Maxim MAX6345 UT-T 6-pin up reset circuit with power-fail comparator Datasheet

19-1568; Rev 2; 12/05
6-Pin µP Reset Circuit with
Power-Fail Comparator
Features
The MAX6342–MAX6345 family of microprocessor (µP)
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
low-battery 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, open-drain reset and an active-high, pushpull reset, respectively. The MAX6345 provides a second
reset output in place of the MR input to give it an activehigh push-pull reset and an active-low push-pull reset.
All of the devices are packaged in a miniature 6-pin
SOT23.
♦ Small 6-Pin SOT23 Package
♦ Precision Factory-Set VCC Reset Thresholds
Between 2.33V and 4.63V
♦ Guaranteed RESET Valid to VCC = +1V
♦ 100ms min Reset Pulse Width
♦ Debounced CMOS-Compatible Manual-Reset
Input
♦ Voltage Monitor for Power-Fail or Low-Battery
Warning
Ordering Information
TEMP RANGE
PIN-PACKAGE
MAX6342_UT-T
PART
-40°C to +125°C
6 SOT23-6
MAX6343_UT-T
MAX6344_UT-T
MAX6345_UT-T
-40°C to +125°C
-40°C to +125°C
-40°C to +125°C
6 SOT23-6
6 SOT23-6
6 SOT23-6
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.
Applications
Portable Computers
Telecom Equipment
Networking Equipment
Devices are available in both leaded and lead-free packaging.
Specify lead-free by replacing “-T” with “+T” when ordering.
Portable/Battery-Powered Equipment
Multivoltage Systems
Pin Configurations
Embedded Control Systems
Typical Operating Circuit appears at end of data sheet.
TOP VIEW
Selector Guide 1
SUFFIX
RESET THRESHOLD (V)
L
4.63
M
4.38
T
3.08
S
2.93
R
2.63
Z
2.33
VCC 1
GND 2
MAX6342
MAX6343
MAX6344
PFI 3
6
RESET (RESET)
5
MR
4
PFO
( ) ARE FOR MAX6344 ONLY.
SOT23-6
Pin Configurations continued at end of data sheet.
Selector Guide 2
PART
PUSH-PULL
RESET OUTPUT
OPEN-DRAIN
RESET OUTPUT
PUSH-PULL RESET
OUTPUT
MANUAL-RESET
INPUT
MAX6342
✔
—
✔
MAX6343
—
—
✔
—
✔
—
—
✔
✔
MAX6344
—
✔
—
MAX6345
✔
________________________________________________________________ Maxim Integrated Products
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
1
MAX6342–MAX6345
General Description
MAX6342–MAX6345
6-Pin µP Reset Circuit with
Power-Fail Comparator
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 = +70°C)
6-Pin SOT23 (derate 4mW/°C above +70°C).............320mW
Operating Temperature Range .........................-40°C to +125°C
Junction Temperature ......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature Range (soldering, 10s)..................... +300°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.
ELECTRICAL CHARACTERISTICS
(VCC = +1.0V to +5.5V, TA = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C and VCC = +3V.) (Note 1)
PARAMETER
SYMBOL
Supply Voltage Range
VCC
Supply Current
Reset Threshold
ICC
VTH
VCC to Reset Delay
VOL
RESET and RESET
Outputs Drive
Capability (Note 2)
VOH
2
CONDITIONS
MIN
TYP
MAX
TA = 0°C to +70°C
1.0
5.5
TA = -40°C to +125°C
VCC = 3V, TA = -40° to +85°C
VCC = 5.5V, TA = -40° to +85°C
No load
VCC = 3V, TA = -40° to +125°C
VCC = 5.5V, TA = -40° to +125°C
TA = +25°C
MAX634_L
TA = -40°C to +85°C
TA = -40°C to +125°C
TA = +25°C
MAX634_M TA = -40°C to +85°C
TA = -40°C to +125°C
TA = +25°C
TA = -40°C to +85°C
MAX634_T
TA = -40°C to +125°C
TA = +25°C
MAX634_S
TA = -40°C to +85°C
TA = -40°C to +125°C
TA = +25°C
MAX634_R TA = -40°C to +85°C
TA = -40°C to +125°C
TA = +25°C
MAX634_Z
TA = -40°C to +85°C
TA = -40°C to +125°C
VCC = VTH to (VTH - 100mV)
VCC > 1.2V, ISINK = 100µA
VCC > 2.7V, ISINK = 1.2mA
VCC > 4.5V, ISINK = 3.2mA
VCC > 1.2V, ISOURCE = 50µA
1.2
5.5
40
50
50
60
4.70
4.75
4.86
4.45
4.50
4.56
3.13
3.15
3.23
2.97
3.00
3.08
2.67
2.70
2.76
2.36
2.38
2.45
0.8 ✕ VCC
VCC > 2.7V, ISOURCE = 500µA
(MAX6342/MAX6345 only)
0.8 ✕ VCC
VCC > 4.5V, ISOURCE = 800µA
(MAX6342/MAX6345 only)
0.8 ✕ VCC
4.56
4.50
4.40
4.31
4.25
4.16
3.03
3.00
2.92
2.89
2.85
2.78
2.59
2.55
2.50
2.30
2.25
2.21
25
30
25
30
4.63
4.38
3.08
2.93
2.63
2.33
20
V
µA
µA
V
µs
0.4
0.3
0.4
_______________________________________________________________________________________
UNITS
V
V
6-Pin µP Reset Circuit with
Power-Fail Comparator
MAX6342–MAX6345
ELECTRICAL CHARACTERISTICS (continued)
(VCC = +1.0V to +5.5V, TA = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C and VCC = +3V.) (Note 1)
PARAMETER
SYMBOL
Reset Timeout Period
tRP
Open-Drain RESET Output
Leakage Current (Note 3)
ILKG
MR Input Low
VIL
MR Input High
VIH
CONDITIONS
MIN
TYP
TA = -40°C to +85°C
100
180
TA = -40°C to +125°C
80
MAX
UNITS
280
ms
360
1
MAX6343 only, VCC > VTH(MAX)
µA
V
0.3 ✕ VCC
V
0.7 ✕ VCC
60
MR Pull-Up Resistance
MR Minimum Pulse Width
kΩ
1
µs
MR Glitch Rejection
0.1
µs
MR to Reset Delay
0.2
µs
PFI Input Threshold
TA = -40°C to +85°C
1.2
TA = -40°C to +125°C
1.15
1.25
±0.01
TA = -40°C to +85°C
PFI Leakage Current (Note 3)
1.3
V
1.35
±25
nA
±100
TA = -85°C to +125°C
PFO Output Voltage
VOL
VCC = 4.5V, ISINK = 3.2mA
PFO Output Voltage
VOH
VCC = 4.5V, ISOURCE = 800µA
0.4
V
V
0.8 ✕ VCC
PFO Output Short-Circuit
Current
Output sink current
20
Output source current
5
PFI to PFO Delay
VOVERDRIVE = 15mV
3
mA
µs
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.
Note 3: Leakage parameters are guaranteed by design and not production tested.
Typical Operating Characteristics
(VPFI = VCC = +5V, TA = +25°C, unless otherwise noted.)
VCC
VCC
VCC = 3.3V
MAX6342-03
VCC = 5V
25
SUPPLY CURRENT (µA)
MAX6342-02
MAX6342-01
30
MAX6342M/MAX6345M
RESET OUTPUT VOLTAGE
vs. SUPPLY VOLTAGE
MAX6344L/MAX6345L
RESET OUTPUT VOLTAGE
vs. SUPPLY VOLTAGE
SUPPLY CURRENT vs. SUPPLY VOLTAGE
AND TEMPERATURE
20
VCC = 2.5V
15
1V/div
10
1V/div
RESET
0
VCC = 1V
5
0
RESET
0
0
0
-40
-15
10
35
60
85
1sec/div
1sec/div
TEMPERATURE (°C)
_______________________________________________________________________________________
3
Typical Operating Characteristics (continued)
(VPFI = VCC = +5V, TA = +25°C, unless otherwise noted.)
PFO OUTPUT-VOLTAGE LOW
vs. SUPPLY VOLTAGE
PFO OUTPUT-VOLTAGE HIGH
vs. SUPPLY VOLTAGE
RL = 10kΩ
5
MAX6342-05
0.60
MAX6342-04
6
RL = 1kΩ
0.55
0.50
4
0.45
PFO (V)
PFO (V)
3
0.40
0.35
2
0.30
1
0.25
0.20
0
1
2
3
4
5
0
6
1
2
3
4
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
MAX6344/MAX6345
RESET RESPONSE TIME
MAX6342/MAX6345
RESET RESPONSE TIME
5V
VCC
4V
5V
4V
5V
5
6
MAX6342-07
0
MAX6342-06
MAX6342–MAX6345
6-Pin µP Reset Circuit with
Power-Fail Comparator
VCC
RESET
4V
4V
RESET
0
0
2µs/div
10µs/div
Pin Description
PIN
NAME
4
FUNCTION
MAX6342
MAX6343
MAX6344
MAX6345
1
1
1
1
VCC
Supply Voltage
2
2
2
2
GND
Ground
3
3
3
3
PFI
Power-Fail Voltage Monitor Input. When PFI is < 1.25V, PFO
goes low. Connect PFI to GND or VCC when not used.
4
4
4
4
PFO
Power-Fail Voltage Monitor Output
_______________________________________________________________________________________
6-Pin µP Reset Circuit with
Power-Fail Comparator
PIN
MAX6342
MAX6343
MAX6344
NAME
FUNCTION
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.
MAX6345
5
5
5
—
MR
6
6
—
5
RESET
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.
—
—
6
6
RESET
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.
1 VCC
1 VCC
RESET
GENERATOR
VTH
GND
RESET
GENERATOR
RESET
VCC (RESET)
RESET 6
VTH
100kΩ
MAX6342
MAX6343
MAX6344
2
6
5
2
MR
MAX6345
GND
3
RESET 5
3
4
PFI
PFO 4
PFI
PFO
1.25V
1.25V
( ) ARE FOR MAX6344 ONLY.
Figure 1. MAX6342/MAX6343/MAX6344 Functional Diagram
_______________Detailed Description
Reset Output
A µP’s reset input starts the µP in a known state. These
µP 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 the Electrical Characteristics table). 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).
Figure 2. MAX6345 Functional Diagram
Open-Drain RESET Output
The MAX6343 has an active-low, open-drain reset output. This output sinks current when RESET is asserted.
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 the Electrical Characteristics table), and small enough to register a logic high while supplying all input current and
leakage paths connected to the RESET line. A 10kΩ
pull-up is sufficient in most applications.
Manual Reset
The MAX6342/MAX6343/MAX6344s’ manual-reset input
(MR) allows reset to be triggered by a pushbutton
switch. The switch is effectively debounced by the 1µs
min reset pulse width. MR is CMOS-logic compatible.
_______________________________________________________________________________________
5
MAX6342–MAX6345
Pin Description (continued)
160
+5.0V
+3.3V
VCC
10kΩ
VCC
µP
RESET
RESET
MAX6343
MAXIMUM TRANSIENT DURATION (µs)
MAX6342–MAX6345
6-Pin µP Reset Circuit with
Power-Fail Comparator
140
120
100
80
MAX634_L/M
60
40
MAX634_T/S/R/Z
20
0
GND
1
10
100
1000
RESET COMPARATOR OVERDRIVE, VTH - VCC (mV)
Figure 3. Open-Drain RESET Output Allows Use with Multiple
Supplies
VCC
VCC
VCC
GND
MAX6342
MAX6345
100kΩ
RESET
VCC
RESET
GND MAX6344
100kΩ
Figure 5. Ensuring RESET Valid to VCC = 0 on Active-Low
Push-Pull Outputs
Power-Fail Comparator
The power-fail comparator is useful for various purposes because the power-fail output (PFO) is independent
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 the Typical
Oper-ating 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 µP 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
6
Figure 4. Maximum Transient Duration Magnitude Rejection
MAX6345
Figure 6. Ensuring RESET Valid to VCC = 0 on Active-High
Push-Pull Outputs
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 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 12µs or less will not cause a
reset pulse. A 1µF 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 pulldown resistor to
active-low outputs (MAX6342/MAX6345) and a pullup
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).
_______________________________________________________________________________________
6-Pin µP Reset Circuit with
Power-Fail Comparator
BUFFERED RESET TO
OTHER SYSTEM
COMPONENTS
RESET
(RESET)
VCC
R1
PFI
R2
TO µP
VCC
MAX6342 MR
MAX6343
MAX6344
VCC
µP
MAX6342
MAX6345
PFO
GND
4.7kΩ
RESET
( ) ARE FOR MAX6344 ONLY.
RESET
GND
GND
Figure 7. Monitoring Two Supplies
VCC
Figure 9. Interfacing to µPs with Bidirectional Reset I/O
Monitoring a Negative Voltage
R1
VCC
100kΩ
MR
MAX6342
MAX6343 PFO
PFI MAX6344
100kΩ
R2
GND
V-
RESET
(RESET)
VCC - 1.25V = 1.25V - VTRIP
R1
R2
VTRIP < 0
( ) ARE FOR MAX6344 ONLY.
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
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.
Interfacing to µPs with
Bidirectional Reset Pins
Figure 8. Monitoring a Negative Voltage
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
output when VCC is above the reset threshold. For most
applications, 100kΩ is adequate.
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 250kΩ and 500kΩ and solve for R1.
Connect PFO to MR in applications that require reset to
assert when the second voltage falls below its threshold.
SOT Top Marks
SOT TOP
MARK
PART
SOT TOP
MARK
MAX6342LUT-T
AACP
MAX6344LUT-T
AADQ
MAX6342MUT-T
AACQ
MAX6344MUT-T
AADR
MAX6342TUT-T
AACR
MAX6344TUT-T
AADS
MAX6342SUT-T
AACS
MAX6344SUT-T
AADT
MAX6342RUT-T
AACT
MAX6344RUT-T
AADU
MAX6342ZUT-T
AACU
MAX6344ZUT-T
AADV
MAX6343LUT-T
AACV
MAX6345LUT-T
AADW
MAX6343MUT-T
AACW
MAX6345MUT-T
AADX
MAX6343TUT-T
AACX
MAX6345TUT-T
AADY
MAX6343SUT-T
AACY
MAX6345SUT-T
AADZ
MAX6343RUT-T
AACZ
MAX6345RUT-T
AAEA
MAX6343ZUT-T
AADA
MAX6345ZUT-T
AAEB
PART
_______________________________________________________________________________________
7
MAX6342–MAX6345
VCC
V+
Typical Operating Circuit
UNREGULATED DC
Pin Configurations (continued)
TOP VIEW
LINEAR
REGULATOR
VCC 1
VCC
PFI
RESET
MAX6342
MR
PFO
VCC
GND 2
RESET
µP
PFI 3
INTERRUPT
MAX6345
6
RESET
5
RESET
4
PFO
SOT23-6
Chip Information
PUSHBUTTON
SWITCH
TRANSISTOR COUNT: 403
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information,
go to www.maxim-ic.com/packages.)
6LSOT.EPS
MAX6342–MAX6345
6-Pin µP Reset Circuit with
Power-Fail Comparator
PACKAGE OUTLINE, SOT 6L BODY
21-0058
G
1
1
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.
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© 2005 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products, Inc.