1
LTC1726
Final Electrical Specifications
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-
tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
Triple Supply Monitor and
P Supervisor with Adjustable
Reset and Watchdog Timer
January 2000
s
Monitors Three Inputs Simultaneously
LTC1726-5: 5V, 3.3V and ADJ
LTC1726-2.5: 2.5V, 3.3V and ADJ
s
1.5% Threshold Accuracy Over Temperature
s
Low Supply Current: 16
A Typ
s
Adjustable Reset Timeout
s
Adjustable Watchdog Timeout
s
Active Low Open-Drain Reset Output
s
Power Supply Glitch Immunity
s
Guaranteed RESET for V
CC3
1V or V
CC25
/V
CC5
1V
s
MS8 and SO-8 Packages
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 (16
A typical) supply current makes the LTC1726
ideal for power-conscious systems.
, LTC and LT are registered trademarks of Linear Technology Corporation.
s
Desktop Computers
s
Notebook Computers
s
Intelligent Instruments
s
Portable Battery-Powered Equipment
s
Network Servers
V
CC5
RT
C
RT
47nF
C
WT
47nF
2
1
4
3
6
R1
66.5k
1%
t
RT
= 155ms
t
WT
= 1s
R2
100k
1%
5
8
0.1
F
7
1726 TA01
LTC1726-5
WT
RST
WDI
V
CC3
5V
3.3V
1.8V
(V
TRIP
= 1.665V)
GND
V
CCA
P
RESET
I/O
0.1
F
V
CC25
RT
C
RT
47nF
C
WT
47nF
2
1
4
3
6
t
RT
= 155ms
t
WT
= 1s
R2
100k
1%
5
8
0.1
F
7
1726 TA02
LTC1726-2.5
WT
RST
WDI
V
CC3
2.5V
3.3V
1.8V
(V
TRIP
= 1.665V)
GND
V
CCA
P
RESET
I/O
0.1
F
R1
66.5k
1%
A 3.3V, 5V and 1.8V Monitor
A 3.3V, 2.5V and 1.8V Monitor
FEATURES
DESCRIPTIO
U
DESCRIPTIO
U
TYPICAL APPLICATIO S
U
2
LTC1726
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) .. 40
C to 85
C
Storage Temperature Range ................ 65
C to 150
C
Lead Temperature (Soldering, 10 sec)................ 300
C
Consult factory for Military grade parts.
T
JMAX
= 125
C,
JA
= 200
C/W
(Notes 1, 2)
T
JMAX
= 125
C,
JA
= 150
C/W
ORDER
PART NUMBER
LTC1726ES8-2.5
LTC1726ES8-5
LTC1726IS8-2.5
LTC1726IS8-5
S8 PART MARKING
172625
726I25
17265
1726I5
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V
RT3
Reset Threshold V
CC3
V
CC3
Input Threshold
q
3.036
3.085
3.135
V
V
RT5
Reset Threshold V
CC5
V
CC5
Input Threshold (5V Version)
q
4.600
4.675
4.750
V
V
RT25
Reset Threshold V
CC25
V
CC25
Input Threshold (2.5V Version)
q
2.300
2.337
2.375
V
V
RTA
Reset Threshold V
CCA
V
CCA
Input Threshold
q
0.985
1.000
1.015
V
V
CC
V
CC3
or V
CC5
Operating Voltage
RST in Correct Logic State
q
1
7
V
I
VCC3
V
CC3
Supply Current
V
CC5
/V
CC25
> V
CC3
q
1
2
A
V
CC5
/V
CC25
< V
CC3
, V
CC3
= 3.3V
q
16
30
A
I
VCC5
V
CC5
Supply Current
V
CC5
= 5V
q
16
30
A
I
VCC25
V
CC25
Supply Current
V
CC25
< V
CC3
, V
CC25
= 2.5V (Note 4)
q
1
2
A
I
VCCA
V
CCA
Input Current
V
CCA
= 1V
q
15
0
15
nA
RT Charge Current Out
V
RT
= 0V
q
1.4
2
2.6
A
WT Charge Current Out
V
WT
= 0V
q
1.4
2
2.6
A
RT Discharge Current Out
V
RT
= 1.3V
q
14
20
26
A
WT Discharge Current Out
V
WT
= 1.3V
q
14
20
26
A
The
q
denotes specifications which apply over the full operating
temperature range, otherwise specificaitons are at T
A
= 25
C. V
CC3
= 3.3V, V
CC5
= 5V, V
CC25
= 2.5V, V
CCA
= V
CC3
unless
otherwise noted.
1
2
3
4
8
7
6
5
TOP VIEW
RT
WT
RST
WDI
V
CC3
V
CCA
GND
S8 PACKAGE
8-LEAD PLASTIC SO
V
CC25
/
V
CC5
ORDER
PART NUMBER
LTC1726EMS8-2.5
LTC1726EMS8-5
MS8 PART MARKING
LTKZ
LTLA
1
2
3
4
V
CC3
V
CC25
/V
CC5
V
CCA
GND
8
7
6
5
RT
WT
RST
WDI
TOP VIEW
MS8 PACKAGE
8-LEAD PLASTIC MSOP
ABSOLUTE AXI U RATI GS
W
W
W
U
PACKAGE/ORDER I FOR ATIO
U
U
W
ELECTRICAL CHARACTERISTICS
3
LTC1726
Note 1: Absolute Maximum Ratings are those values beyond which the life
of the device may be impaired.
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.
The
q
denotes specifications which apply over the full operating
temperature range, otherwise specificaitons are at T
A
= 25
C. V
CC3
= 3.3V, V
CC5
= 5V, V
CC25
= 2.5V, V
CCA
= V
CC3
unless
otherwise noted.
V
CC5
Threshold Voltage
vs Temperature
TEMPERATURE (
C)
60
4.600
V
CC5
THRESHOLD VOLTAGE, V
RT5
(V)
4.625
4.650
4.675
4.700
20
20
60
100
1726 G01
4.725
4.750
40
0
40
80
V
CC3
Threshold Voltage
vs Temperature
TEMPERATURE (
C)
60
3.035
V
CC3
THRESHOLD VOLTAGE, V
RT3
(V)
3.045
3.065
3.075
3.085
3.135
3.105
20
20
40
1726 G02
3.055
3.115
3.125
3.095
40
0
60
80
100
TEMPERATURE (
C)
60
V
CCA
THRESHOLD VOLTAGE, V
RTA
(V)
1.000
1.005
1.015
1.010
0
40
100
1726 G03
0.995
0.990
0.985
40 20
20
60
80
V
CCA
Threshold Voltage
vs Temperature
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
t
RT
Reset Time-Out Period
C
RT
= 1500pF
q
3.5
5
6.5
ms
t
UV
V
CC
Undervoltage Detect to RST
V
CC25
/V
CC5
, V
CC3
or V
CCA
Less Than Reset
130
s
Threshold V
RT
by More Than 1%
V
OH
RST Output Voltage High (Note 5)
I
SOURCE
= 1
A
q
V
CC3
1
V
V
OL
RST Output Voltage Low
I
SINK
= 2.5mA, V
CC5
/V
CC25
= 0V
q
0.15
0.4
V
I
SINK
= 100
A, V
CC3
= 1V, V
CC5
/V
CC25
= 0V
q
0.05
0.3
V
I
SINK
= 100
A, V
CC3
= 0V, V
CC5
/V
CC25
= 1V
q
0.05
0.3
V
I
SINK
= 100
A, V
CC3
= 1V, V
CC5
/V
CC25
= 1V
q
0.05
0.3
V
V
IH
WDI Input Threshold High
q
0.7 V
CC3
V
V
IL
WDI Input Threshold Low
q
0.3 V
CC3
V
t
WP
WDI Pulse Width
q
40
ns
t
WT
Watchdog Time-Out Period
C
WT
= 1500pF
q
23
33
43
ms
WDI Leakage Current
q
1
A
LTC1726-5 Only
V
OVR
V
CC5
Reset Override Voltage (Note 6)
Override V
CC5
Ability to Assert RST
V
CC3
0.025
V
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: The output pin RST has weak internal pull-ups to V
CC3
of typically
6
A. However, external pull-up resistors may be used when faster rise
times are required or for V
OH
voltages greater than V
CC3
.
Note 6: 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.
ELECTRICAL CHARACTERISTICS
TYPICAL PERFOR A CE CHARACTERISTICS
U
W
4
LTC1726
V
CC25
Threshold Voltage
vs Temperature
I
VCC5
vs Temperature
TYPICAL PERFOR A CE CHARACTERISTICS
U
W
TEMPERATURE (
C)
60
V
CC25
THRESHOLD VOLTAGE, V
RT25
(V)
0
40
100
1726 G04
2.300
2.315
2.330
2.345
2.360
2.375
40 20
20
60
80
TEMPERATURE (
C)
60
10
I
VCC5
(
A)
11
13
14
15
20
17
20
20
40
1726 G05
12
18
19
16
40
0
60
80
100
V
CC5
= 5V
V
CC3
= 3.3V
I
VCC3
vs Temperature (LTC1726-5)
TEMPERATURE (
C)
60
0.5
I
VCC3
(
A)
0.6
0.8
0.9
1.0
1.5
1.2
20
20
40
1726 G06
0.7
1.3
1.4
1.1
40
0
60
80
100
V
CC5
= 5V
V
CC3
= 3.3V
I
VCC25
vs Temperature
(LTC1726-2.5)
I
VCC3
vs Temperature
(LTC1726-2.5)
Typical Transient Duration
vs Comparator Overdrive
TEMPERATURE (
C)
60
0.5
I
VCC25
(
A)
0.6
0.8
0.9
1.0
1.5
1.2
20
20
40
1726 G07
0.7
1.3
1.4
1.1
40
0
60
80
100
V
CC3
= 3.3V
V
CC25
= 2.5V
TEMPERATURE (
C)
60
10
I
VCC3
(
A)
11
13
14
15
20
17
20
20
40
1726 G08
12
18
19
16
40
0
60
80
100
V
CC3
= 3.3V
V
CC25
= 2.5V
RESET COMPARATOR OVERDRIVE VOLTAGE (% OF V
CC
)
0.1
400
TYPICAL TRANSIENT DURATION (
s)
500
600
700
1
10
100
1726 G09
300
200
100
0
RESET OCCURS
ABOVE CURVE
T
A
= 25
C
Watchdog Time-Out Period
vs Temperature
Reset Pulse Width vs Temperature
TEMPERATURE (
C)
60 40
WATCHDOG TIME PERIOD, t
WT
(ms)
34
36
38
60
80
1726 G10
32
30
20
0
20
40
100
28
26
40
C
WT
= 1500pF
TEMPERATURE (
C)
60
4.0
RESET PULSE WIDTH, t
RT
(ms)
4.2
4.6
4.8
5.0
6.0
5.4
20
20
40
1726 G11
4.4
5.6
5.8
5.2
40
0
60
80
100
C
RT
= 1500pF
V
CCA
Input Current
vs Input Voltage
INPUT VOLTAGE (V)
0.80 0.85
0.95
1.05
1.15
INPUT CURRENT (nA)
0
1.0
1.20
1726 G14
1.0
2.0
0.5
1.5
0.90
1
1.10
2.0
0.5
1.5
T
A
= 25
C
5
LTC1726
timer is not cleared, a reset pulse will occur. The watch-
dog timer is cleared during a reset and restarts when the
reset is deasserted. When disabling the watchdog func-
tion, this pin should be connected to either V
CC3
or
ground and WT must be grounded.
RST (Pin 6): Reset Logic Output. Active low, open-drain
logic output with weak pull-up to V
CC3
. Asserted when
one or more of the supplies are below trip thresholds.
After all supplies become valid, the reset remains as-
serted for the period set by the capacitor on the RT pin.
The watchdog timer can also trigger the reset whenever
the watchdog time-out period is exceeded. This pin can
be pulled up greater than V
CC3
when interfacing to 5V
logic.
WT (Pin 7): Watchdog Time-Out Input. Place a capacitor
between this pin and ground to adjust the watchdog time-
out period. To determine the watchdog time-out period:
t
WT
= 21.8 C
WT
with t
WT
in
s and C
WT
in pF. As an example, a 47nF
capacitor will generate a 1s watchdog time-out period.
The watchdog function can be disabled by connecting
this pin to ground.
V
CC3
(Pin 1): 3.3V Sense Input. This pin also supplies
power to the part when the voltage on this pin is greater
than the voltage on V
CC25
/V
CC5
. Bypass this pin to ground
with a 0.1
F or larger ceramic capacitor.
V
CC5
(Pin 2): 5V Sense Input (LTC1726-5). This pin also
supplies power to the part when the voltage on this pin is
greater than the voltage on V
CC3
. Bypass this pin to
ground with a 0.1
F or larger ceramic capacitor.
V
CC25
(Pin 2): 2.5V Sense Input (LTC1726-2.5). This pin
also supplies power to the part when the voltage on this
pin is greater than the voltage on V
CC3
. Bypass this pin to
ground with a 0.1
F or larger ceramic capacitor.
V
CCA
(Pin 3): 1V Sense, High Impedance Input. If unused
it can be tied to either V
CC3
, V
CC5
or V
CC25
.
GND (Pin 4): Ground.
WDI (Pin 5): Watchdog Input. A logic input whose rising
or falling edge must occur on this pin within the selected
watchdog time-out period or a reset pulse will occur. The
watchdog time-out period is set by the value of the
capacitor that is placed on the WT pin. The rising or falling
edge of this pin clears the voltage on the WT capacitor,
preventing a reset pulse from occurring. If the watchdog
Time-Out Period vs Capacitance
C
RT
OR C
WT
(pF)
0.1
1
10
t
RT
OR t
WT
(
s)
10
6
10
5
10
4
10
3
10
2
10
2
10
3
10
4
10
1726 G12
t
WT
t
RT
T
A
= 25
C
RST Output Voltage vs
Supply Voltage (LTC1726-2.5)
TYPICAL PERFOR A CE CHARACTERISTICS
U
W
V
CC3
(V)
0
2
1726 F13
1
1
2
3
0
3
RST OUTPUT VOLTAGE (V)
V
CC3
= V
CC25
= V
CCA
10k PULL-UP FROM V
CC3
TO RST
T
A
= 25
C
U
U
U
PI FU CTIO S
6
LTC1726
V
CC
Monitor Timing
BANDGAP
REFERENCE
ADJUSTABLE
RESET
PULSE
GENERATOR
TRANSITION DETECT
+
+
+
1
5
7
V
CC3
WDI
2
V
CC5
/V
CC25
3
V
CCA
4
GND
1V
1726 BD
6
RST
2
A
22
A
6
A
V
CC3
V
CC3
V
CC5
/V
CC25
V
CC
INTERNAL
WT
WATCHDOG
TIMER
POWER
DETECT
8
RT
C
RT
+
2
A
22
A
C
WT
+
Watchdog Timing Diagram
t
RT
1726 TD01
V
RTX
V
CCX
RST
t
WP
t
WT
t
RT
t
WT
1726 TD02
WDI
RST
t
RT
U
U
U
PI FU CTIO S
RT (Pin 8): Reset Time-Out Input. Place a capacitor
between this pin and ground to adjust the reset time-out
period. To determine the reset time-out period:
t
RT
= 3.30 C
RT
with t
RT
in
s and C
RT
in pF. As an example, a 47nF
capacitor will generate a 155ms watchdog time-out
period.
BLOCK DIAGRA
W
TI I G DIAGRA S
W
U
W
7
LTC1726
manner, the part can function as a 5V monitor with the
3.3V monitor disabled.
When monitoring either 3.3V or 5V with V
CC3
strapped to
V
CC5
, (see Figure 1) the part determines which is the
appropriate range. The part handles this situation as
shown in Figure 2. Above 1V and below V
RT3
, RST is held
low. From V
RT3
to approximately 4.15V, the part as-
sumes 3.3V supply monitoring and RST is deasserted.
Above approximately 4.15V, the part operates as a 5V
monitor. In most systems, the 5V supply will pass
through the 3.1V to 4.15V region in < 200ms during
power-up, and the RST output will behave as desired.
Table 1 summarizes the state of RST at various operating
voltages with V
CC3
= V
CC5
.
Table 1. Override Truth Table (V
CC3
= V
CC5
)
INPUTS (V
CC3
= V
CC5
= V
CC
)
RST
0V
V
CC
1V
--
1V
V
CC
V
RT3
0
V
RT3
V
CC
4.15V
1
4.15V
V
CC
V
RT5
0
V
RT5
V
CC
1
Supply Monitoring
The LTC1726 is a low power, high accuracy triple supply
monitor and watchdog timer. The watchdog and reset
periods are both adjustable using external capacitors.
All three V
CC
inputs must be above predetermined thresh-
olds for reset not to be asserted. The LTC1726 will assert
reset during power-up, power-down and brownout condi-
tions on any one or all of the V
CC
inputs.
Upon power-up, either the V
CC5
/V
CC25
or V
CC3
pin can
power the drive circuits for the RST pin. This ensures that
RST will be low when either V
CC5
/V
CC25
or V
CC3
reaches
1V. As long as any one of the V
CC
inputs is below its
predetermined threshold, RST will stay a logic low. Once
all of the V
CC
inputs rise above their thresholds, the
adjustable reset timer is started and RST is released after
the reset time-out period.
On power-down, once any of the V
CC
inputs drops below its
threshold, RST is held at a logic low. A logic low of 0.3V is
guaranteed until both V
CC3
and V
CC5
/V
CC25
drop below 1V.
3V or 5V/2.5V Power Detect
Since the LTC1726 is a multisupply monitor, it will be
required to assert reset as soon as there is power on any
one of the monitor inputs. Therefore, the part derives its
power from either the V
CC3
or V
CC5
/V
CC25
input, which-
ever pin has the greatest potential. This ensures the part
pulls the RST pin low as soon as either input pin is
1V.
The adjustable input is excluded from being a potential
supply pin because of its 1V nominal operating range.
Override Functions (5V Versions Only)
The V
CCA
pin, if unused, can be tied to either V
CC3
or V
CC5
.
This is an obvious solution since the trip points for V
CC3
and V
CC5
will always be greater than the trip point for V
CCA
.
The V
CC5
input trip point is disabled if its voltage is equal
to the voltage on V
CC3
25mV and the voltage on V
CC5
is
less than 4.15V. In this manner the LTC1726-5 behaves
as a 3.3V monitor and the 5V reset function is disabled.
The V
CC5
trip point is re-enabled when the voltage on
V
CC5
is equal to the voltage on V
CC3
25mV and the two
inputs are greater than approximately 4.15V. In this
V
CC3
V
CC5
V
CCA
GND
6
1
2
3
4
RST
LTC1726-5
1726 F01
TO SYSTEM
RESET
PINS 5, 7 AND 8 NOT SHOWN FOR CLARITY
R1
10k
V
CC
3.3V OR 5V
Figure 2. RST Voltage vs Supply Voltage
Figure 1. Single Supply Monitor with Others Disabled
SUPPLY VOLTAGE (V)
0
RST OUTPUT VOLTAGE (V)
3
4
5
4
1726 F02
2
1
0
1
2
3
5
V
CC3
= V
CC5
= V
CCA
= 0V TO 5V
10k PULL-UP FROM RST TO V
CC3
T
A
= 25
C
APPLICATIO S I FOR ATIO
W
U
U
U
8
LTC1726
Figure 4. RST Output Voltage
Characteristics of the Circuit in Figure 3
Figure 3. LTC1726-5 Monitoring a Single 5V
Supply. D1 Used to Avoid RST High Near 3.1V
to 4V (See Figure 2).
V
CC3
V
CC5
V
CCA
GND
6
1
2
3
4
RST
LTC1726-5
1726 F03
TO SYSTEM
RESET
R1
10k
5V
0.1
F
D1
D1: MMBD914 OR EQUIVALENT
PINS 5, 7 AND 8 NOT SHOWN FOR CLARITY
V
CC5
(V)
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
RST OUTPUT VOLTAGE (V)
1726 F04
5
4
3
2
1
0
V
CC5
= V
CCA
= 0V TO 5V
10k PULL-UP FROM RST TO V
CC5
T
A
= 25
C
Figure 3 contains a simple circuit for 5V systems that can't
risk the RST output going high in the 3.1V to 4.15V range
(possibly due to very slow rise time on the 5V supply).
Diode D1 powers the LTC1726-5 while dropping
0.6V
from the V
CC5
pin to the V
CC3
pin. This prevents the part's
internal override circuit from being activated. Without the
override circuit active, the RST pin stays low until V
CC5
reaches V
RT5
4.675V. (See Figure 4.)
Watchdog Timer
The watchdog circuit monitors a
P's activity. The
P is
required to change the logic state of the WDI pin on a
periodic basis in order to clear the watchdog timer and
prevent the LTC1726 from issuing a reset.
During power-up, the watchdog timer remains cleared
while reset is asserted. As soon as the reset timer times
out, the watchdog timer is started. The watchdog timer will
continue to run until a transition is detected on the WDI
input or until the watchdog timer times out. Once the
watchdog timer times out, the internal circuitry asserts the
reset and starts the reset timer. When the reset timer times
out and reset is deasserted, the watchdog timer is again
started. If no WDI transition is received within the watch-
dog time-out period, the reset will be reasserted at the end
of the watchdog time-out period. If a transition is received
on the WDI input during the watchdog time-out period, the
watchdog timer will be restarted and reset will remain
deasserted.
Selecting the Reset and Watchdog
Time-Out Capacitors
The reset time-out period is adjustable in order to accom-
modate a variety of
P applications. The reset time-out
period, t
RT
, is adjusted by connecting a capacitor, C
RT
,
between the RT pin and ground. The value of this capacitor
is determined as follows:
C
RT
= t
RT
/3.30
with C
RT
in pF and t
RT
in
s (i.e., 1500pF
4.95ms).
The watchdog period is also adjustable so that the watch-
dog time-out period can be optimized for software execu-
tion. The watchdog time-out period, t
WT
, is adjusted by
connecting a capacitor, C
WT
, between the WT pin and
ground. Once the optimum watchdog time-out period
(t
WT
) is determined, the value of the capacitor is calculated
as follows:
C
WT
= t
WT
/21.8
with C
WT
in pF and t
WT
in
s (i.e., 1500pF
32.7ms).
LTC1726-2.5 Override Functions
The V
CCA
pin, if unused, can be tied to either V
CC3
or V
CC25
.
This is an obvious solution since the trip points for V
CC3
and V
CC25
will always be greater than the trip point for
V
CCA
. Likewise, the V
CC25
, if unused, can be tied to V
CC3
.
V
CC3
must always be used. Tying V
CC3
to V
CC25
and
operating off of a 2.5V supply will result in the continuous
assertion of RST.
APPLICATIO S I FOR ATIO
W
U
U
U
9
LTC1726
Disabling the Watchdog Timer
1
2
3
4
8
7
6
5
V
CC3
V
CCA
GND
RT
WT
RST
WDI
LTC1726-5/2.5
3.3V
SYSTEM
RESET
*TO PRESERVE THRESHOLD ACCURACY, SET PARALLEL
COMBINATION OF R1 AND R2
66.5k
THE WATCHDOG TIMER CAN BE DISABLED BY CONNECTING
THE WDI AND WT PINS TO GROUND. THE PART WILL ACT
STRICTLY AS A TRIPLE SUPPLY MONITOR WITH AN
ADJUSTABLE RESET TIME-OUT PERIOD
C
RT
5V/2.5V
R2*
R1*
1726 TA03
ADJUSTABLE
SUPPLY
V
CC5
/
V
CC25
1
2
3
4
8
7
6
5
V
CC3
V
CC5
V
CCA
GND
RT
WT
RST
WDI
LTC1726-5
3.3V
SYSTEM RESET
*TO PRESERVE THRESHOLD ACCURACY, SET PARALLEL
COMBINATION OF R1 AND R2
66.5k
C
RT
C
WT
WDI
5V
R2*
R1*
1726 TA04
ADJUSTABLE SUPPLY
OR DC/DC FEEDBACK
DIVIDER
Triple Supply Monitor (3.3V, 5V and Adjustable)
Dual Supply Monitor (3.3V and 5V, Defeat V
CCA
Input)
1
2
3
4
8
7
6
5
V
CC3
V
CC5
V
CCA
GND
RT
WT
RST
WDI
LTC1726-5
3.3V
SYSTEM RESET
WDI
5V
1726 TA05
C
RT
C
WT
TYPICAL APPLICATIO S
U
10
LTC1726
Dual Supply Monitor (3.3V or 5V Plus Adjustable)
Dual Supply Monitor (3.3V Plus Adjustable)
Using V
CCA
Tied to DC/DC Feedback Divider
1
2
3
4
8
7
6
5
V
CC3
V
CC5
V
CCA
GND
RT
WT
RST
WDI
LTC1726-5
R2*
1726 TA06
R1*
ADJUSTABLE
SUPPLY
3.3V OR
5V
4.7k
SYSTEM RESET
*TO PRESERVE THRESHOLD ACCURACY, SET PARALLEL
COMBINATION OF R1 AND R2
66.5k
C
RT
C
WT
WDI
REFER TO LTC1726-X OVERRIDE FUNCTIONS IN
THE APPLICATIONS INFORMATION SECTION
1
2
3
4
8
7
6
5
V
CC3
V
CC25
V
CCA
GND
RT
WT
RST
WDI
LTC1726-2.5
SYSTEM RESET
WDI
R2*
1726 TA07
R1*
ADJUSTABLE
SUPPLY
3.3V
4.7k
*TO PRESERVE THRESHOLD ACCURACY, SET PARALLEL
COMBINATION OF R1 AND R2
66.5k
C
RT
C
WT
1
2
3
4
8
7
6
5
V
CC3
V
CC5
V
CCA
GND
RT
WT
RST
WDI
LTC1726-5
3.3V
SYSTEM RESET
WDI
5V
22.1k
1%
1726 TA08
35.7k
1%
LTC1435
ADJUSTABLE
RESET TRIP
THRESHOLD 2.74V
2.9V
2.8k
1%
6
V
OSENSE
C
RT
C
WT
TYPICAL APPLICATIO S
U
11
LTC1726
S8 Package
8-Lead Plastic Small Outline (Narrow 0.150)
(LTC DWG # 05-08-1610)
0.016 0.050
(0.406 1.270)
0.010 0.020
(0.254 0.508)
45
0
8
TYP
0.008 0.010
(0.203 0.254)
SO8 1298
0.053 0.069
(1.346 1.752)
0.014 0.019
(0.355 0.483)
TYP
0.004 0.010
(0.101 0.254)
0.050
(1.270)
BSC
1
2
3
4
0.150 0.157**
(3.810 3.988)
8
7
6
5
0.189 0.197*
(4.801 5.004)
0.228 0.244
(5.791 6.197)
DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH
SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD
FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE
*
**
Dimensions in (inches) unless otherwise noted.
MS8 Package
8-Lead Plastic MSOP
(LTC DWG # 05-08-1660)
MSOP (MS8) 1098
* DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. MOLD FLASH,
PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
** DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS.
INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
0.021
0.006
(0.53
0.015)
0
6
TYP
SEATING
PLANE
0.007
(0.18)
0.040
0.006
(1.02
0.15)
0.012
(0.30)
REF
0.006
0.004
(0.15
0.102)
0.034
0.004
(0.86
0.102)
0.0256
(0.65)
BSC
1
2
3
4
0.193
0.006
(4.90
0.15)
8
7 6
5
0.118
0.004*
(3.00
0.102)
0.118
0.004**
(3.00
0.102)
U
PACKAGE DESCRIPTIO
12
LTC1726
1726i LT/TP 0100 4K PRINTED IN USA
LINEAR TECHNOLOGY CORPORATION 2000
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900
q
FAX: (408) 434-0507
q
www.linear-tech.com
PART NUMBER
DESCRIPTION
COMMENTS
LTC690
5V Supply Monitor, Watchdog Timer and Battery Backup
4.65V Threshold
LTC694-3.3
3.3V Supply Monitor, Watchdog Timer and Battery Backup
2.9V Threshold
LTC699
5V Supply Monitor and Watchdog Timer
4.65V Threshold
LTC1232
5V Supply Monitor, Watchdog Timer and Push-Button Reset
4.37V/4.62V Threshold
LTC1326
Micropower Precision Triple Supply Monitor for 5V, 3.3V and ADJ
4.725V, 3.118V, 1V Thresholds (
0.75%) 5V, 3.3V, ADJ
LTC1326-2.5
Micropower Precision Triple Supply Monitor for 2.5V, 3.3V and ADJ
2.363V, 3.118V, 1V Thresholds (
0.75%) 2.5V, 3.3V, ADJ
LTC1536
Precision Triple Supply Monitor for PCI Applications
Meets PCI t
FAIL
Timing Specifications
LTC1727-5
Micropower Triple Supply Monitor with Individual Outputs
4.675V, 3.086V, 1V Thresholds (
1.5%) 5V, 3.3V, ADJ
LTC1727-2.5
Micropower Triple Supply Monitor with Individual Outputs
2.338V, 3.086V, 1V Thresholds (
1.5%) 2.5V, 3.3V, ADJ
LTC1728-5
Micropower Triple Supply Monitor in 5-Pin SOT-23 Package
4.675V, 3.086V, 1V Thresholds (
1.5%) 5V, 3.3V, ADJ
LTC1728-2.5
Micropower Triple Supply Monitor in 5-Pin SOT-23 Package
2.338V, 3.086V, 1V Thresholds (
1.5%) 2.5V, 3.3V, ADJ
RELATED PARTS
Triple Supply Monitor with Watchdog Timer and Manual Reset Button
V
CC3
V
CC5
V
CCA
GND
RT
WT
RST
WDI
LTC1726-5
1726 TA09
100nF
1
5V
3.3V
12V (
5%)
V
TRIP
= 11.2V
(
0.17V)
8
6
5
1500pF
7
R2
105k
0.1%
*OPTIONAL RESISTOR RECOMMENDED
TO EXTEND ESD TOLERANCE
R3*
10k
5%
MANUAL
RESET BUTTON
(NORMALLY OPEN)
2
3
4
R1
1.07M
0.1%
1500pF
100nF
V
TRIP
=
(R1 + R2)
R1 = R2
1
V
CCA
R2
( )
V
TRIP
V
CCA
P
RESET
I/O
TYPICAL APPLICATIO
U
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