View MAX6342_151805.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

19-1568; Rev 0; 10/99
6-Pin P Reset Circuit with Power-Fail Comparator
General Description
The MAX6342-MAX6345 family of microprocessor (P) supervisory circuits monitors power supplies in digital systems. These devices significantly improve system reliability and accuracy compared to separate ICs or discrete components. The MAX6342-MAX6345 provide factory-trimmed VCC reset threshold voltages from 2.33V to 4.63V and operate with supply voltages between +1V and +5.5V. A +1.25V threshold detector allows for a power-fail warning, for lowbattery detection, or for monitoring another power supply. The MAX6342 contains an MR input and an active-low push-pull reset. The MAX6343 and MAX6344 are identical to the MAX6342 except they provide an active-low, opendrain reset and an active-high, push-pull reset, respectively. The MAX6345 provides a second reset output in place of the MR input to give it an active-high push-pull reset and an active-low push-pull reset. All of the devices are packaged in a miniature 6-pin SOT23. o Small 6-Pin SOT23 Package o Precision Factory-Set VCC Reset Thresholds Between 2.33V and 4.63V o Guaranteed RESET Valid to VCC = +1V o 100ms min Reset Pulse Width o Debounced CMOS-Compatible Manual-Reset Input o Voltage Monitor for Power-Fail or Low-Battery Warning
Features
MAX6342-MAX6345
Ordering Information
PART MAX6342_UT-T MAX6343_UT-T MAX6344_UT-T MAX6345_UT-T TEMP. RANGE -40C to +85C -40C to +85C -40C to +85C -40C to +85C PIN-PACKAGE 6 SOT23-6 6 SOT23-6 6 SOT23-6 6 SOT23-6
Applications
Portable Computers Telecom Equipment Networking Equipment Portable/Battery-Powered Equipment Multivoltage Systems Embedded Control Systems
Typical Operating Circuit appears at end of data sheet.
Note: The MAX6342-MAX6345 are available with factory-set reset thresholds from 2.33V to 4.63V (see Selector Guides 1, 2). Insert the letter corresponding to the desired nominal reset threshold into the blank following the part number. There is a 2500 piece order increment required for the SOT package. SOT Top Marks table appears at end of data sheet. All versions of these products may not be available at time of announcement. Contact factory for availability.
Pin Configurations
TOP VIEW
VCC 1 6 RESET (RESET)
Selector Guide 1
SUFFIX RESET THRESHOLD (V) 4.63 4.38 3.08 2.93 2.63 2.33
L
M T S R Z
GND 2
MAX6342 MAX6343 MAX6344
5
MR
PFI 3
4
PFO
( ) ARE FOR MAX6344 ONLY. SOT23-6 Pin Configurations continued at end of data sheet.
Selector Guide 2
PART MAX6342 MAX6343 MAX6344 MAX6345 -- -- -- -- -- 1 PUSH-PULL RESET OUTPUT OPEN-DRAIN RESET OUTPUT -- PUSH-PULL RESET OUTPUT -- -- MANUAL-RESET INPUT
________________________________________________________________ Maxim Integrated Products
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800. For small orders, phone 1-800-835-8769.
6-Pin P Reset Circuit with Power-Fail Comparator MAX6342-MAX6345
ABSOLUTE MAXIMUM RATINGS
VCC to GND ..............................................................-0.3V to +6V RESET, RESET (MAX6342/MAX6344/MAX6345) ......... -0.3V to (VCC + 0.3V) RESET (MAX6343)................................................... -0.3V to +6V MR, PFI, PFO ..............................................-0.3V to (VCC + 0.3V) Input Current, VCC ..............................................................50mA Output Current, RESET, RESET ..........................................50mA Continuous Power Dissipation (TA = +70C) 6-Pin SOT23 (derate 4mW/C above +70C).............320mW Operating Temperature Range ...........................-40C to +85C Junction Temperature ......................................................+150C Storage Temperature Range .............................-65C to +150C Lead Temperature Range (soldering, 10sec)................. +300C
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.
ELECTRICAL CHARACTERISTICS
(VCC = +1.0V to +5.5V, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C and VCC = +3V.) (Note 1) PARAMETER Supply Voltage Range SYMBOL VCC ICC CONDITIONS TA = 0C to +70C TA = -40C to +85C Supply Current No load MAX634_L MAX634_M MAX634_T Reset Threshold VTH MAX634_S MAX634_R MAX634_Z VCC to Reset Delay Reset Timeout Period tRP VCC > 1.2V, ISINK = 100A VOL RESET and RESET Outputs Drive Capability (Note 2) VOH VCC > 2.7V, ISINK = 1.2mA VCC > 4.5V, ISINK = 3.2mA VCC > 1.2V, ISOURCE = 50A VCC > 2.7V, ISOURCE = 500A (MAX6342/MAX6345 only) VCC > 4.5V, ISOURCE = 800A (MAX6342/MAX6345 only) 0.8 * VCC 0.8 * VCC 0.8 * VCC VCC = 3V VCC = 5.5V TA = +25C TA = -40C to +85C TA = +25C TA = -40C to +85C TA = +25C TA = -40C to +85C TA = +25C TA = -40C to +85C TA = +25C TA = -40C to +85C TA = +25C TA = -40C to +85C 4.56 4.50 4.31 4.25 3.03 3.00 2.89 2.85 2.59 2.55 2.30 2.25 20 100 180 280 0.4 0.3 0.4 V V 2.33 2.63 2.93 3.08 4.38 MIN 1.0 1.2 25 30 4.63 TYP MAX 5.5 5.5 40 50 4.70 4.75 4.45 4.50 3.13 3.15 2.97 3.00 2.67 2.70 2.36 2.38 s ms V A UNITS V
VCC = VTH to (VTH - 100mV)
2
_______________________________________________________________________________________
6-Pin P Reset Circuit with Power-Fail Comparator
ELECTRICAL CHARACTERISTICS (continued)
(VCC = +1.0V to +5.5V, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C and VCC = +3V.) (Note 1) PARAMETER Open-Drain RESET Output Leakage Current MR Input Low MR Input High MR Pull-Up Resistance MR Minimum Pulse Width MR Glitch Rejection MR to Reset Delay PFI Input Threshold PFI Leakage Current PFO Output Voltage PFO Output Voltage PFO Output Short-Circuit Current PFI to PFO Delay VOL VOH VCC = 4.5V, ISINK = 3.2mA VCC = 4.5V, ISOURCE = 800A Output sink current Output source current VOVERDRIVE = 15mV 0.8 * VCC 20 5 3 1.2 SYMBOL ILKG VIL VIH 0.7 * VCC 60 1 0.1 0.2 1.25 0.01 1.3 25 0.4 CONDITIONS MAX6343 only, VCC > VTH(MAX) MIN TYP MAX 1 0.3 * VCC UNITS A V V k s s s V nA V V mA s
MAX6342-MAX6345
Note 1: Overtemperature limits are guaranteed by design and not production tested. Note 2: Apply to each part in accordance with threshold voltage, output configuration, and manual reset status selected.
Typical Operating Characteristics
(VPFI = VCC = +5V, TA = +25C, unless otherwise noted.)
MAX6344L/MAX6345L RESET OUTPUT VOLTAGE vs. SUPPLY VOLTAGE
MAX6342-02
SUPPLY CURRENT vs. SUPPLY VOLTAGE AND TEMPERATURE
VCC = 5V 25 SUPPLY CURRENT (A) VCC = 3.3V 20 15 10 VCC = 1V 5 0 -40 -15 10 35 60 85 VCC = 2.5V 1V/div
MAX6342-01
MAX6342M/MAX6345M RESET OUTPUT VOLTAGE vs. SUPPLY VOLTAGE
MAX6342-03
30
VCC
VCC
1V/div RESET 0 0 RESET
0 0
1sec/div
1sec/div
TEMPERATURE (C)
_______________________________________________________________________________________
3
6-Pin P Reset Circuit with Power-Fail Comparator MAX6342-MAX6345
Typical Operating Characteristics (continued)
(VPFI = VCC = +5V, TA = +25C, unless otherwise noted.)
PFO OUTPUT VOLTAGE HIGH vs. SUPPLY VOLTAGE
MAX6342-04
PFO OUTPUT VOLTAGE LOW vs. SUPPLY VOLTAGE
RL = 1k 0.55 0.50
MAX6342-05
6 RL = 10k 5 4 PFO (V) 3 2 1 0 0 1 2 3 4 5 6 SUPPLY VOLTAGE (V)
0.60
0.45 PFO (V) 0.40 0.35 0.30 0.25 0.20 0 1 2 3 4 5 6 SUPPLY VOLTAGE (V)
MAX6344/MAX6345 RESET RESPONSE TIME
5V 4V 4V VCC
MAX6342-06
MAX6342/MAX6345 RESET RESPONSE TIME
5V 4V 5V 4V
MAX6342-07
VCC RESET
RESET
0
0
10s/div
2s/div
Pin Description
PIN NAME MAX6342 1 2 3 4 4 MAX6343 1 2 3 4 MAX6344 1 2 3 4 MAX6345 1 2 3 4 VCC GND PFI PFO Supply Voltage Ground Power-Fail Voltage Monitor Input. When PFI is <1.25V, PFO goes low. Connect PFI to GND or VCC when not used. Power-Fail Voltage Monitor Output FUNCTION
_______________________________________________________________________________________
6-Pin P Reset Circuit with Power-Fail Comparator
Pin Description (continued)
PIN NAME MAX6342 MAX6343 MAX6344 MAX6345 Manual-Reset Input. Pull low to force a reset. RESET or RESET remains active as long as MR is low and for the reset timeout period after MR goes high. Leave unconnected or connect to VCC if unused. Active-Low Reset Output. Push-pull for MAX6342/MAX6345. Open-drain for MAX6343. It remains low for 180ms after VCC rises above the reset threshold or MR goes from low to high. Active-High Push-Pull Reset Output. It remains high for 180ms after VCC rises above the reset threshold or MR goes from low to high. FUNCTION
MAX6342-MAX6345
5
5
5
--
MR
6
6
--
5
RESET
--
--
6
6
RESET
1 VCC RESET GENERATOR 6 RESET VCC (RESET) 100k
1 VCC RESET GENERATOR
RESET 6
VTH 2 GND 3 PFI
VTH 5 MR 3 PFI PFO 4 2 GND
MAX6342 MAX6343 MAX6344
MAX6345
RESET 5
4 PFO 1.25V
1.25V
( ) ARE FOR MAX6344 ONLY.
Figure 1. MAX6342/MAX6343/MAX6344 Functional Diagram
Figure 2. MAX6345 Functional Diagram
_______________Detailed Description
Reset Output
A P's reset input starts the P in a known state. These P supervisory circuits assert reset to prevent codeexecution errors during power-up, power-down, or brownout conditions. RESET and RESET are guaranteed to be asserted at a valid logic level for VCC > +1V (see Electrical Characteristics). Once RESET asserts, it remains asserted for at least 100ms (tRP) after VCC rises above its threshold value or after MR returns high (Figures 1 and 2).
Connect a pull-up resistor from RESET to any positive supply voltage up to +5.5V (Figure 3). Select a resistor value large enough to register a logic low (see Electrical Characteristics), and small enough to register a logic high while supplying all input current and leakage paths connected to the RESET line. A 10k pull-up is sufficient in most applications.
Manual Reset
The MAX6342-MAX6344's manual-reset input (MR) allows reset to be triggered by a pushbutton switch. The switch is effectively debounced by the 1s minimum reset pulse width. MR is CMOS-logic compatible.
Open-Drain RESET Output
The MAX6343 has an active-low, open-drain reset output. This output sinks current when RESET is asserted.
Power-Fail Comparator
The power-fail comparator is useful for various purposes because the power-fail output (PFO) is independent
5
_______________________________________________________________________________________
6-Pin P Reset Circuit with Power-Fail Comparator MAX6342-MAX6345
+5.0V MAXIMUM TRANSIENT DURATION (s) +3.3V VCC VCC RESET 10k P RESET 160 140 120 100 80 MAX634_L/M 60 40 20 0 1 10 100 1000 RESET COMPARATOR OVERDRIVE , VTH - VCC (mV) MAX634_T/S/R/Z
MAX6343
GND
Figure 3. Open-Drain RESET Output Allows Use with Multiple Supplies
VCC
Figure 4. Maximum Transient Duration Magnitude Rejection
VCC
100k
VCC GND
MAX6342 MAX6345
RESET 100k
VCC GND MAX6344
RESET
MAX6345
Figure 5. Ensuring RESET Valid to VCC = 0 on Active-Low Push-Pull Outputs
Figure 6. Ensuring RESET Valid to VCC = 0 on Active-High Push-Pull Outputs
of the reset output. The inverting input is internally connected to a +1.25V reference. To build an early-warning circuit for power failure, connect the PFI pin to a voltage divider (see Typical Operating Circuit). Choose the voltage-divider ratio so that the voltage at PFI falls below +1.25V just before the +5V regulator drops out. Use PFO to interrupt the P to prepare for an orderly shutdown.
__________Applications Information
Negative-Going VCC Transients
The MAX6342-MAX6345 supervisors are immune to short-duration, negative-going VCC transients (glitches) that usually do not require the entire system to shut down. Figure 4 shows typical transient duration vs. reset comparator overdrive, for which the MAX6342-MAX6345 do not generate a reset pulse. The graph was generated using a negative-going pulse applied 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
6
negative-going VCC transient can have without causing a reset pulse. As the magnitude of the transient increases (goes further below the reset threshold), the maximum allowable pulse width decreases. Typically, a VCC transient that goes 100mV below the reset threshold and lasts 12s or less will not cause a reset pulse. A 1F bypass capacitor mounted as close as possible to the VCC pin provides additional transient immunity.
Ensuring a Valid Reset Output Down to VCC = 0
The MAX6342-MAX6345 are guaranteed to operate properly down to VCC = +1V. In applications that require valid reset levels down to VCC = 0, a pull-down resistor to active-low outputs (MAX6342/MAX6345) and a pull-up resistor to active-high outputs (MAX6344/MAX6345) ensure that the reset line is valid when the reset output is no longer sinking or sourcing current (Figures 5 and 6). Note that this method does not work with the open-drain output of the MAX6343. The resistor value used is not critical, but it must be large enough not to load the reset
_______________________________________________________________________________________
6-Pin P Reset Circuit with Power-Fail Comparator MAX6342-MAX6345
VCC V+ R1 VCC PFI R2 RESET (RESET) TO P VCC VCC P 4.7k RESET BUFFERED RESET TO OTHER SYSTEM COMPONENTS
MAX6342 MR MAX6343 MAX6344
GND
PFO
MAX6342 MAX6345
RESET
( ) ARE FOR MAX6344 ONLY. GND GND
Figure 7. Monitoring Two Supplies
VCC
Figure 9. Interfacing to Ps with Bidirectional Reset I/O
R1
VCC MR
100k
MAX6342 MAX6343 PFO PFI MAX6344
R2 VGND RESET (RESET)
100k
resistors and transistor as shown, a high PFO triggers reset. As long as PFO remains high, the MAX6342/ MAX6343/MAX6344 will keep reset asserted. Note that the accuracy of this circuit depends on the PFI threshold tolerance, the VCC line voltage, and the resistors. Also, ensure that the voltage at PFI remains above GND.
VCC - 1.25V = 1.25V - VTRIP R1 R2 ( ) ARE FOR MAX6344 ONLY. VTRIP < 0
Interfacing to Ps with Bidirectional Reset Pins
Use the circuit shown in Figure 9 to interface the MAX6342 or MAX6345 with a P with bidirectional reset pins. The 4.7k resistor between the reset output and the P I/O line will ensure that the resets do not cause an indeterminate logic level.
Figure 8. Monitoring a Negative Voltage
output when VCC is above the reset threshold. For most applications, 100k is adequate.
SOT Top Marks
PART MAX6342LUT-T MAX6342MUT-T MAX6342TUT-T MAX6342SUT-T MAX6342RUT-T MAX6342ZUT-T MAX6343LUT-T MAX6343MUT-T MAX6343TUT-T MAX6343SUT-T MAX6343RUT-T MAX6343ZUT-T SOT TOP MARK AACP AACQ AACR AACS AACT AACU AACV AACW AACX AACY AACZ AADA PART MAX6344LUT-T MAX6344MUT-T MAX6344TUT-T MAX6344SUT-T MAX6344RUT-T MAX6344ZUT-T MAX6345LUT-T MAX6345MUT-T MAX6345TUT-T MAX6345SUT-T MAX6345RUT-T MAX6345ZUT-T SOT TOP MARK AADQ AADR AADS AADT AADU AADV AADW AADX AADY AADZ AAEA AAEB
Monitoring Two Supplies
Monitor another voltage by connecting a resistor-divider to PFI as shown in Figure 7. The threshold voltage will then be given by: VTH(PFI) = 1.25[(R1 + R2) / R2] where VTH(PFI) is the threshold at which the monitored voltage will trip PFO. A good rule of thumb for selecting the resistors is to choose R2 between 250k and 500k and solve for R1. Connect PFO to MR in applications that require reset to assert when the second voltage falls below its threshold.
Monitoring a Negative Voltage
Connect the circuit as shown in Figure 8 to use the power-fail comparator to monitor a negative supply rail. PFO stays low when V- is good. When V- rises to cause PFI to be above +1.25V, PFO goes high. By adding the
_______________________________________________________________________________________
7
6-Pin P Reset Circuit with Power-Fail Comparator MAX6342-MAX6345
Typical Operating Circuit
UNREGULATED DC LINEAR REGULATOR
Pin Configurations (continued)
TOP VIEW
VCC 1 6 RESET
VCC PFI RESET
VCC RESET P INTERRUPT
GND 2
MAX6345
5
RESET
MAX6342
MR PFO
PFI 3
4
PFO
SOT23-6
PUSHBUTTON SWITCH
Chip Information
TRANSISTOR COUNT: 403
________________________________________________________Package Information
6LSOT.EPS
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
8 _____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 (c) 1999 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

▲Up To Search▲

Price & Availability of MAX6342

	To Download MAX6342 Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .