Page 1
LTC1727/LTC1728
Micropower Precision
Triple Supply Monitors
in 8-Lead MSOP and
5-Lead SOT-23 Packages
FeaTures
n
Monitors Three Inputs Simultaneously
LTC1727-5: 5V, 3.3V and ADJ
LTC1727-2.5: 2.5V, 3.3V and ADJ
LTC1728-5: 5V, 3.3V and ADJ
LTC1728-2.5: 2.5V, 3.3V and ADJ
LTC1728-1.8: 3V, 1.8V and ADJ
LTC1728-3.3: 3.3V, 1.8V and ADJ
n
±1.5% Threshold Accuracy Over Temperature
n
Very Low Supply Current: 10µA Typ
n
200ms Reset Time Delay
n
Active Low RESET Output
n
Power Supply Glitch Immunity
n
Guaranteed RESET for V
or V
n
n
n
CC5/VCC25/VCC18
LTC1727 Includes Monitor Output for Each Supply
LTC1727: 8-Lead MSOP and SO Packages
LTC1728: 5-Lead SOT-23 Package
≥ 1V
CC3
≥ 1V
applicaTions
n
Desktop Computers
n
Notebook Computers
n
Intelligent Instruments
n
Portable Battery-Powered Equipment
n
Network Servers
DescripTion
The LTC®1727 is a triple supply monitor intended for
systems with multiple supply voltages. Each supply monitor has its own open-drain output for individual supply
monitoring. A common open-drain reset output remains
low until all three supplies have been in compliance for
200ms. Tight 1.5% accuracy specifications and glitch
immunity ensure reliable reset operation without false
triggering.
The LTC1728 is functionally identical to the LTC1727
without the individual monitor outputs.
The RST output is guaranteed to be in the correct state
for V
CC5/VCC25/VCC18
or V
LTC1728 may also be configured to monitor any one or
two V
inputs instead of three, depending on system
CC
requirements.
Very low (10µA typical) supply current makes the LTC1727/
LTC1728 ideal for power conscious systems.
The LTC1727 is available in an 8-lead MSOP or SO package and the LTC1728 is available in a 5-lead SOT-23
package.
L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
down to 1V. The LTC1727/
CC3
Typical applicaTion
3.3V
DC/DC
CONVERTER
5V
1.8V
0.1µF
0.1µF
5 1
4
R1
61.9k
3
1%
R2
100k
1%
V
CC3
LTC1728-5
V
CC5
V
CCA
RST
GND
1727/28 TA01
SYSTEM
LOGIC
2
ADJUSTABLE
SUPPLY
Triple Supply Monitor with Power Good Output
(3.3V, 2.5V and Adjustable)
R3
LTC1727-2.5
1
3.3V
2.5V
R1
R2
V
CC3
2
COMP25
V
CC25
3
V
CCA
4
GND
COMP3
RST
COMPA
8
7
6
5
1727/28 TA08
10k
R4
10k
POWER
GOOD
SYSTEM
RESET
17278fb
1
Page 2
LTC1727/LTC1728
absoluTe MaxiMuM raTings
V
, V
CC3
CC5/VCC25/VCC18
, V
CCA ........................
–0.3V to 7V
(Notes 1. 2)
RST ............................................................. – 0.3V to 7V
COMPA, COMP3, COMP25/COMP5
(MS8 and SO-8 Only) ............................. – 0.3V to 7V
pin conFiguraTion
TOP VIEW
TOP VIEW
V
1
CC3
V
CC5/VCC25
2
3
V
CCA
4
GND
MS8 PACKAGE
8-LEAD PLASTIC MSOP
= 125°C, θJA = 200°C/W
T
JMAX
ORDER
PART NUMBER
8
COMP3
7
COMP25/COMP5
6
RST
5
COMPA
MS8
PART MARKING
V
1
CC3
V
/
CC5
2
V
CC25
V
3
CCA
GND
4
S8 PACKAGE
8-LEAD PLASTIC SO
= 125°C, θJA = 150°C/W
T
JMAX
ORDER
PART NUMBER
Operating Temperature Range
LTC1727/LTC1728E (Note 3) ............... – 40°C to 85°C
LTC1728H ..........................................– 40°C to 125°C
LTC1727I..............................................– 40°C to 85°C
Storage Temperature Range .................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec) ................. 300°C
COMP3
8
COMP25/
7
COMP5
RST
6
COMPA
5
S8
PART MARKING
RST 1
GND 2
V
ORDER
PART NUMBER
TOP VIEW
3
CCA
S5 PACKAGE
5-LEAD PLASTIC SOT-23
= 125°C, θJA = 250°C/W
T
JMAX
PART MARKING
5 V
4
V
V
V
CC3
CC5
CC25
CC18
S5
/
/
LTC1727EMS8-2.5
LTC1727EMS8-5
LTHY
LTHX
LTC1727ES8-2.5
LTC1727IS8-2.5
LTC1727ES8-5
LTC1727IS8-5
172725
727I25
17275
172715
LTC1728ES5-1.8
LTC1728ES5-2.5
LTC1728ES5-3.3
LTC1728ES5-5
LTC1728HS5-5
LTPH
LTIA
LTY P
LTHZ
LTHZ
Order Options Tape and Reel: Add #TR Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF
Lead Free Part Marking: http://www.linear.com/leadfree/
Consult LTC Marketing for parts specified with wider operating temperature ranges.
All except LTC1728-1.8/LTC1728-3.3. The l denotes specifications which
elecTrical cHaracTerisTics
apply over the full operating temperature range, otherwise specifications are at TA = 25°C. V
V
CC25
= 2.5V, V
CCA
= V
unless otherwise noted.
CC3
= 3.3V, V
CC3
CC5
= 5V,
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
V
RT3
V
RT5
V
RT25
V
RTA
V
CCOP
V
CCOPAVCC3
Reset Threshold V
Reset Threshold V
Reset Threshold V
Reset Threshold V
V
, V
CC3
CC5/VCC25
, V
CC5/VCC25
V
CC3
CC5
CC25
CCA
Input Threshold
CC3
V
Input Threshold (5V Version)
CC5
V
Input Threshold (2.5V Version)
CC25
V
Input Threshold
CCA
Operating Voltage RST, COMP3, COMP5, COMP25 in Correct Logic State
Operating Voltage Minimum Supply Voltage to Guarantee COMPA
l
3.036 3.086 3.135 V
l
4.600 4.675 4.750 V
l
2.300 2.338 2.375 V
l
0.985 1.000 1.015 V
l
1 7 V
l
2 2.3 V
in Correct Logic State
2
17278fb
Page 3
LTC1727/LTC1728
elecTrical cHaracTerisTics
All except LTC1728-1.8/LTC1728-3.3. The l denotes specifications which
apply over the full operating temperature range, otherwise specifications are at TA = 25°C. V
V
= 2.5V, V
CC25
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
I
VCC3
I
VCC25
I
VCC5
I
VCCA
t
RST
t
UV
V
V
V
V
Reset Pulse Width RST Low with 10k Pull-Up to V
VCC Undervoltage Detect to RST
or COMPX
V
OL
V
OH
Output Voltage Low, RST, COMPX I
Output Voltage High, RST, COMPX (Note 6) I
LTC1727-5/LTC1728-5 Only
V
OVR
V
= V
CCA
Supply Current V
CC3
Supply Current V
CC25
Supply Current V
CC5
Input Current V
CCA
unless otherwise noted.
CC3
CC5/VCC25
V
CC5/VCC25
CC25
CC5
CCA
–40°C < T
–40°C < T
V
CC5
Threshold V
SINK
I
SINK
I
SINK
I
SINK
SOURCE
Reset Override Voltage (Note 7) Override V
CC5
> V
< V
< V
, V
CC3
= 5V, V
CC3
= 1V
< 125°C
A
< 125°C
A
, V
, V
CC25
CC3
by More Than 1% (Note 5)
RT
= 2.5mA, V
= 100µA, V
= 100µA, V
= 100µA, V
= 1µA
Ability to Assert RST V
CC5
CC3
, V
CC3
= 3.3V (Note 4)
CC3
= 2.5V (Note 4)
CC25
< V
CC5
or V
CCA
= 3V, V
CC3
= 1V, V
CC3
= 0V, V
CC3
= 1V, V
CC3
(Note 5)
CC3
Less Than Reset
CC5/VCC25
CC5/VCC25
CC5/VCC25
CC5/VCC25
= 0V
= 0V
= 1V
= 1V
= 3.3V, V
CC3
= 5V,
CC5
l
l
l
l
l
l
l
l
–15
–20
140
140
1
10
1 2 µA
10 20 µA
0
0
200 280
110 µs
l
l
l
l
l
V
– 1 V
CC3
0.15
0.05
0.05
0.05
±0.025 V
CC3
2
20
15
50
350
0.4
0.3
0.3
0.3
µA
µA
nA
nA
ms
ms
V
V
V
V
LTC1728-1.8 The l denotes specifications which apply over the full operating temperature range, otherwise specifications are at
TA = 25°C. V
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
V
RT3
V
RT18
V
RTA
V
CCOP
I
VCC3
I
VCC18
I
VCCA
t
RST
t
UV
V
OL
V
OH
= 3V, V
CC3
Reset Threshold V
Reset Threshold V
Reset Threshold V
V
, V
CC3
V
Supply Current V
CC3
V
Supply Current V
CC18
V
Input Current V
CCA
= 1.8V, V
CC18
CC3
CC18
CCA
Operating Voltage RST in Correct Logic State
CC18
CCA
= V
unless otherwise noted.
CC3
V
Input Threshold
CC3
V
Input Threshold
CC18
V
Input Threshold
CCA
> V
CC18
V
< V
CC18
< V
CC18
= 1V
CCA
CC3
CC3
CC3
, V
, V
Reset Pulse Width RST Low (Note 5)
VCC Undervoltage Detect to RST V
Output Voltage Low, RST I
Output Voltage High, RST I
, V
CC18
CC3
Threshold V
= 2.5mA, V
SINK
I
= 100µA, V
SINK
I
= 100µA, V
SINK
I
= 100µA, V
SINK
= 1µA (Note 6)
SOURCE
or V
by More Than 1%
RT
= 3V (Note 4)
CC3
= 1.8V (Note 4)
CC18
Less Than Reset (Note 5)
CCA
CC3
CC3
CC3
CC3
= 3V, V
= 1V, V
= 0V, V
= 1V, V
CC18
CC18
CC18
CC18
= 0V
= 0V
= 1V
= 1V
l
2.760 2.805 2.850 V
l
1.656 1.683 1.710 V
l
0.985 1.000 1.015 V
l
1 7 V
l
l
l
l
–15 0 15 nA
l
140 200 280 ms
1
10
2
20
1 2 µA
110 µs
l
l
l
l
l
V
CC3
0.15
0.05
0.05
0.05
0.4
0.3
0.3
0.3
– 1 V
µA
µA
V
V
V
V
17278fb
3
Page 4
LTC1727/LTC1728
elecTrical cHaracTerisTics
LTC1728-3.3 The l denotes specifications which apply over the full operating temperature range, otherwise specifications are at
TA = 25°C. V
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
V
RT3
V
RT18
V
RTA
V
CCOP
I
VCC3
I
VCC18
I
VCCA
t
RST
t
UV
V
OL
V
OH
= 3.3V, V
CC3
Reset Threshold V
Reset Threshold V
Reset Threshold V
V
, V
CC3
CC18
V
Supply Current V
CC3
V
Supply Current V
CC18
V
Input Current V
CCA
CC18
CC3
CC18
CCA
= 1.8V, V
CCA
= V
unless otherwise noted.
CC3
V
Input Threshold
CC3
V
Input Threshold
CC18
V
Input Threshold
CCA
Operating Voltage RST in Correct Logic State
> V
CC18
CC18
CC18
CCA
< V
< V
= 1V
CC3
CC3
CC3
, V
, V
CC3
CC18
V
Reset Pulse Width RST Low (Note 5)
VCC Undervoltage Detect to RST V
Output Voltage Low, RST I
Output Voltage High, RST I
, V
CC18
CC3
Threshold V
= 2.5mA, V
SINK
I
= 100µA, V
SINK
I
= 100µA, V
SINK
I
= 100µA, V
SINK
= 1µA (Note 6)
SOURCE
or V
by More Than 1%
RT
= 3.3V (Note 4)
= 1.8V (Note 4)
Less Than Reset (Note 5)
CCA
= 3.3V, V
CC3
= 1V, V
CC3
= 0V, V
CC3
= 1V, V
CC3
CC18
CC18
CC18
CC18
= 0V
= 0V
= 1V
= 1V
l
3.036 3.086 3.135 V
l
1.656 1.683 1.710 V
l
0.985 1.000 1.015 V
l
1 7 V
l
l
l
l
–15 0 15 nA
l
140 200 280 ms
1
10
2
20
1 2 µA
110 µs
l
l
l
l
l
V
CC3
0.15
0.05
0.05
0.05
0.4
0.3
0.3
0.3
– 1 V
µA
µA
V
V
V
V
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 LTC1727E/LTC1728E are guaranteed to meet specified
performance from 0°C to 70°C and are designed, characterized and
assured to meet the extended temperature limits of –40°C to 85°C
but are not tested at these temperatures.
Note 4: Both V
CC3
and V
CC5/VCC25/VCC18
can act as the supply depending
on which pin has the greatest potential.
Note 5: Measured from when input passes through the input threshold
(V
) until RST or COMPX passes through 1.5V.
RTX
Note 6: The output pins RST and COMPX have internal pull-ups to V
CC3
of
typically 6µA. However, external pull-up resistors may be used when faster
rise times are required or for V
Note 7: The V
reset override voltage is valid for an operating range less
CC5
voltages greater than V
OH
CC3
.
than approximately 4.15V. Above this point the override is turned off and
the V
pin functions normally.
CC5
4
17278fb
Page 5
Typical perForMance cHaracTerisTics
LTC1727/LTC1728
Input Current
V
CCA
vs Input Voltage
2.0
TA = 25°C
1.5
1.0
0.5
0
–0.5
INPUT CURRENT (nA)
–1.0
–1.5
–2.0
0.80 0.85 0.95 1.05 1.15
0.90
1
INPUT VOLTAGE (V)
Reset Pulse Width
vs Temperature
280
260
(ms)
240
RST
220
200
180
RESET PULSE WIDTH, t
160
140
–60 –40
–20 20 40 800 100
TEMPERATURE (°C)
1.10
60
1727/28 G01
1727/28 G04
1.015
(V)
1.010
RTA
1.005
1.000
0.995
THRESHOLD VOLTAGE, V
0.990
CCA
V
1.20
0.985
(mA)
SINK
I
V
Threshold Voltage
CCA
vs Temperature
–40 0
–60
–20 20
TEMPERATURE (°C)
RST, COMPX I
vs Supply Voltage
10
TA = 25°C
9
8
7
6
5
4
3
2
1
0
0
1
Typical Transient Duration
vs Comparator Overdrive
SINK
450
400
350
300
250
200
150
100
TYPICAL TRANSIENT DIRATION (µs)
50
0
40
60
80
100
1727/28 G02
0.1
RESET COMPARATOR OVERDRIVE VOLTAGE (% OF VCC)
I
vs Temperature
VCC25
RESET OCCURS
ABOVE CURVE
1 10 100
TA = 25°C
1727/28 G03
(LTC1727-2.5/LT1728-2.5)
1.5
V
= 3.3V
CC3
1.4
1.1
(µA)
VCC25
I
0.5
1.3
1.2
1.0
0.9
0.8
0.7
0.6
VOL = 0.4V
VOL = 0.2V
(V)
5
1727/28 G05
6
3 4
2
V
OR V
CC3
CC5
V
CC25
V
CCA
–60
–40 0
= 2.5V
= 3.3V
–20
TEMPERATURE (°C)
80
20
60
40
100
1727/28 G06
I
vs Temperature (LTC1727-
VCC3
2.5/LTC1728-2.5/LTC1728-3.3)
15
V
= 3.3V
CC3
(µA)
VCC3
I
14
13
12
11
10
V
V
9
8
7
6
5
–60
= 2.5V
CC25
= 3.3V
CCA
–40 0
–20
20
TEMPERATURE (°C)
I
vs Temperature
VCC3
(LTC1727-5/LTC1728-5)
1.5
V
= 5V
CC5
1.4
1.3
1.2
1.1
(µA)
1.0
VCC3
I
0.9
0.8
0.7
80
60
40
100
1727/28 G07
0.5
0.6
–60
= 3.3V
V
CC3
= 3.3V
V
CCA
–40 0
–20
20
TEMPERATURE (°C)
40
80
60
100
1727/28 G08
I
vs Temperature
VCC5
(LTC1727-5/LTC1728-5)
15
V
= 5V
CC5
14
= 3.3V
V
CC3
= 3.3V
V
CCA
13
12
11
(µA)
10
VCC5
I
9
8
7
6
5
–60
–40 0
–20
TEMPERATURE (°C)
80
20
60
40
100
1727/28 G09
17278fb
5
Page 6
LTC1727/LTC1728
Typical perForMance cHaracTerisTics
Threshold Voltage
V
CC25
vs Temperature
(LTC1727-2.5/LTC1728-2.5)
2.3750
2.3675
(V)
2.3600
RT25
2.3525
2.3450
2.3375
2.3300
2.3225
THRESHOLD VOLTAGE, V
2.3150
CC25
2.3075
V
2.3000
–60
–40 0
–20
TEMPERATURE (°C)
(µA)
VCC18
I
1.710
(V)
1.700
RT18
1.690
1.680
1.670
THRESHOLD VOLTAGE, V
1.660
CC18
V
1.650
80
20
I
VCC18
60
40
100
1727/28 G10
vs Temperature
(LTC1728-1.8/LTC1728-3.3)
1.5
V
= 3V
CC3
1.4
1.3
1.2
1.1
1.0
0.9
0.8
0.7
0.6
0.5
= 1.8V
V
CC18
= 3V
V
CCA
–60
–40 0
–20
V
Threshold Voltage
CC18
20
TEMPERATURE (°C)
vs Temperature
(LTC1728-1.8/LTC1728-3.3)
–40 0
–60
–20 20
TEMPERATURE (°C)
V
Threshold Voltage
CC3
vs Temperature
(All But LTC1728-1.8)
3.135
3.125
(V)
3.115
RT3
3.105
3.095
3.085
3.075
3.065
THRESHOLD VOLTAGE, V
3.055
CC3
V
3.045
3.035
–60
–40 0
80
60
40
40
60
1727/28 G13
80
1727/28 G15
100
100
–20
20
TEMPERATURE (°C)
(V)
THESHOLD VOLTAGE, V
V
80
60
40
I
VCC3
100
1727/28 G11
vs Temperature
(LTC1728-1.8)
15
V
= 3V
CC3
14
= 1.8V
V
CC18
= 3V
V
CCA
13
12
11
(µA)
10
VCC3
I
9
8
7
6
5
–60
–40 0
–20
V
Threshold Voltage
CC3
20
TEMPERATURE (°C)
vs Temperature (LTC1728-1.8)
2.845
2.835
(V)
RT3
2.825
2.815
2.805
2.795
2.785
THRESHOLD VOLTAGE, V
CC3
2.775
V
2.765
–60
–40 0
–20
20
TEMPERATURE (°C)
V
Threshold Voltage
CC5
vs Temperature
(LTC1727-5/LTC1728-5)
4.750
4.725
RT5
4.700
4.675
4.650
4.625
CC5
4.600
–60
–40 –20
TEMPERATURE (°C)
80
60
40
60
40
1727/28 G14
80
1727/28 G16
100
100
20
0 40 100
60 80
1727/28 G12
6
17278fb
Page 7
LTC1727/LTC1728
pin FuncTions
V
(Pin 1/Pin 5): 3.3V Sense Input and Power Supply
CC3
(LTC1727/LTC1728)
Pin. (3V Sense Input and Power Supply Pin for LTC1728-
1.8.) This pin provides power to the part when the voltage
on V
is greater than the voltage on V
CC3
CC5/VCC25/VCC18
Bypass to ground with a ≥0.1µF ceramic capacito
(Pin 2/Pin 4): 5V Sense Input and Power Supply Pin.
V
CC5
.
r
.
This pin is used on the LTC1727-5/LTC1728-5 to provide
power to the part when the voltage on V
than the voltage on V
ceramic capacito
(Pin 2/Pin 4): 2.5V Sense Input and Power Supply
V
CC25
r
. Bypass to ground with a ≥0.1µF
CC3
.
is greater
CC5
Pin. This pin is used on the LTC1727-2.5/LTC1728-2.5 to
provide power to the part when the voltage on V
greater than the voltage on V
a ≥0.1µF ceramic capacito
(Pin 2/Pin 4): 1.8V Sense Input and Power Supply
V
CC18
. Bypass to ground with
CC3
r
.
CC25
is
Pin. This pin is used on the LTC1728-1.8/LTC1728-3.3 to
provide power to the part when the voltage on V
greater than the voltage on V
a ≥0.1µF ceramic capacito
(Pin 3/Pin 3): 1V Sense, High Impedance Input. If un-
V
CCA
used, it can be tied to either V
. Bypass to ground with
CC3
r
.
or V
CC3
CC5/VCC25/VCC18
CC18
is
.
GND (Pin 4/Pin 2): Ground.
COMPA (Pin 5): V
Comparator Output for the LTC1727.
CCA
Active high, open-drain logic output with weak pull-up to
. Asserted when V
V
CC3
is below V
V
CCA
RTA
is above V
CCA
or if both the V
. Deasserted when
RTA
and V
CC3
CC5
supply
pins are too low to power the internal bandgap reference
(typically <2.0V). Can be pulled greater than V
CC3
using
an external pull-up.
RST (Pin 6/Pin 1): Reset Logic Output. Active low, open-
drain logic output with weak pull-up to V
up greater than V
when interfacing to 5V logic. Asserted
CC3
. Can be pulled
CC3
when one or all of the supplies are below trip thresholds
and held for 200ms after all supplies become valid.
COMP5 (Pin 7): V
Comparator Output for the
CC5
LTC1727-5. Active high, open-drain logic output with weak
pull-up to V
. Asserted when V
CC3
be pulled greater than V
COMP25 (Pin 7): V
CC25
using an external pull-up.
CC3
Comparator Output for the
is above V
CC5
RT5
. Can
LTC1727-2.5. Active high, open-drain logic output with
weak pull-up to V
. Can be pulled greater than V
V
RT25
. Asserted when V
CC3
using an external
CC3
is above
CC25
pull-up.
COMP3 (Pin 8): V
Comparator Output for the LTC1727.
CC3
Active high, open-drain logic output with weak pull-up to
. Asserted when V
V
CC3
greater than V
using an external pull-up.
CC3
is above V
CC3
. Can be pulled
RT3
17278fb
7
Page 8
LTC1727/LTC1728
block DiagraMs
LTC1727-5/LTC1727-2.5
6µA
V
CC3
CC3
1V
–
8
COMP3
+
V
CC3
POWER
DETECT
/
V
CC5
2
V
CC25
INTERNAL
V
CC
6µA
7
COMP25/
COMP5
–
V
6µA
6µA
CC3
6 RST
V
CC3
5 COMPA
CCA
+
3V
4GND
–
+
BANDGAP
REFERENCE
200ms PULSE GENERATOR
200ms
DELAY
8
1727 BD1
17278fb
Page 9
block DiagraMs
LTC1727/LTC1728
LTC1728-5/LTC1728-2.5/LTC1728-1.8/LTC1728-3.3
V
V
CC25
V
CC3
CC5
CC18
CCA
5V
–
+
POWER
DETECT
/
/
4
3V
2GND
INTERNAL
V
CC
–
+
–
+
BANDGAP
REFERENCE
200ms PULSE GENERATOR
200ms
DELAY
6µA
V
CC3
1 RST
TiMing DiagraM
V
CCX
RST
COMPX
1727 BD2
VCC Monitor Timing
V
RTX
t
t
UV
RST
1.5V
1727 TD01
17278fb
9
Page 10
LTC1727/LTC1728
applicaTions inForMaTion
Supply Monitoring
The LTC1727 is a low power, high accuracy triple supply monitoring circuit with three monitor outputs and a
200ms microprocessor reset output.
The LTC1728 is a low power, high accuracy triple supply
monitoring circuit with a single 200ms microprocessor
reset output.
All three VCC inputs must be above predetermined thresholds for reset not to be invoked. The LTC1727/LTC1728 will
assert reset during power-up, power-down and brownout
conditions on any one or all of the V
inputs.
CC
Power Detect
The LTC1727/LTC1728 are powered from the 3.3V/3V input
pin (V
(V
CC25
), the 1.8V input pin (V
CC3
) or the 5V input pin (V
CC5
), the 2.5V input pin
CC18
), whichever pin has the
highest potential. This ensures the part pulls the RST pin
V
low as soon as either input pin is ≥1
.
Power-Up
Upon power-up, either the V
CC5/VCC25
CC18
or V
CC3
pin,
/
V
can power the part. This ensures that RST will be low
when either V
CC5/VCC25/VCC18
as any one of the V
inputs is below its predetermined
CC
or V
threshold, RST will stay a logic low. Once all of the V
reaches 1V. As long
CC3
CC
inputs rise above their thresholds, an internal timer is
started and RST is released after 200ms.
Power-Down
On power-down, once any of the VCC inputs drop below
RST
its threshold,
0.3V is guaranteed until both V
is held at a logic low. A logic low of
and V
CC3
CC5/VCC25/VCC18
drop below 1V.
Glitch Immunity
The RST output of the LTC1727/LTC1728 have two forms
of glitch immunity built in. First, the input monitors require
the input voltage to transition at least 10% of the input
threshold (0.1 • V
) below the input threshold for ap-
RTH
proximately 50µs in order to force the monitor output low.
The duration of the transition must be longer for voltage
transitions of lesser magnitude (see Figure 1). Secondly,
the reset pulse width of approximately 200ms acts to
debounce the RST output ensuring that the RST output
will always be in the correct state.
The individual monitor outputs of the LTC1727 do not have
hysteresis and will track the monitor inputs relative to the
monitor’s input threshold (V
RTA
, V
RT25
, V
RT3
and V
RT5
). A
very slow moving input voltage with ripple riding on it may
cause the individual monitor outputs (COMPA, COMP25,
COMP3 and COMP5) to toggle on the ripple as the input
voltage passes the input threshold. The slow response
time of the LTC1727’s input monitors has a tendency to
integrate signals on the inputs improving their immunity
to noise and ripple.
is reasserted whenever any one of the VCC inputs
RST
drops below its predetermined threshold and remains
asserted until 200ms after all of the V
inputs are above
CC
their thresholds.
On the LTC1727, each of the comparator outputs will be
low until the V
input that is monitored by that compara-
CC
tor rises above the appropriate predetermined threshold.
The COMP3, and COMP5/COMP25 outputs are guaranteed to be in the correct logic state for either V
V
CC5/VCC25
greater than 1V. The COMPA output requires
CC3
or
the internal bandgap reference to be valid before the
correct logic state can be output. Therefore, the COMPA
output will be held low until V
or V
CC5/VCC25
is greater than 2V (typ).
is above 1V and V
CCA
CC3
10
450
400
350
300
250
200
150
TRANSIENT DURATION (µs)
100
50
0
0.1
RESET MONITOR OVERDRIVE VOLTAGE (% OF VCC)
Figure 1. Transient Duration vs Comparator Overdrive
1 10 100
1727/28 F01
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Page 11
applicaTions inForMaTion
LTC1727/LTC1728
Override Functions (5V Versions Only)
The V
V
CC5
V
CC3
for V
The V
equal to the voltage on V
V
CC5
pin, if unused, can be tied to either V
CCA
. This is an obvious solution since the trip points for
and V
CCA
CC5
will always be greater than the trip point
CC5
.
input trip point is disabled if its voltage is
±25mV and the voltage on
CC3
is less than 4.15V. In this manner, the LTC1727-5/
LTC1728-5 will behave as a 3.3V monitor and V
CC5
or
CC3
reset
capability will be disabled.
The V
V
CC5
trip point is reenabled when the voltage on
CC5
is equal to the voltage on V
±25mV and the
CC3
two inputs are greater than approximately 4.15V. In this
manner, the part can function as a 5V monitor with the
3.3V monitor disabled.
When monitoring either 3.3V or 5V with V
to V
(see Figure 2), the part determines which is the
CC5
strapped
CC3
appropriate range. The part handles this situation as
,
RST
shown in Figure 3. Above 1V and below V
low. From V
3.3V supply monitoring and
to approximately 4.15V the part assumes
RT3
RST
is deasserted. Above
RT3
is held
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
RST
the
rizes the state of
V
Table 1. Override Truth Table (V
INPUTS (V
0V ≤ V
1V ≤ V
V
RT3
4.15V ≤ V
V
RT5
output will behave as desired. Table 1 summa-
RST
at various operating voltages with
= V
CC3
CC
CC
≤ VCC ≤ 4.15V 1
≤ V
.
CC5
= V
CC5
)
CC3
= V
CC3
≤ 1V —
≤ V
≤ V
CC
CC
= VCC) RST
CC5
RT3
RT5
0
0
1
V
CC
3.3V OR 5V
5
4
3
2
LTC1728-5
V
CC3
V
CC5
V
CCA
GND
RST
R1
10k
1
TO SYSTEM
RESET
1727/28 F02
Figure 2. Single Supply Monitor with Others Disabled
5
V
= V
= V
CC3
CC5
10k PULL-UP FROM RST TO V
4
3
2
RST OUTPUT VOLTAGE (V)
1
0
1
0
= 0V TO 5V
CCA
2
SUPPLY VOLTAGE (V)
CC3
3
4
5
1727/28 F03
Figure 3. RST Voltage vs Supply Voltage
17278fb
11
Page 12
LTC1727/LTC1728
applicaTions inForMaTion
Figure 4 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 LTC1728-5 while dropping ≈0.6V
from the V
pin to the V
CC5
pin. This prevents the part’s
CC3
internal override circuit from being activated. Without the
override circuit active, the RST pin stays low until V
reaches V
5V
0.1µF
≅ 4.675V. (See Figure 5.)
RT5
D1
LTC1728-5
5
V
CC3
4
V
CC5
3
V
CCA
2
GND
D1: MMBD914 OR EQUIVALENT
RST
1
R1
10k
TO SYSTEM
RESET
1727/28 F04
Figure 4. LTC1728-5 Monitoring a Single 5V
Supply. D1 Used to Avoid RST High Near 3.1V
to 4V (See Figure 3).
CC5
LTC1727-2.5/LTC1728-2.5/LTC1728-1.8/LTC1728-3.3
Override Functions
The V
V
CC18
V
CC3
point for V
be tied to V
V
CC25/VCC18
pin, if unused, can be tied to either V
CCA
. This is an obvious solution since the trip points for
and V
CC25/VCC18
. Likewise, the V
CCA
. V
CC3
will always be greater than the trip
CC25/VCC18
must always be used. Tying V
CC3
and operating off of a 2.5V/1.8V supply will
or V
CC3
CC25
, if unused, can
to
CC3
result in the continuous assertion of RST.
5
V
= V
CC5
10k PULL-UP FROM RST TO V
TA = 25°C
4
3
2
RST OUTPUT VOLTAGE (V)
1
0
0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
= 0V TO 5V
CCA
CC5
V
(V)
CC5
1727/28 F05
/
Typical applicaTions
ADJUSTABLE SUPPLY
OR DC/DC FEEDBACK
Figure 5. RST Output Voltage
Characteristics of the Circuit in Figure 4
Triple Supply Monitor (3.3V, 5V and Adjustable)
LTC1728-5
DIVIDER
3.3V
R1*
*TO PRESERVE THRESHOLD ACCURACY, SET PARALLEL
COMBINATION OF R1 AND R2 ≤ 66.5k
5
V
CC3
4
5V
R2*
V
CC5
3
V
CCA
2
GND
RST
1
SYSTEM RESET
1727/28 TA03
12
17278fb
Page 13
Typical applicaTions
LTC1727/LTC1728
Dual Supply Monitor (3.3V and 5V, Defeat V
LTC1728-5
3.3V SYSTEM RESET
5V
5
V
CC3
4
V
CC5
3
V
CCA
2
GND
Dual Supply Monitor (3.3V or 5V Plus Adjustable)
3.3V OR
ADJUSTABLE
SUPPLY
5V
R1*
R2*
*TO PRESERVE THRESHOLD ACCURACY, SET PARALLEL
COMBINATION OF R1 AND R2 ≤ 66.5k
REFER TO LTC1728-5 OVERRIDE FUNCTIONS IN
THE APPLICATIONS INFORMATION SECTION
5
4
3
2
LTC1728-5
V
CC3
V
CC5
V
CCA
GND
RST
RST
1
1727/28 TA04
1
1727/28 TA05
10k
Input)
CCA
SYSTEM RESET
ADJUSTABLE
SUPPLY
LTC1435
V
OSENSE
ADJUSTABLE
RESET TRIP
THRESHOLD 2.74V
Dual Supply Monitor (3.3V Plus Adjustable)
3.3V
R1*
R2*
*TO PRESERVE THRESHOLD ACCURACY, SET PARALLEL
COMBINATION OF R1 AND R2 ≤ 66.5k
Using V
CCA
2.9V
6
LTC1728-2.5
5
V
CC3
4
V
CC25
3
V
CCA
2
GND
RST
1
1727/28 TA06
10k
SYSTEM RESET
Tied to DC/DC Feedback Divider
35.7k
1%
2.8k
1%
22.1k
1%
3.3V
5V
5
4
3
2
LTC1728-5
V
CC3
V
CC5
V
CCA
GND
RST
1727/28 TA07
1
SYSTEM RESET
17278fb
13
Page 14
LTC1727/LTC1728
package DescripTion
MS8 Package
8-Lead Plastic MSOP
(Reference LTC DWG # 05-08-1660)
3.00 ± 0.102
(.118 ± .004)
(NOTE 3)
0.52
8
7
(.0205)
6
5
REF
5.23
(.206)
MIN
0.42 ± 0.038
(.0165 ± .0015)
TYP
RECOMMENDED SOLDER PAD LAYOUT
0.889 ± 0.127
(.035 ± .005)
3.20 – 3.45
(.126 – .136)
0.65
(.0256)
BSC
.050 BSC
PLANE
4.90 ± 0.152
(.193 ± .006)
0.22 – 0.38
(.009 – .015)
TYP
1.10
(.043)
MAX
12
0.65
(.0256)
BSC
DETAIL “A”
0.254
(.010)
GAUGE PLANE
0.18
(.007)
NOTE:
1. DIMENSIONS IN MILLIMETER/(INCH)
2. DRAWING NOT TO SCALE
3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS.
MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS.
INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX
0° – 6° TYP
0.53 ± 0.152
(.021 ± .006)
DETAIL “A”
SEATING
S8 Package
8-Lead Plastic Small Outline (Narrow 0.150)
(Reference LTC DWG # 05-08-1610)
.189 – .197
.045 ±.005
(4.801 – 5.004)
8
NOTE 3
7
5
6
3.00 ± 0.102
(.118 ± .004)
(NOTE 4)
4
3
0.86
(.034)
REF
0.127 ± 0.076
(.005 ± .003)
MSOP (MS8) 0204
14
.245
MIN
.030 ±.005
TYP
RECOMMENDED SOLDER PAD LAYOUT
.010 – .020
(0.254 – 0.508)
.008 – .010
(0.203 – 0.254)
.016 – .050
NOTE:
1. DIMENSIONS IN
2. DRAWING NOT TO SCALE
3. THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.
MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .006" (0.15mm)
(0.406 – 1.270)
INCHES
(MILLIMETERS)
× 45°
.160
±.005
0°– 8° TYP
.228 – .244
(5.791 – 6.197)
.053 – .069
(1.346 – 1.752)
.014 – .019
(0.355 – 0.483)
TYP
.150 – .157
(3.810 – 3.988)
NOTE 3
1
3
2
4
.050
(1.270)
BSC
.004 – .010
(0.101 – 0.254)
SO8 0303
17278fb
Page 15
package DescripTion
LTC1727/LTC1728
S5 Package
5-Lead Plastic SOT-23
(Reference LTC DWG # 05-08-1633)
(Reference LTC DWG # 05-08-1635)
2.80 – 3.10
(.110 – .118)
(NOTE 3)
SOT-23
(Original)
.90 – 1.45
A
(.035 – .057)
.00 – .15
A1
(.00 – .006)
.90 – 1.30
A2
(.035 – .051)
.35 – .55
L
(.014 – .021)
.20
(.008)
DATUM ‘A’
L
NOTE:
1. CONTROLLING DIMENSION: MILLIMETERS
2. DIMENSIONS ARE IN
3. DRAWING NOT TO SCALE
4. DIMENSIONS ARE INCLUSIVE OF PLATING
5. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR
6. MOLD FLASH SHALL NOT EXCEED .254mm
7. PACKAGE EIAJ REFERENCE IS:
SC-74A (EIAJ) FOR ORIGINAL
JEDEC MO-193 FOR THIN
SOT-23
(ThinSOT)
1.00 MAX
(.039 MAX)
.01 – .10
(.0004 – .004)
.80 – .90
(.031 – .035)
.30 – .50 REF
(.012 – .019 REF)
MILLIMETERS
(INCHES)
2.60 – 3.00
(.102 – .118)
.09 – .20
(.004 – .008)
(NOTE 2)
1.50 – 1.75
(.059 – .069)
(NOTE 3)
PIN ONE
A
.95
(.037)
REF
A2
1.90
(.074)
REF
.25 – .50
(.010 – .020)
(5PLCS, NOTE 2)
A1
S5 SOT-23 0401
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.
17278fb
15
Page 16
LTC1727/LTC1728
Typical applicaTion
Triple Supply Monitor with Manual Reset Button
12V (±5%)
V
= 11.2V
TRIP
(±0.17V)
5V 3.3V
MANUAL
RESET BUTTON
(NORMALLY OPEN)
R3*
10k
5%
*OPTIONAL RESISTOR RECOMMENDED
TO EXTEND ESD TOLERANCE
R1
1.07M
0.1%
R2
105k
0.1%
100nF
100nF
V
R1 = R2
5
V
CC3
LTC1728-5
4
V
CC5
3
V
CCA
V
CCA
= (R1 + R2)
TRIP
R2
V
TRIP
( )
V
CCA
RST
GND
1727/28 TA02
– 1
1
2
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%)
LTC1326-2.5 Micropower Precision Triple Supply Monitor for 2.5V, 3.3V and ADJ 2.363V, 3.118V, 1V Thresholds (±0.75%)
LTC1443/LTC1444
LTC1445
LTC1536 Precision Triple Supply Monitor for PCI Applications Meets PCI t
LTC1540 Nanopower Comparator with 2% Reference 1.182V Reference, 300nA Supply Current, 8-Pin MSOP
LTC1726-2.5 Micropower Triple Supply Monitor for 2.5V, 3.3V and ADJ Adjustable RESET and Watchdog Time Outs
LTC1726-5 Micropower Triple Supply Monitor for 5V, 3.3V and ADJ Adjustable RESET and Watchdog Time Outs
LTC1985-1.8 Micropower Triple Supply Monitor for 3.3V, 1.8V and ADJ Push-Pull RESET Output, SOT-23
Micropower Quad Comparators with 1% Reference LTC1443 Has 1.182V Reference, LTC1444/LTC1445
Have 1.221V Reference and Adjustable Hysteresis
Timing Specifications
FAIL
16
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507
●
www.linear.com
17278fb
LT 0207 REV B • PRINTED IN USA
LINEAR TECHNOLOGY CORPORATION 1999
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