MAX6316-MAX6322 [MAXIM]
5-Pin レP Supervisory Circuits with Watchdog and Manual Reset; 5引脚微处理器监控电路，带有看门狗和手动复位
| 型号： | MAX6316-MAX6322 |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | 5-Pin レP Supervisory Circuits with Watchdog and Manual Reset |
| 文件： | 总16页 (文件大小：177K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-0496; Rev 3; 1/99
5 -P in µP S u p e rvis o ry Circ u it s w it h
Wa t c h d o g a n d Ma n u a l Re s e t
1–MAX632
________________Ge n e ra l De s c rip t io n
____________________________Fe a t u re s
♦ Small 5-Pin SOT23 Package
The MAX6316–MAX6322 family of microprocessor (µP)
s up e rvis ory c irc uits monitors p owe r s up p lie s a nd
microprocessor activity in digital systems. It offers sev-
eral combinations of push/pull, open-drain, and bidirec-
tional (such as Motorola 68HC11) reset outputs, along
with watchdog and manual-reset features. The Selector
Guide below lists the specific functions available from
each device. These devices are specifically designed
♦ Available in 26 Reset Threshold Voltages
2.5V to 5V, in 100mV Increments
♦ Four Reset Timeout Periods
1ms, 20ms, 140ms, or 1.12sec (min)
♦ Four Watchdog Timeout Periods
6.3ms, 102ms, 1.6sec, or 25.6sec (typ)
♦ Four Reset Output Stages
Active-High, Push/Pull
Active-Low, Push/Pull
to ignore fast negative transients on V . Resets are
CC
guaranteed valid for V down to 1V.
CC
Active-Low, Open-Drain
Active-Low, Bidirectional
These devices are available in 26 factory-trimmed reset
threshold voltages (from 2.5V to 5V, in 100mV incre-
ments), featuring four minimum power-on reset timeout
periods (from 1ms to 1.12sec), and four watchdog time-
out periods (from 6.3ms to 25.6sec). Nine standard ver-
sions are available with an order increment requirement
of 2500 pieces (see Standard Versions table); contact
the factory for availability of other versions, which have
an order increment requirement of 10,000 pieces.
♦ Guaranteed Reset Valid to V
♦ Immune to Short Negative V
♦ Low Cost
= 1V
CC
Transients
CC
♦ No External Components
_______________Ord e rin g In fo rm a t io n
The MAX6316–MAX6322 a re offe re d in a minia ture
5-pin SOT23 package.
PART
TEMP. RANGE
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
5 SOT23-5
5 SOT23-5
5 SOT23-5
5 SOT23-5
5 SOT23-5
MAX6316LUK____-T
MAX6316MUK____-T
MAX6317HUK____-T
MAX6318HUK____-T
________________________Ap p lic a t io n s
Portable Computers
Computers
MAX6318MHUK____-T -40°C to +85°C
Controllers
Intelligent Instruments
Ordering Information continued at end of data sheet.
Portable/Battery-Powered Equipment
Embedded Control Systems
Typical Operating Circuit and Pin Configurations appear at
end of data sheet.
___________________________________________________________________S e le c t o r Gu id e
RESET OUTPUTS*
MANUAL
WATCHDOG
PART
RESET
INPUT
ACTIVE-LOW
PUSH/PULL
ACTIVE-HIGH
PUSH/PULL
ACTIVE-LOW
BIDIRECTIONAL
ACTIVE-LOW
OPEN-DRAIN
INPUT
✔
✔
✔
✔
✔
✔
✔
✔
✔
MAX6316L
—
—
✔
✔
✔
✔
✔
—
—
—
—
—
—
—
—
✔
✔
MAX6316M
MAX6317H
—
—
✔
—
—
✔
MAX6318LH
MAX6318MH**
MAX6319LH
MAX6319MH**
MAX6320P
—
—
✔
✔
✔
—
✔
—
—
✔
✔
—
✔
—
—
—
—
—
✔
✔
—
—
—
✔
MAX6321HP
MAX6322HP
—
✔
✔
—
* The MAX6318/MAX6319/MAX6321/MAX6322 feature two types of reset output on each device.
**Future product—contact factory for availability.
________________________________________________________________ Maxim Integrated Products
1
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.
5 -P in µP S u p e rvis o ry Circ u it s w it h
Wa t c h d o g a n d Ma n u a l Re s e t
ABSOLUTE MAXIMUM RATINGS
Voltage (with respect to GND)
......................................................................-0.3V to +6V
Continuous Power Dissipation (T = +70°C)
A
V
CC
SOT23-5 (derate 7.1mW/°C above +70°C)...............571mW
Operating Temperature Range ............................-40°C to +85°C
Junction Temperature ......................................................+150°C
Storage Temperature Range..............................-65°C to +160°C
Lead Temperature (soldering, 10sec)..............................+300°C
RESET (MAX6320/MAX6321/MAX6322 only)...... -0.3V to +6V
All Other Pins.........................................-0.3V to (V + 0.3V)
CC
Input/Output Current, All Pins .............................................20mA
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
(V = 2.5V to 5.5V, T = -40°C to +85°C, unless otherwise noted. Typical values are at T = +25°C.) (Note 1)
CC
A
A
PARAMETER
SYMBOL
CONDITIONS
= -40°C to +85°C
A
MIN
TYP
MAX UNITS
Operating Voltage Range
Supply Current
V
CC
T
1
5.5
20
V
MAX6316/MAX6317/MAX6318/
MAX6320/MAX6321:
MR and WDI unconnected
V
= 5.5V
= 3.6V
10
5
CC
V
CC
12
I
CC
µA
1–MAX632
V
= 5.5V
= 3.6V
5
3
12
8
MAX6319/MAX6322:
MR unconnected
CC
V
CC
Reset Threshold Temperature
Coefficient
∆V /°C
40
ppm/°C
TH
T
= +25°C
V
-1.5%
V
V
TH
+1.5%
+2.5%
A
TH
TH
Reset Threshold (Note 2)
Reset Threshold Hysteresis
V
V
RST
T
A
= -40°C to +85°C
V
TH
-2.5%
V
V
TH TH
3
1.4
28
mV
MAX63_ _A_-T
MAX63_ _B_-T
MAX63_ _C_-T
MAX63_ _D_-T
1
2
20
40
Reset Active Timeout Period
t
t
ms
µs
RP
140
200
1600
40
280
2240
1120
V
falling at 1mV/µs
V
CC
to RESET Delay
RD
CC
PUSH/PULL RESET OUTPUT (MAX6316L/MAX6317H/MAX6318_H/MAX6319_H/MAX6321HP/MAX6322HP)
V
≥ 1.0V, I
≥ 1.2V, I
≥ 2.7V, I
≥ 4.5V, I
≥ 2.7V, I
≥ 4.5V, I
≥ 2.7V, I
≥ 4.5V, I
≥ 1.8V, I
≥ 2.7V, I
≥ 4.5V, I
= 50µA
0.3
0.3
0.3
0.4
CC
SINK
SINK
SINK
SINK
V
CC
= 100µA
= 1.2mA
= 3.2mA
V
OL
V
CC
V
V
RESET Output Voltage
V
CC
V
CC
= 500µA
= 800µA
0.8 x V
CC
SOURCE
SOURCE
V
OH
V
CC
V
CC
- 1.5
V
CC
= 1.2mA
0.3
0.4
SINK
V
OL
V
CC
= 3.2mA
SINK
RESET Output Voltage
V
CC
= 150µA
= 500µA
= 800µA
0.8 x V
CC
SOURCE
SOURCE
SOURCE
V
OH
V
CC
0.8 x V
CC
V
CC
V
CC
- 1.5
Note 1: Over-temperature limits are guaranteed by design, not production tested.
Note 2: A factory-trimmed voltage divider programs the nominal reset threshold (V ). Factory-trimmed reset thresholds are
TH
available in 100mV increments from 2.5V to 5V (see Table 1 at end of data sheet).
2
_______________________________________________________________________________________
5 -P in µP S u p e rvis o ry Circ u it s w it h
Wa t c h d o g a n d Ma n u a l Re s e t
1–MAX632
ELECTRICAL CHARACTERISTICS (continued)
(V = 2.5V to 5.5V, T = -40°C to +85°C, unless otherwise noted. Typical values are at T = +25°C.) (Note 1)
CC
A
A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX UNITS
BIDIRECTIONAL RESET OUTPUT (MAX6316M/MAX6318MH/MAX6319MH)
Transition Flip-Flop Setup Time
t
(Note 3)
= 3.0V, C = 120pF
400
ns
S
V
333
CC
L
V
= 5.0V, C = 200pF
333
ns
CC
L
RESET Output Rise Time
(Note 4)
t
R
V
CC
= 3.0V, C = 250pF
666
L
V
CC
= 5.0V, C = 400pF
L
666
Active Pull-Up Enable Threshold
RESET Active Pull-Up Current
RESET Pull-Up Resistance
V
PTH
V
= 5.0V
= 5.0V
0.4
4.2
0.65
20
V
CC
V
CC
mA
kΩ
4.7
5.2
OPEN-DRAIN RESET OUTPUT (MAX6320P/MAX6321HP/MAX6322HP)
V
≥ 1.0V, I
≥ 1.2V, I
≥ 2.7V, I
≥ 4.5V, I
= 50µA
0.3
0.3
0.3
0.4
CC
SINK
SINK
SINK
SINK
V
CC
= 100µA
= 1.2mA
= 3.2mA
V
OL
V
RESET Output Voltage
V
CC
V
CC
Open-Drain Reset Output
Leakage Current
I
1.0
µA
ms
LKG
WATCHDOG INPUT (MAX6316/MAX6317H/MAX6318_H/MAX6320P/MAX6321HP)
MAX63_ _ _ W-T
MAX63_ _ _ X-T
4.3
71
6.3
102
1.6
9.3
153
2.4
Watchdog Timeout Period
t
WD
MAX63_ _ _ Y-T
MAX63_ _ _ Z-T
1.12
17.9
50
sec
ns
25.6
38.4
WDI Pulse Width
t
V = 0.3 x V , V = 0.7 x V
IL CC IH CC
WDI
V
0.3 x V
CC
IL
WDI Input Threshold
(Note 5)
WDI = V , time average
V
V
IH
0.7 x V
CC
120
-15
160
CC
WDI Input Current
(Note 6)
I
µA
V
WDI
V
WDI
= 0, time average
-20
0.8
MANUAL-RESET INPUT (MAX6316_/MAX6317H/MAX6319_H/MAX6320P/MAX6322HP)
V
IL
V
> 4.0V
< 4.0V
TH
V
IH
2.0
MR Input Threshold
V
IL
0.3 x V
CC
V
TH
V
IH
0.7 x V
CC
1
µs
ns
MR Input Pulse Width
MR Glitch Rejection
MR Pull-Up Resistance
MR to Reset Delay
100
52
kΩ
ns
35
75
V
CC
= 5V
230
Note 3: This is the minimum time RESET must be held low by an external pull-down source to set the active pull-up flip-flop.
Note 4: Measured from RESET V to (0.8 x V ), R = ∞.
OL
CC
LOAD
Note 5: WDI is internally serviced within the watchdog period if WDI is left unconnected.
Note 6: The WDI input current is specified as the average input current when the WDI input is driven high or low. The WDI input is
designed for a three-stated-output device with a 10µA maximum leakage current and capable of driving a maximum capaci-
tive load of 200pF. The three-state device must be able to source and sink at least 200µA when active.
_______________________________________________________________________________________
3
5 -P in µP S u p e rvis o ry Circ u it s w it h
Wa t c h d o g a n d Ma n u a l Re s e t
__________________________________________Typ ic a l Op e ra t in g Ch a ra c t e ris t ic s
(T = +25°C, unless otherwise noted.)
A
MAX6316/17/19/20/22
MANUAL-RESET TO RESET
PROPAGATION DELAY vs. TEMPERATURE
MAX6316/17/18/20/21
SUPPLY CURRENT vs. TEMPERATURE
V
CC
FALLING TO RESET PROPAGATION
DELAY vs. TEMPERATURE
320
300
280
260
240
220
200
180
160
140
10
100
90
80
70
60
50
40
30
20
10
0
V
FALLING AT 1mV/µs
- V = 100mV
V = 5V
CC
CC
9
V
RST CC
V
= 5V
CC
8
7
6
5
4
V
CC
= 3V
= 1V
3
2
V
CC
1
0
-40 -20
0
20
40
60
80 100
-40 -20
0
20
40
60
80 100
-40 -20
0
20
40
60
80 100
1–MAX632
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
MAX6316/17/18/20/21
NORMALIZED RESET TIMEOUT
PERIOD vs. TEMPERATURE
NORMALIZED WATCHDOG TIMEOUT
PERIOD vs. TEMPERATURE
1.05
1.04
1.03
1.02
1.01
1.00
0.99
0.98
0.97
0.96
0.95
1.05
1.04
1.03
1.02
1.01
1.00
0.99
0.98
0.97
0.96
0.95
-40 -20
0
20
40
60
80 100
-40 -20
0
20
40
60
80 100
TEMPERATURE (°C)
TEMPERATURE (°C)
MAX6316M/6318MH/6319MH
BIDIRECTIONAL
MAXIMUM V TRANSIENT DURATION
CC
vs. RESET THRESHOLD OVERDRIVE
PULL-UP CHARACTERISTICS
MAX6316toc09
80
70
60
+5V
4.7k
PASSIVE
4.7kΩ
PULL-UP
2V/div
RESET OCCURS ABOVE LINES
74HC05
V
= 3.3V
RST
100pF
INPUT
V
= 4.63V
RST
50
40
30
20
10
0
RESET, ACTIVE
PULL-UP
2V/div
+5V
V
= 2.63V
RST
74HC05
100pF
V
CC
INPUT
RESET
RESET
INPUT
5V/div
GND
MR
10
100
1000
200ns/div
RESET THRESHOLD OVERDRIVE (mV) V - V
RST CC
4
_______________________________________________________________________________________
5 -P in µP S u p e rvis o ry Circ u it s w it h
Wa t c h d o g a n d Ma n u a l Re s e t
1–MAX632
______________________________________________________________P in De s c rip t io n
PIN
MAX6316L
MAX6316M
MAX6320P
MAX6318LH
MAX6318MH
MAX6321HP
MAX6319LH
MAX6319MH
MAX6322HP
NAME
FUNCTION
MAX6317H
MAX6316L/MAX6318LH/MAX6319LH:
Active-Low, Reset Output. CMOS push/pull
output (sources and sinks current).
MAX6316M/MAX6318MH/MAX6319MH:
Bidirectional, Active-Low, Reset Output.
Intended to interface directly to microprocessors
with bidirectional resets such as the Motorola
68HC11.
1
—
1
1
RESET
MAX6320P/MAX6321HP/MAX6322HP:
Open-Drain, Active-Low, Reset Output. NMOS out-
put (sinks current only). Connect a pull-up resistor
from RESET to any supply voltage up to 6V.
Active-High, Reset Output. CMOS push/pull output
(sources and sinks current). Inverse of RESET.
—
2
1
2
3
2
3
2
RESET
GND
Ground
Active-Low, Manual Reset Input. Pull low to force a
reset. Reset remains asserted for the duration of
the Reset Timeout Period after MR transitions from
low to high. Leave unconnected or connected to
3
4
5
3
4
5
—
4
—
5
MR
V
CC
if not used.
Watchdog Input. Triggers a reset if it remains
either high or low for the duration of the watchdog
timeout period. The internal watchdog timer clears
whenever a reset asserts or whenever WDI sees a
rising or falling edge. To disable the watchdog fea-
ture, leave WDI unconnected or three-state the dri-
ver connected to WDI.
4
WDI
Supply Voltage. Reset is asserted when V
CC
drops below the Reset Threshold Voltage (V ).
RST
5
V
CC
Reset remains asserted until V rises above
CC
V
RST
and for the duration of the Reset Timeout
Period (t ) once V rises above V .
RST
RP
CC
_______________________________________________________________________________________
5
5 -P in µP S u p e rvis o ry Circ u it s w it h
Wa t c h d o g a n d Ma n u a l Re s e t
V
CC
MAX6316–MAX6322
RESET
(ALL EXCEPT MAX6317)
RESET
GENERATOR
RESET
(ALL EXCEPT
MAX6316/MAX6320P)
V
CC
1.23V
52k
MR
(ALL EXCEPT
MAX6318/MAX6321)
WATCHDOG
TRANSITION
DETECTOR
1–MAX632
WATCHDOG
TIMER
WDI
(ALL EXCEPT
MAX6319/MAX6322)
52k
GND
Figure 1. Functional Diagram
the watchdog timeout period (t ). Reset remains assert-
WD
_______________De t a ile d De s c rip t io n
ed for the specified reset active timeout period (t ) after
RP
A microprocessor’s (µP) reset input starts or restarts the
µP in a known state. The reset output of the MAX6316–
MAX6322 µP supervisory circuits interfaces with the
reset input of the µP, preventing code-execution errors
during power-up, power-down, and brownout condi-
tions (see the Typical Operating Circuit). The MAX6316/
MAX6317/MAX6318/MAX6320/MAX6321 are also capa-
ble of asserting a reset should the µP become stuck in
an infinite loop.
V
rises above the reset threshold, after MR transitions
CC
low to high, or after the watchdog timer asserts the reset
(MAX6316_/MAX6317H/MAX6318_H/MAX6320P/
MAX6321HP). After the reset active timeout period (t
expires, the reset output deasserts, and the watchdog
timer restarts from zero (Figure 2).
)
RP
V
CC
V
V
RST
RST
1V
1V
GND
Re s e t Ou t p u t
The MAX6316L/MAX6318LH/MAX6319LH feature an
a c tive -low re s e t outp ut, while the MAX6317H/
MAX6318_H/MAX6319_H/MAX6321HP/MAX6322HP
feature an active-high reset output. RESET is guaran-
teed to be a logic low and RESET is guaranteed to be a
t
RP
t
RD
RESET
t
RP
logic high for V down to 1V.
t
RD
CC
RESET
GND
The MAX6316–MAX6322 assert reset when V is below
CC
the re s e t thre s hold (V ), whe n MR is p ulle d low
RST
(MAX6316_/MAX6317H/MAX6319_H/MAX6320P/
MAX6322HP only), or if the WDI pin is not serviced within
Figure 2. Reset Timing Diagram
6
_______________________________________________________________________________________
5 -P in µP S u p e rvis o ry Circ u it s w it h
Wa t c h d o g a n d Ma n u a l Re s e t
1–MAX632
scratch. If, on the other hand, RESET is high after a
d e la y of two e xte rna l-c loc k c yc le s , the p roc e s s or
knows that it caused the reset itself and can jump to a
different vector and use stored-state information to
determine what caused the reset.
RESET
Bid ire c t io n a l
Ou t p u t
The MAX6316M/MAX6318MH/MAX6319MH are designed
to interface with µPs that have bidirectional reset pins,
such as the Motorola 68HC11. Like an open-drain output,
these devices allow the µP or other devices to pull the
bidirectional reset (RESET) low and assert a reset condi-
tion. However, unlike a standard open-drain output, it
includes the commonly specified 4.7kΩ pull-up resistor
with a P-channel active pull-up in parallel.
A problem occurs with faster µPs; two external-clock
cycles are only 500ns at 4MHz. When there are several
devices on the reset line, and only a passive pull-up resis-
tor is used, the input capacitance and stray capacitance
can prevent RESET from reaching the logic high state (0.8
This configuration allows the MAX6316M/MAX6318MH/
MAX6319MH to solve a problem associated with µPs
that have bidirectional reset pins in systems where sev-
eral devices connect to RESET (Figure 3). These µPs
can often determine if a reset was asserted by an exter-
nal device (i.e., the supervisor IC) or by the µP itself
(due to a watchdog fault, clock error, or other source),
and then jump to a vector appropriate for the source of
the reset. However, if the µP does assert reset, it does
not re ta in the informa tion, b ut mus t d e te rmine the
cause after the reset has occurred.
x V ) in the time allowed. If this happens, all resets will
CC
be interpreted as external. The µP output stage is guaran-
teed to sink 1.6mA, so the rise time can not be reduced
considerably by decreasing the 4.7kΩ internal pull-up
resistance. See Bidirectional Pull-Up Characteristics in the
Typical Operating Characteristics.
The MAX6316M/MAX6318MH/MAX6319MH overcome
this problem with an active pull-up FET in parallel with the
4.7kΩ resistor (Figures 4 and 5). The pull-up transistor
holds RESET high until the µP reset I/O or the supervisory
circuit itself forces the line low. Once RESET goes below
The following procedure describes how this is done in
the Motorola 68HC11. In all cases of reset, the µP pulls
RESET low for about four external-clock cycles. It then
releases RESET, waits for two external-clock cycles,
then checks RESET’s state. If RESET is still low, the µP
concludes that the source of the reset was external
and, when RESET eventually reaches the high state, it
jumps to the normal reset vector. In this case, stored-
state information is erased and processing begins from
V , a comparator sets the transition edge flip-flop, indi-
PTH
cating that the next transition for RESET will be low to
high. When RESET is released, the 4.7kΩ resistor pulls
RESET up toward V . Once RESET rises above V
CC
PTH
but is below (0.85 x V ), the active P-channel pull-up
CC
turns on. Once RESET rises above (0.85 x V ) or the
CC
2µs one-shot times out, the active pull-up turns off. The
p a ra lle l c omb ina tion of the 4.7kΩ p ull-up a nd the
V
CC
V
CC
WDI*
MR**
4.7k
68HC11
RESET
CIRCUITRY
RESET
RESET
RESET
RESET
CIRCUITRY
RESET***
C
IN
C
STRAY
C
IN
MAX6316M
MAX6318MH
MAX6319MH
C
IN
OTHER DEVICES
*
**
MAX6316M/MAX6318MH
MAX6316M/MAX6319MH
***
ACTIVE-HIGH PUSH/PULL MAX6318MH/MAX6319MH
Figure 3. MAX6316M/MAX6318MH/MAX6319MH Supports Additional Devices on the Reset Bus
_______________________________________________________________________________________
7
5 -P in µP S u p e rvis o ry Circ u it s w it h
Wa t c h d o g a n d Ma n u a l Re s e t
V
CC
MAX6316M
MAX6318MH
MAX6319MH
LASER-
TRIMMED
RESISTORS
V
CC
VREF
52k
MR
(MAX6316M/
MAX6319MH)
RESET
GENERATOR
(MAX6316M/
MAX6318MH)
WATCHDOG ON
CIRCUITRY
6
WDI
V
CC
2µs ONE SHOT
TRANSITION
FLIP-FLOP
R
Q
4.7k
FF
S
RESET
ACTIVE PULL-UP
ENABLE COMPARATOR
0.65V
0.85V
CC
GND
Figure 4. MAX6316/MAX6318MH/MAX6319MH Bidirectional Reset Output Functional Diagram
8
_______________________________________________________________________________________
5 -P in µP S u p e rvis o ry Circ u it s w it h
Wa t c h d o g a n d Ma n u a l Re s e t
1–MAX632
P-c ha nne l tra ns is tor on-re s is ta nc e q uic kly c ha rg e s
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 10kΩ pull-up is sufficient in most applications.
stray capacitance on the reset line, allowing RESET to
transition from low to high within the required two elec-
tronic-clock cycles, even with several devices on the
reset line. This process occurs regardless of whether
Ma n u a l-Re s e t In p u t
The MAX6316_/MAX6317H/MAX6319_H/MAX6320P/
MAX6322HP feature a manual-reset input. A logic low on
MR asserts a reset. After MR transitions low to high, reset
remains asserted for the duration of the reset timeout peri-
the reset was caused by V
dipping below the reset
CC
threshold, the watchdog timing out, MR being asserted,
or the µP or other device asserting RESET. The parts do
not require an external pull-up. To minimize supply cur-
rent consumption, the internal 4.7kΩ pull-up resistor
disconnects from the supply whenever the MAX6316M/
MAX6318MH/MAX6319MH assert reset.
od (t ). The MR input is connected to V through an
RP
CC
internal 52kΩ pull-up resistor and therefore can be left
unconnected when not in use. MR can be driven with
TTL-logic levels in 5V systems, with CMOS-logic levels in
3V systems, or with open-drain or open-collector output
devices. A normally-open momentary switch from MR to
g round c a n a ls o b e us e d ; it re q uire s no e xte rna l
debouncing circuitry. MR is designed to reject fast,
negative-going transients (typically 100ns pulses). A
0.1µF capacitor from MR to ground provides additional
noise immunity.
Op e n -Dra in RESET Ou t p u t
The MAX6320P/MAX6321HP/MAX6322HP ha ve a n
active-low, open-drain reset output. This output struc-
ture will sink current when RESET is asserted. Connect
a pull-up resistor from RESET to any supply voltage up
to 6V (Figure 6). Select a resistor value large enough to
V
CC
The MR input pin is equipped with internal ESD-protection
circuitry that may become forward biased. Should MR be
t
0.8 x V
RP
CC
RESET
OR
driven by voltages higher than V , excessive current
CC
µC RESET DELAY
0.7V
would be drawn, which would damage the part. For
example, assume that MR is driven by a +5V supply other
t
R
t
S
than V . If V drops lower than +4.7V, MR’s absolute
CC
CC
maximum rating is violated [-0.3V to (V + 0.3V)], and
CC
ACTIVE
PULL-UP
TURNS ON
RESET PULLED LOW
BY µC OR
RESET GENERATOR
undesirable current flows through the ESD structure from
MR to V . To avoid this, use the same supply for MR as
CC
the supply monitored by V . This guarantees that the
CC
voltage at MR will never exceed V
.
CC
Figure 5. Bidirectional RESET Timing Diagram
Wa t c h d o g In p u t
The MAX6316_/MAX6317H/MAX6318_H/MAX6320P/
MAX6321HP feature a watchdog circuit that monitors
the µP’s activity. If the µP does not toggle the watchdog
+3.3V
+5.0V
input (WDI) within the watchdog timeout period (t ),
WD
V
CC
reset asserts. The internal watchdog timer is cleared by
reset or by a transition at WDI (which can detect pulses
as short as 50ns). The watchdog timer remains cleared
while reset is asserted. Once reset is released, the
timer begins counting again (Figure 7).
MR*
10k
WDI**
RESET***
RESET
5V SYSTEM
The WDI input is designed for a three-stated output
device with a 10µA maximum leakage current and the
capability of driving a maximum capacitive load of 200pF.
The three-state device must be able to source and sink at
least 200µA when active. Disable the watchdog function
by leaving WDI unconnected or by three-stating the driver
connected to WDI. When the watchdog timer is left open
circuited, the timer is cleared internally at intervals equal
to 7/8 of the watchdog period.
MAX6320
MAX6321
MAX6322
* MAX6320/MAX6322
** MAX6320/MAX6321
*** MAX6321/MAX6322
GND
Figure 6. MAX6320P/MAX6321HP/MAX6322HP Open-Drain
RESET Output Allows Use with Multiple Supplies
_______________________________________________________________________________________
9
5 -P in µP S u p e rvis o ry Circ u it s w it h
Wa t c h d o g a n d Ma n u a l Re s e t
V
CC
t
RST
V
CC
MAX6316
MAX6318
MAX6319
RESET
WDI
t
RP
t
t
RP
WD
V
CC
GND
RESET
100k
MAX6316/MAX6317
MAX6318/MAX6320
MAX6321
Figure 7. Watchdog Timing Relationship
Figure 8. Ensuring RESET Valid to V = 0 on Active-Low
CC
Push/Pull and Bidirectional Outputs
Ap p lic a t io n s In fo rm a t io n
1–MAX632
Wa t c h d o g In p u t Cu rre n t
The WDI input is internally driven through a buffer and
series resistor from the watchdog counter. For minimum
watchdog input current (minimum overall power con-
sumption), leave WDI low for the majority of the watch-
dog timeout period. When high, WDI can draw as much
as 160µA. Pulsing WDI high at a low duty cycle will
reduce the effect of the large input current. When WDI
is left unconnected, the watchdog timer is serviced
within the watchdog timeout period by a low-high-low
pulse from the counter chain.
MAX6317
V
CC
MAX6318
MAX6319
MAX6321*
MAX6322*
100k
V
CC
GND
RESET
*THIS SCHEMATIC DOES NOT WORK ON THE OPEN-DRAIN
OUTPUTS OF THE MAX6321/MAX6322.
Ne g a t ive -Go in g V
These supervisors are immune to short-duration, nega-
tive-going V transients (glitches), which usually do
Tra n s ie n t s
CC
Figure 9. Ensuring RESET Valid to V = 0 on Active-High
CC
Push/Pull Outputs
CC
not require the entire system to shut down. Typically,
source current. This scheme does not work with the
open-drain outputs of the MAX6320/MAX6321/MAX6322.
The resistor value used is not critical, but it must be
200ns large-amplitude pulses (from ground to V ) on
CC
the supply will not cause a reset. Lower amplitude puls-
es result in greater immunity. Typically, a V transient
CC
large enough not to load the reset output when V
is
CC
that goes 100mV under the reset threshold and lasts
less than 4µs will not trigger a reset. An optional 0.1µF
a b ove the re s e t thre s hold . For mos t a p p lic a tions ,
100kΩ is adequate.
bypass capacitor mounted close to V provides addi-
CC
tional transient immunity.
Wa t c h d o g S o ft w a re Co n s id e ra t io n s
(MAX6 3 1 6 /MAX6 3 1 7 /MAX6 3 1 8 /
En s u rin g Va lid Re s e t Ou t p u t s
MAX6 3 2 0 /MAX6 3 2 1 )
Do w n t o V
= 0
CC
One way to help the watchdog timer monitor software
execution more closely is to set and reset the watchdog
input at different points in the program, rather than
pulsing the watchdog input high-low-high or low-high-
low. This technique avoids a stuck loop, in which the
watchdog timer would continue to be reset inside the
loop, keeping the watchdog from timing out.
The MAX6316_/MAX6317H/MAX6318_H/MAX6319_H/
MAX6321HP/MAX6322HP are guaranteed to operate
properly down to V = 1V. In applications that require
CC
valid reset levels down to V = 0, a pull-down resistor
CC
to active-low outputs (push/pull and bidirectional only,
Figure 8) and a pull-up resistor to active-high outputs
(push/pull only, Figure 9) will ensure that the reset line
is valid while the reset output can no longer sink or
10 ______________________________________________________________________________________
5 -P in µP S u p e rvis o ry Circ u it s w it h
Wa t c h d o g a n d Ma n u a l Re s e t
1–MAX632
Figure 10 shows an example of a flow diagram where
the I/O driving the watchdog input is set high at the
beginning of the program, set low at the end of every
subroutine or loop, then set high again when the pro-
gram returns to the beginning. If the program should
hang in any subroutine, the problem would be quickly
corrected, since the I/O is continually set low and the
watchdog timer is allowed to time out, causing a reset
or interrupt to be issued. As described in the Watchdog
Input Current section, this scheme results in higher time
average WDI current than does leaving WDI low for the
majority of the timeout period and periodically pulsing it
low-high-low.
START
SET WDI
HIGH
PROGRAM
CODE
POSSIBLE
INFINITE LOOP PATH
SUBROUTINE OR
PROGRAM LOOP
SET WDI LOW
RETURN
Figure 10. Watchdog Flow Diagram
__________________P in Co n fig u ra t io n s
Typ ic a l Op e ra t in g Circ u it
TOP VIEW
RESET
GND
MR
1
2
3
5
4
V
RESET
GND
MR
1
2
3
5
4
V
CC
CC
V
IN
V
V
CC
MAX6316
MAX6320
MAX6317
CC
RESET
RESET
I/O
MAX6316
µP
WDI
WDI
MR
WDI
MANUAL
RESET
GND
GND
SOT23-5
SOT23-5
RESET
GND
1
2
3
5
4
V
RESET
GND
1
2
3
5
4
V
CC
CC
MAX6318
MAX6321
MAX6319
MAX6322
RESET
WDI
RESET
MR
SOT23-5
SOT23-5
______________________________________________________________________________________ 11
5 -P in µP S u p e rvis o ry Circ u it s w it h
Wa t c h d o g a n d Ma n u a l Re s e t
Table 1. Factory-Trimmed Reset Thresholds
T
= +25°C
TYP
T = -40°C to +85°C
A
A
PART
MIN
MAX
5.075
4.974
4.872
4.771
4.699
4.568
4.446
4.365
4.263
4.162
4.060
3.959
3.857
3.756
3.654
3.553
3.451
3.350
3.248
3.126
3.045
2.974
2.842
2.741
2.669
2.538
MIN
MAX
MAX63___50_ _-T
MAX63___49_ _-T
MAX63___48_ _-T
MAX63___47_ _-T
MAX63___46_ _-T
MAX63___45_ _-T
MAX63___44_ _-T
MAX63___43_ _-T
MAX63___42_ _-T
MAX63___41_ _-T
MAX63___40_ _-T
MAX63___39_ _-T
MAX63___38_ _-T
MAX63___37_ _-T
MAX63___36_ _-T
MAX63___35_ _-T
MAX63___34_ _-T
MAX63___33_ _-T
MAX63___32_ _-T
MAX63___31_ _-T
MAX63___30_ _-T
MAX63___29_ _-T
MAX63___28_ _-T
MAX63___27_ _-T
MAX63___26_ _-T
MAX63___25_ _-T
4.925
7.827
4.728
4.630
4.561
4.433
4.314
4.236
4.137
4.039
3.940
3.842
3.743
3.645
3.546
3.448
3.349
3.251
3.152
3.034
2.955
2.886
2.758
2.660
2.591
2.463
5.000
4.900
4.800
4.700
4.630
4.500
4.390
4.300
4.200
4.100
4.000
3.900
3.800
3.700
3.600
3.500
3.400
3.300
3.200
3.080
3.000
2.930
2.800
2.700
2.630
2.500
4.875
4.778
4.680
4.583
4.514
4.388
4.270
4.193
4.095
3.998
3.900
3.803
3.705
3.608
3.510
3.413
3.315
3.218
3.120
3.003
2.925
2.857
2.730
2.633
2.564
2.438
5.125
5.023
4.920
4.818
4.746
4.613
4.490
4.408
4.305
4.203
4.100
3.998
3.895
3.793
3.690
3.588
3.485
3.383
3.280
3.157
3.075
3.000
2.870
2.768
2.696
2.563
1–MAX632
Table 2. Standard Versions
RESET
THRESHOLD
(V)
MINIMUM RESET
TIMEOUT
(ms)
TYPICAL
WATCHDOG
TIMEOUTS (sec)
SOT
TOP MARK
PART
MAX6316LUK46CY-T
MAX6316LUK29CY-T
MAX6316MUK46CY-T
MAX6316MUK29CY-T
MAX6317HUK46CY-T
MAX6318LHUK46CY-T
4.63
2.93
4.63
2.93
4.63
4.63
4.63
4.63
2.93
140
140
140
140
140
140
140
140
140
1.6
1.6
1.6
1.6
1.6
1.6
—
ACDD
ACDE
ACDF
ACDG
ACDQ
ACDH
ACDK
ACDN
ACDO
†
MAX6319LHUK46C-T
MAX6320PUK46CY-T
MAX6320PUK29CY-T
1.6
1.6
Note: Nine standard versions are available, with a required order increment of 2500 pieces. Sample stock is generally held on standard
versions only. The required order increment for nonstandard versions is 10,000 pieces. Contact factory for availability.
Contact factory for availability of these versions.
†
12 ______________________________________________________________________________________
5 -P in µP S u p e rvis o ry Circ u it s w it h
Wa t c h d o g a n d Ma n u a l Re s e t
1–MAX632
__Ord e rin g In fo rm a t io n (c o n t in u e d )
Table 3. Reset/Watchdog Timeout Periods
PART
TEMP. RANGE
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
5 SOT23-5
5 SOT23-5
5 SOT23-5
5 SOT23-5
5 SOT23-5
RESET TIMEOUT PERIODS
MAX6319LHUK____-T
MAX6319MHUK____-T
MAX6320PUK____-T
MAX6321HPUK____-T
MAX6322HPUK____-T
SUFFIX
MIN
1
TYP
1.6
MAX
2
UNITS
ms
A
B
C
D
20
30
40
140
1.12
200
1.60
280
2.24
sec
Note: These devices are available with factory-set V
reset
CC
thresholds from 2.5V to 5V, in 0.1V increments. Insert the
desired nominal reset threshold (25 to 50, from Table 1) into the
blanks following the letters UK. All devices offer factory-pro-
grammed reset timeout periods. Insert the letter corresponding
to the desired reset timeout period (A, B, C, or D from Table 3)
into the blank following the reset threshold suffix. Parts that offer
a watchdog feature (see Selector Guide) are factory-trimmed to
one of four watchdog timeout periods. Insert the letter corre-
sponding to the desired watchdog timeout period (W, X, Y, or Z
from Table 3) into the blank following the reset timeout suffix.
WATCHDOG TIMEOUT
W
X
Y
Z
4.3
6.3
102
1.6
9.3
ms
71
153
2.4
1.12
17.9
sec
25.6
38.4
Ch ip In fo rm a t io n
TRANSISTOR COUNT: 191
SUBSTRATE IS INTERNALLY CONNECTED TO V+
______________________________________________________________________________________ 13
5 -P in µP S u p e rvis o ry Circ u it s w it h
Wa t c h d o g a n d Ma n u a l Re s e t
P a c k a g e In fo rm a t io n
1–MAX632
14 ______________________________________________________________________________________
5 -P in µP S u p e rvis o ry Circ u it s w it h
Wa t c h d o g a n d Ma n u a l Re s e t
1–MAX632
NOTES
______________________________________________________________________________________ 15
5 -P in µP S u p e rvis o ry Circ u it s w it h
Wa t c h d o g a n d Ma n u a l Re s e t
NOTES
1–MAX632
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.
16 ____________________Ma x im In t e g ra t e d P ro d u c t s , 1 2 0 S a n Ga b rie l Drive , S u n n yva le , CA 9 4 0 8 6 4 0 8 -7 3 7 -7 6 0 0
© 1999 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.
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