LTC1726
Triple Supply Monitor and
µP Supervisor with Adjustable
Reset and Watchdog Timer
FeaTures
n
DescripTion
The
LTC
®
1726
is a triple supply monitor and microproces-
sor supervisory circuit with adjustable reset and watchdog
functions intended for systems with multiple supply volt-
ages. The part has a common open-drain reset output
with an adjustable delay. The reset and watchdog time-out
periods are both adjustable using external capacitors.
Tight 1.5% accuracy specifications and glitch immunity
ensure reliable reset operation without false triggering.
The
RST
output is guaranteed to be in the correct state for
V
CC5
/V
CC25
or V
CC3
down to 1V. The LTC1726 may also be
configured to monitor any one or two V
CC
inputs instead
of three, depending on system requirements.
The low (16µA typical) supply current makes the LTC1726
ideal for power-conscious systems.
L,
LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and
ThinSOT is a trademark of Linear Technology Corporation. All other trademarks are the property
of their respective owners.
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Monitors Three Inputs Simultaneously
LTC1726-5: 5V, 3.3V and ADJ
LTC1726-2.5: 2.5V, 3.3V and ADJ
±1.5% Threshold Accuracy Over Temperature
Low Supply Current: 16µA Typ
Adjustable Reset Timeout
Adjustable Watchdog Timeout
Active Low Open-Drain Reset Output
Power Supply Glitch Immunity
Guaranteed
RESET
for V
CC3
≥ 1V or V
CC25
/V
CC5
≥ 1V
MS8 and SO-8 Packages
applicaTions
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Desktop Computers
Notebook Computers
Intelligent Instruments
Portable Battery-Powered Equipment
Network Servers
Typical applicaTion
A 3.3V, 5V and 1.8V Monitor
1.8V
(V
TRIP
= 1.665V)
3.3V
0.1µF
5V
0.1µF
C
RT
47nF
C
WT
47nF
2
8
1
3
6
R1
66.5k
1%
R2
100k
1%
RESET
µP
I/O
C
WT
47nF
3.3V
0.1µF
2.5V
0.1µF
C
RT
47nF
2
8
1
3
6
A 3.3V, 2.5V and 1.8V Monitor
1.8V
(V
TRIP
= 1.665V)
R1
66.5k
1%
R2
100k
1%
RESET
µP
I/O
V
CC5
V
CC3
V
CCA
RT
RST
LTC1726-5
V
CC25
V
CC3
V
CCA
RT
RST
LTC1726-2.5
7
WT
GND
WDI
7
WT
GND
WDI
5
5
t
RT
= 155ms
t
WT
= 1s
4
1726 TA01
t
RT
= 155ms
t
WT
= 1s
4
1726 TA02
1726fd
For more information
www.linear.com/LTC1726
1
LTC1726
absoluTe MaxiMuM raTings
(Notes 1, 2)
Terminal Voltage
V
CC3
, V
CC5
/V
CC25
, V
CCA
........................... –0.3V to 7V
RST
.......................................................... –0.3V to 7V
WDI ......................................................... –0.3V to 7V
RT, WT ..................................................... –0.3V to 7V
Operating Temperature Range (Note 3)
LTC1726E, LTC1726I ............................–40°C to 85°C
LTC1726H .......................................... –40°C to 125°C
Storage Temperature Range .................. –65°C to 150°C
Lead Temperature (Soldering, 10 sec)................... 300°C
pin conFiguraTion
TOP VIEW
TOP VIEW
V
CC3
V
CC25
/V
CC5
V
CCA
GND
1
2
3
4
8
7
6
5
RT
WT
RST
WDI
V
CC3
1
V
CC25
/V
CC5
2
V
CCA
3
GND 4
8
7
6
5
RT
WT
RST
WDI
MS8 PACKAGE
8-LEAD PLASTIC MSOP
T
JMAX
= 125°C,
θ
JA
= 200°C/W
S8 PACKAGE
8-LEAD PLASTIC SO
T
JMAX
= 125°C,
θ
JA
= 150°C/W
orDer inForMaTion
LEAD FREE FINISH
LTC1726EMS8-2.5#PBF
LTC1726EMS8-5#PBF
LTC1726HMS8-5#PBF
LTC1726ES8-2.5#PBF
LTC1726ES8-5#PBF
LTC1726IS8-2.5#PBF
LTC1726IS8-5#PBF
TAPE AND REEL
LTC1726EMS8-2.5#TRPBF
LTC1726EMS8-5#TRPBF
LTC1726HMS8-5#TRPBF
LTC1726ES8-2.5#TRPBF
LTC1726ES8-5#TRPBF
LTC1726IS8-2.5#TRPBF
LTC1726IS8-5#TRPBF
PART MARKING
LTKZ
LTLA
LTLA
172625
17265
726I25
1726I5
PACKAGE DESCRIPTION
8-Lead Plastic MSOP
8-Lead Plastic MSOP
8-Lead Plastic MSOP
8-Lead Plastic SO
8-Lead Plastic SO
8-Lead Plastic SO
8-Lead Plastic SO
TEMPERATURE RANGE
–40°C to 85°C
–40°C to 85°C
–40°C to 125°C
–40°C to 85°C
–40°C to 85°C
–40°C to 85°C
–40°C to 85°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
Consult LTC Marketing for information on non-standard lead based finish parts.
For more information on lead free part marking, go to:
http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to:
http://www.linear.com/tapeandreel/
1726fd
2
For more information
www.linear.com/LTC1726
LTC1726
elecTrical characTerisTics
SYMBOL
V
RT3
V
RT5
V
RT25
V
RTA
V
CC
I
VCC3
I
VCC5
I
VCC25
I
VCCA
PARAMETER
Reset Threshold V
CC3
Reset Threshold V
CC5
Reset Threshold V
CC25
Reset Threshold V
CCA
V
CC3
or V
CC5
Operating Voltage
V
CC3
Supply Current
V
CC5
Supply Current
V
CC25
Supply Current
V
CCA
Input Current
RT Charge Current Out
CONDITIONS
V
CC3
Input Threshold
H-Grade
V
CC5
Input Threshold (5V Version)
H-Grade
V
CC25
Input Threshold (2.5V Version),
V
CCA
Input Threshold
H-Grade
RST
in Correct Logic State
V
CC5
/V
CC25
> V
CC3
V
CC5
/V
CC25
< V
CC3
, V
CC3
= 3.3V
V
CC5
= 5V
V
CC25
< V
CC3
, V
CC25
= 2.5V (Note 4)
V
CCA
= 1V
V
RT
= 0V
H-Grade
WT Charge Current Out
V
WT
= 0V
H-Grade
RT Discharge Current Out
V
RT
= 1.3V
H-Grade
WT Discharge Current Out
V
WT
= 1.3V
H-Grade
∆t
RT
t
UV
V
OH
V
OL
Reset Time-Out Period Variation
C
RT
= 1500pF Deviation from t
RT
= 5ms (Note 5)
H-Grade
V
CC
Undervoltage Detect to
RST
RST
Output Voltage High (Note 6)
RST
Output Voltage Low
V
CC25
/V
CC5
, V
CC3
or V
CCA
Less Than Reset
Threshold V
RT
by More Than 1%
I
SOURCE
= 1µA
I
SINK
= 2.5mA, V
CC5
/V
CC25
= 0V
I
SINK
= 100µA, V
CC3
= 1V, V
CC5
/V
CC25
= 0V
I
SINK
= 100µA, V
CC3
= 0V, V
CC5
/V
CC25
= 1V
I
SINK
= 100µA, V
CC3
= 1V, V
CC5
/V
CC25
= 1V
l
l
l
l
l
l
l
0.3 • V
CC3
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
l
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
CC3
= 3.3V, V
CC5
= 5V, V
CC25
= 2.5V, V
CCA
= V
CC3
unless otherwise noted.
MIN
3.036
3.023
4.600
4.582
2.300
0.985
0.978
1
1
16
16
1
–15
1.4
1.3
1.4
1.3
14
13
14
13
–30
–45
0
2
2
2
2
20
20
20
20
0
0
130
V
CC3
– 1
0.15
0.05
0.05
0.05
0.4
0.3
0.3
0.3
0.7 • V
CC3
40
–30
–45
0
0
30
45
±1
V
CC3
±0.025
TYP
3.085
3.085
4.675
4.675
2.337
1.000
1.000
MAX
3.135
3.147
4.750
4.769
2.375
1.015
1.022
7
2
30
30
2
15
2.6
2.6
2.6
2.6
26
28
26
28
30
45
UNITS
V
V
V
V
V
V
V
V
µA
µA
µA
µA
nA
µA
µA
µA
µA
µA
µA
µA
µA
%
%
µs
V
V
V
V
V
V
V
ns
%
%
µA
V
V
IH
V
IL
t
WP
∆t
WT
WDI Input Threshold High
WDI Input Threshold Low
WDI Pulse Width
Watchdog Time-Out Period Variation C
WT
= 1500pF Deviation from t
WT
= 33ms (Note 5)
H-Grade
WDI Leakage Current
LTC1726-5 Only
V
OVR
V
CC5
Reset Override Voltage (Note 7) Override V
CC5
Ability to Assert
RST
1726fd
For more information
www.linear.com/LTC1726
3
LTC1726
elecTrical characTerisTics
Note 1:
Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2:
All voltage values are with respect to GND.
Note 3:
The LTC1726E is guaranteed to meet performance specifications
from 0°C to 70°C. Specifications over the –40°C to 85°C operating
temperature range are assured by design, characterization and correlation
with statistical process controls.
Note 4:
Both V
CC3
and V
CC25
/V
CC5
can act as the supply depending on
which pin has the greatest potential.
Note 5:
Timing measured with respect to
RST
passing through 1.5V.
Note 6:
The output pin
RST
has a weak internal pull-up to V
CC3
of typically
6µA. However, external pull-up resistors may be used when faster rise
times are required or for V
OH
voltages greater than V
CC3
.
Note 7:
The V
CC5
reset override voltage is valid for an operating range less
than approximately 4.15V. Above this point the override is turned off and
the V
CC5
pin functions normally.
Typical perForMance characTerisTics
V
CC5
Threshold Voltage
vs Temperature (LTC1726-5)
4.750
V
CC5
THRESHOLD VOLTAGE, V
RT5
(V)
4.725
4.700
4.675
4.650
4.625
4.600
20 40 60
–60 –40 –20 0
TEMPERATURE (°C)
V
CC3
THRESHOLD VOLTAGE, V
RT3
(V)
3.135
V
CCA
THRESHOLD VOLTAGE, V
RTA
(V)
3.125
3.115
3.105
3.095
3.085
3.075
3.065
3.055
3.045
3.035
– 60 –40 – 20 0 20 40 60
TEMPERATURE (°C)
80
100
V
CC3
Threshold Voltage
vs Temperature
1.015
1.010
1.005
1.000
0.995
0.990
V
CCA
Threshold Voltage
vs Temperature
80
100
1726 G01
0.985
20
40 60
–60 –40 –20 0
TEMPERATURE (°C)
80 100
1726 G03
1726 G02
V
CC25
Threshold Voltage
vs Temperature (LTC1726-2.5)
2.375
V
CC25
THRESHOLD VOLTAGE, V
RT25
(V)
20
I
VCC5
vs Temperature (LTC1726-5)
V
CC5
= 5V
19 V
CC3
= 3.3V
18
17
I
VCC5
(µA)
15
14
13
I
VCC3
(µA)
80
1.5
I
VCC3
vs Temperature (LTC1726-5)
V
CC5
= 5V
1.4 V
CC3
= 3.3V
1.3
1.2
1.1
1.0
0.9
0.8
0.7
0.6
2.360
2.345
16
2.330
2.315
12
11
2.300
20
40 60
–60 –40 –20 0
TEMPERATURE (°C)
80 100
1726 G04
10
–60 –40 –20 0 20 40 60
TEMPERATURE (°C)
100
0.5
–60 –40 –20 0 20 40 60
TEMPERATURE (°C)
80
100
1726 G05
1726 G06
1726fd
4
For more information
www.linear.com/LTC1726
LTC1726
Typical perForMance characTerisTics
I
VCC25
vs Temperature
(LTC1726-2.5)
1.5
V
CC3
= 3.3V
1.4 V
CC25
= 2.5V
1.3
1.2
I
VCC25
(µA)
I
VCC3
(µA)
1.1
1.0
0.9
0.8
0.7
0.6
0.5
–60 –40 –20 0 20 40 60
TEMPERATURE (°C)
80
100
20
I
VCC3
vs Temperature
(LTC1726-2.5)
TYPICAL TRANSIENT DURATION (µs)
V
CC3
= 3.3V
19 V
CC25
= 2.5V
18
17
16
15
14
13
12
11
10
–60 –40 –20 0 20 40 60
TEMPERATURE (°C)
80
100
700
600
500
400
300
200
100
Typical Transient Duration
vs Comparator Overdrive
T
A
= 25°C
RESET OCCURS
ABOVE CURVE
1726 G07
1726 G08
0
1
10
100
0.1
RESET COMPARATOR OVERDRIVE VOLTAGE (% OF V
CC
)
1726 G09
V
CCA
Input Current
vs Input Voltage
2.0
1.5
INPUT CURRENT (nA)
1.0
0.5
0
– 0.5
–1.0
–1.5
– 2.0
0.80 0.85 0.90 0.95 1 1.05 1.10 1.15 1.20
INPUT VOLTAGE (V)
1726 G14
Watchdog Time-Out Period
vs Temperature
40
WATCHDOG TIME PERIOD, t
WT
(ms)
38
36
34
32
30
28
26
20 40 60
–60 –40 –20 0
TEMPERATURE (°C)
80
100
C
WT
= 1500pF
(SILVER MICA)
RESET PULSE WIDTH, t
RT
(ms)
6.0
Reset Pulse Width vs
Temperature
C
RT
= 1500pF
5.8 (SILVER MICA)
5.6
5.4
5.2
5.0
4.8
4.6
4.4
4.2
4.0
–60 –40 –20 0 20 40 60
TEMPERATURE (°C)
80
100
T
A
= 25°C
1726 G10
1726 G11
Watchdog Time-Out Period vs
Capacitance
1000
WATCHDOG TIME-OUT PERIOD, t
WT
(sec)
100
10
1
100m
10m
1m
100
1p
10p 100p
10n 100n
C
WT
(FARAD)
1n
1
10
1726 G12
Reset Time-Out Period vs
Capacitance
100
RESET TIME-OUT PERIOD, t
RT
(sec)
10
1
100m
10m
1m
100
10
1p
10p 100p
10n 100n
C
RT
(FARAD)
1n
1
10
0
RST OUTPUT VOLTAGE (V)
T
A
= 25°C
RST
Output Voltage vs
Supply Voltage (LTC1726-2.5)
V
CC3
= V
CC25
= V
CCA
10k PULL-UP FROM V
CC3
TO RST
3
T
A
= 25°C
T
A
= 25°C
2
1
0
1
2
V
CC3
(V)
3
1726 F13
1726
G15
1726fd
For more information
www.linear.com/LTC1726
5
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