LINER LTC1726IS8-2.5

Final Electrical Specifications
LTC1726
Triple Supply Monitor and
µP Supervisor with Adjustable
Reset and Watchdog Timer
January 2000
U
FEATURES
■
■
■
■
■
■
■
■
■
DESCRIPTIO
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 VCC3 ≥ 1V or VCC25 /VCC5 ≥ 1V
MS8 and SO-8 Packages
U
DESCRIPTIO
■
■
■
■
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
VCC5/VCC25 or VCC3 down to 1V. The LTC1726 may also be
configured to monitor any one or two VCC inputs instead
of three, depending on system requirements.
The low (16µA typical) supply current makes the LTC1726
ideal for power-conscious systems.
Desktop Computers
Notebook Computers
Intelligent Instruments
Portable Battery-Powered Equipment
Network Servers
, LTC and LT are registered trademarks of Linear Technology Corporation.
U
■
The LTC®1726 is a triple supply monitor and microprocessor supervisory circuit with adjustable reset and watchdog
functions intended for systems with multiple supply voltages. 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.
TYPICAL APPLICATIO S
A 3.3V, 5V and 1.8V Monitor
A 3.3V, 2.5V and 1.8V Monitor
1.8V
(VTRIP = 1.665V)
3.3V
0.1µF
5V
0.1µF
2
CRT
47nF
1
3
VCC5 VCC3 VCCA
8
RST
RT
CWT
47nF
6
1.8V
(VTRIP = 1.665V)
R1
66.5k
1%
3.3V
R2
100k
1%
2.5V
0.1µF
µP
5
WT
WDI
2
CRT
47nF
CWT
47nF
GND
tRT = 155ms
tWT= 1s
4
R2
100k
1%
3
RT
RST
6
RESET
µP
LTC1726-2.5
7
I/O
1
VCC25 VCC3 VCCA
8
RESET
LTC1726-5
7
R1
66.5k
1%
0.1µF
5
WT
WDI
I/O
GND
1726 TA01
tRT = 155ms
tWT= 1s
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 representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
4
1726 TA02
1
LTC1726
W W
W
AXI U
U
ABSOLUTE
RATI GS
Terminal Voltage
VCC3, VCC5/VCC25, VCCA .........................
RST .......................................................
WDI .......................................................
RT, WT ..................................................
(Notes 1, 2)
– 0.3V to 7V
– 0.3V to 7V
– 0.3V to 7V
– 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
U
U
W
PACKAGE/ORDER I FOR ATIO
ORDER
PART NUMBER
TOP VIEW
VCC3
VCC25 /VCC5
VCCA
GND
1
2
3
4
8
7
6
5
RT
WT
RST
WDI
LTC1726EMS8-2.5
LTC1726EMS8-5
MS8 PACKAGE
8-LEAD PLASTIC MSOP
MS8 PART MARKING
TJMAX = 125°C, θJA = 200°C/W
LTKZ
LTLA
ORDER
PART NUMBER
LTC1726ES8-2.5
LTC1726ES8-5
LTC1726IS8-2.5
LTC1726IS8-5
TOP VIEW
VCC3 1
VCC25/
2
VCC5
VCCA 3
8
RT
7
WT
6
RST
GND 4
5
WDI
S8 PART MARKING
S8 PACKAGE
8-LEAD PLASTIC SO
172625
726I25
17265
1726I5
TJMAX = 125°C, θJA = 150°C/W
Consult factory for Military grade parts.
ELECTRICAL CHARACTERISTICS
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
otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
VRT3
Reset Threshold VCC3
VCC3 Input Threshold
●
3.036
3.085
3.135
V
VRT5
Reset Threshold VCC5
VCC5 Input Threshold (5V Version)
●
4.600
4.675
4.750
V
VRT25
Reset Threshold VCC25
VCC25 Input Threshold (2.5V Version)
●
2.300
2.337
2.375
V
VRTA
Reset Threshold VCCA
VCCA Input Threshold
●
0.985
1.000
1.015
V
VCC
VCC3 or VCC5 Operating Voltage
RST in Correct Logic State
●
1
7
V
IVCC3
VCC3 Supply Current
VCC5/VCC25 > VCC3
VCC5/VCC25 < VCC3, VCC3 = 3.3V
●
●
1
16
2
30
µA
µA
IVCC5
VCC5 Supply Current
VCC5 = 5V
●
16
30
µA
IVCC25
VCC25 Supply Current
VCC25 < VCC3, VCC25 = 2.5V (Note 4)
●
1
2
µA
IVCCA
VCCA Input Current
VCCA = 1V
●
– 15
0
15
nA
RT Charge Current Out
VRT = 0V
●
1.4
2
2.6
µA
WT Charge Current Out
VWT = 0V
●
1.4
2
2.6
µA
RT Discharge Current Out
VRT = 1.3V
●
14
20
26
µA
WT Discharge Current Out
VWT = 1.3V
●
14
20
26
µA
2
LTC1726
ELECTRICAL CHARACTERISTICS
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
otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
tRT
Reset Time-Out Period
CRT = 1500pF
tUV
VCC Undervoltage Detect to RST
VCC25/VCC5, VCC3 or VCCA Less Than Reset
Threshold VRT by More Than 1%
VOH
RST Output Voltage High (Note 5)
ISOURCE = 1µA
●
VOL
RST Output Voltage Low
ISINK = 2.5mA, VCC5/VCC25 = 0V
ISINK = 100µA, VCC3 = 1V, VCC5/VCC25 = 0V
ISINK = 100µA, VCC3 = 0V, VCC5/VCC25 = 1V
ISINK = 100µA, VCC3 = 1V, VCC5/VCC25 = 1V
●
●
●
●
VIH
WDI Input Threshold High
●
VIL
WDI Input Threshold Low
●
0.3 • VCC3
V
tWP
WDI Pulse Width
●
40
ns
tWT
Watchdog Time-Out Period
●
23
●
MIN
TYP
MAX
3.5
5
6.5
WDI Leakage Current
ms
µs
130
CWT = 1500pF
UNITS
VCC3 – 1
V
0.15
0.05
0.05
0.05
0.4
0.3
0.3
0.3
V
V
V
V
0.7 • VCC3
V
33
●
43
ms
±1
µA
LTC1726-5 Only
VOVR
VCC5 Reset Override Voltage (Note 6)
VCC3 ±0.025
Override VCC5 Ability to Assert RST
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.
V
Note 4: Both VCC3 and VCC25/VCC5 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 VCC3 of typically
6µA. However, external pull-up resistors may be used when faster rise
times are required or for VOH voltages greater than VCC3.
Note 6: The VCC5 reset override voltage is valid for an operating range less
than approximately 4.15V. Above this point the override is turned off and
the VCC5 pin functions normally.
U W
TYPICAL PERFOR A CE CHARACTERISTICS
VCC5 Threshold Voltage
vs Temperature
VCC3 Threshold Voltage
vs Temperature
3.135
4.725
4.700
4.675
4.650
4.625
80
100
1726 G01
1.015
3.125
VCCA THRESHOLD VOLTAGE, VRTA (V)
VCC3 THRESHOLD VOLTAGE, VRT3 (V)
VCC5 THRESHOLD VOLTAGE, VRT5 (V)
4.750
4.600
–60 –40 –20 0
20 40 60
TEMPERATURE (°C)
VCCA Threshold Voltage
vs Temperature
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
1726 G02
1.010
1.005
1.000
0.995
0.990
0.985
20
40 60
–60 –40 –20 0
TEMPERATURE (°C)
80 100
1726 G03
3
LTC1726
U W
TYPICAL PERFOR A CE CHARACTERISTICS
VCC25 Threshold Voltage
vs Temperature
IVCC5 vs Temperature
1.5
VCC5 = 5V
1.4 VCC3 = 3.3V
2.360
18
1.3
17
1.2
2.345
16
1.1
2.330
2.315
2.300
20
40 60
–60 –40 –20 0
TEMPERATURE (°C)
IVCC3 (µA)
VCC5 = 5V
19 VCC3 = 3.3V
IVCC5 (µA)
VCC25 THRESHOLD VOLTAGE, VRT25 (V)
IVCC3 vs Temperature (LTC1726-5)
20
2.375
15
14
13
0.8
0.7
11
0.6
80
IVCC25 vs Temperature
(LTC1726-2.5)
16
1.0
0.9
15
14
0.8
13
0.7
12
0.6
11
80
10
–60 –40 –20 0 20 40 60
TEMPERATURE (°C)
100
80
100
TA = 25°C
600
500
400
VCCA Input Current
vs Input Voltage
300
200
100
0
1
10
100
0.1
RESET COMPARATOR OVERDRIVE VOLTAGE (% OF VCC)
1726 G09
Watchdog Time-Out Period
vs Temperature
40
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
Reset Pulse Width vs Temperature
6.0
CWT = 1500pF
5.8
38
RESET PULSE WIDTH, tRT (ms)
WATCHDOG TIME PERIOD, tWT (ms)
TA = 25°C
1.5
RESET OCCURS
ABOVE CURVE
1726 G08
1726 G07
INPUT CURRENT (nA)
TYPICAL TRANSIENT DURATION (µs)
1.1
IVCC3 (µA)
IVCC25 (µA)
18
17
4
700
VCC3 = 3.3V
19 VCC25 = 2.5V
1.2
36
34
32
30
28
26
20 40 60
–60 –40 –20 0
TEMPERATURE (°C)
100
Typical Transient Duration
vs Comparator Overdrive
20
1.3
80
1726 G06
IVCC3 vs Temperature
(LTC1726-2.5)
1.5
VCC3 = 3.3V
1.4 VCC25 = 2.5V
2.0
0.5
–60 –40 –20 0 20 40 60
TEMPERATURE (°C)
100
1726 G05
1726 G04
0.5
–60 –40 –20 0 20 40 60
TEMPERATURE (°C)
0.9
12
10
–60 –40 –20 0 20 40 60
TEMPERATURE (°C)
80 100
1.0
CRT = 1500pF
5.6
5.4
5.2
5.0
4.8
4.6
4.4
4.2
80
100
1726 G10
4.0
–60 –40 –20 0 20 40 60
TEMPERATURE (°C)
80
100
1726 G11
LTC1726
U W
TYPICAL PERFOR A CE CHARACTERISTICS
RST Output Voltage vs
Supply Voltage (LTC1726-2.5)
Time-Out Period vs Capacitance
106
TA = 25°C
RST OUTPUT VOLTAGE (V)
105
tRT OR tWT (µs)
VCC3 = VCC25 = VCCA
10k PULL-UP FROM VCC3 TO RST
TA = 25°C
3
tWT
104
tRT
103
102
10
0.1
1
10
102
CRT OR CWT (pF)
103
104
2
1
0
0
1
2
3
VCC3 (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
than the voltage on VCC25/VCC5. Bypass this pin to ground
with a 0.1µF or larger ceramic capacitor.
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.
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.
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
timer is not cleared, a reset pulse will occur. The watchdog timer is cleared during a reset and restarts when the
reset is deasserted. When disabling the watchdog function, this pin should be connected to either VCC3 or
ground and WT must be grounded.
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 asserted 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.
WT (Pin 7): Watchdog Time-Out Input. Place a capacitor
between this pin and ground to adjust the watchdog timeout period. To determine the watchdog time-out period:
tWT = 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
between this pin and ground to adjust the reset time-out
period. To determine the reset time-out period:
with tRT in µs and CRT in pF. As an example, a 47nF
capacitor will generate a 155ms watchdog time-out
period.
tRT = 3.30 • CRT
W
BLOCK DIAGRA
2µA
WDI 5
TRANSITION DETECT
WATCHDOG
TIMER
7
WT
+
CWT
–
VCC3 1
22µA
VCC3
+
POWER
DETECT
VCC
INTERNAL
–
VCC5/VCC25 2
VCC5 /VCC25
VCC3
+
6µA
–
VCCA 3
1V
GND 4
6 RST
ADJUSTABLE
RESET
PULSE
GENERATOR
+
2µA
22µA
BANDGAP
REFERENCE
8
+
1726 BD
RT
CRT
W
UW
TI I G DIAGRA S
VCC Monitor Timing
VCCX
Watchdog Timing Diagram
VRTX
WDI
tRT
tWT
tRT
tWT
tRT
RST
RST
1726 TD01
6
tWP
1726 TD02
LTC1726
U
W
U U
APPLICATIO S I FOR ATIO
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 VCC inputs must be above predetermined thresholds for reset not to be asserted. The LTC1726 will assert
reset during power-up, power-down and brownout conditions 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.
On power-down, once any of the VCC inputs drops below its
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.
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 VCC3 or VCC5/VCC25 input, whichever 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.
manner, the part can function as a 5V monitor with the
3.3V monitor disabled.
When monitoring either 3.3V or 5V with VCC3 strapped to
VCC5, (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 assumes 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 VCC3 = VCC5.
Table 1. Override Truth Table (VCC3 = VCC5)
INPUTS (VCC3 = VCC5 = VCC)
0V ≤ VCC ≤ 1V
—
1V ≤ VCC ≤ VRT3
0
VRT3 ≤ VCC ≤ 4.15V
1
4.15V ≤ VCC ≤ VRT5
0
VRT5 ≤ VCC
1
VCC
3.3V OR 5V
2
3
4
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
R1
10k
VCC3
VCC5
VCCA
RST
6
TO SYSTEM
RESET
GND
1726 F01
PINS 5, 7 AND 8 NOT SHOWN FOR CLARITY
Figure 1. Single Supply Monitor with Others Disabled
5
RST OUTPUT VOLTAGE (V)
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.
LTC1726-5
1
Override Functions (5V Versions Only)
The VCCA pin, if unused, can be tied to either VCC3 or VCC5.
This is an obvious solution since the trip points for VCC3
and VCC5 will always be greater than the trip point for VCCA.
RST
VCC3 = VCC5 = VCCA = 0V TO 5V
10k PULL-UP FROM RST TO VCC3
TA = 25°C
4
3
2
1
0
0
1
3
4
2
SUPPLY VOLTAGE (V)
5
1726 F02
Figure 2. RST Voltage vs Supply Voltage
7
LTC1726
U
W
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.)
5V
D1
LTC1726-5
1
2
3
4
0.1µF
R1
10k
VCC3
VCC5
VCCA
RST
6
TO SYSTEM
RESET
GND
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).
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, 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 watchdog 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.
RST OUTPUT VOLTAGE (V)
5
VCC5 = VCCA = 0V TO 5V
10k PULL-UP FROM RST TO VCC5
TA = 25°C
4
Selecting the Reset and Watchdog
Time-Out Capacitors
The reset time-out period is adjustable in order to accommodate a variety of µP applications. The reset time-out
period, tRT, is adjusted by connecting a capacitor, CRT,
between the RT pin and ground. The value of this capacitor
is determined as follows:
3
2
1
CRT = tRT/3.30
0
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
VCC5 (V)
1726 F04
Figure 4. RST Output Voltage
Characteristics of the Circuit in Figure 3
LTC1726-2.5 Override Functions
The VCCA pin, if unused, can be tied to either VCC3 or VCC25.
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.
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
with CRT in pF and tRT in µs (i.e., 1500pF ⇒ 4.95ms).
The watchdog period is also adjustable so that the watchdog time-out period can be optimized for software execution. 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) is determined, the value of the capacitor is calculated
as follows:
CWT = tWT/21.8
with CWT in pF and tWT in µs (i.e., 1500pF ⇒ 32.7ms).
LTC1726
U
TYPICAL APPLICATIO S
Disabling the Watchdog Timer
LTC1726-5/2.5
3.3V
ADJUSTABLE
SUPPLY
R1*
5V/2.5V
R2*
1
VCC3
2 V /
CC5
VCC25
3
VCCA
4
GND
RT
WT
RST
WDI
CRT
8
7
6
5
SYSTEM
RESET
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
3.3V
ADJUSTABLE SUPPLY
OR DC/DC FEEDBACK
DIVIDER
R1*
5V
1
2
3
R2*
4
VCC3
RT
VCC5
WT
VCCA
RST
GND
WDI
CRT
8
CWT
7
6
5
SYSTEM RESET
WDI
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
3.3V
5V
1
2
3
4
VCC3
RT
VCC5
WT
VCCA
RST
GND
WDI
CRT
8
CWT
7
6
5
SYSTEM RESET
WDI
1726 TA05
9
LTC1726
U
TYPICAL APPLICATIO S
Dual Supply Monitor (3.3V or 5V Plus Adjustable)
3.3V OR
5V
LTC1726-5
1
2
ADJUSTABLE
SUPPLY
R1*
3
R2*
4
VCC3
RT
VCC5
WT
VCCA
RST
GND
WDI
4.7k CRT
8
REFER TO LTC1726-X OVERRIDE FUNCTIONS IN
THE APPLICATIONS INFORMATION SECTION
CWT
7
6
SYSTEM RESET
5
WDI
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
1
2
ADJUSTABLE
SUPPLY
R1*
3
R2*
4
VCC3
RT
VCC25
WT
VCCA
RST
GND
WDI
4.7k CRT
8
CWT
7
6
SYSTEM RESET
5
WDI
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
LTC1435
VOSENSE
ADJUSTABLE
RESET TRIP
THRESHOLD 2.74V
10
6
35.7k
1%
3.3V
2.8k
5V
1%
22.1k
1%
LTC1726-5
1
2
3
4
VCC3
RT
VCC5
WT
VCCA
RST
GND
WDI
1726 TA08
CRT
8
CWT
7
6
5
SYSTEM RESET
WDI
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
4
2 3
0.040 ± 0.006
(1.02 ± 0.15)
0.007
(0.18)
0.034 ± 0.004
(0.86 ± 0.102)
0° – 6° TYP
SEATING
PLANE 0.012
(0.30)
0.0256
REF
(0.65)
BSC
0.021 ± 0.006
(0.53 ± 0.015)
0.006 ± 0.004
(0.15 ± 0.102)
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)
8
7
6
5
0.150 – 0.157**
(3.810 – 3.988)
0.228 – 0.244
(5.791 – 6.197)
1
0.010 – 0.020
× 45°
(0.254 – 0.508)
0.008 – 0.010
(0.203 – 0.254)
0.053 – 0.069
(1.346 – 1.752)
0°– 8° TYP
0.016 – 0.050
(0.406 – 1.270)
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
2
3
4
0.004 – 0.010
(0.101 – 0.254)
0.050
(1.270)
BSC
SO8 1298
11
LTC1726
U
TYPICAL APPLICATIO
Triple Supply Monitor with Watchdog Timer and Manual Reset Button
12V (± 5%)
VTRIP = 11.2V
(± 0.17V)
5V
3.3V
1500pF
1
100nF
R3*
10k
5%
MANUAL
RESET BUTTON
(NORMALLY OPEN)
R1
1.07M
0.1%
VCC3
RT
8
1500pF
LTC1726-5
2
VCC5
WT
VCCA
RST
GND
WDI
7
100nF
3
R2
105k
0.1%
4
6
RESET
µP
5
I/O
1726 TA09
*OPTIONAL RESISTOR RECOMMENDED
TO EXTEND ESD TOLERANCE
V
VTRIP = CCA (R1 + R2)
R2
V
R1 = R2 TRIP – 1
VCCA
(
)
RELATED PARTS
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 tFAIL 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
12
Linear Technology Corporation
1726i LT/TP 0100 4K • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408)432-1900 ● FAX: (408) 434-0507 ● www.linear-tech.com
 LINEAR TECHNOLOGY CORPORATION 2000