LTC1726IS8-2.5 [Linear]
Triple Supply Monitor and uP Supervisor with Adjustable Reset and Watchdog Timer; 三路电源监控器和多达监控器可调复位和看门狗定时器
| 型号： | LTC1726IS8-2.5 |
| 厂家： | 
Linear |
| 描述： | Triple Supply Monitor and uP Supervisor with Adjustable Reset and Watchdog Timer |
| 文件： | 总12页 (文件大小：176K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
Final Electrical Specifications
LTC1726
Triple Supply Monitor and
µP Supervisor with Adjustable
Reset and Watchdog Timer
January 2000
U
FEATURES
DESCRIPTIO
TheLTC®1726 isatriplesupplymonitorandmicroproces-
sorsupervisorycircuitwithadjustableresetandwatchdog
functions intended for systems with multiple supply volt-
ages. Theparthasacommonopen-drainresetoutputwith
an adjustable delay. The reset and watchdog time-out
periods are both adjustable using external capacitors.
■
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
Tight 1.5% accuracy specifications and glitch immunity
ensure reliable reset operation without false triggering.
■
Active Low Open-Drain Reset Output
■
Power Supply Glitch Immunity
■
■
The RST output is guaranteed to be in the correct state for
CC5/VCC25 orVCC3 downto1V. TheLTC1726 mayalsobe
configured to monitor any one or two VCC inputs instead
of three, depending on system requirements.
Guaranteed RESET for VCC3 ≥ 1V or VCC25/VCC5 ≥ 1V
V
MS8 and SO-8 Packages
U
DESCRIPTIO
The low (16µA typical) supply current makes the LTC1726
ideal for power-conscious systems.
■
Desktop Computers
■
Notebook Computers
, LTC and LT are registered trademarks of Linear Technology Corporation.
■
Intelligent Instruments
■
Portable Battery-Powered Equipment
■
Network Servers
U
TYPICAL APPLICATIO S
A 3.3V, 5V and 1.8V Monitor
A 3.3V, 2.5V and 1.8V Monitor
1.8V
TRIP
1.8V
TRIP
(V
= 1.665V)
(V
= 1.665V)
R1
66.5k
1%
3.3V
5V
3.3V
2.5V
R1
66.5k
1%
0.1µF
0.1µF
0.1µF
0.1µF
R2
100k
1%
R2
100k
1%
2
1
3
2
1
3
C
C
RT
47nF
RT
V
V
V
V
V V
CC25 CC3 CCA
47nF
CC5 CC3 CCA
8
7
6
5
8
7
6
5
RT
RST
LTC1726-5
WDI
RESET
µP
RT
RST
WDI
RESET
µP
C
C
WT
47nF
WT
LTC1726-2.5
47nF
WT
I/O
WT
I/O
GND
4
GND
4
1726 TA01
1726 TA02
t
t
= 155ms
= 1s
t
t
= 155ms
= 1s
RT
WT
RT
WT
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 ofits circuits as described herein willnotinfringe on existing patentrights.
1
LTC1726
W W
U W
ABSOLUTE AXI U RATI GS
(Notes 1, 2)
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
Terminal Voltage
V
CC3, VCC5/VCC25, VCCA ......................... –0.3V to 7V
RST ....................................................... –0.3V to 7V
WDI ....................................................... –0.3V to 7V
RT, WT .................................................. –0.3V to 7V
U W
U
PACKAGE/ORDER I FOR ATIO
ORDER
PART NUMBER
ORDER
PART NUMBER
TOP VIEW
LTC1726EMS8-2.5
LTC1726EMS8-5
LTC1726ES8-2.5
TOP VIEW
LTC1726ES8-5
V
1
2
3
4
8
7
6
5
RT
CC3
/
V
1
2
3
4
8 RT
CC3
V
CC25
LTC1726IS8-2.5
LTC1726IS8-5
V
/V
7 WT
6 RST
5 WDI
WT
RST
WDI
CC25 CC5
V
V
CC5
V
GND
CCA
CCA
GND
MS8 PACKAGE
8-LEAD PLASTIC MSOP
MS8 PART MARKING
S8 PART MARKING
S8 PACKAGE
8-LEAD PLASTIC SO
TJMAX = 125°C, θJA = 200°C/W
LTKZ
LTLA
172625
726I25
17265
TJMAX = 125°C, θJA = 150°C/W
1726I5
Consult factory for Military grade parts.
ELECTRICAL CHARACTERISTICS
otherwise noted.
The ● denotes specifications which apply over the full operating
temperature range, otherwise specificaitons are at TA = 25°C. VCC3 = 3.3V, VCC5 = 5V, VCC25 = 2.5V, VCCA = VCC3 unless
SYMBOL PARAMETER
CONDITIONS
MIN
3.036
4.600
2.300
0.985
1
TYP
MAX
3.135
4.750
2.375
1.015
7
UNITS
V
V
V
V
V
Reset Threshold V
Reset Threshold V
Reset Threshold V
Reset Threshold V
V
V
V
V
Input Threshold
●
●
●
●
●
3.085
4.675
2.337
1.000
V
V
V
V
V
RT3
RT5
CC3
CC5
CC25
CCA
CC3
Input Threshold (5V Version)
CC5
Input Threshold (2.5V Version)
RT25
RTA
CC
CC25
Input Threshold
CCA
V
V
or V
Operating Voltage
RST in Correct Logic State
CC3
CC3
CC5
I
Supply Current
V
V
/V
> V
CC3
< V , V
●
●
1
16
2
30
µA
µA
VCC3
CC5 CC25
/V
= 3.3V
CC5 CC25
CC3 CC3
I
I
I
V
V
V
Supply Current
V
V
V
V
V
V
V
= 5V
●
●
●
●
●
●
●
16
1
30
2
µA
µA
nA
µA
µA
µA
µA
VCC5
VCC25
VCCA
CC5
CC5
Supply Current
< V , V
= 2.5V (Note 4)
CC25
CC25
CC3 CC25
Input Current
= 1V
CCA
–15
1.4
1.4
14
0
15
2.6
2.6
26
26
CCA
RT Charge Current Out
WT Charge Current Out
RT Discharge Current Out
WT Discharge Current Out
= 0V
2
RT
WT
RT
WT
= 0V
2
= 1.3V
= 1.3V
20
20
14
2
LTC1726
ELECTRICAL CHARACTERISTICS
otherwise noted.
The ● denotes specifications which apply over the full operating
temperature range, otherwise specificaitons are at TA = 25°C. VCC3 = 3.3V, VCC5 = 5V, VCC25 = 2.5V, VCCA = VCC3 unless
SYMBOL PARAMETER
CONDITIONS
MIN
TYP
5
MAX
UNITS
ms
t
t
Reset Time-Out Period
Undervoltage Detect to RST
C
= 1500pF
RT
●
3.5
6.5
RT
UV
V
V
/V , V
CC25 CC5 CC3
or V Less Than Reset
CCA
130
µs
CC
Threshold V by More Than 1%
RT
V
V
RST Output Voltage High (Note 5)
RST Output Voltage Low
I
= 1µA
●
V – 1
CC3
V
OH
OL
SOURCE
I
I
I
I
= 2.5mA, V /V
= 0V
●
●
●
●
0.15
0.05
0.05
0.05
0.4
0.3
0.3
0.3
V
V
V
V
SINK
SINK
SINK
SINK
CC5 CC25
= 100µA, V
= 100µA, V
= 100µA, V
= 1V, V /V
= 0V
= 1V
= 1V
CC3
CC3
CC3
CC5 CC25
= 0V, V /V
CC5 CC25
= 1V, V /V
CC5 CC25
V
V
WDI Input Threshold High
WDI Input Threshold Low
WDI Pulse Width
●
●
●
●
●
0.7 • V
V
V
IH
IL
CC3
0.3 • V
40
CC3
t
t
ns
ms
µA
WP
WT
Watchdog Time-Out Period
WDI Leakage Current
C
= 1500pF
23
33
43
WT
±1
LTC1726-5 Only
V
V
Reset Override Voltage (Note 6)
Override V
Ability to Assert RST
V ±0.025
CC3
V
OVR
CC5
CC5
Note 1: Absolute Maximum Ratings are those values beyond which the life
of the device may be impaired.
Note 4: Both V
which pin has the greatest potential.
and V
/V
can act as the supply depending on
CC3
CC25 CC5
Note 2: All voltage values are with respect to GND.
Note 5: The output pin RST has weak internal pull-ups to V
6µA. However, external pull-up resistors may be used when faster rise
of typically
CC3
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.
times are required or for V voltages greater than V
.
CC3
OH
Note 6: The V
reset override voltage is valid for an operating range less
CC5
than approximately 4.15V. Above this point the override is turned off and
the V pin functions normally.
CC5
U W
TYPICAL PERFOR A CE CHARACTERISTICS
VCC5 Threshold Voltage
vs Temperature
VCC3 Threshold Voltage
vs Temperature
VCCA Threshold Voltage
vs Temperature
3.135
3.125
3.115
3.105
3.095
3.085
3.075
3.065
3.055
3.045
3.035
1.015
1.010
1.005
1.000
0.995
0.990
0.985
4.750
4.725
4.700
4.675
4.650
4.625
4.600
40 60
TEMPERATURE (°C)
20
TEMPERATURE (°C)
–60 –40 –20
0
20
80 100
–60
80
–60 –40 –20
0
40 60 80 100
–40 –20
0
20 40 60
TEMPERATURE (°C)
100
1726 G01
1726 G02
1726 G03
3
LTC1726
U W
TYPICAL PERFOR A CE CHARACTERISTICS
VCC25 Threshold Voltage
vs Temperature
IVCC5 vs Temperature
IVCC3 vs Temperature (LTC1726-5)
20
19
18
17
16
15
14
13
12
11
10
1.5
1.4
1.3
1.2
1.1
1.0
0.9
0.8
0.7
0.6
0.5
2.375
2.360
2.345
2.330
2.315
2.300
V
V
= 5V
V
V
= 5V
CC5
CC3
CC5
CC3
= 3.3V
= 3.3V
20
TEMPERATURE (°C)
–60
80
–60
80
–60 –40 –20
0
40 60 80 100
20
TEMPERATURE (°C)
60
20
TEMPERATURE (°C)
60
–40 –20
0
40
100
–40 –20
0
40
100
1726 G04
1726 G05
1726 G06
IVCC25 vs Temperature
(LTC1726-2.5)
IVCC3 vs Temperature
(LTC1726-2.5)
Typical Transient Duration
vs Comparator Overdrive
1.5
1.4
1.3
1.2
1.1
1.0
0.9
0.8
0.7
0.6
0.5
20
19
18
17
16
15
14
13
12
11
10
700
600
500
400
300
200
100
0
T
= 25°C
V
V
= 3.3V
= 2.5V
V
V
= 3.3V
= 2.5V
A
CC3
CC25
CC3
CC25
RESET OCCURS
ABOVE CURVE
–60
60 80
–60
60 80
0.1
1
10
100
–40 –20
20
TEMPERATURE (°C)
0
40
100
–40 –20
20
TEMPERATURE (°C)
0
40
100
RESET COMPARATOR OVERDRIVE VOLTAGE (% OF V
)
CC
1726 G09
1726 G07
1726 G08
VCCA Input Current
vs Input Voltage
Watchdog Time-Out Period
vs Temperature
Reset Pulse Width vs Temperature
6.0
5.8
5.6
5.4
5.2
5.0
4.8
4.6
4.4
4.2
4.0
40
38
2.0
1.5
C
WT
= 1500pF
C
= 1500pF
T
A
= 25°C
RT
1.0
36
0.5
34
32
30
28
0
–0.5
–1.0
–1.5
–2.0
26
–20
0
20 40
100
1
–60 –40
60 80
–60
20
60 80
100
0.80 0.85 0.90 0.95
1.05 1.10 1.15 1.20
–40 –20
0
40
TEMPERATURE (°C)
TEMPERATURE (°C)
INPUT VOLTAGE (V)
1726 G10
1726 G14
1726 G11
4
LTC1726
U W
TYPICAL PERFOR A CE CHARACTERISTICS
RST Output Voltage vs
Supply Voltage (LTC1726-2.5)
Time-Out Period vs Capacitance
6
10
T
A
= 25°C
V
= V
= V
CC3
CC25 CCA
10k PULL-UP FROM V
TO RST
CC3
3
T
= 25°C
5
4
3
2
A
10
10
10
10
t
WT
2
1
t
RT
10
0.1
0
2
10
3
10
4
10
10
1
2
3
0
1
C
RT
OR C (pF)
WT
V
CC3
(V)
1726 G12
1726 F13
U
U
U
PI FU CTIO S
VCC3 (Pin 1): 3.3V Sense Input. This pin also supplies
power to the part when the voltage on this pin is greater
thanthevoltageonVCC25/VCC5.Bypassthispintoground
with a 0.1µF or larger ceramic capacitor.
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 VCC3 or
ground and WT must be grounded.
VCC5 (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 VCC3. Bypass this pin to
ground with a 0.1µF or larger ceramic capacitor.
RST (Pin 6): Reset Logic Output. Active low, open-drain
logic output with weak pull-up to VCC3. 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 VCC3 when interfacing to 5V
logic.
VCC25 (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 VCC3. Bypass this pin to
ground with a 0.1µF or larger ceramic capacitor.
VCCA (Pin 3): 1V Sense, High Impedance Input. If unused
it can be tied to either VCC3, VCC5 or VCC25
.
WT (Pin 7): Watchdog Time-Out Input. Place a capacitor
betweenthispinandgroundtoadjustthewatchdogtime-
out period. To determine the watchdog time-out period:
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
capacitorthatisplacedontheWTpin.Therisingorfalling
edge of this pin clears the voltage on the WT capacitor,
preventing a reset pulse from occurring. If the watchdog
t
WT = 21.8 • CWT
with tWT in µs and CWT 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.
5
LTC1726
U
U
U
PI FU CTIO S
RT (Pin 8): Reset Time-Out Input. Place a capacitor with tRT in µs and CRT in pF. As an example, a 47nF
between this pin and ground to adjust the reset time-out capacitor will generate a 155ms watchdog time-out
period. To determine the reset time-out period:
period.
t
RT = 3.30 • CRT
W
BLOCK DIAGRA
2µA
WT
WATCHDOG
TIMER
WDI
5
1
TRANSITION DETECT
7
+
C
WT
–
+
22µA
V
CC3
V
CC3
POWER
DETECT
V
CC
INTERNAL
–
+
V
/V
2
CC5 CC25
V
/V
CC5 CC25
V
CC3
6µA
–
6
RST
ADJUSTABLE
RESET
V
3
4
CCA
PULSE
1V
GENERATOR
+
GND
2µA
22µA
BANDGAP
REFERENCE
8
RT
+
1726 BD
C
RT
W U
W
TI I G DIAGRA S
VCC Monitor Timing
Watchdog Timing Diagram
V
RTX
t
t
t
WT
V
WDI
RST
WP
WT
CCX
t
t
RT
RT
t
RT
RST
1726 TD01
1726 TD02
6
LTC1726
W U U
APPLICATIO S I FOR ATIO
U
Supply Monitoring
manner, the part can function as a 5V monitor with the
3.3V monitor disabled.
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.
When monitoring either 3.3V or 5V with VCC3 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 VRT3, RST is held
low. From VRT3 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
All three VCC 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 VCC inputs.
Upon power-up, either the VCC5/VCC25 or VCC3 pin can
power the drive circuits for the RST pin. This ensures that
RST will be low when either VCC5/VCC25 or VCC3 reaches
1V. As long as any one of the VCC inputs is below its
predetermined threshold, RST will stay a logic low. Once
all of the VCC inputs rise above their thresholds, the
adjustable reset timer is started and RST is released after
the reset time-out period.
voltages with VCC3 = VCC5
.
Table 1. Override Truth Table (VCC3 = VCC5
)
INPUTS (V
= V
= V
)
CC
RST
—
0
CC3
CC5
0V ≤ V ≤ 1V
CC
Onpower-down, onceanyoftheVCC inputsdropsbelowits
threshold, RST is held at a logic low. A logic low of 0.3V is
guaranteed until both VCC3 and VCC5/VCC25 drop below 1V.
1V ≤ V ≤ V
CC
RT3
V
≤ V ≤ 4.15V
1
RT3
CC
4.15V ≤ V ≤ V
0
CC
RT5
V
≤ V
1
RT5
CC
3V or 5V/2.5V Power Detect
V
CC
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 VCC3 or VCC5/VCC25 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.
3.3V OR 5V
LTC1726-5
1
2
3
4
R1
10k
V
V
V
CC3
CC5
CCA
6
TO SYSTEM
RESET
RST
GND
1726 F01
PINS 5, 7 AND 8 NOT SHOWN FOR CLARITY
Figure 1. Single Supply Monitor with Others Disabled
5
Override Functions (5V Versions Only)
V
= V
= V
= 0V TO 5V
CCA
CC3
CC5
10k PULL-UP FROM RST TO V
CC3
T
= 25°C
The VCCA pin, if unused, can be tied to either VCC3 or VCC5
This is an obvious solution since the trip points for VCC3
andVCC5 willalwaysbegreaterthanthetrippointforVCCA
.
4
3
A
.
The VCC5 input trip point is disabled if its voltage is equal
to the voltage on VCC3 ±25mV and the voltage on VCC5 is
less than 4.15V. In this manner the LTC1726-5 behaves
as a 3.3V monitor and the 5V reset function is disabled.
2
1
0
The VCC5 trip point is re-enabled when the voltage on
VCC5 is equal to the voltage on VCC3 ±25mV and the two
inputs are greater than approximately 4.15V. In this
0
1
2
3
4
5
SUPPLY VOLTAGE (V)
1726 F02
Figure 2. RST Voltage vs Supply Voltage
7
LTC1726
W U U
U
APPLICATIO S I FOR ATIO
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 VCC5 pin to the VCC3 pin. This prevents the part’s
internal override circuit from being activated. Without the
override circuit active, the RST pin stays low until VCC5
reaches VRT5 4.675V. (See Figure 4.)
Watchdog Timer
The watchdog circuit monitors a µP’s activity. The µP 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,thewatchdogtimerisstarted.Thewatchdogtimerwill
continue to run until a transition is detected on the WDI
input or until the watchdog timer times out. Once the
watchdogtimertimesout,theinternalcircuitryassertsthe
resetandstartstheresettimer.Whentheresettimertimes
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
ontheWDIinputduringthewatchdogtime-outperiod, the
watchdog timer will be restarted and reset will remain
deasserted.
5V
LTC1726-5
D1
1
2
3
4
R1
10k
V
V
V
CC3
CC5
CCA
6
TO SYSTEM
RESET
RST
GND
0.1µF
1726 F03
D1: MMBD914 OR EQUIVALENT
PINS 5, 7 AND 8 NOT SHOWN FOR CLARITY
Figure 3. LTC1726-5 Monitoring a Single 5V
Supply. D1 Used to Avoid RST High Near 3.1V
to 4V (See Figure 2).
5
V
CC5
= V
CCA
= 0V TO 5V
Selecting the Reset and Watchdog
Time-Out Capacitors
10k PULL-UP FROM RST TO V
CC5
T
= 25°C
4
3
2
1
0
A
The reset time-out period is adjustable in order to accom-
modate a variety of µP applications. The reset time-out
period, tRT, is adjusted by connecting a capacitor, CRT,
betweentheRTpinandground. Thevalueofthiscapacitor
is determined as follows:
CRT = tRT/3.30
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
(V)
with CRT in pF and tRT in µs (i.e., 1500pF 4.95ms).
V
CC5
1726 F04
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, tWT, is adjusted by
connecting a capacitor, CWT, between the WT pin and
ground. Once the optimum watchdog time-out period
(tWT)isdetermined, thevalueofthecapacitoriscalculated
as follows:
Figure 4. RST Output Voltage
Characteristics of the Circuit in Figure 3
LTC1726-2.5 Override Functions
TheVCCA pin, ifunused, canbetiedtoeitherVCC3 orVCC25
This is an obvious solution since the trip points for VCC3
and VCC25 will always be greater than the trip point for
VCCA. Likewise, the VCC25, if unused, can be tied to VCC3
.
CWT = tWT/21.8
.
with CWT in pF and tWT in µs (i.e., 1500pF 32.7ms).
VCC3 must always be used. Tying VCC3 to VCC25 and
operating off of a 2.5V supply will result in the continuous
assertion of RST.
8
LTC1726
U
TYPICAL APPLICATIO S
Disabling the Watchdog Timer
LTC1726-5/2.5
C
RT
1
2
3
4
8
7
6
5
3.3V
V
RT
WT
CC3
/
V
V
CC5
CC25
5V/2.5V
R1*
SYSTEM
RESET
ADJUSTABLE
SUPPLY
V
CCA
RST
WDI
R2*
GND
1726 TA03
*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
Triple Supply Monitor (3.3V, 5V and Adjustable)
LTC1726-5
C
RT
1
2
3
4
8
7
6
5
3.3V
5V
V
V
V
RT
CC3
CC5
CCA
C
WT
WT
RST
WDI
ADJUSTABLE SUPPLY
OR DC/DC FEEDBACK
DIVIDER
R1*
SYSTEM RESET
WDI
R2*
GND
1726 TA04
*TO PRESERVE THRESHOLD ACCURACY, SET PARALLEL
COMBINATION OF R1 AND R2 ≤ 66.5k
Dual Supply Monitor (3.3V and 5V, Defeat VCCA Input)
LTC1726-5
C
RT
1
2
3
4
8
7
6
5
3.3V
5V
V
V
V
RT
CC3
CC5
CCA
C
WT
WT
RST
WDI
SYSTEM RESET
WDI
GND
1726 TA05
9
LTC1726
U
TYPICAL APPLICATIO S
Dual Supply Monitor (3.3V or 5V Plus Adjustable)
3.3V OR
5V
REFER TO LTC1726-X OVERRIDE FUNCTIONS IN
THE APPLICATIONS INFORMATION SECTION
LTC1726-5
C
RT
4.7k
1
2
3
4
8
7
6
5
V
V
V
RT
CC3
CC5
CCA
C
WT
WT
RST
WDI
R1*
ADJUSTABLE
SUPPLY
SYSTEM RESET
WDI
R2*
GND
1726 TA06
*TO PRESERVE THRESHOLD ACCURACY, SET PARALLEL
COMBINATION OF R1 AND R2 ≤ 66.5k
Dual Supply Monitor (3.3V Plus Adjustable)
3.3V
LTC1726-2.5
C
4.7k RT
1
2
3
4
8
7
6
5
V
RT
CC3
C
WT
V
V
WT
RST
WDI
CC25
CCA
R1*
ADJUSTABLE
SUPPLY
SYSTEM RESET
WDI
R2*
GND
1726 TA07
*TO PRESERVE THRESHOLD ACCURACY, SET PARALLEL
COMBINATION OF R1 AND R2 ≤ 66.5k
Using VCCA Tied to DC/DC Feedback Divider
2.9V
35.7k
1%
LTC1726-5
LTC1435
C
RT
1
2
3
4
8
7
6
5
6
3.3V
V
V
V
RT
V
CC3
CC5
CCA
OSENSE
C
WT
2.8k
1%
5V
WT
RST
WDI
SYSTEM RESET
WDI
22.1k
1%
GND
ADJUSTABLE
RESET TRIP
THRESHOLD 2.74V
1726 TA08
10
LTC1726
U
PACKAGE DESCRIPTIO
Dimensions in (inches) unless otherwise noted.
MS8 Package
8-Lead Plastic MSOP
(LTC DWG # 05-08-1660)
0.118 ± 0.004*
(3.00 ± 0.102)
8
7
6
5
0.118 ± 0.004**
(3.00 ± 0.102)
0.193 ± 0.006
(4.90 ± 0.15)
1
0.040 ± 0.006
2
3
4
0.034 ± 0.004
(0.86 ± 0.102)
(1.02 ± 0.15)
0.007
(0.18)
0° – 6° TYP
SEATING
PLANE
0.012
(0.30)
REF
0.021 ± 0.006
(0.53 ± 0.015)
0.006 ± 0.004
(0.15 ± 0.102)
0.0256
(0.65)
BSC
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
S8 Package
8-Lead Plastic Small Outline (Narrow 0.150)
(LTC DWG # 05-08-1610)
0.189 – 0.197*
(4.801 – 5.004)
7
5
8
6
0.150 – 0.157**
(3.810 – 3.988)
0.228 – 0.244
(5.791 – 6.197)
1
3
4
2
0.010 – 0.020
(0.254 – 0.508)
× 45°
0.053 – 0.069
(1.346 – 1.752)
0.004 – 0.010
(0.101 – 0.254)
0.008 – 0.010
(0.203 – 0.254)
0°– 8° TYP
0.016 – 0.050
(0.406 – 1.270)
0.050
(1.270)
BSC
0.014 – 0.019
(0.355 – 0.483)
TYP
*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
SO8 1298
11
LTC1726
U
TYPICAL APPLICATIO
Triple Supply Monitor with Watchdog Timer and Manual Reset Button
12V (±5%)
V
TRIP
= 11.2V
(±0.17V)
5V 3.3V
1500pF
1
2
3
4
8
7
V
V
V
RT
CC3
CC5
CCA
100nF
1500pF
LTC1726-5
R1
WT
RST
WDI
R3*
10k
5%
1.07M
100nF
0.1%
6
5
RESET
µP
R2
105k
0.1%
MANUAL
RESET BUTTON
(NORMALLY OPEN)
GND
I/O
1726 TA09
V
CCA
R2
V
TRIP
=
(R1 + R2)
V
V
TRIP
*OPTIONAL RESISTOR RECOMMENDED
TO EXTEND ESD TOLERANCE
– 1
R1 = R2
(
)
CCA
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
LTC690
5V Supply Monitor, Watchdog Timer and Battery Backup
3.3V Supply Monitor, Watchdog Timer and Battery Backup
5V Supply Monitor and Watchdog Timer
4.65V Threshold
2.9V Threshold
4.65V Threshold
LTC694-3.3
LTC699
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
2.363V, 3.118V, 1V Thresholds (±0.75%) 2.5V, 3.3V, ADJ
LTC1326-2.5
LTC1536
Micropower Precision Triple Supply Monitor for 2.5V, 3.3V and ADJ
Precision Triple Supply Monitor for PCI Applications
Meets PCI t
Timing Specifications
FAIL
LTC1727-5
LTC1727-2.5
LTC1728-5
LTC1728-2.5
Micropower Triple Supply Monitor with Individual Outputs
Micropower Triple Supply Monitor with Individual Outputs
Micropower Triple Supply Monitor in 5-Pin SOT-23 Package
Micropower Triple Supply Monitor in 5-Pin SOT-23 Package
4.675V, 3.086V, 1V Thresholds (±1.5%) 5V, 3.3V, ADJ
2.338V, 3.086V, 1V Thresholds (±1.5%) 2.5V, 3.3V, ADJ
4.675V, 3.086V, 1V Thresholds (±1.5%) 5V, 3.3V, ADJ
2.338V, 3.086V, 1V Thresholds (±1.5%) 2.5V, 3.3V, ADJ
1726i LT/TP 0100 4K • PRINTED IN USA
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
12
●
●
(408)432-1900 FAX:(408)434-0507 www.linear-tech.com
LINEAR TECHNOLOGY CORPORATION 2000
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