Page 1
FEATURES
1
2
3
4
8
7
6
5
LTC1727-2.5
R2
1727/28 TA08
R1
ADJUSTABLE
SUPPLY
3.3V
2.5V
R3
10k
POWER
GOOD
SYSTEM
RESET
R4
10k
V
CC3
V
CC25
V
CCA
GND
COMP3
COMP25
RST
COMPA
■
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
■
±1.5% Threshold Accuracy Over Temperature
■
Very Low Supply Current: 10µA Typ
■
200ms Reset Time Delay
■
Active Low RESET Output
■
Power Supply Glitch Immunity
■
Guaranteed RESET for V
or V
■
■
■
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
U
APPLICATIO S
LTC1727/LTC1728
Micropower Precision
Triple Supply Monitors
in 8-Lead MSOP and
5-Lead SOT-23 Packages
U
DESCRIPTIO
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
LTC1728 may also be configured to monitor any one or
two VCC inputs instead of three, depending on system
requirements.
Very low (10µA typical) supply current makes the LTC1727/
LTC1728 ideal for power conscious systems.
or V
down to 1V. The LTC1727/
CC3
■
Desktop Computers
■
Notebook Computers
■
Intelligent Instruments
■
Portable Battery-Powered Equipment
■
Network Servers
TYPICAL APPLICATIO
3.3V
5V
1.8V
51
V
4
V
R1
61.9k
1%
R2
100k
1%
3
V
0.1µF
0.1µF
DC/DC
CONVERTER
U
CC3
LTC1728-5
CC5
CCA
RST
GND
1727/28 TA01
SYSTEM
LOGIC
2
The LTC1727 is available in an 8-lead MSOP or SO
package and the LTC1728 is available in a 5-lead SOT-23
package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Triple Supply Monitor with Power Good Output
(3.3V, 2.5V and Adjustable)
1
Page 2
LTC1727/LTC1728
A
V
O
LUTEXI TIS
S
, V
CC3
CC5/VCC25/VCC18
W
A
, V
WUW
ARB
................... –0.3V to 7V
CCA
U
G
(Notes 1, 2)
RST ........................................................... –0.3V to 7V
COMPA, COMP3, COMP25/COMP5
(MS8 and SO-8 Only) ............................ –0.3V to 7V
WU
/
PACKAGE
V
CC3
V
CC5/VCC25
V
CCA
GND
T
JMAX
ORDER
PART NUMBER
O
RDER I FOR ATIO
TOP VIEW
1
2
3
4
MS8 PACKAGE
8-LEAD PLASTIC MSOP
= 125°C, θ
= 200°C/W
JA
PART MARKING
8
COMP3
7
COMP25/COMP5
6
RST
5
COMPA
MS8
TOP VIEW
1
V
CC3
V
/
CC5
2
V
CC25
V
3
CCA
GND
4
S8 PACKAGE
8-LEAD PLASTIC SO
T
= 125°C, θ
JMAX
ORDER
PART NUMBER
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
8
COMP3
COMP25/
7
COMP5
RST
6
COMPA
5
= 150°C/W
JA
S8
PART MARKING
RST 1
GND 2
V
ORDER
PART NUMBER
TOP VIEW
3
CCA
S5 PACKAGE
5-LEAD PLASTIC SOT-23
T
= 125°C, θ
JMAX
JA
PART MARKING
5 V
4
= 250°C/W
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
Consult factory for Military grade parts.
ELECTRICAL CHARACTERISTICS
full operating temperature range, otherwise specifications are at TA = 25°C. V
All except LTC1728-1.8. The ● denotes specifications which apply over the
172725
727I25
17275
1727I5
= 3.3V, V
CC3
LTC1728ES5-1.8
LTC1728ES5-2.5
LTC1728ES5-5
CC5
= 5V, V
= 2.5V, V
CC25
CCA
LTPH
LTIA
LTHZ
= V
CC3
unless
otherwise noted.
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
V
RT3
V
RT5
V
RT25
V
RTA
V
CCOP
V
CCOPA
I
VCC3
I
VCC25
I
VCC5
I
VCCA
t
RST
Reset Threshold V
Reset Threshold V
Reset Threshold V
Reset Threshold V
V
, V
CC3
CC5/VCC25
V
, V
CC3
CC5/VCC25
V
Supply Current V
CC3
V
Supply Current V
CC25
V
Supply Current V
CC5
V
Input Current V
CCA
Reset Pulse Width RST Low with 10k Pull-Up to V
CC3
CC5
CC25
CCA
Operating Voltage RST, COMP3, COMP5, COMP25 in Correct Logic State ● 17V
Operating Voltage Minimum Supply Voltage to Guarantee COMPA ● 2 2.3 V
V
Input Threshold ● 3.036 3.086 3.135 V
CC3
V
Input Threshold (5V Version) ● 4.600 4.675 4.750 V
CC5
V
Input Threshold (2.5V Version) ● 2.300 2.338 2.375 V
CC25
V
Input Threshold ● 0.985 1.000 1.015 V
CCA
in Correct Logic State
CC5/VCC25
V
CC5/VCC25
CC25
CC5
CCA
> V
CC3
< V
, V
CC3
< V
, V
CC3
= 5V, V
CC3
= 1V ● –15 0 15 nA
= 3.3V (Note 4) ● 10 20 µA
CC3
= 2.5V (Note 4) ● 12 µA
CC25
< V
CC5
● 12 µA
● 10 20 µA
(Note 5) ● 140 200 280 ms
CC3
2
Page 3
LTC1727/LTC1728
ELECTRICAL CHARACTERISTICS
full operating temperature range, otherwise specifications are at TA = 25°C. V
All except LTC1728-1.8. The ● denotes specifications which apply over the
= 3.3V, V
CC3
CC5
= 5V, V
= 2.5V, V
CC25
CCA
= V
CC3
unless
otherwise noted.
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
t
UV
V
OL
V
OH
VCC Undervoltage Detect to RST V
CC5
, V
CC25
or COMPX Threshold V
Output Voltage Low, RST, COMPX I
Output Voltage High, RST, COMPX (Note 6) I
= 2.5mA, V
SINK
= 100µA, V
I
SINK
= 100µA, V
I
SINK
I
= 100µA, V
SINK
= 1µA ● V
SOURCE
, V
or V
CC3
by More Than 1% (Note 5)
RT
CC3
CC3
CC3
CC3
Less Than Reset 110 µs
CCA
= 3V, V
CC5/VCC25
= 1V, V
CC5/VCC25
= 0V, V
CC5/VCC25
= 1V, V
CC5/VCC25
= 0V ● 0.15 0.4 V
= 0V ● 0.05 0.3 V
= 1V ● 0.05 0.3 V
= 1V ● 0.05 0.3 V
– 1 V
CC3
LTC1727-5/LTC1728-5 Only
V
OVR
V
Reset Override Voltage (Note 7) Override V
CC5
Ability to Assert RST V
CC5
±0.025 V
CC3
LTC1728-1.8 The ● 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
CC18
V
Supply Current V
CC3
V
Supply Current V
CC18
V
Input Current V
CCA
= 1.8V, V
CC18
CC3
CC18
CCA
CCA
= V
unless otherwise noted.
CC3
V
Input Threshold ● 2.760 2.805 2.850 V
CC3
V
Input Threshold ● 1.656 1.683 1.710 V
CC18
V
Input Threshold ● 0.985 1.000 1.015 V
CCA
Operating Voltage RST in Correct Logic State ● 17V
> V
CC18
V
CC3
< V
, V
CC18
CC3
< V
CC18
CC3
= 1V ● –15 0 15 nA
CCA
= 3V (Note 4) ● 10 20 µA
CC3
, V
= 1.8V (Note 4) ● 12 µA
CC18
● 12 µA
Reset Pulse Width RST Low (Note 5) ● 140 200 280 ms
VCC Undervoltage Detect to RST V
Output Voltage Low, RST I
Output Voltage High, RST I
, V
or V
CC18
CC3
Threshold V
= 2.5mA, V
SINK
I
= 100µA, V
SINK
= 100µA, V
I
SINK
= 100µA, V
I
SINK
= 1µA (Note 6) ● V
SOURCE
Less Than Reset (Note 5) 110 µs
CCA
by More Than 1%
RT
CC3
CC3
CC3
CC3
= 3V, V
= 1V, V
= 0V, V
= 1V, V
= 0V ● 0.15 0.4 V
CC18
= 0V ● 0.05 0.3 V
CC18
= 1V ● 0.05 0.3 V
CC18
= 1V ● 0.05 0.3 V
CC18
– 1 V
CC3
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 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
) until RST or COMPX passes through 1.5V.
(V
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 VOH voltages greater than V
Note 7: The V
reset override voltage is valid for an operating range less
CC5
CC3
.
than approximately 4.15V. Above this point the override is turned off and
the V
pin functions normally.
CC5
3
Page 4
LTC1727/LTC1728
TEMPERATURE (°C)
–60
0.5
I
VCC25
(µA)
0.6
0.8
0.9
1.0
1.5
1.2
–20
20
40
1727/28 G06
0.7
1.3
1.4
1.1
–40 0
60
80
100
V
CC3
= 3.3V
V
CC25
= 2.5V
V
CCA
= 3.3V
TEMPERATURE (°C)
–60
5
I
VCC5
(µA)
6
8
9
10
15
12
–20
20
40
1727/28 G09
7
13
14
11
–40 0
60
80
100
V
CC5
= 5V
V
CC3
= 3.3V
V
CCA
= 3.3V
UW
TYPICAL PERFOR A CE CHARACTERISTICS
V
V
Input Current
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)
1.10
1727/28 G01
1.015
(V)
1.010
RTA
1.005
1.000
0.995
THRESHOLD VOLTAGE, V
0.990
CCA
V
0.985
1.20
Threshold Voltage
CCA
vs Temperature
–40 0
–60
–20 20
TEMPERATURE (°C)
40
60
80
1727/28 G02
100
Typical Transient Duration
vs Comparator Overdrive
450
400
350
300
250
200
150
100
TYPICAL TRANSIENT DIRATION (µs)
50
0
0.1
RESET COMPARATOR OVERDRIVE VOLTAGE (% OF VCC)
RESET OCCURS
ABOVE CURVE
1 10 100
TA = 25°C
1727/28 G03
280
260
(ms)
240
RST
220
200
180
RESET PULSE WIDTH, t
160
140
–60 –40
15
14
13
12
11
(µA)
10
VCC3
I
9
8
7
6
5
4
–60
Reset Pulse Width
vs Temperature
–20 20 40 800 100
TEMPERATURE (°C)
I
vs Temperature
VCC3
60
(LTC1727-2.5/LT1728-2.5)
V
= 3.3V
CC3
V
= 2.5V
CC25
V
= 3.3V
CCA
–40 0
–20
TEMPERATURE (°C)
20
40
60
1727/28 G04
80
1727/28 G07
100
RST, COMPX I
vs Supply Voltage
10
TA = 25°C
9
8
7
6
(mA)
5
SINK
I
4
3
2
1
0
1
0
I
VCC3
2
V
CC3
vs Temperature
(LTC1727-5/LTC1728-5)
1.5
V
= 5V
CC5
1.4
V
= 3.3V
CC3
V
= 3.3V
CCA
1.3
1.2
1.1
(µA)
1.0
VCC3
I
0.9
0.8
0.7
0.6
0.5
–60
–40 0
–20
TEMPERATURE (°C)
SINK
VOL = 0.2V
34
OR V
(V)
CC5
20
40
VOL = 0.4V
60
5
1727/28 G05
80
1727/28 G08
100
I
vs Temperature
VCC25
(LTC1727-2.5/LT1728-2.5)
6
I
vs Temperature
VCC5
(LTC1727-5/LTC1728-5)
Page 5
UW
TEMPERATURE (°C)
–60
V
CC5
THESHOLD VOLTAGE, V
RT5
(V)
4.675
4.700
4.750
4.725
0 40 100
1727/28 G12
4.650
4.625
4.600
–40 –20
20
60 80
TYPICAL PERFOR A CE CHARACTERISTICS
V
V
Threshold Voltage
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
–20
–40 0
TEMPERATURE (°C)
1.5
1.4
1.3
1.2
1.1
(µA)
1.0
VCC18
0.9
I
0.8
0.7
0.5
20
40
I
vs Temperature
VCC18
(LTC1728-1.8)
V
= 3V
CC3
= 1.8V
V
CC18
= 3V
V
CCA
0.6
–60
–40 0
80
60
–20
100
1727/28 G10
20
TEMPERATURE (°C)
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
Threshold Voltage
CC3
vs Temperature
(All But LTC1728-1.8)
–60
–40 0
80
1727/28 G13
–20
100
20
TEMPERATURE (°C)
40
(µA)
VCC3
I
60
15
14
13
12
11
10
9
8
7
6
5
–60
80
100
1727/28 G11
I
vs Temperature
VCC3
(LTC1728-1.8)
V
= 3V
CC3
= 1.8V
V
CC18
= 3V
V
CCA
–40 0
–20
TEMPERATURE (°C)
LTC1727/LTC1728
V
Threshold Voltage
CC5
vs Temperature
(LTC1727-5/LTC1728-5)
80
20
60
40
100
1727/28 G14
V
CC18
vs Temperature (LTC1728-1.8)
1.710
(V)
1.700
RT18
1.690
1.680
1.670
THRESHOLD VOLTAGE, V
1.660
CC18
V
1.650
–60
–40 0
Threshold Voltage
–20 20
TEMPERATURE (°C)
40
V
Threshold Voltage
CC3
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
60
80
100
1727/28 G15
2.765
–60
–40 0
–20
20
TEMPERATURE (°C)
40
100
1727/28 G16
80
60
5
Page 6
LTC1727/LTC1728
U
PI FU CTIO S
V
(Pin 1/Pin 5): 3.3V Sense Input and Power
CC3
UU
(LTC1727/LTC1728)
Supply Pin. (3V Sense Input and Power Supply Pin for
LTC1728-1.8.) This pin provides power to the part
when the voltage on V
V
CC5/VCC25/VCC18
. Bypass to ground with a ≥0.1µF
is greater than the voltage on
CC3
ceramic capacitor.
V
(Pin 2/Pin 4): 5V Sense Input and Power Supply
CC5
Pin. This pin is used on the LTC1727-5/LTC1728-5 to
provide power to the part when the voltage on V
greater than the voltage on V
. Bypass to ground with
CC3
CC5
is
a ≥0.1µF ceramic capacitor.
V
(Pin 2/Pin 4): 2.5V Sense Input and Power Supply
CC25
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
. Bypass to ground with
CC3
CC25
is
a ≥0.1µF ceramic capacitor.
V
(Pin 2/Pin 4): 1.8V Sense Input and Power Supply
CC18
Pin. This pin is used on the LTC1728-1.8 to provide
power to the part when the voltage on V
than the voltage on V
. Bypass to ground with a ≥0.1µF
CC3
is greater
CC18
ceramic capacitor.
COMPA (Pin 5): V
Comparator Output for the LTC1727.
CCA
Active high, open-drain logic output with weak pull-up to
V
. Asserted when V
CC3
when V
is below V
CCA
is above V
CCA
or if both the V
RTA
. Deasserted
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
using an external pull-up.
CC3
RST (Pin 6/Pin 1): Reset Logic Output. Active low, opendrain logic output with weak pull-up to V
up greater than V
when interfacing to 5V logic. As-
CC3
. Can be pulled
CC3
serted 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
Can be pulled greater than V
COMP25 (Pin 7): V
. Asserted when V
CC3
CC3
Comparator Output for the
CC25
is above V
CC5
RT5
using an external pull-up.
.
LTC1727-2.5. Active high, open-drain logic output with
weak pull-up to V
V
. Can be pulled greater than V
RT25
. Asserted when V
CC3
is above
CC25
using an external
CC3
pull-up.
V
(Pin 3/Pin 3): 1V Sense, High Impedance Input. If
CCA
unused, it can be tied to either V
CC3
or V
CC5/VCC25/VCC18
GND (Pin 4/Pin 2): Ground.
COMP3 (Pin 8): V
.
Active high, open-drain logic output with weak pull-up to
V
. Asserted when V
CC3
greater than V
Comparator Output for the LTC1727.
CC3
is above V
CC3
using an external pull-up.
CC3
. Can be pulled
RT3
6
Page 7
BLOCK DIAGRA S
W
LTC1727-5/LTC1727-2.5
LTC1727/LTC1728
V
CC3
6µA
V
V
CC3
CC5
CC25
CCA
1V
–
8
COMP3
+
V
CC3
POWER
DETECT
/
2
V
INTERNAL
CC
6µA
7
COMP25/
COMP5
–
V
6µA
6µA
CC3
6 RST
V
CC3
5 COMPA
+
3V
4GND
–
+
BANDGAP
REFERENCE
200ms PULSE GENERATOR
200ms
DELAY
1727 BD1
7
Page 8
LTC1727/LTC1728
W
BLOCK DIAGRA S
LTC1728-5/LTC1728-2.5/LTC1728-1.8
V
V
CC25
V
CC18
CC3
CC5
CCA
5V
–
+
POWER
DETECT
/
/
4
3V
2GND
INTERNAL
V
CC
–
+
–
+
BANDGAP
REFERENCE
200ms PULSE GENERATOR
200ms
DELAY
6µA
V
CC3
1 RST
UWW
TI I G DIAGRA
V
CCX
RST
COMPX
1727 BD2
VCC Monitor Timing
V
RTX
t
t
UV
RST
1.5V
1727 TD01
8
Page 9
LTC1727/LTC1728
U
WUU
APPLICATIO S I FOR ATIO
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 VCC inputs.
Power Detect
The LTC1727/LTC1728 are powered from the 3.3V/3V
input pin (V
input pin (V
pin has the highest potential. This ensures the part pulls
the RST pin low as soon as either input pin is ≥1V.
Power-Up
Upon power-up, either the V
can power the part. This ensures that RST will be low when
either V
CC5/VCC25/VCC18
any one of the VCC inputs is below its predetermined
threshold, RST will stay a logic low. Once all of the V
inputs rise above their thresholds, an internal timer is
started and RST is released after 200ms.
), the 1.8V input pin (V
CC3
) or the 5V input pin (V
CC25
CC5/VCC25
or V
CC3
), the 2.5V
CC18
), whichever
CC5
/
V
CC18
or V
CC3
pin,
reaches 1V. As long as
CC
Power-Down
On power-down, once any of the VCC inputs drop 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/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
RTH
approximately 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
V
). A very slow moving input voltage with ripple riding
RT5
RTA
, V
RT25
, V
RT3
and
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.
RST is reasserted whenever any one of the VCC inputs
drops below its predetermined threshold and remains
asserted until 200ms after all of the VCC inputs are above
their thresholds.
On the LTC1727, each of the comparator outputs will be
low until the VCC input that is monitored by that comparator 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
V
CC5/VCC25
is greater than 2V (typ).
is above 1V and V
CCA
CC3
or
450
400
350
300
250
200
150
100
TRANSIENT DURATION (µs)
50
0
0.1
RESET MONITOR OVERDRIVE VOLTAGE (% OF VCC)
Figure 1. Transient Duration vs Comparator Overdrive
1 10 100
1727/28 F01
9
Page 10
LTC1727/LTC1728
U
WUU
APPLICATIO S I FOR ATIO
Override Functions (5V Versions Only)
The V
This is an obvious solution since the trip points for V
and V
The V
to the voltage on V
less than 4.15V. In this manner, the LTC1727-5/
LTC1728-5 will behave as a 3.3V monitor and V
capability will be disabled.
The V
is equal to the voltage on V
are greater than approximately 4.15V. In this manner, the
part can function as a 5V monitor with the 3.3V monitor
disabled.
pin, if unused, can be tied to either V
CCA
will always be greater than the trip point for V
CC5
input trip point is disabled if its voltage is equal
CC5
±25mV and the voltage on V
CC3
CC3
or V
CC5
trip point is reenabled when the voltage on V
CC5
±25mV and the two inputs
CC3
CC5
CC3
CCA
is
CC5
reset
CC5
.
.
When monitoring either 3.3V or 5V with V
V
(see Figure 2), the part determines which is the
CC5
strapped to
CC3
appropriate range. The part handles this situation as
shown in Figure 3. Above 1V and below V
low. From V
to approximately 4.15V the part assumes
RT3
, RST is held
RT3
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
= V
CC3
Table 1. Override Truth Table (V
INPUTS (V
0V ≤ VCC ≤ 1V —
1V ≤ VCC ≤ V
V
≤ VCC ≤ 4.15V 1
RT3
4.15V ≤ VCC ≤ V
V
≤ V
RT5
CC
CC5
CC3
.
= V
CC5
)
CC3
= V
= 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
10
Figure 3. RST Voltage vs Supply Voltage
Page 11
LTC1727/LTC1728
U
WUU
APPLICATIO S I FOR ATIO
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
internal override circuit from being activated. Without the
override circuit active, the RST pin stays low until V
reaches V
pin to the V
CC5
≅ 4.675V. (See Figure 5.)
RT5
pin. This prevents the part’s
CC3
5V
0.1µF
CC5
D1
LTC1728-5
5
V
CC3
4
V
CC5
3
V
CCA
2
GND
D1: MMBD914 OR EQUIVALENT
LTC1727-2.5/LTC1728-2.5/LTC1728-1.8
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
result in the continuous assertion of RST.
R1
10k
RST
1
TO SYSTEM
RESET
1727/28 F04
or V
CC3
CC25
, if unused, can
to
CC3
/
Figure 4. LTC1728-5 Monitoring a Single 5V
Supply. D1 Used to Avoid RST High Near 3.1V
to 4V (See Figure 3).
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
Figure 5. RST Output Voltage
Characteristics of the Circuit in Figure 4
11
Page 12
LTC1727/LTC1728
TYPICAL APPLICATIO S
ADJUSTABLE SUPPLY
OR DC/DC FEEDBACK
DIVIDER
U
Triple Supply Monitor (3.3V, 5V and Adjustable)
LTC1728-5
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
Dual Supply Monitor (3.3V and 5V, Defeat V
LTC1728-5
3.3V SYSTEM RESET
5V
5
4
3
2
V
CC3
V
CC5
V
CCA
GND
RST
Dual Supply Monitor (3.3V or 5V Plus Adjustable)
3.3V OR
ADJUSTABLE
SUPPLY
5V
R1*
R2*
5
4
3
2
LTC1728-5
V
CC3
V
CC5
V
CCA
GND
RST
1
1727/28 TA04
1
1727/28 TA05
10k
Input)
CCA
SYSTEM RESET
12
*TO PRESERVE THRESHOLD ACCURACY, SET PARALLEL
COMBINATION OF R1 AND R2 ≤ 66.5k
REFER TO LTC1728-5 OVERRIDE FUNCTIONS IN
THE APPLICATIONS INFORMATION SECTION
Page 13
TYPICAL APPLICATIO S
LTC1727/LTC1728
U
Dual Supply Monitor (3.3V Plus Adjustable)
ADJUSTABLE
SUPPLY
3.3V
R1*
R2*
*TO PRESERVE THRESHOLD ACCURACY, SET PARALLEL
COMBINATION OF R1 AND R2 ≤ 66.5k
Using V
CCA
LTC1435
V
OSENSE
ADJUSTABLE
RESET TRIP
THRESHOLD 2.74V
LTC1728-2.5
5
V
CC3
4
V
CC25
3
V
CCA
2
GND
RST
1
1727/28 TA06
Tied to DC/DC Feedback Divider
2.9V
35.7k
1%
6
2.8k
1%
22.1k
1%
3.3V
5
V
4
5V
V
3
V
2
GND
10k
LTC1728-5
CC3
CC5
CCA
1727/28 TA07
SYSTEM RESET
1
RST
SYSTEM RESET
13
Page 14
LTC1727/LTC1728
PACKAGE DESCRIPTIO
U
Dimensions in inches (millimeters) 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
0.193 ± 0.006
(4.90 ± 0.15)
12
0.040
± 0.006
SEATING
PLANE
(1.02 ± 0.15)
0.012
(0.30)
0.0256
REF
(0.65)
BSC
0.007
(0.18)
0.021
± 0.006
(0.53 ± 0.015)
* 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
° – 6° TYP
0
0.118 ± 0.004**
4
3
0.034 ± 0.004
(0.86 ± 0.102)
(3.00 ± 0.102)
0.006 ± 0.004
(0.15 ± 0.102)
MSOP (MS8) 1098
S5 Package
5-Lead Plastic SOT-23
(LTC DWG # 05-08-1633)
2.80 – 3.00
(0.110 – 0.118)
(NOTE 3)
14
1.90
2.60 – 3.00
(0.102 – 0.118)
1.50 – 1.75
(0.059 – 0.069)
0.35 – 0.55
(0.014 – 0.022)
NOTE:
1. DIMENSIONS ARE IN MILLIMETERS
2. DIMENSIONS ARE INCLUSIVE OF PLATING
3. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR
4. MOLD FLASH SHALL NOT EXCEED 0.254mm
5. PACKAGE EIAJ REFERENCE IS SC-74A (EIAJ)
0.09 – 0.20
(0.004 – 0.008)
(NOTE 2)
(0.074)
REF
0.00 – 0.15
(0.00 – 0.006)
0.35 – 0.50
(0.014 – 0.020)
FIVE PLACES (NOTE 2)
0.95
(0.037)
REF
0.90 – 1.45
(0.035 – 0.057)
0.90 – 1.30
(0.035 – 0.051)
S5 SOT-23 0599
Page 15
PACKAGE DESCRIPTIO
LTC1727/LTC1728
U
Dimensions in inches (millimeters) unless otherwise noted.
S8 Package
8-Lead Plastic Small Outline (Narrow 0.150)
(LTC DWG # 05-08-1610)
0.189 – 0.197*
(4.801 – 5.004)
7
8
5
6
0.228 – 0.244
(5.791 – 6.197)
0.010 – 0.020
(0.254 – 0.508)
0.008 – 0.010
(0.203 – 0.254)
*
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
× 45°
0°– 8° TYP
0.016 – 0.050
(0.406 – 1.270)
0.053 – 0.069
(1.346 – 1.752)
0.014 – 0.019
(0.355 – 0.483)
TYP
0.150 – 0.157**
(3.810 – 3.988)
1
3
2
4
0.004 – 0.010
(0.101 – 0.254)
0.050
(1.270)
BSC
SO8 1298
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.
15
Page 16
LTC1727/LTC1728
TYPICAL APPLICATIO
U
Triple Supply Monitor with Manual Reset Button
12V (±5%)
= 11.2V
V
TRIP
(±0.17V)
5V 3.3V
RST
GND
1727/28 TA02
– 1
1
2
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
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PART NUMBER DESCRIPTION COMMENTS
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LTC1443/LTC1444 Micropower Quad Comparators with 1% Reference LTC1443 Has 1.182V Reference, LTC1444/LTC1445
LTC1445 Have 1.221V Reference and Adjustable Hysteresis
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
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Timing Specifications
FAIL
16
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507
●
www.linear-tech.com
17278f LT/TP 0400 4K • PRINTED IN THE USA
LINEAR TECHNOLOGY CORPORATION 1999
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