Maxim MAX6735KAZID3-T Single-/dual-/triple-voltage up supervisory circuits with independent watchdog output Datasheet

19-2629; Rev 6; 11/11
Single-/Dual-/Triple-Voltage µP Supervisory
Circuits with Independent Watchdog Output
Features
The MAX6730–MAX6735 single-/dual-/triple-voltage
microprocessor (µP) supervisors feature a watchdog
timer and manual reset capability. The MAX6730–
MAX6735 offer factory-set reset thresholds for monitoring voltages from +0.9V to +5V and an adjustable reset
input for monitoring voltages down to +0.63V. The combination of these features significantly improves system
reliability and accuracy when compared to separate
ICs or discrete components.
The active-low reset output asserts and remains asserted
for the reset timeout period after all the monitored voltages exceed their respective thresholds. Multiple factoryset reset threshold combinations reduce the number of
external components required. The MAX6730/MAX6731
monitor a single fixed voltage, the MAX6732/MAX6733
monitor two fixed voltages, and the MAX6734/MAX6735
monitor two fixed voltages and one adjustable voltage. All
devices are offered with six minimum reset timeout periods ranging from 1.1ms to 1120ms.
The MAX6730–MAX6735 feature a watchdog timer with
an independent watchdog output. The watchdog timer
prevents system lockup during code execution errors.
A watchdog startup delay of 54s after reset asserts
allows system initialization during power-up. The watchdog operates in normal mode with a 1.68s delay after
initialization. The MAX6730/MAX6732/MAX6734 provide
an active-low, open-drain watchdog output. The
MAX6731/MAX6733/MAX6735 provide an active-low,
push-pull watchdog output.
o VCC1 (Primary Supply) Reset Threshold Voltages
from +1.575V to +4.63V
Other features include a manual reset input (MAX6730/
MAX6731/MAX6734/MAX6735) and push-pull reset output (MAX6731/MAX6733/MAX6735) or open-drain reset
output (MAX6730/MAX6732/MAX6734). The MAX6730–
MAX6733 are offered in a tiny SOT23-6 package. The
MAX6734/MAX6735 are offered in a space-saving
SOT23-8 package. All devices are fully specified over
the extended -40°C to +85°C temperature range.
Applications
Multivoltage Systems
Telecom/Networking Equipment
Computers/Servers
Portable/Battery-Operated Equipment
Industrial Equipment
Printer/Fax
Set-Top Boxes
Typical Operating Circuit and Pin Configurations appear at
end of data sheet.
o VCC2 (Secondary Supply) Reset Threshold
Voltages from +0.79V to +3.08V
o Adjustable RSTIN Threshold for Monitoring
Voltages Down to +0.63V (MAX6734/MAX6735 Only)
o Six Reset Timeout Options
o Watchdog Timer with Independent Watchdog Output
35s (min) Initial Watchdog Startup Period
1.12s (min) Normal Watchdog Timeout Period
o Manual Reset Input
(MAX6730/MAX6731/MAX6734/MAX6735)
o Guaranteed Reset Valid down to
VCC1 or VCC2 = +0.8V
o Push-Pull RESET or Open-Drain RESET Output
o Immune to Short VCC Transients
o Low Supply Current: 14µA (typ) at +3.6V
o Small 6-Pin and 8-Pin SOT23 Packages
Ordering Information
TEMP RANGE
PIN-PACKAGE
MAX6730UT_D_ -T
PART*
-40°C to +85°C
6 SOT23
MAX6731UT_D_ -T
-40°C to +85°C
6 SOT23
MAX6732UT_ _D_ -T
-40°C to +85°C
6 SOT23
MAX6733UT_ _D_ -T
-40°C to +85°C
6 SOT23
MAX6734KA_ _D_ -T
-40°C to +85°C
8 SOT23
MAX6734KA_ _D_ /V-T
-40°C to +85°C
8 SOT23
MAX6735KA_ _D_ -T
-40°C to +85°C
8 SOT23
*Insert the threshold level suffixes for VCC1 and VCC2 (Table 1)
after “UT” or “KA.” For the MAX6730/MAX6731, insert only the
VCC1 threshold suffix after the “UT.” Insert the reset timeout
delay (Table 2) after “D” to complete the part number. For example, the MAX6732UTLTD3-T provides a VCC1 threshold of
+4.625V, a VCC2 threshold of +3.075V, and a 210ms reset timeout period. Sample stock is generally held on standard versions
only (see the Standard Versions table). Standard versions have
an order increment requirement of 2500 pieces. Nonstandard
versions have an order increment requirement of 10,000 pieces.
Contact factory for availability.
Devices are available in both leaded and lead(Pb)-free/RoHScompliant packaging.
Specify lead-free by replacing “-T” with “+T” when ordering.
/V Denotes an automotive qualified part.
________________________________________________________________ Maxim Integrated Products
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
1
MAX6730–MAX6735
General Description
MAX6730–MAX6735
Single-/Dual-/Triple-Voltage µP Supervisory
Circuits with Independent Watchdog Output
ABSOLUTE MAXIMUM RATINGS
VCC1, VCC2, RSTIN, MR, WDI to GND .....................-0.3V to +6V
RST, WDO to GND (open drain)...............................-0.3V to +6V
RST, WDO to GND (push-pull) .................-0.3V to (VCC1 + 0.3V)
Input Current/Output Current (all pins) ...............................20mA
Continuous Power Dissipation (TA = +70°C)
6-Pin SOT23-6 (derate 8.7mW/°C above +70°C) ........696mW
8-Pin SOT23-8 (derate 8.9mW/°C above +70°C) ........714mW
Operating Temperature Range ...........................-40°C to +85°C
Storage Temperature Range .............................-65°C to +150°C
Junction Temperature ......................................................+150°C
Lead Temperature (soldering, 10s) .................................+300°C
Soldering Temperature (reflow)
Lead (Pb)-free packages.............................................+260°C
Package containing lead (Pb) .....................................+240°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
(VCC1 = VCC2 = +0.8V to +5.5V, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1)
PARAMETER
Supply Voltage
SYMBOL
CONDITIONS
VCC1,
VCC2
ICC1
MIN
TYP
0.8
MAX
UNITS
5.5
V
VCC1 < +5.5V, all I/O connections
open, outputs not asserted
15
39
VCC1 < +3.6V, all I/O connections
open, outputs not asserted
10
28
VCC2 < +3.6V, all I/O connections
open, outputs not asserted
4
11
VCC2 < +2.75V, all I/O connections
open, outputs not asserted
3
9
µA
Supply Current
ICC2
VCC1 Reset Threshold
2
VTH1
L (falling)
4.500
4.625
4.750
M (falling)
4.250
4.375
4.500
T (falling)
3.000
3.075
3.150
S (falling)
2.850
2.925
3.000
R (falling)
2.550
2.625
2.700
Z (falling)
2.250
2.313
2.375
Y (falling)
2.125
2.188
2.250
W (falling)
1.620
1.665
1.710
V (falling)
1.530
1.575
1.620
_______________________________________________________________________________________
V
Single-/Dual-/Triple-Voltage µP Supervisory
Circuits with Independent Watchdog Output
MAX6730–MAX6735
ELECTRICAL CHARACTERISTICS (continued)
(VCC1 = VCC2 = +0.8V to +5.5V, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1)
PARAMETER
VCC2 Reset Threshold
SYMBOL
VTH2
MIN
TYP
MAX
T (falling)
CONDITIONS
3.000
3.075
3.150
S (falling)
2.850
2.925
3.000
R (falling)
2.550
2.625
2.700
Z (falling)
2.250
2.313
2.375
Y (falling)
2.125
2.188
2.250
W (falling)
1.620
1.665
1.710
V (falling)
1.530
1.575
1.620
I (falling)
1.350
1.388
1.425
H (falling)
1.275
1.313
1.350
G (falling)
1.080
1.110
1.140
F (falling)
1.020
1.050
1.080
E (falling)
0.810
0.833
0.855
D (falling)
0.765
0.788
0.810
Reset Threshold Tempco
Reset Threshold Hysteresis
VCC_ to RST Output Delay
V
20
ppm/oC
VHYST
Referenced to VTH typical
0.5
%
tRD
VCC1 = (VTH1 + 100mV) to
(VTH1 - 100mV) or
VCC2 = (VTH2 + 75mV) to
(VTH2 - 75mV)
45
µs
D1
Reset Timeout Period
UNITS
tRP
1.1
1.65
2.2
D2
8.8
13.2
17.6
D3
140
210
280
D5
280
420
560
D6
560
840
1120
D4
1120
1680
2240
626.5
ms
ADJUSTABLE RESET COMPARATOR INPUT (MAX6734/MAX6735)
RSTIN Input Threshold
VRSTIN
611
RSTIN Input Current
IRSTIN
-25
RSTIN Hysteresis
RSTIN to Reset Output Delay
tRSTIND
VRSTIN to (VRSTIN - 30mV)
642
+25
mV
nA
3
mV
22
µs
MANUAL RESET INPUT (MAX6730/MAX6731/MAX6734/MAX6735)
0.3 × VCC1
VIL
MR Input Threshold
VIH
MR Minimum Pulse Width
0.7 × VCC1
1
MR Glitch Rejection
µs
100
MR to Reset Output Delay
MR Pullup Resistance
tMR
ns
200
25
V
50
ns
80
kΩ
_______________________________________________________________________________________
3
MAX6730–MAX6735
Single-/Dual-/Triple-Voltage µP Supervisory
Circuits with Independent Watchdog Output
ELECTRICAL CHARACTERISTICS (continued)
(VCC1 = VCC2 = +0.8V to +5.5V, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
35
54
72
1.12
1.68
2.24
UNITS
WATCHDOG INPUT
Watchdog Timeout Period
WDI Pulse Width
WDI Input Voltage
WDI Input Current
tWD-L
First watchdog period after reset
timeout period
tWD-S
Normal mode
tWDI
(Note 2)
50
IWDI
ns
0.3 × VCC1
VIL
0.7 × VCC1
VIH
VWDI = 0V or VCC1
s
-1
+1
V
µA
RESET/WATCHDOG OUTPUT
RST / WDO Output Low Voltage
(Push-Pull or Open Drain)
RST / WDO Output High Voltage
(Push-Pull Only)
RST / WDO Output Open-Drain
Leakage Current
VOL
VOH
VCC1 or VCC2 ≥ +0.8V,
ISINK = 1µA, output asserted
0.3
VCC1 or VCC2 ≥ +1.0V,
ISINK = 50µA, output asserted
0.3
VCC1 or VCC2 ≥ +1.2V,
ISINK = 100µA, output asserted
0.3
VCC1 or VCC2 ≥ +2.7V,
ISINK = 1.2mA, output asserted
0.3
VCC1 or VCC2 ≥ +4.5V,
ISINK = 3.2mA, output asserted
0.4
VCC1 ≥ +1.8V, ISOURCE = 200µA,
output not asserted
0.8 × VCC1
VCC1 ≥ +2.7V, ISOURCE = 500µA,
output not asserted
0.8 × VCC1
VCC1 ≥ +4.5V, ISOURCE = 800µA,
output not asserted
0.8 × VCC1
Output not asserted
V
0.5
Note 1: Devices tested at TA = +25°C. Overtemperature limits are guaranteed by design and not production tested.
Note 2: Parameter guaranteed by design.
4
_______________________________________________________________________________________
V
µA
Single-/Dual-/Triple-Voltage µP Supervisory
Circuits with Independent Watchdog Output
ICC1
12
10
8
6
16
ICC2
4
14
TOTAL
12
10
8
ICC1
6
4
2
18
16
10
35
60
85
TOTAL
10
8
ICC1
6
ICC2
0
-40
-15
10
TEMPERATURE (°C)
35
60
-40
85
-15
SUPPLY CURRENT vs. TEMPERATURE
(VCC1 = +1.8V, VCC2 = +1.2V)
14
12
10
TOTAL
8
6
ICC1
4
2
60
85
ICC2
1.010
MAX6730-35 toc05
16
35
NORMALIZED THRESHOLD VOLTAGE
vs. TEMPERATURE
NORMALIZED THRESHOLD VOLTAGE
18
10
TEMPERATURE (°C)
TEMPERATURE (°C)
MAX6730-35 toc04
-15
12
2
0
-40
14
4
ICC2
2
0
MAX6730-35 toc03
14
18
MAX6730-35 toc02
TOTAL
SUPPLY CURRENT (µA)
SUPPLY CURRENT (µA)
16
SUPPLY CURRENT (µA)
MAX6730-35 toc01
18
SUPPLY CURRENT vs. TEMPERATURE
(VCC1 = +2.5V, VCC2 = +1.8V)
SUPPLY CURRENT vs. TEMPERATURE
(VCC1 = +3.3V, VCC2 = +2.5V)
SUPPLY CURRENT (µA)
SUPPLY CURRENT vs. TEMPERATURE
(VCC1 = +5V, VCC2 = +3.3V)
1.008
1.006
1.004
1.002
1.000
0.998
0.996
0.994
0.992
0.990
0
-40
-15
10
35
TEMPERATURE (°C)
60
85
-40
-15
10
35
60
85
TEMPERATURE (°C)
_______________________________________________________________________________________
5
MAX6730–MAX6735
Typical Operating Characteristics
(VCC1 = +5V, VCC2 = +3.3V, TA = +25°C, unless otherwise noted.)
Typical Operating Characteristics (continued)
(VCC1 = +5V, VCC2 = +3.3V, TA = +25°C, unless otherwise noted.)
MAXIMUM VCC_ TRANSIENT DURATION
vs. RESET THRESHOLD OVERDRIVE
NORMALIZED TIMEOUT PERIOD
vs. TEMPERATURE
1.0030
1.0025
1.0020
1.0015
1.0010
1.0005
1.0000
0.9995
0.9990
MAX6730-35 toc07
MAX6730-35 toc06
1.0035
RST ASSERTS
ABOVE THIS LINE
1000
MR
2V/div
100
RST
2V/div
10
-40
-15
10
35
60
85
1
TEMPERATURE (°C)
10
100
1000
RESET THRESHOLD OVERDRIVE (mV)
70
65
60
55
50
45
MAX6730-35 toc10
75
30
RSTIN TO RESET OUTPUT DELAY (µs)
MAX6730-35 toc09
VCC_ TO RESET OUTPUT DELAY (µs)
80
40ns/div
RSTIN TO RESET OUTPUT DELAY
vs. TEMPERATURE
VCC_ TO RESET OUTPUT DELAY
vs. TEMPERATURE (100mV OVERDRIVE)
28
26
24
22
20
18
16
14
12
10
40
-45
-15
10
35
TEMPERATURE (°C)
6
MR TO RESET OUTPUT DELAY
MAX6730-35 toc08
10,000
MAXIMUM VCC_ TRANSIENT DURATION (µs)
1.0040
NORMALIZED TIMEOUT PERIOD
MAX6730–MAX6735
Single-/Dual-/Triple-Voltage µP Supervisory
Circuits with Independent Watchdog Output
60
85
-45
-15
10
35
60
TEMPERATURE (°C)
_______________________________________________________________________________________
85
Single-/Dual-/Triple-Voltage µP Supervisory
Circuits with Independent Watchdog Output
PIN
MAX6730
MAX6731
MAX6732
MAX6733
MAX6734
MAX6735
NAME
FUNCTION
1
1
1
RST
Active-Low Reset Output. The MAX6730/MAX6732/MAX6734 provide an open-drain
output. The MAX6731/MAX6733/MAX6735 provide a push-pull output. RST asserts
low when any of the following conditions occur: VCC1 or VCC2 drops below its
preset threshold, RSTIN drops below its reset threshold, or MR is driven low. Opendrain versions require an external pullup resistor.
2
2
2
GND
Ground
WDO
Active-Low Watchdog Output. The MAX6730/MAX6732/MAX6734 provide an opendrain WDO output. The MAX6731/MAX6733/MAX6735 provide a push-pull WDO
output. WDO asserts low when no low-to-high or high-to-low transition occurs on
WDI within the watchdog timeout period (tWD) or if an undervoltage lockout
condition exists for VCC1, VCC2, or RSTIN. WDO deasserts without a timeout period
when VCC1, VCC2, and RSTIN exceed their reset thresholds, or when the manual
reset input is asserted. Open-drain versions require an external pullup resistor.
MR
Active-Low Manual Reset Input. Drive MR low to force a reset. RST remains
asserted as long as MR is low and for the reset timeout period after MR releases
high. MR has a 50kΩ pullup resistor to VCC1; leave MR open or connect to VCC1 if
unused.
3
4
3
—
4
5
5
5
3
WDI
Watchdog Input. If WDI remains high or low for longer than the watchdog timeout
period, the internal watchdog timer expires and the watchdog output asserts low.
The internal watchdog timer clears whenever RST asserts or a rising or falling edge
on WDI is detected. The watchdog has an initial watchdog timeout period (35s min)
after each reset event and a short timeout period (1.12s min) after the first valid
WDI transition. Leaving WDI unconnected does not disable the watchdog timer
function.
6
6
8
VCC1
Primary Supply-Voltage Input. VCC1 provides power to the device when it is greater
than VCC2. VCC1 is the input to the primary reset threshold monitor.
—
4
6
VCC2
Secondary Supply-Voltage Input. VCC2 provides power to the device when it is
greater than VCC1. VCC2 is the input to the secondary reset threshold monitor.
7
Undervoltage Reset Comparator Input. RSTIN provides a high-impedance
comparator input for the adjustable reset monitor. RST asserts low if the voltage at
RSTIN RSTIN drops below the 626mV internal reference voltage. Connect a resistive
voltage-divider to RSTIN to monitor voltages higher than 626mV. Connect RSTIN to
VCC1 or VCC2 if unused.
—
—
_______________________________________________________________________________________
7
MAX6730–MAX6735
Pin Description
MAX6730–MAX6735
Single-/Dual-/Triple-Voltage µP Supervisory
Circuits with Independent Watchdog Output
Table 1. Reset Voltage Threshold Suffix Guide**
PART NO. SUFFIX
LT
MS
MR
TZ
SY
RY
TW
SV
RV
TI
SH
RH
TG
SF
RF
TE
SD
RD
ZW
YV
ZI
YH
ZG
YF
ZE
YD
WI
VH
WG
VF
WE
VD
VCC1 NOMINAL
VOLTAGE
THRESHOLD(V)
4.625
4.375
4.375
3.075
2.925
2.625
3.075
2.925
2.625
3.075
2.925
2.625
3.075
2.925
2.625
3.075
2.925
2.625
2.313
2.188
2.313
2.188
2.313
2.188
2.313
2.188
1.665
1.575
1.665
1.575
1.665
1.575
VCC2 NOMINAL
VOLTAGE
THRESHOLD (V)
3.075
2.925
2.625
2.313
2.188
2.188
1.665
1.575
1.575
1.388
1.313
1.313
1.110
1.050
1.050
0.833
0.788
0.788
1.665
1.575
1.388
1.313
1.110
1.050
0.833
0.788
1.388
1.313
1.110
1.050
0.833
0.788
**Standard versions are shown in bold and are available in a
D3 timeout option only. Standard versions require 2500-piece
order increments and are typically held in sample stock. There
is a 10,000-piece order increment on nonstandard versions.
Other threshold voltages may be available; contact factory
for availability.
8
Table 2. Reset Timeout Period Suffix Guide
TIMEOUT
PERIOD SUFFIX
ACTIVE TIMEOUT PERIOD
MIN (ms)
MAX (ms)
D1
1.1
2.2
D2
8.8
17.6
D3
140
280
D5
280
560
D6
560
1120
D4
1120
2240
Detailed Description
Supply Voltages
The MAX6730–MAX6735 microprocessor (µP) supervisors maintain system integrity by alerting the µP to fault
conditions. The MAX6730–MAX6735 monitor one to
three supply voltages in µP-based systems and assert
an active-low reset output when any monitored supply
voltage drops below its preset threshold. The output
state remains valid for VCC1 or VCC2 greater than +0.8V.
Threshold Levels
The two-letter code in the Reset Voltage Threshold
Suffix Guide (Table 1) indicates the threshold level
combinations for VCC1 and VCC2.
Reset Output
The MAX6730–MAX6735 feature an active-low reset output (RST). RST asserts when the voltage at either VCC1 or
VCC2 falls below the voltage threshold level, VRSTIN
drops below its threshold, or MR is driven low (Figure 1).
RST remains low for the reset timeout period (Table 2)
after V CC 1, V CC 2, and RSTIN increase above their
respective thresholds and after MR releases high.
Whenever VCC1, VCC2, or RSTIN go below the reset
threshold before the end of the reset timeout period, the
internal timer restarts. The MAX6730/MAX6732/ MAX6734
provide an open-drain RST output, and the MAX6731/
MAX6733/MAX6735 provide a push-pull RST output.
_______________________________________________________________________________________
Single-/Dual-/Triple-Voltage µP Supervisory
Circuits with Independent Watchdog Output
Adjustable Input Voltage (RSTIN)
MAX6730–MAX6735
Manual Reset Input
Many µP-based products require manual reset capability, allowing the operator, a test technician, or external
logic circuitry to initiate a reset. A logic low on MR
asserts the reset output, clears the watchdog timer,
and deasserts the watchdog output. Reset remains
asserted while MR is low and for the reset timeout period (tRP) after MR returns high. An internal 50kΩ pullup
resistor allows MR to be left open if unused. Drive MR
with TTL or CMOS-logic levels or with open-drain/collector outputs. Connect a normally open momentary
switch from MR to GND to create a manual reset function; external debounce circuitry is not required.
Connect a 0.1µF capacitor from MR to GND to provide
additional noise immunity when driving MR over long
cables or if the device is used in a noisy environment.
VEXT_TH
R1
MAX6734
MAX6735
RSTIN
R2
GND
Figure 2. Monitoring a Third Voltage
The MAX6734/MAX6735 provide an additional highimpedance comparator input with a 626mV threshold to
monitor a third supply voltage. To monitor a voltage
higher than 626mV, connect a resistive-divider to the
circuit as shown in Figure 2 to establish an externally
controlled threshold voltage, VEXT_TH.
VEXT_TH = 626mV ×
VCC1,
VCC2
RSTIN
RST
VCC
(MIN)
(R1 + R2)
R2
VTH
tRP
tRP
WDO
MR
Figure 1. RST, WDO, and MR Timing Diagram
_______________________________________________________________________________________
9
MAX6730–MAX6735
Single-/Dual-/Triple-Voltage µP Supervisory
Circuits with Independent Watchdog Output
The RSTIN comparator derives power from VCC1, and
the input voltage must remain less than or equal to
VCC1. Low leakage current at RSTIN allows the use of
large-valued resistors, resulting in reduced power consumption of the system.
Watchdog
The watchdog feature monitors µP activity through
the watchdog input (WDI). A rising or falling edge on
WDI within the watchdog timeout period (tWD) indicates normal µP operation. WDO asserts low if WDI
remains high or low for longer than the watchdog
timeout period. Leaving WDI unconnected does not
disable the watchdog timer.
The MAX6730–MAX6735 include a dual-mode watchdog timer to monitor µP activity. The flexible timeout
architecture provides a long-period initial watchdog
mode, allowing complicated systems to complete
lengthy boots, and a short-period normal watchdog
mode, allowing the supervisor to provide quick alerts
when processor activity fails. After each reset event
(VCC power-up, brownout, or manual reset), there is a
long initial watchdog period of 35s (min). The long
watchdog period mode provides an extended time for
the system to power up and fully initialize all µP and
system components before assuming responsibility for
routine watchdog updates.
VCC1,
VCC2
RSTIN
RST
VCC
(MIN)
The usual watchdog timeout period (1.12s min) begins
after the initial watchdog timeout period (tWD-L) expires
or after the first transition on WDI (Figure 3). During normal operating mode, the supervisor asserts the WDO
output if the µP does not update the WDI with a valid
transition (high to low or low to high) within the standard
timeout period (tWD-S) (1.12s min).
Connect MR to WDO to force a system reset in the
event that no rising or falling edge is detected at WDI
within the watchdog timeout period. WDO asserts low
when no edge is detected by WDI, the RST output
asserts low, the watchdog counter immediately clears,
and WDO returns high. The watchdog counter restarts,
using the long watchdog period, when the reset timeout
period ends (Figure 4).
Ensuring a Valid RESET
Output Down to VCC = 0V
The MAX6730–MAX6735 guarantee proper operation
down to VCC = +0.8V. In applications that require valid
reset levels down to VCC = 0V, use a 100kΩ pulldown
resistor from RST to GND. 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. Note that this
configuration does not work for the open-drain outputs
of MAX6730/MAX6732/MAX6734.
VTH
tRP
WDO
WDI
< tWD-L
< tWD-S
< tWD-S
> tWD-S
< tWD-S
tWD-S
Figure 3. Watchdog Input/Output Timing Diagram (MR and WDO Not Connected)
10
______________________________________________________________________________________
< tWD-S
Single-/Dual-/Triple-Voltage µP Supervisory
Circuits with Independent Watchdog Output
RST
VCC
(MIN)
MAX6730–MAX6735
VCC1,
VCC2
RSTIN
VTH
tRP
tRP
WDO
WDI
< tWD-L
< tWD-S
> tWD-S
< tWD-L
MR
tMR
Figure 4. Watchdog Input/Output Timing Diagram (MR and WDO Connected)
Applications Information
Interfacing to µPs with Bidirectional
Reset Pins
Microprocessors with bidirectional reset pins can interface directly with the open-drain RST output options.
However, conditions might occur in which the push-pull
output versions experience logic contention with the
bidirectional reset pin of the µP. Connect a 10kΩ resistor between RST and the µP’s reset I/O port to prevent
logic contention (Figure 5).
Falling VCC Transients
The MAX6730–MAX6735 µP supervisors are relatively
immune to short-duration falling VCC_ transients (glitches). Small glitches on V CC _ are ignored by the
MAX6730–MAX6735, preventing undesirable reset
pulses to the µP. The Typical Operating Characteristics
show Maximum Transient Duration vs. Reset Threshold
VCC2 VCC1
RESET TO
OTHER
SYSTEM
COMPONENTS
VCC1
MAX6731
MAX6733 RST
MAX6735
µP
10kΩ
RESET
VCC2
GND
GND
Figure 5. Interfacing to µPs with Bidirectional Reset I/O
______________________________________________________________________________________
11
MAX6730–MAX6735
Single-/Dual-/Triple-Voltage µP Supervisory
Circuits with Independent Watchdog Output
Functional Diagram
Overdrive, for which reset pulses are not generated.
The graph was produced using falling VCC_ pulses,
starting above VTH and ending below the reset threshold by the magnitude indicated (reset threshold overdrive). The graph shows the maximum pulse width that
a falling V CC transient typically might have without
causing a reset pulse to be issued. As the amplitude of
the transient increases (i.e., goes further below the
reset threshold), the maximum allowable pulse width
decreases. A 0.1µF bypass capacitor mounted close to
VCC_ provides additional transient immunity.
Watchdog Software Considerations
Setting and resetting the watchdog input at different
points in the program rather than “pulsing” the watchdog input high-low-high or low-high-low helps the
watchdog timer closely monitor software execution.
This technique avoids a “stuck” loop, in which the
watchdog timer continues to be reset within the loop,
preventing the watchdog from timing out. Figure 6
shows an example flow diagram in which the I/O driving the watchdog input is set high at the beginning of
the program, set low at the beginning of every subroutine or loop, and then set high again when the program
returns to the beginning. If the program “hangs” in any
subroutine, the I/O continually asserts low (or high),
and the watchdog timer expires, issuing a reset or
interrupt.
VCC1
MR
VCC1
MAX6730–
MAX6735
VCC1
VCC2
RESET
TIMEOUT
PERIOD
VCC2
RESET
OUTPUT
DRIVER
RST
VCC1
WATCHDOG
TIMER
RSTIN
WDO
WDI
VCC1
REF
VREF / 2
START
SET WDI
HIGH
PROGRAM
CODE
SUBROUTINE OR
PROGRAM LOOP
SET WDI LOW
HANG IN
SUBROUTINE
RETURN
Figure 6. Watchdog Flow Diagram
12
VCC1
VREF
GND
SUBROUTINE
COMPLETED
MR
PULLUP
______________________________________________________________________________________
Single-/Dual-/Triple-Voltage µP Supervisory
Circuits with Independent Watchdog Output
PART
TOP MARK
PART
TOP MARK
MAX6730UTLD3-T
ABCC
MAX6733UTZGD3-T
ABQI
MAX6730UTSD3-T
ABPB
MAX6733UTYDD3-T
ABQG
MAX6730UTRD3-T
ABPA
MAX6733UTVHD3-T
ABQE
MAX6730UTZD3-T
ABPD
MAX6733UTWGD3-T
ABQF
MAX6730UTVD3-T
ABPC
MAX6733UTVDD3-T
ABQD
MAX6731UTLD3-T
ABPE
MAX6734KALTD3-T
AEHN
MAX6731UTTD3-T
ABCD
MAX6734KASYD3-T
AEHS
MAX6731UTSD3-T
ABPG
MAX6734KASVD3-T
AEHR
MAX6731UTRD3-T
ABPF
MAX6734KARVD3-T
AEHO
MAX6731UTZD3-T
ABPI
MAX6734KASHD3-T
AEHQ
MAX6731UTVD3-T
ABPH
MAX6734KATGD3-T
AEHT
MAX6732UTLTD3-T
ABCE
MAX6734KASDD3-T
AEHP
MAX6732UTSYD3-T
ABPN
MAX6734KAZWD3-T
AEIA
MAX6732UTSVD3-T
ABPM
MAX6734KAYHD3-T
AEHY
MAX6732UTRVD3-T
ABPJ
MAX6734KAZGD3-T
AEHZ
MAX6732UTSHD3-T
ABPL
MAX6734KAYDD3-T
AEHX
MAX6732UTTGD3-T
ABPO
MAX6734KAVHD3-T
AEHV
MAX6732UTSDD3-T
ABPK
MAX6734KAWGD3-T
AEHW
MAX6732UTZWD3-T
ABPV
MAX6734KAVDD3-T
AEHU
MAX6732UTYHD3-T
ABPT
MAX6735KALTD3-T
AEIB
MAX6732UTZGD3-T
ABPU
MAX6735KASYD3-T
AEIG
MAX6732UTYDD3-T
ABPS
MAX6735KASVD3-T
AEIF
MAX6732UTVHD3-T
ABPQ
MAX6735KARVD3-T
AEIC
MAX6732UTWGD3-T
ABPR
MAX6735KASHD3-T
AEIE
MAX6732UTVDD3-T
ABPP
MAX6735KATGD3-T
AEIH
MAX6733UTLTD3-T
ABPW
MAX6735KASDD3-T
AEID
MAX6733UTSYD3-T
ABQB
MAX6735KAZWD3-T
AEIO
MAX6733UTSVD3-T
ABQA
MAX6735KAZID3-T
AAJZ
MAX6733UTRVD3-T
ABPX
MAX6735KAYHD3-T
AEIM
MAX6733UTSHD3-T
ABPZ
MAX6735KAZGD3-T
AEIN
MAX6733UTTGD3-T
ABQC
MAX6735KAYDD3-T
AEIL
MAX6733UTSDD3-T
ABPY
MAX6735KAVHD3-T
AEIJ
MAX6733UTZWD3-T
ABQJ
MAX6735KAWGD3-T
AEIK
MAX6733UTYHD3-T
ABQH
MAX6735KAVDD3-T
AEII
Note: Sample stock is generally held on standard versions only. Standard versions have an order increment requirement of 2500
pieces. Nonstandard versions have an order increment requirement of 10,000 pieces. Contact factory for availability of nonstandard
versions.
______________________________________________________________________________________
13
MAX6730–MAX6735
Standard Versions
Single-/Dual-/Triple-Voltage µP Supervisory
Circuits with Independent Watchdog Output
MAX6730–MAX6735
Pin Configurations
TOP VIEW
RST 1
MAX6730
MAX6731
GND 2
WDO 3
6
VCC1
RST 1
5
WDI
GND 2
4
MR
WDO 3
SOT23-6
MAX6732
MAX6733
6
VCC1
5
WDI
4
VCC2
RST
1
GND
2
WDI
MAX6734
MAX6735
3
WDO 4
SOT23-6
Typical Operating Circuit
8
VCC1
7
RSTIN
6
VCC2
5
MR
SOT23-8
___________________Chip Information
PROCESS: BiCMOS
+1.8V
+0.9V
VCORE
+3.3V
VCC2
VCC1
RSTIN
RST
MAX6734
WDI
MAX6735
PUSHBUTTON
SWITCH
WDO
VCC
(I/O)
Package Information
VDD
(MEMORY)
RESET
I/O
µP
PACKAGE
TYPE
NMI
MR
GND
For the latest package outline information and land patterns
(footprints), go to www.maxim-ic.com/packages. Note that a
“+”, “#”, or “-” in the package code indicates RoHS status only.
Package drawings may show a different suffix character, but
the drawing pertains to the package regardless of RoHS status.
PACKAGE
CODE
OUTLINE
NO.
LAND
PATTERN NO.
6 SOT23
U6-1
21-0058
90-0175
8 SOT23
K85N-1
21-0078
90-0176
GND
Selector Guide
14
PART NUMBER
VOLTAGE
MONITORS
RST OUTPUT
MANUAL RESET
WATCHDOG
INPUT
WATCHDOG
OUTPUT
MAX6730
1
Open Drain
√
√
Open Drain
MAX6731
1
Push-Pull
√
√
Push-Pull
MAX6732
2
Open Drain
—
√
Open Drain
MAX6733
2
Push-Pull
—
√
Push-Pull
MAX6734
3
Open Drain
√
√
Open Drain
MAX6735
3
Push-Pull
√
√
Push-Pull
______________________________________________________________________________________
Single-/Dual-/Triple-Voltage µP Supervisory
Circuits with Independent Watchdog Output
REVISION
NUMBER
REVISION
DATE
DESCRIPTION
PAGES
CHANGED
0
10/02
Initial release.
—
1
12/02
Released MAX6730/MAX6731.
1
2
1/03
Released MAX6733.
1
3
3/04
Updated Typical Operating Circuit.
14
4
12/05
Added lead-free notation to Ordering Information.
5
3/09
Updated Pin Description and added Package Table.
6
11/11
Added automotive-qualified part information
1
7, 14
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. The parametric values (min and max limits) shown in
the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 15
© 2011 Maxim Integrated Products
Maxim is a registered trademark of Maxim Integrated Products, Inc.
MAX6730–MAX6735
Revision History
Similar pages