions, the MAX803/
MAX809/MAX810 are relatively immune to short-duration negative-going VCC transients (glitches).
Figure 1 shows typical transient duration vs. reset
comparator overdrive, for which the MAX803/MAX809/
to VCC, starting 0.5V above the actual reset threshold and ending below it by the magnitude indicated (reset comparator overdrive). The graph indicates the maximum pulse width a negative-going VCC transient can have with-out causing a reset pulse. As the magnitude of the transient increases (goes farther below the reset threshold), the maximum allowable pulse width decreases. Typically, for the MAX8__L and MAX8__M, a VCC transient that goes 100mV below the reset threshold and lasts 20μs or less will not cause a reset pulse. A 0.1μF bypass capacitor mounted
as close as possible to the VCC pin provides additional transient immunity.
Ensuring a Valid Reset Output Down to
VCC = 0VWhen VCC falls below 1V, the MAX809 RESET output no longer sinks current—it becomes an open circuit.
Therefore, high-impedance CMOS logic inputs connect-
ed to RESET can drift to undetermined voltages. This
presents no problem in most applications since most μP and other circuitry is inoperative with VCC below 1V.
However, in applications where RESET must be valid down to 0V, adding a pull-down resistor to RESET causes any stray leakage currents to flow to ground, holding
RESET low (Figure 2). R1’s value is not critical; 100kΩ is large enough not to load RESET and small enough to pull
RESET to ground.
A 100kΩ pullup resistor to VCC is also recommended for the MAX810 if RESET is required to remain valid for VCC < 1V.
Interfacing to μPs with Bidirectional Reset
PinsSince the RESET output on the MAX803 is open drain, this device interfaces easily with μPs that have bidirectional reset pins, such as the Motorola 68HC11. Connecting the μP supervisor’s RESET output directly to the μC’s RESET pin with a single pullup resistor allows either device to assert reset (Figure 3).
MAX803 Open-Drain RESET Output Allows Use with Multiple SuppliesGenerally, the pullup connected to the MAX803 will connect to the supply voltage that is being monitored at the IC’s VCC pin. However, some systems may use the open-
drain output to level-shift from the monitored supply to reset circuitry powered by some other supply (Figure 4). Note that as the MAX803’s VCC decreases below 1V, so does the IC’s ability to sink current at RESET. Also, with any
pullup, RESET will be pulled high as VCC decays toward 0. The voltage where this occurs depends on the pullup
PINNAMEFUNCTIONGNDGround
RESET
(MAX803/ MAX809)
RESET Output remains low while VCC
is below the reset threshold, and for at
least 140ms after VCC rises above the reset threshold.
RESET (MAX810)
RESET Output remains high while VCC
is below the reset threshold, and for at
least 140ms after VCC rises above the reset threshold.VCCSupply Voltage (+5V, +3.3V, +3.0V, or +2.5V)
TOP VIEW
RESET (RESET)GND
VCC
MAX803
MAX809
MAX810
SC70-3/SOT23-3( ) ARE FOR MAX810.
MAX803 AVAILABLE IN SC70-3 ONLY.
MAX803/MAX809/
MAX810
3-Pin Microprocessor Reset Circuits
Pin Description
Pin Coniguration
Beneits of Highly Accurate Reset ThresholdMost μP supervisor ICs have reset-threshold voltages
between 5% and 10% below the value of nominal supply voltages. This ensures a reset will not occur within 5% of
the nominal supply, but will occur when the supply is 10% below nominal.
When using ICs rated at only the nominal supply ±5%,
this leaves a zone of uncertainty where the supply is
between 5% and 10% low, and where the reset may or may not be asserted.
The MAX8_ _L/T/Z use highly accurate circuitry to ensure that reset is asserted close to the 5% limit, and long before the supply has declined to 10% below nominal.
RESET COMPARATOR OVERDRIVE, VTH - VCC (mV)
MAXIMUM TRANSIENT DURATION (µs)
TA = +25°C
MAX8_ _J/L/M
MAX8_ _R/S/T/Z
RESET
GND
RESET
INPUT
MAX803MOTOROLA
68HCXXGND
VCC
VCC
VCC
100kΩ
VCC
GND
MAX809RESET
RESET
GND
RESET
INPUT
RPULLUP
MAX8035V SYSTEM
GND
VCC
+3.3V+5.0V
VCC
Figure 1. Maximum Transient Duration Without Causing a
Reset Pulse vs. Reset Comparator OverdriveFigure 3. Interfacing to μPs with Bidirectional Reset I/O
Figure 2. RESET Valid to VCC = Ground Circuit
Figure 4. MAX803 Open-Drain RESET Output Allows Use with
Multiple Supplies
MAX803/MAX809/
MAX810
3-Pin Microprocessor Reset Circuits
