MAX6860UK17D5+ [MAXIM]
Power Supply Support Circuit, Fixed, 1 Channel, BICMOS, PDSO5, LEAD FREE, MO-178AA, SOT-23, 5 PIN;
| 型号： | MAX6860UK17D5+ |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | Power Supply Support Circuit, Fixed, 1 Channel, BICMOS, PDSO5, LEAD FREE, MO-178AA, SOT-23, 5 PIN 信息通信管理 光电二极管 |
| 文件： | 总17页 (文件大小：489K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-3139; Rev 4; 12/05
Nanopower µP Supervisory Circuits with
Manual Reset and Watchdog Timer
General Description
Features
The MAX6854/MAX6855/MAX6856/MAX6858/MAX6860–
MAX6869 ultra-low-current (170nA, typ) microprocessor
(µP) supervisory circuits combine voltage monitoring,
watchdog timer, and manual reset input functions in a 5-
pin SOT23 package. These devices assert a reset signal
whenever the monitored voltage drops below the factory-
trimmed reset threshold voltage, manual reset is assert-
ed, or the watchdog timer expires. The reset output
♦ Ultra-Low 170nA (typ) Supply Current
♦ Reset Thresholds from +1.575V to +4.625V in
Approximately 100mV Increments
♦ Six Minimum Reset Timeout Period Options from
10ms to 1200ms
♦ Manual Reset Option
♦ Watchdog Timer Option
remains asserted for a minimum timeout period after V
CC
♦ Pin-Selectable 10ms/150ms (min) Reset Timeout
rises above the reset threshold and manual reset is
deasserted. Factory-trimmed reset threshold voltages
are offered from +1.575V to +4.625V in approximately
100mV increments (see the Threshold Suffix Guide).
Each device is offered with six minimum reset timeout
options, ranging from 10ms to 1200ms.
Period (MAX6861/MAX6862/MAX6863)
♦ Immune to Short VCC Transients
♦ Guaranteed Reset Valid to VCC = +1.1V
♦ Three Reset Output Options:
Push-Pull RESET
The MAX6854/MAX6855/MAX6856/MAX6858/MAX6860–
MAX6869 are offered in a variety of configurations (see
the Selector Guide). The MAX6854/MAX6855/MAX6856/
MAX6861–MAX6869 provide a manual reset input, MR.
The MAX6864–MAX6869 offer a watchdog timer that
monitors activity at the WDI input to prevent code execu-
tion errors. The MAX6864–MAX6869 offer watchdog
timeout options of 3.3s or 209s (typ). The MAX6861/
MAX6862/MAX6863 feature a pin-selectable reset delay
period of 10ms or 150ms (min). Push-pull active-low,
push-pull active-high, and open-drain active-low reset
outputs are available.
Push-Pull RESET
Open-Drain RESET
♦ No External Components
♦ Small 5-Pin SOT23 Package
♦ Pin Compatible to the TPS3836/TPS3837/TPS3838
(MAX6861/MAX6862/MAX6863)
Ordering Information
†
PART
TEMP RANGE PIN-PACKAGE
-40°C to +85°C 5 SOT23-5
-40°C to +85°C 5 SOT23-5
Applications
Portable/Battery-Powered Equipment
MAX6854UK_ _D_-T
MAX6855UK_ _D_-T
PDAs/Cell Phones
†
Insert reset threshold suffix (see Table 2, Threshold Suffix
Guide) after UK. Insert the number corresponding to the
desired reset timeout period (see Table 4, Reset Timeout
Period) after D.
MP3 Players/Pagers
Glucose Monitors/Patient Monitors
Note: Sample stock is generally held on standard versions
only (see Table 5, Standard Versions Table). Standard versions
have an order increment of 2500 pieces. Nonstandard versions
have an order increment of 10,000 pieces. Contact factory for
availability of nonstandard versions.
Typical Operating Circuit
V
CC
0.1µF
Devices are available in both leaded and lead-free packaging.
Specify lead-free by replacing “-T” with “+T” when ordering.
V
CC
V
CC
RESET
RESET
Pin Configurations and Selector Guide appear at end of
data sheet.
µP
MAX6864
MAX6867
Ordering Information continued at end of data sheet.
MR
I/O
WDI
MANUAL
RESET
GND
GND
________________________________________________________________ Maxim Integrated Products
1
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.
Nanopower µP Supervisory Circuits with
Manual Reset and Watchdog Timer
ABSOLUTE MAXIMUM RATINGS
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature .....................................................+150°C
Storage Temperature Range.............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
V
, Open-Drain RESET to GND ..........................-0.3V to +6.0V
CC
MR, Push-Pull RESET, RESET,
WDI, CT, I.C............................................-0.3V to (V
Input Current, Output Current (all pins)............................ 20mA
+ 0.3V)
CC
Continuous Power Dissipation (T = +70°C)
A
5-Pin SOT23 (derate 7.1mW/°C above +70°C)............571mW
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
= 1.2V to 5.5V, T = -40°C to +85°C, unless otherwise specified. Typical values are at V
= 2.5V, T = +25°C.) (Note 1)
CC A
CC
A
PARAMETER
SYMBOL
CONDITIONS
MIN
1.1
TYP
MAX
5.5
UNITS
T
T
≥ 0°C
A
Supply Voltage
Supply Current
V
V
CC
= -40°C to +85°C
1.2
5.5
A
V
V
V
= 5.0V
= 3.3V
= 1.8V
210
190
170
7
400
380
370
15
CC
CC
CC
V
> V , no load,
CC
TH
nA
reset output
I
CC
deasserted (Note 2)
V
V
< V , no load, reset output asserted
TH
µA
V
CC
CC
V
-
V
+
TH
TH
V
Reset Threshold
V
falling (see Table 2)
V
TH
CC
TH
2.5%
2.5%
Reset Threshold Hysteresis
V
Reset asserted to reset deasserted
0.5
15
%V
TH
HYST
D1
D2
10
40
25
80
60
D3
D4
D5
D6
150
1200
300
600
225
1800
450
900
300
2400
600
1200
V
= V + 150mV
TH
CC
Reset Timeout Period
t
ms
RP
(Figures 2 and 3)
V
falling from (V + 100mV) to
TH
CC
V
to Reset Delay
t
40
µs
CC
RD
(V - 100mV) at 10mV/µs
TH
V
≥ 1.1V, I
= 50µA,
A
CC
SINK
0.3
0.3
0.3
RESET asserted, T ≥ 0°C
V
≥ 1.2V, I
= 100µA,
CC
SINK
V
OL
RESET asserted
V
≥ 2.12V, I
= 1.2mA,
SINK
CC
RESET Output Voltage
V
RESET asserted
V
≥ 1.71V, I
= 200µA,
SOURCE
CC
0.8 x V
0.8 x V
CC
CC
RESET deasserted, push-pull RESET only
V
OH
V
≥ 2.38V, I = 500µA,
CC
SOURCE
RESET deasserted, push-pull RESET only
Open-Drain RESET Leakage
Current
I
RESET deasserted
25
nA
LKG
2
_______________________________________________________________________________________
Nanopower µP Supervisory Circuits with
Manual Reset and Watchdog Timer
ELECTRICAL CHARACTERISTICS (continued)
(V
= 1.2V to 5.5V, T = -40°C to +85°C, unless otherwise specified. Typical values are at V
= 2.5V, T = +25°C.) (Note 1)
CC A
CC
A
PARAMETER
SYMBOL
CONDITIONS
≥ 1.1V, I = 10µA,
SOURCE
MIN
TYP
MAX
UNITS
V
CC
0.8 x V
0.8 x V
0.8 x V
0.8 x V
CC
CC
CC
CC
RESET asserted, T ≥ 0°C
A
V
≥ 1.2V, I
= 10µA,
CC
SOURCE
RESET asserted
V
OH
V
≥ 1.53V, I
RESET asserted
= 200µA,
= 500µA,
CC
SOURCE
RESET Output Voltage
V
V
≥ 2.12V, I
CC
SOURCE
RESET asserted
V
≥ 1.71V, I
= 500µA,
SINK
CC
0.3
RESET deasserted
V
OL
V
≥ 2.38V, I = 1.2mA,
SINK
CC
0.3
20
RESET deasserted
CT Input Current
CT = GND or V
nA
V
CC
V
0.8 x V
IH
CC
CC
CT Input Voltage
V
0.2 x V
IL
CC
CC
MANUAL RESET INPUT
MR Input Voltage
V
0.7 x V
1
IH
V
V
0.3 x V
IL
MR Minimum Pulse Width
MR Glitch Rejection
MR to Reset Delay
t
µs
ns
ns
kΩ
MPW
200
250
10
t
MRD
MR Pullup Resistance
5
20
WATCHDOG TIMER (MAX6864–MAX6869)
V
0.7 x V
IH
CC
WDI Input Voltage
V
V
0.3 x V
20
IL
CC
WDI Input Current
WDI Pulse Width
WDI = GND or V
nA
ns
CC
t
(Note 3)
150
1.5
95
WDI
S
L
3.3
7.75
487
Watchdog Timeout Period
t
s
WD
209
Note 1: Devices are tested at T = +25°C. Specifications for T = -40°C to +85°C are guaranteed by design.
A
A
Note 2: For the MAX6864–MAX6869, the watchdog period is 1s with t
Note 3: Guaranteed by design.
and t
< 50ns.
RISE
FALL
_______________________________________________________________________________________
3
Nanopower µP Supervisory Circuits with
Manual Reset and Watchdog Timer
Typical Operating Characteristics
(V = +2.5V, T = +25°C, unless otherwise noted.)
CC
A
SUPPLY CURRENT
vs. SUPPLY VOLTAGE
SUPPLY CURRENT
vs. TEMPERATURE
NORMALIZED RESET TIMEOUT PERIOD
vs. TEMPERATURE
0.22
0.20
0.18
0.16
0.14
0.12
0.10
1.02
1.01
1.00
0.99
0.98
10.0
V
= 2.23V
RESET IS NOT ASSERTED
= 1.575V
TH
V
TH
V
= 3.3V
CC
V
= 5.5V
CC
T
= +85°C
A
T
= +25°C
A
V
= 2.5V
CC
1.0
0.1
T
= -40°C
A
V
= 1.8V
35
CC
1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
(V)
-40
-15
10
60
85
-40
-15
10
35
60
85
V
TEMPERATURE (°C)
TEMPERATURE (°C)
CC
NORMALIZED WATCHDOG TIMEOUT PERIOD
vs. TEMPERATURE
MAXIMUM V TRANSIENT DURATION
CC
vs. RESET THRESHOLD OVERDRIVE
1.8
1000
100
10
RESET OCCURS ABOVE THIS LINE
1.6
1.4
1.2
1.0
0.8
0.6
0.4
1
V
FALLING FROM V +100mV
TH
CC
0.1
-40
-15
10
35
60
85
10
100
1000
TEMPERATURE (°C)
RESET THRESHOLD OVERDRIVE (mV)
NORMALIZED RESET THRESHOLD VOLTAGE
vs. TEMPERATURE
V
TO RESET DELAY
CC
vs. TEMPERATURE
1.010
1.005
1.000
0.995
0.990
70
60
50
40
30
20
V
= V + 100mV TO V - 100mV
TH
CC
TH
-40
-15
10
35
60
85
-40
-15
10
35
60
85
TEMPERATURE (°C)
TEMPERATURE (°C)
4
_______________________________________________________________________________________
Nanopower µP Supervisory Circuits with
Manual Reset and Watchdog Timer
Typical Operating Characteristics (continued)
(V = +2.5V, T = +25°C, unless otherwise noted.)
CC
A
OUTPUT LOW VOLTAGE
vs. SINK CURRENT
OUTPUT HIGH VOLTAGE
vs. SOURCE CURRENT
SUPPLY CURRENT vs. WATCHDOG
SWITCHING FREQUENCY
0.30
0.25
0.20
0.15
0.10
0.05
0
0.50
0.45
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0
100
10
1
V
= 2.5V
CC
V
= 2.5V
CC
V
= 2.5V
CC
V
= 1.8V
V
= 1.8V
CC
CC
V
= 3.3V
CC
V
= 3.3V
CC
0.1
0
1000
2000
I
3000
(µA)
4000
5000
0
200
400
I
600
800
1000
10
100
1k
10k
100k
1M
10M
(µA)
WATCHDOG SWITCHING FREQUENCY (Hz)
SINK
SOURCE
MANUAL RESET DELAY
V
CC
TO RESET DELAY
MAX6854 toc11
MAX6854 toc12
V
CC
MR
1V/div
1.7V
1.5V
200mV/div
t
V
= 1.575V
MRD
TH
t
RD
RESET
1V/div
RESET
1V/div
0
200ns/div
10µs/div
_______________________________________________________________________________________
5
Nanopower µP Supervisory Circuits with
Manual Reset and Watchdog Timer
MAX6854/MAX6855/MAX6856 Pin Description
PIN
NAME
FUNCTION
MAX6854/
MAX6856
MAX6855
Active-Low Open-Drain or Push-Pull Reset Output. RESET transitions from high to
low when V drops below the selected reset threshold or MR is pulled low.
CC
1
—
RESET
RESET remains low for the reset timeout period after V
exceeds the device
CC
reset threshold and MR deasserts. Push-pull RESET outputs are referenced to
. Open-drain RESET outputs require an external pullup resistor.
V
CC
2, 4
3
2, 4
3
GND
Ground. Connect all GND inputs to the same potential.
Active-Low Manual Reset Input. Drive MR low to initiate a reset. The reset output
remains asserted while MR is held low and for the reset timeout period after MR
transitions high. Leave MR unconnected or connect to V
MR
if unused. MR is
CC
internally pulled up to V
through 10kΩ.
CC
Supply Voltage. Input for V
a 0.1µF capacitor to GND.
reset monitor. For noisy systems, bypass V
with
CC
CC
5
5
1
V
CC
Active-High Push-Pull Reset Output. RESET transitions from low to high when
drops below the selected reset threshold or MR is pulled low. RESET
V
CC
—
RESET
remains high for the reset timeout period after V exceeds the device reset
CC
threshold and MR deasserts. RESET is referenced to V
.
CC
MAX6858/MAX6860 Pin Description
PIN
NAME
FUNCTION
MAX6858/
MAX6860
1, 2
3
I.C.
Internally Connected. For increased noise immunity, connect I.C. to GND.
Ground
GND
Active-Low Open-Drain or Push-Pull Reset Output. RESET transitions from high to low when V
CC
drops below the selected reset threshold. RESET remains low for the reset timeout period after
exceeds the device reset threshold. Push-pull RESET outputs are referenced to V . Open-
drain RESET outputs require an external pullup resistor.
4
5
RESET
V
CC
CC
Supply Voltage. Input for V
capacitor to GND.
reset monitor. For noisy systems, bypass V
with a 0.1µF
CC
CC
V
CC
6
_______________________________________________________________________________________
Nanopower µP Supervisory Circuits with
Manual Reset and Watchdog Timer
MAX6861/MAX6862/MAX6863 Pin Description
PIN
NAME
FUNCTION
MAX6861/
MAX6863
MAX6862
Reset Timeout Select Input. Connect CT low to select the D1 reset timeout output
1
2
1
2
CT
period (see Tables 1 and 4). Connect CT high (normally V ) to select the D3
CC
reset timeout period.
GND
Ground
Active-Low Manual Reset Input. Drive MR low to initiate a reset. The reset output
remains asserted while MR is held low and for the reset timeout period after MR
3
3
MR
transitions high. Leave MR unconnected or connect to V
if unused. MR is
CC
internally pulled up to V
through 10kΩ.
CC
Active-Low Open-Drain or Push-Pull Reset Output. RESET transitions from high to
low when V drops below the selected reset threshold or MR is pulled low.
CC
4
—
RESET
RESET remains low for the reset timeout period after V
exceeds the device
CC
reset threshold and MR deasserts. Push-pull RESET outputs are referenced to
. Open-drain RESET outputs require an external pullup resistor.
V
CC
Supply Voltage. Input for V
a 0.1µF capacitor to GND.
reset monitor. For noisy systems, bypass V
with
CC
CC
5
5
4
V
CC
Active-High Push-Pull Reset Output. RESET transitions from low to high when
drops below the selected reset threshold or MR is pulled low. RESET
V
CC
—
RESET
remains high for the reset timeout period after V exceeds the device reset
CC
threshold and MR deasserts. RESET is referenced to V
.
CC
_______________________________________________________________________________________
7
Nanopower µP Supervisory Circuits with
Manual Reset and Watchdog Timer
MAX6864/MAX6865/MAX6866 Pin Description
PIN
NAME
FUNCTION
MAX6864/
MAX6866
MAX6865
Active-Low Open-Drain or Push-Pull Reset Output. RESET transitions from high to
low when V drops below the selected reset threshold, MR is pulled low, or the
CC
watchdog timer expires. RESET remains low for the reset timeout period after
1
—
RESET
V
exceeds the device reset threshold, MR deasserts, or after the watchog
CC
timer expires. Push-pull RESET outputs are referenced to V . Open-drain
CC
RESET outputs require an external pullup resistor.
2
3
2
3
GND
Ground
Active-Low Manual Reset Input. Drive MR low to initiate a reset. The reset output
remains asserted while MR is held low and for the reset timeout period after MR
transitions high. Leave MR unconnected or connect to V
MR
if unused. MR is
CC
internally pulled up to V
through 10kΩ.
CC
Watchdog Input. If WDI remains high or low for longer than the watchdog timeout
period, the internal watchdog timer expires, and a reset is triggered for the reset
timeout period. The internal watchdog timer clears whenever reset is asserted,
the manual reset is asserted, or WDI sees a rising or falling edge.
4
5
4
5
WDI
Supply Voltage. Input for V
a 0.1µF capacitor to GND.
reset monitor. For noisy systems, bypass V
with
CC
CC
V
CC
Active-High Push-Pull Reset Output. RESET transitions from low to high when
drops below the selected reset threshold, MR is pulled low, or the watchdog
V
CC
—
1
RESET
timer expires. RESET remains high for the reset timeout period after V exceeds
CC
the device reset threshold, MR deasserts, or after the watchdog timer expires.
RESET is referenced to V
.
CC
8
_______________________________________________________________________________________
Nanopower µP Supervisory Circuits with
Manual Reset and Watchdog Timer
MAX6867/MAX6868/MAX6869 Pin Description
PIN
NAME
FUNCTION
MAX6867/
MAX6869
MAX6868
Watchdog Input. If WDI remains high or low for longer than the watchdog timeout
period, the internal watchdog timer expires, and a reset is triggered for the reset
timeout period. The internal watchdog timer clears whenever reset is asserted,
the manual reset is asserted, or WDI sees a rising or falling edge.
1
2
3
1
2
3
WDI
GND
MR
Ground
Active-Low Manual Reset Input. Drive MR low to initiate a reset. The reset output
remains asserted while MR is held low and for the reset timeout period after MR
transitions high. Leave MR unconnected or connect to V
if unused. MR is
CC
internally pulled up to V
through 10kΩ.
CC
Active-Low Open-Drain or Push-Pull Reset Output. RESET transitions from high to
low when V drops below the selected reset threshold, MR is pulled low, or the
CC
watchdog timer expires. RESET remains low for the reset timeout period after
4
—
RESET
V
exceeds the device reset threshold, MR deasserts, or after the watchdog
CC
timer expires. Push-pull RESET outputs are referenced to V . Open-drain
CC
RESET outputs require an external pullup resistor.
Supply Voltage. Input for V
a 0.1µF capacitor to GND.
reset monitor. For noisy systems, bypass V
with
CC
CC
5
5
4
V
CC
Active-High Push-Pull Reset Output. RESET transitions from low to high when
drops below the selected reset threshold, MR is pulled low, or the watchdog
V
CC
—
RESET
timer expires. RESET remains high for the reset timeout period after V
CC
exceeds the device reset threshold, MR deasserts, or after the watchdog timer
expires. RESET is referenced to V
.
CC
_______________________________________________________________________________________
9
Nanopower µP Supervisory Circuits with
Manual Reset and Watchdog Timer
MAX6854
MAX6855
MAX6856
MAX6858
MAX6860–
MAX6869
V
CC
RESET
(MAX6854/MAX6856/MAX6858/
MAX6860/MAX6861
MAX6863/MAX6864/MAX6866/
MAX6867/MAX6869)
RESET
TIMEOUT
GENERATOR
RESET
(MAX6855/MAX6862/MAX6865/
MAX6868)
1.25V
V
CC
10kΩ
CT
MR
(MAX6854/MAX6855/MAX6856/
MAX6861–MAX6869)
(MAX6861/MAX6862/MAX6863)
WATCHDOG
TRANSITION
DETECTOR
WATCHDOG
TIMER
WDI
(MAX6864–MAX6869)
GND
Figure 1. Functional Diagram
V
TH
V
CC
t
RP
t
RP
t
RD
t
MRD
RESET*
t
MPW
MR
*RESET IS THE INVERSE OF RESET.
Figure 2. RESET Timing Relationship
10 ______________________________________________________________________________________
Nanopower µP Supervisory Circuits with
Manual Reset and Watchdog Timer
V
CC
t
t
RP
t
WD
WDI
WDI
OV
V
CC
RESET*
OV
*RESET IS THE INVERSE OF RESET.
Figure 3. Detailed Watchdog Input Timing Relationship
Watchdog Input
Detailed Description
The MAX6864–MAX6869’s watchdog timer circuitry
monitors the µP’s activity. If the µP does not toggle
(low-to-high or high-to-low) the watchdog input (WDI)
RESET/RESET Output
A µP’s reset input starts the µP in a known state. The
MAX6854/MAX6855/MAX6856/MAX6858/MAX6860–
MAX6869 µP supervisory circuits assert a reset to prevent
code-execution errors during power-up, power-down, and
brownout conditions. The MAX6854/MAX6855/MAX6856/
MAX6858/MAX6860–MAX6869 reset output is guaranteed
within the watchdog timeout period (t
), reset asserts
WDI
for the reset timeout period (t ). The internal timer is
RP
cleared when reset asserts, when manual reset is
asserted, or by a rising or falling edge on WDI. The
watchdog input detects pulses as short as 150ns.
While reset is asserted the watchdog timer does not
count. As soon as reset deasserts, the watchdog timer
resumes counting (Figure 3).
to be valid for V down to 1.1V.
CC
Whenever V
falls below the reset threshold, the reset
output asserts low for RESET and high for RESET.
Once V exceeds the reset threshold, an internal
timer keeps the reset output asserted for the specified
reset timeout period, then after this interval the reset
output deasserts (see Figure 2).
CC
CC
Applications Information
Selecting the Reset Timeout Period
The reset timeout period for the MAX6854/MAX6855/
MAX6856/MAX6858/MAX6860/MAX6864–MAX6869 is
fixed (see Table 4). The MAX6861/MAX6862/MAX6863
feature a reset timeout select input, CT. Connect CT
according to Table 1 to select between the available
10ms and 150ms (min) reset timeout periods. The time-
out period can be changed while a reset timeout period
is in progress, but will not update until the reset timeout
period has expired.
Manual Reset Input
Many µP-based products require manual reset capabil-
ity, allowing the operator, a test technician, or external
logic circuitry to initiate a reset. The MAX6854/
MAX6855/MAX6856/MAX6861–MAX6869 feature an
MR input. A logic low on MR asserts a reset. Reset
remains asserted while MR is low and for the timeout
period, t , after MR returns high. The devices provide
RP
an internal 10kΩ pullup from MR to V . Leave MR
CC
unconnected or connect to V
if unused. MR can be
CC
Table 1. MAX6861/MAX6862/MAX6863
Reset Timeout Period Selection
driven with CMOS logic levels or with open-drain/col-
lector outputs. Connect a normally open momentary
switch from MR to GND to implement a manual reset
function; external debounce circuitry is not required. If
MR is driven by long cables or the device is used in a
noisy environment, connect a 0.1µF capacitor from MR
to GND to provide additional noise immunity.
CT CONNECTION
LOW
MIN
10
TYP
15
MAX
25
UNITS
ms
HIGH
150
225
300
______________________________________________________________________________________ 11
Nanopower µP Supervisory Circuits with
Manual Reset and Watchdog Timer
open-drain output to level-shift from the monitored sup-
ply to reset circuitry powered by another supply voltage.
Keep in mind that as the supervisor’s V decreases,
Transient Immunity
In addition to issuing a reset to the µP during power-up,
power-down, and brownout conditions, the MAX6854/
MAX6855/MAX6856/MAX6858/MAX6860–MAX6869 are
relatively immune to short-duration supply transients, or
CC
so does the IC’s ability to sink current at RESET.
Ensuring a Valid RESET Down to V
= 0V
CC
glitches. The Maximum V
Transient Duration vs. Reset
CC
(Push-Pull RESET)
Threshold Overdrive graph in the Typical Operating
Characteristics shows this relationship.
When V
falls below 1.1V, RESET’s current-sinking
CC
capability declines drastically. The high-impedance
CMOS logic inputs connected to RESET can drift to
undetermined voltages. This presents no problems in
most applications, since most µPs and other circuitry
The area below the curve of the graph is the region in
which these devices typically do not generate a reset
pulse. This graph was generated using a falling pulse
applied to V , starting 100mV above the actual reset
CC
do not operate with V
below 1.1V.
CC
threshold, V , and ending below this threshold (reset-
TH
In those applications where RESET must be valid down
to 0, add a pulldown resistor between RESET and GND
for the MAX6854/MAX6858/MAX6861/MAX6864/
MAX6867 push-pull outputs. The resistor sinks any stray
leakage currents, holding RESET low (Figure 5). Choose
a pulldown resistor that accommodates leakages, such
that RESET is not significantly loaded and is capable of
pulling to GND. The external pulldown cannot be used
with the open-drain reset outputs.
threshold overdrive). As the magnitude of the transient
increases, the maximum allowable pulse width
decreases. Typically, a 100mV V
transient duration
CC
of 40µs or less does not cause a reset.
Interfacing to Other Voltages for Logic
Compatibility
The open-drain RESET output can be used to interface
to a µP with other logic levels. As shown in Figure 4, the
open-drain output can be connected to voltages from 0
to 5.5V.
Watchdog Software Considerations
One way to help the watchdog timer monitor software
execution more closely is to set and reset the watchdog
Generally, the pullup resistor connected to RESET con-
nects to the supply voltage that is being monitored at
the IC’s V
input. However, some systems use the
CC
V
CC
1.8V
3.3V
V
CC
V
CC
MAX6856
MAX6860
MAX6863
MAX6866
MAX6869
100kΩ
MAX6854
MAX6858
MAX6861
MAX6864
MAX6867
V
CC
RESET
µP
RESET
N
RESET
2MΩ
GND
GND
GND
Figure 5. Ensuring RESET Valid to V
= Ground
Figure 4. Interfacing with Other Voltage Levels
CC
12 ______________________________________________________________________________________
Nanopower µP Supervisory Circuits with
Manual Reset and Watchdog Timer
input at different points in the program, rather than
Table 2. Threshold Suffix Guide
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.
V
CC
THRESHOLD FALLING
SUFFIX
UNITS
MIN
TYP
MAX
46
45
44
43
42
41
40
39
38
37
36
35
34
33
32
31
30
29
28
27
26
25
24
23
225
22
21
20
19
18
17
16
4.509
4.388
4.266
4.193
4.095
3.998
3.900
3.802
3.705
3.608
3.510
3.413
3.315
3.218
3.120
2.998
2.925
2.852
2.730
2.633
2.559
2.438
2.340
2.255
2.180
2.133
2.048
1.950
1.853
1.755
1.623
1.536
4.625
4.500
4.375
4.300
4.200
4.100
4.000
3.900
3.800
3.700
3.600
3.500
3.400
3.300
3.200
3.075
3.000
2.925
2.800
2.700
2.625
2.500
2.400
2.313
2.235
2.188
2.100
2.000
1.900
1.800
1.665
1.575
4.741
4.613
4.484
4.408
4.305
4.203
4.100
3.998
3.895
3.793
3.690
3.588
3.485
3.383
3.280
3.152
3.075
2.998
2.870
2.768
2.691
2.563
2.460
2.371
2.290
2.243
2.153
2.050
1.948
1.845
1.707
1.614
Figure 6 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 beginning of
every subroutine or loop, then set high again when the
program returns to the beginning. If the program
should hang in any subroutine, the problem would
quickly be 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.
START
SET WDI
HIGH
V
PROGRAM
CODE
SUBROUTINE OR
PROGRAM LOOP
SET WDI LOW
RETURN
Figure 6. Watchdog Flow Diagram
Table 3. Watchdog Timeout
WATCHDOG TIMEOUT PERIOD
SUFFIX
MIN
1.5
95
TYP
3.3
MAX
7.75
487
UNITS
S
L
s
209
______________________________________________________________________________________ 13
Nanopower µP Supervisory Circuits with
Manual Reset and Watchdog Timer
Ordering Information (continued)
Table 4. Reset Timeout Periods
RESET TIMEOUT PERIODS
TIMEOUT
†
PART
TEMP RANGE PIN-PACKAGE
-40°C to +85°C 5 SOT23-5
-40°C to +85°C 5 SOT23-5
-40°C to +85°C 5 SOT23-5
-40°C to +85°C 5 SOT23-5
-40°C to +85°C 5 SOT23-5
-40°C to +85°C 5 SOT23-5
-40°C to +85°C 5 SOT23-5
-40°C to +85°C 5 SOT23-5
-40°C to +85°C 5 SOT23-5
-40°C to +85°C 5 SOT23-5
-40°C to +85°C 5 SOT23-5
-40°C to +85°C 5 SOT23-5
OPTION
MIN
10
TYP
15
MAX
25
UNITS
MAX6856UK_ _D_-T
MAX6858UK_ _D_-T
MAX6860UK_ _D_-T
MAX6861UK_ _-T
D1
D2
D3
D4
D5
D6
40
60
80
150
1200
300
600
225
1800
450
900
300
2400
600
1200
ms
MAX6862UK_ _-T
MAX6863UK_ _-T
MAX6864UK_ _D_ _-T
MAX6865UK_ _D_ _-T
MAX6866UK_ _D_ _-T
MAX6867UK_ _D_ _-T
MAX6868UK_ _D_ _-T
MAX6869UK_ _D_ _-T
Table 5. Standard Versions
PART
MAX6854UK16D3
MAX6854UK23D3
MAX6854UK26D3
MAX6854UK29D3
MAX6854UK31D3
MAX6856UK16D3
MAX6856UK23D3
MAX6856UK26D3
MAX6856UK29D3
MAX6856UK31D3
MAX6861UK17
TOP MARK
AEFS
AEFY
AEFZ
†
Insert reset threshold suffix (see Table 2, Threshold Suffix
Guide) after UK. Insert the number corresponding to the desired
reset timeout period (see Table 4, Reset Timeout Period) after D.
Insert the letter corresponding to the desired watchdog timeout
period (S or L, see Table 3) into the blank following the reset
timeout period suffix for the MAX6864–MAX6869.
AEGA
AEGB
AEGR
AEGS
AEGT
AEGU
AEGV
AEKO
AEKS
AEKP
AEKQ
AEOS
AEOT
AEOU
AEOV
AEOW
AEOX
AEOY
AEOZ
AEGC
AEGD
AEGE
AEGF
AEGG
AEGW
AEGX
AEGY
AEFT
Note: Sample stock is generally held on standard versions
only (see Table 5, Standard Versions Table). Standard versions
have an order increment of 2500 pieces. Nonstandard versions
have an order increment of 10,000 pieces. Contact factory for
availability of nonstandard versions.
MAX6861UK225
MAX6861UK26
Devices are available in both leaded and lead-free packaging.
Specify lead-free by replacing “-T” with “+T” when ordering.
MAX6861UK29
MAX6862UK17
MAX6862UK225
MAX6862UK26
MAX6862UK29
MAX6863UK17
MAX6863UK225
MAX6863UK26
MAX6863UK29
MAX6864UK16D3S
MAX6864UK23D3S
MAX6864UK26D3S
MAX6864UK29D3S
MAX6864UK31D3S
MAX6866UK16D3S
MAX6866UK23D3S
MAX6866UK26D3S
MAX6866UK29D3S
MAX6866UK31D3S
AEGZ
14 ______________________________________________________________________________________
Nanopower µP Supervisory Circuits with
Manual Reset and Watchdog Timer
Pin Configurations
TOP VIEW
I.C.
I.C.
1
2
3
5
4
V
CT
GND
MR
1
2
3
5
4
V
CC
CC
RESET
(RESET)
1
2
3
5
4
V
CC
MAX6858
MAX6860
MAX6861
MAX6862
MAX6863
MAX6854
MAX6855
MAX6856
GND
GND
RESET
RESET
(RESET)
MR
GND
SOT23
SOT23
( ) MAX6862 ONLY
SOT23
( ) MAX6855 ONLY
RESET
(RESET)
1
2
3
5
4
V
WDI
1
2
3
5
4
V
CC
CC
MAX6864
MAX6865
MAX6866
MAX6867
MAX6868
MAX6869
GND
GND
MR
MR
WDI
RESET
(RESET)
SOT23
( ) MAX6865 ONLY
SOT23
( ) MAX6868 ONLY
______________________________________________________________________________________ 15
Nanopower µP Supervisory Circuits with
Manual Reset and Watchdog Timer
Selector Guide
RESET OUTPUT
PART
MR
WDI
CT
PUSH-PULL
ACTIVE LOW
PUSH-PULL
ACTIVE HIGH
OPEN-DRAIN ACTIVE
LOW
MAX6854
MAX6855
MAX6856
MAX6858
MAX6860
MAX6861
MAX6862
MAX6863
MAX6864
MAX6865
MAX6866
MAX6867
MAX6868
MAX6869
√
—
√
—
—
√
√
√
—
—
—
—
—
—
—
—
√
—
—
—
—
—
√
—
—
√
—
—
—
—
√
√
—
√
—
—
√
—
√
—
—
√
—
—
√
√
√
—
—
√
√
√
—
—
√
√
—
—
—
—
—
—
—
—
√
√
√
—
—
√
√
√
—
—
√
√
√
—
—
√
√
—
√
√
Chip Information
TRANSISTOR COUNT: 2848
PROCESS: BiCMOS
16 ______________________________________________________________________________________
Nanopower µP Supervisory Circuits with
Manual Reset and Watchdog Timer
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.)
PACKAGE OUTLINE, SOT-23, 5L
1
21-0057
E
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.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 17
© 2005 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products, Inc.
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