LTC2918IDDB-A1#PBF [Linear]
LTC2918 - Voltage Supervisor with 27 Selectable Thresholds and Watchdog Timer; Package: DFN; Pins: 10; Temperature Range: -40°C to 85°C;型号: | LTC2918IDDB-A1#PBF |
厂家: | Linear |
描述: | LTC2918 - Voltage Supervisor with 27 Selectable Thresholds and Watchdog Timer; Package: DFN; Pins: 10; Temperature Range: -40°C to 85°C |
文件: | 总16页 (文件大小:169K) |
中文: | 中文翻译 | 下载: | 下载PDF数据表文档文件 |
LTC2917/LTC2918
Low Voltage Supervisor
with 27 Selectable Thresh-
olds and Watchdog Timer
DESCRIPTION
The LTC®2917-A/LTC2917-B and LTC2918-A/LTC2918-B
are low voltage single-supply monitors with selectable
thresholds and an adjustable watchdog timer. The parts
operate from 1.5V to 5.5V and consume a quiescent cur-
rent of only 30μA.
FEATURES
■
9 Selectable Supply Voltages
12V, 5V, 3.3V, 2.5V, 1.8V
1.5V, 1.2V, 1V, +ADJ (0.5V)
■
3 Selectable Tolerances
–5%, –10%, –15% (LTC2917)
■
Manual Reset Input (LTC2918)
Two three state inputs select one of nine internally pro-
grammedthresholdswithouttheneedforexternalresistors.
FortheLTC2917,anadditionalthreestateinputdetermines
the tolerance (–5%, –10%, –15%). The tolerance for the
LTC2918isfixedat–5%.Thresholdaccuracyisguaranteed
at 1.5% over the entire operating temperature range.
Glitch filtering ensures reliable reset operation without
false triggering.
■
1.5V to 5.5V Supply Operation
■
Adjustable Watchdog Timeout
■
Windowed Watchdog Timeout for Higher Reliability
Applications (LTC2917-B, LTC2918-B)
■
6.2V Shunt Regulator for High Voltage Operation
■
Guaranteed to 125˚C
■
Guaranteed Threshold Accuracy: 1.5%
■
Low Quiescent Current: 30μA Typical
■
The reset timeout and the watchdog timeout may be set
with no external components, or adjusted using an exter-
nal capacitor. A windowed watchdog feature is available
for high-reliability applications (B1 versions). A separate
manual reset input on the LTC2918-A/LTC2918-B allows
a simple push button interface.
Power Supply Glitch Immunity
■
Guaranteed RST for V ≥ 0.8V
CC
■
10-Lead MSOP Packages and (3mm × 2mm) DFN
Packages
APPLICATIONS
■
Handheld Devices
Operation to 125°C makes the LTC2917-A/LTC2917-B
and LTC2918-A/LTC2918-B suitable for automotive ap-
plications.
■
Cell Phone Base Stations
■
Automotive Control Systems
■
Network Servers
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
■
Optical Networking Systems
TYPICAL APPLICATION
1.8V Supply Monitor with Manual
Monitor Selection Table
Reset and Internal Timers Selected
1.8V
NOMINAL VOLTAGE
SEL1
SEL2
12V
5V
V
V
V
V
CC
CC
CC
CC
0.1μF
10k
Open
GND
3.3V
V
CC
2.5V
Open
Open
Open
GND
GND
GND
V
CC
LTC2918-A
μP
1.8V
Open
GND
VM
RST
WDI
RST
I/O
RT
1.5V
29178 TA01
WT
MR
SEL1
SEL2
1.2V
V
CC
GND
t = 1.6s
WDU
t = 200ms
RST
1V
Open
GND
ADJ (0.5V)
29178f
1
LTC2917/LTC2918
ABSOLUTE MAXIMUM RATINGS
(Note 1, 2)
Terminal Voltages
Operating Temperature Range
V
(Note 3).......................................... –0.3V to 5.7V
LTC2917C/LTC2918C............................... 0°C to 70°C
LTC2917I/LTC2918I............................. –40°C to 85°C
LTC2917H/LTC2918H ........................ –40°C to 125°C
Storage Temperature Range................... –65°C to 150°C
Lead Temperature (Soldering, 10 sec)
CC
SEL1, SEL2, TOL, WDI, MR, RST ......... –0.3V to 7.5V
VM......................................................... –0.3V to 15V
RT, WT......................................–0.3V to (V + 0.3)V
CC
Terminal Currents
V
(Note 3)....................................................... 5mA
MSOP-10.......................................................... 300°C
CC
PIN CONFIGURATION
TOP VIEW
1
2
3
4
5
10
9
GND
TOL
RST
RT
TOP VIEW
GND
TOL
SEL2
SEL1
VM
1
2
3
4
5
10 RST
9
8
7
6
RT
11
8
SEL2
SEL1
VM
WT
WDI
WT
WDI
CC
7
V
6
V
CC
MS PACKAGE
10-LEAD PLASTIC MSOP
DDB PACKAGE
10-LEAD (3mm × 2mm) PLASTIC DFN
= 125°C, θ = 43°C/W
EXPOSED PAD (PIN 11) PCB GND
CONNECTION OPTIONAL
LTC2917
T
= 125°C, θ = 200°C/W
JMAX
JA
T
JMAX
JA
LTC2917
TOP VIEW
1
2
3
4
5
10
9
GND
MR
RST
RT
TOP VIEW
GND
MR
SEL2
SEL1
VM
1
2
3
4
5
10 RST
9
8
7
6
RT
11
8
SEL2
SEL1
VM
WT
WDI
WT
WDI
CC
7
V
6
V
CC
MS PACKAGE
10-LEAD PLASTIC MSOP
DDB PACKAGE
10-LEAD (3mm × 2mm) PLASTIC DFN
= 125°C, θ = 43°C/W
EXPOSED PAD (PIN 11) PCB GND
CONNECTION OPTIONAL
LTC2918
T
= 125°C, θ = 200°C/W
JMAX
JA
T
JMAX
JA
LTC2918
29178f
2
LTC2917/LTC2918
ORDER INFORMATION
LEAD FREE FINISH
TAPE AND REEL
PART MARKING*
LTCQP
LTCQP
LTCQP
LTDGD
LTDGD
LTDGD
LTDCT
LTDCT
LTDCT
LTDGG
LTDGG
LTDGG
PART MARKING*
LCQR
PACKAGE DESCRIPTION
TEMPERATURE RANGE
0°C to 70°C
LTC2917CMS-B1#PBF
LTC2917IMS-B1#PBF
LTC2917HMS-B1#PBF
LTC2917CMS-A1#PBF
LTC2917IMS-A1#PBF
LTC2917HMS-A1#PBF
LTC2918CMS-B1#PBF
LTC2918IMS-B1#PBF
LTC2918HMS-B1#PBF
LTC2918CMS-A1#PBF
LTC2918IMS-A1#PBF
LTC2918HMS-A1#PBF
TAPE AND REEL (MINI)
LTC2917CMS-B1#TRPBF
LTC2917IMS-B1#TRPBF
LTC2917HMS-B1#TRPBF
LTC2917CMS-A1#TRPBF
LTC2917IMS-A1#TRPBF
LTC2917HMS-A1#TRPBF
LTC2918CMS-B1#TRPBF
LTC2918IMS-B1#TRPBF
LTC2918HMS-B1#TRPBF
LTC2918CMS-A1#TRPBF
LTC2918IMS-A1#TRPBF
LTC2918HMS-A1#TRPBF
TAPE AND REEL
10-Lead Plastic MSOP
10-Lead Plastic MSOP
–40°C to 85°C
–40°C to 125°C
0°C to 70°C
10-Lead Plastic MSOP
10-Lead Plastic MSOP
10-Lead Plastic MSOP
–40°C to 85°C
–40°C to 125°C
0°C to 70°C
10-Lead Plastic MSOP
10-Lead Plastic MSOP
10-Lead Plastic MSOP
–40°C to 85°C
–40°C to 125°C
0°C to 70°C
10-Lead Plastic MSOP
10-Lead Plastic MSOP
10-Lead Plastic MSOP
–40°C to 85°C
–40°C to 125°C
TEMPERATURE RANGE
0°C to 70°C
10-Lead Plastic MSOP
PACKAGE DESCRIPTION
LTC2917CDDB-B1#TRMPBF LTC2917CDDB-B1#TRPBF
LTC2917IDDB-B1#TRMPBF LTC2917IDDB-B1#TRPBF
10-Lead (3mm × 2mm) Plastic DFN
10-Lead (3mm × 2mm) Plastic DFN
10-Lead (3mm × 2mm) Plastic DFN
10-Lead (3mm × 2mm) Plastic DFN
10-Lead (3mm × 2mm) Plastic DFN
10-Lead (3mm × 2mm) Plastic DFN
10-Lead (3mm × 2mm) Plastic DFN
10-Lead (3mm × 2mm) Plastic DFN
10-Lead (3mm × 2mm) Plastic DFN
10-Lead (3mm × 2mm) Plastic DFN
10-Lead (3mm × 2mm) Plastic DFN
10-Lead (3mm × 2mm) Plastic DFN
LCQR
–40°C to 85°C
–40°C to 125°C
0°C to 70°C
LTC2917HDDB-B1#TRMPBF LTC2917HDDB-B1#TRPBF
LTC2917CDDB-A1#TRMPBF LTC2917CDDB-A1#TRPBF
LCQR
LDGF
LTC2917IDDB-A1#TRMPBF
LTC2917IDDB-A1#TRPBF
LDGF
–40°C to 85°C
–40°C to 125°C
0°C to 70°C
LTC2917HDDB-A1#TRMPBF LTC2917HDDB-A1#TRPBF
LTC2918CDDB-B1#TRMPBF LTC2918CDDB-B1#TRPBF
LDGF
LDCV
LTC2918IDDB-B1#TRMPBF
LTC2918IDDB-B1#TRPBF
LDCV
–40°C to 85°C
–40°C to 125°C
0°C to 70°C
LTC2918HDDB-B1#TRMPBF LTC2918HDDB-B1#TRPBF
LTC2918CDDB-A1#TRMPBF LTC2918CDDB-A1#TRPBF
LDCV
LDGH
LTC2918IDDB-A1#TRMPBF
LTC2918IDDB-A1#TRPBF
LDGH
–40°C to 85°C
–40°C to 125°C
LTC2918HDDB-A1#TRMPBF LTC2918HDDB-A1#TRPBF
LDGH
TRM = 500 pieces. *Temperature grades are identified by a label on the shipping container.
Consult LTC Marketing for information on non-standard lead based finish parts.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/
29178f
3
LTC2917/LTC2918
ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCC = 2.5V, unless otherwise noted. (Note 2)
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
●
●
●
V
V
V
Minimum Supply Voltage
Supply Undervoltage Lockout
Shunt Regulation Voltage
RST in Correct Logic State
0.8
V
V
V
CC(MIN)
1.5
7.0
CC(UVLO)
CC(SHUNT)
I
= 0.5mA
5.7
6.2
VCC
●
●
I
CC
V
CC
Pin Current
SEL1, SEL2, TOL, MR = Open
30
45
50
80
μA
μA
SEL1, SEL2, TOL = GND (LTC2917)
MR = V (LTC2918)
CC
Monitor Input (VM)
●
●
●
V
V
V
V
V
V
V
V
V
12V, 5% Reset Threshold
12V, 10% Reset Threshold
12V, 15% Reset Threshold
11.04
10.44
9.84
11.22
10.62
10.02
11.40
10.80
10.20
V
V
V
MT120
MT50
MT33
MT25
MT18
MT15
MT12
MT10
MTADJ
●
●
●
5V, 5% Reset Threshold
5V, 10% Reset Threshold
5V, 15% Reset Threshold
4.600
4.350
4.100
4.675
4.425
4.175
4.750
4.500
4.250
V
V
V
●
●
●
3.3V, 5% Reset Threshold
3.3V, 10% Reset Threshold
3.3V, 15% Reset Threshold
3.036
2.871
2.706
3.086
2.921
2.756
3.135
2.970
2.805
V
V
V
●
●
●
2.5V, 5% Reset Threshold
2.5V, 10% Reset Threshold
2.5V, 15% Reset Threshold
2.300
2.175
2.050
2.338
2.213
2.088
2.375
2.250
2.125
V
V
V
●
●
●
1.8V, 5% Reset Threshold
1.8V, 10% Reset Threshold
1.8V, 15% Reset Threshold
1.656
1.566
1.476
1.683
1.593
1.503
1.710
1.620
1.530
V
V
V
●
●
●
1.5V, 5% Reset Threshold
1.5V, 10% Reset Threshold
1.5V, 15% Reset Threshold
1.380
1.305
1.230
1.403
1.328
1.253
1.425
1.350
1.275
V
V
V
●
●
●
1.2V, 5% Reset Threshold
1.2V, 10% Reset Threshold
1.2V, 15% Reset Threshold
1.104
1.044
0.984
1.122
1.062
1.002
1.140
1.080
1.020
V
V
V
●
●
●
1V, 5% Reset Threshold
1V, 10% Reset Threshold
1V, 15% Reset Threshold
0.920
0.870
0.820
0.935
0.885
0.835
0.950
0.900
0.850
V
V
V
●
●
●
ADJ (0.5V), 5% Reset Threshold
ADJ (0.5V), 10% Reset Threshold
ADJ (0.5V), 15% Reset Threshold
460.0
435.0
410.0
467.5
442.5
417.5
475.0
450.0
425.0
mV
mV
mV
●
●
R
VM Input Impedance (Note 4)
ADJ Input Current
Fixed Threshold Modes
VM = 0.5V
0.5
8
MΩ
VM
I
15
nA
VM(ADJ)
Three-State Inputs (SEL1, SEL2), (TOL, LTC2917)
●
●
V
V
V
Low Level Input Voltage
High Level Input Voltage
Pin Voltage when Open
Allowable Leakage in Open State
Pin Input Current
0.5
V
V
TPIN, LOW
TPIN, HIGH
TPIN, Z
1.4
I = 0μA
0.9
V
●
●
I
I
5
μA
μA
TPIN, Z
V
TPIN
= 0V, V
CC
20
TPIN, H/L
Reset Timer Control (RT)
●
●
●
●
I
I
I
RT Pull Up Current
V
RT
V
RT
V
RT
V
RT
= 0.25V
= 1.1V
–2
2
–3
3
–4
4
μA
μA
μA
RT(UP)
RT Pull Down Current
RT(DOWN)
RT(INT)
Internal RT V Detect Current
= V
1
8
CC
CC
V
RT Internal Timer Threshold
Rising, Referenced to V
–100
–160
–300
mV
RT(INT, LH)
CC
29178f
4
LTC2917/LTC2918
ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCC = 2.5V, unless otherwise noted. (Note 2)
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Reset Output (RST)
●
●
●
t
t
t
Internal Reset Timeout Period
Adjustable Reset Timeout Period
V
C
= V
CC
150
16
200
20
260
25
ms
ms
μs
RST(INT)
RST(EXT)
UV
RT
= 2.2nF
RT
VM Undervoltage Detect to RST
Asserted
VM Less Than Reset Threshold
10
80
150
V
by More Than 5%
MTX
●
●
●
V
Output Voltage Low RST
V
CC
V
CC
V
CC
= 3.3V, I = 2.5mA
RST
0.15
0.15
0.05
0.4
0.3
0.2
V
V
V
OL
= 1V, I
= 100μA
RST
= 0.8V, I
= 15μA
RST
●
I
RST Output Voltage High Leakage
RST = V
1
μA
OH(RST)
CC
Watchdog Timer Control (WT)
●
●
●
●
I
I
WT Pull Up Current
V
WT
V
WT
V
WT
V
WT
V
WT
= 0.25V
= 1.1V
–2
2
–3
3
–4
4
μA
μA
mV
μA
μA
WT(UP)
WT Pull Down Current
WT Internal Timer Threshold
WT(DOWN)
V
Rising, Referenced to V
–100
–160
1
–300
8
WT(INT, LH)
CC
I
I
Internal WT V Detect Current
= V
CC
WT(INT)
CC
Watchdog Disable Hold Current
= 0V
–3.5
WT(DIS)
Watchdog Input (WDI)
●
●
t
t
Internal Watchdog Upper Boundary
V
= V
CC
1.3
1.6
50
2
s
WDU(INT)
WDL(INT)
WT
Internal Watchdog Lower Boundary
(Note 5)
B Versions, V = V
37.5
62.5
ms
WT
CC
●
●
t
t
External Watchdog Upper Boundary
C
= 2.2nF
WT
130
160
200
0.4
ms
ms
WDU(EXT)
External Watchdog Lower Boundary
(Note 5)
B Versions, C = 2.2nF
t
/32
WDU(EXT)
WDL(EXT)
WT
●
●
●
●
V
V
Input Low Voltage
Input High Voltage
Input Pulsewidth
V
V
IL(WDI)
IH(WDI)
PW(WDI)
1.1
t
400
ns
μA
WDI Leakage Current
1
Manual Reset Input (LTC2918)
●
●
●
●
V
Input Low Voltage
Input High Voltage
Pull Up Resistance
Pulsewidth
0.2 • V
150
V
V
IL(MR)
IH(MR)
CC
V
0.8 • V
50
CC
R
100
kΩ
ns
PU
t
250
PW(MR)
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.
from higher voltage supplies requires a series dropping resistor. See
Applications Information.
Note 4: Input impedance is dependent on the configuration of the SEL
pins.
Note 2: All currents into pins are positive; all voltages are referenced to
GND unless otherwise noted.
Note 5: In the LTC2917-B/LTC2918-B, edges must occur on WDI with a
period between the lower and upper boundary or RST is invoked. For the
LTC2917-A/LTC2918-A, the edges must simply occur before the upper
boundary. See Applications Information.
Note 3: V maximum pin voltage is limited by input current. Since the
CC
V
pin has an internal 6.2V shunt regulator, a low impedance supply
CC
which exceeds 5.7V may exceed the rated terminal current. Operation
29178f
5
LTC2917/LTC2918
TYPICAL PERFORMANCE CHARACTERISTICS
Threshold Voltage vs
Temperature
Quiescent Supply Current vs
Temperature
Allowable Glitch Duration vs
Magnitude
40
35
30
25
1.5
1.0
0.5
0
300
250
200
150
100
50
SEL1 = 0V
SEL2 = 2.5V
TOL = OPEN
V
V
= 5.5V
= 2.5V
CC
CC
V
RESET OCCURS
ABOVE CURVE
MTADJ
V
= 1.5V
–0.5
–1.0
–1.5
CC
V
MT120
V
MT25
75
20
0
–50 –25
0
25
50
75 100 125
50
100 125
0.1
1
10
100
–50 –25
0
25
TEMPERATURE (°C)
GLITCH PERCENTAGE PAST THRESHOLD (%)
TEMPERATURE (˚C)
29178 G02
29178 G01
29178 G03
Reset Timeout Period vs RT
Capacitance
Internal Reset Timeout Period vs
Temperature
Internal Watchdog Timeout
Period vs Temperature
250
230
210
190
170
150
2.0
1.8
1.6
1.4
1.2
1.0
10000
1000
100
10
RT = V
CC
WT = V
CC
1
0.1
–50 –25
0
25
50
75 100 125
–50 –25
0
25
50
75 100 125
0.001 0.01
0.1
1
10
100 1000
RT PIN CAPACITANCE, C (nF)
TEMPERATURE (°C)
TEMPERATURE (°C)
RT
29178 G04
29178 G05
29178 G06
Watchdog Timeout Period vs
Capacitance
Shunt Regulation Voltage vs
Temperature
Shunt Regulation Voltage vs
Supply Current
10000
1000
100
10
6.4
6.3
6.2
6.1
7.0
6.8
6.6
6.4
6.2
6.0
I
= 5mA
CC
I
= 1mA
CC
I
CC
= 100μA
1
0.01
0.1
1
10
100
0.001
0.01
0.1
1
10
100
–50 –25
0
25
50
75 100 125
WT PIN CAPACITANCE, C (nF)
TEMPERATURE (°C)
SUPPLY CURRENT, I (mA)
WT
CC
29178 G07
29178 G09
29178 G08
29178f
6
LTC2917/LTC2918
TYPICAL PERFORMANCE CHARACTERISTICS
RST Output Voltage vs VCC
RST Pull-Down Current vs VCC
RST VOL vs IRST
6
1.0
6
10k PULL-UP R TO V
CC
NO PULL-UP R
SEL1 = SEL2 = TOL = 0V
V
= 2.5V
CC
5
VM = 0.5V
5
0.8
T
= 125°C
A
4
3
4
3
0.6
RST AT 150mV
T
= 25°C
A
0.4
0.2
0
2
1
0
2
1
0
T
= –40°C
RST AT 50mV
A
0
1
2
3
4
5
0
2
6
8
10
4
0
1
2
3
4
5
SUPPLY VOLTAGE, V (V)
SUPPLY VOLTAGE, V (V)
I
(mA)
RST
CC
CC
29178 G10
29178 G12
29178 G11
PIN FUNCTIONS
GND: Device Ground.
a 0.1μF ceramic capacitor. A minimum of 1.5V on V
CC
ensures that the part is out of under voltage lockout and
that the voltage thresholds are accurate. Operates as a
direct supply input for voltages up to 5.5V. Operates as a
shunt regulator for supply voltages greater than 5.7V and
should have a resistor between this pin and the supply
MR (LTC2918 only): Manual Reset Input (Active Low). A
low level on the MR input causes the part to issue a reset,
which is released one reset timeout after the input goes
high. The pin has an internal 100k pull-up to V , and
CC
thus may interface directly to a momentary pushbutton.
Leave open if unused.
to limit V input current to no greater than 5mA. When
CC
used without a current-limiting resistor, pin voltage must
not exceed 5.7V.
RST: Open Drain RST Output. Asserts low when VM is
belowthethresholdselectedbySEL1,SEL2andTOLinput
pins. Held low for an adjustable timeout after VM input is
above threshold.
VM:VoltageMonitorInputtoRSTcomparator.SEL1,SEL2
and TOL inputs select the exact threshold that asserts the
RST output.
RT: Reset Timeout Control Pin. Attach an external capaci-
WDI: Watchdog Input. This pin must be driven to change
state within a time less than the watchdog upper bound-
ary time, or RST will be asserted low. On the LTC2917-B,
LTC2918-B, the period must also be greater than the
watchdog lower boundary time, and only falling edges
are considered. Tie WT and WDI to GND to disable the
watchdog timer.
tor (C ) to GND to set a reset timeout of 9ms/nF. Leave
RT
RT open to generate a reset timeout of approximately
400μs. Tie RT to V to generate a reset timeout of ap-
CC
proximately 200ms.
SEL1, SEL2: Monitor Voltage Select Three-State Input.
SEL1, and SEL2 control the nominal threshold voltage
that VM is set to monitor. Connect to V , GND or leave
CC
WT: Watchdog Timer Control Pin. Attach an external
unconnected in open state. (See Table 1).
capacitor (C ) to GND to set a watchdog upper bound-
WT
TOL (LTC2917 only): Three-State Input for Supply Tol-
erance Selection (–5%, –10% or –15%). Controls the
tolerance band at which the VM supply is monitored.
ary timeout time of 72ms/nF. Tie WT to V to generate a
CC
timeoutofapproximately1.6s.LeaveWTopentogenerate
a timeout of approximately 3.2ms. Tie WT and WDI to
GND to disable the watchdog timer.
Connect to V , GND, or leave unconnected in open state.
CC
(See Table 2)
Exposed Pad (DFN Only): Exposed pad may be left open
V : Power Supply input. Bypass this pin to ground with
CC
or connected to device ground.
29178f
7
LTC2917/LTC2918
BLOCK DIAGRAM
LTC2917
LTC2918
SEL1
SEL2
TOL
MR
RT
V
CC
V
CC
V
CC
V
CC
DETECT
3 STATE
DECODE
100k
6.2V
INTERNAL
200ms TIMER
MONITOR
DIVIDER
MATRIX
VM
RST
–
+
RESET
DRIVER LOGIC
REFERENCE
DIVIDER
MATRIX
GND
ADJUSTABLE
RESET TIMER
+
0.5V
–
INTERNAL
1.6 SECOND
TIMER
WATCHDOG
LOGIC
ADJUSTABLE
WATCHDOG
TIMER
V
CC
DETECT
WT
WDI
29178 BD
TIMING DIAGRAM
V
MTx
VM
t
UV
t
RST
RST
1V
29178 TD01
Monitor Input Timing
WDI
RST
t
WDU
29178 TD01
t
RST
Watchdog Timing (LTC2917-A, LTC2918-A)
WDI
RST
t > t
t
WDU
WDL
29178 TD03
t < t
t
t
RST
WDL
RST
Watchdog Timing (LTC2917-B, LTC2918-B)
29178f
8
LTC2917/LTC2918
APPLICATIONS INFORMATION
Supply Monitoring
Monitor Threshold Control
The LTC2917/LTC2918 are low voltage single supply
monitorswithselectablethresholds.Twothree-stateinputs
select one of nine internally programmed thresholds. For
theLTC2917,athirdthree-stateinputselectsthetolerance
at which the supply connected to the VM pin is monitored
(–5%, –10%, –15%). The tolerance for the LTC2918 is
fixed at –5%. Threshold accuracy is guaranteed at 1.5%
over the entire operating temperature range.
The monitor threshold on the VM pin is controlled by
the SEL1, SEL2 and TOL three-state pins. The SEL1 and
SEL2 pins select one of nine preset nominal voltages
(including one externally adjustable threshold) as shown
in Table 1.
The SEL1 and SEL2 three-state input pins should be con-
nected to GND, V or left unconnected during normal
CC
operation. Notethatwhenleftunconnected, themaximum
The LTC2917/LTC2918 asserts the RST output low when
VM is below the programmed threshold, and for a reset
leakage allowable from the pin to either GND or V is
CC
5μA.
timeout period (t ) after VM goes above the threshold.
RST
The tolerance at which the monitored supply is measured
is set by the TOL pin (LTC2917 only) as shown in Table 2.
If desired (e.g. for margining purposes), the TOL pin may
be driven by a three-state buffer. That three-state buffer
The reset timeout can be configured to use one of two
internal timers with no external components, or an ad-
justed timer programmed by placing an external capacitor
from RT to ground. Glitch filtering ensures reliable reset
operation without false triggering.
must have a V and V which meet the V and V of
OL
OH
IL
IH
the TOL pin specified in the Electrical Characteristics, and
maintain less than 5μA of leakage in the open state.
Power-Up
Table 1. Voltage Threshold Settings
V
powers the drive circuits for the RST pin. Therefore,
CC
NOMINAL VOLTAGE
SEL1
SEL2
as soon as V reaches 0.8V during power up, the RST
CC
12V
5V
V
V
output asserts low.
CC
CC
V
V
Open
GND
CC
CC
Until V reaches the undervoltage lockout threshold
CC
3.3V
2.5V
1.8V
*1.5V
*1.2V
*1V
(guaranteed less than 1.5V), RST is held low regardless
Open
Open
Open
GND
GND
GND
V
CC
of the state of VM.
Open
GND
Once V is above the undervoltage lockout threshold
CC
and VM is above the programmed threshold, the reset
timer is started. After the reset timeout, the open drain
pull-down releases RST and the external pull-up resistor
pulls high.
V
CC
Open
GND
*ADJ (0.5V)
*Require a separate supply for V
CC
Power-Down
Table 2. System Voltage Tolerance Settings
On power-down, once VM drops below its threshold or
CC
logic low.
TOLERANCE
–5%
TOL
V
drops below the undervoltage lockout, RST asserts
V
CC
–10%
Open
GND
–15%
29178f
9
LTC2917/LTC2918
APPLICATIONS INFORMATION
Threshold Accuracy
Twotechniquesareusedtocombatspuriousresetwithout
sacrificing threshold accuracy. First, the timeout period
helps prevent high-frequency variation whose frequency
The trip threshold for the supplies monitored is selected
by configuring the three-state input pins. When using the
adjustable input, a external resistive divider sets the trip
threshold, allowing the user complete control over the
trip point. Selection of this trip voltage is crucial to the
reliability of the system.
is above 1/ t
from appearing at the RST output.
RST
When the voltage at VM goes below the threshold, the
RST pin asserts low. When the supply recovers past
the threshold, the reset timer starts (assuming it is not
disabled), and RST does not go high until it finishes. If
the supply becomes invalid any time during the timeout
period, the timer resets and starts a fresh when the supply
next becomes valid.
Any power supply has some tolerance band within which
it is expected to operate (e.g. 5V 10%). It is generally
undesirablethatasupervisorissuearesetwhenthepower
supply is inside this tolerance band. Such a “nuisance”
reset reduces reliability by preventing the system from
functioning under normal conditions.
While the reset timeout is useful at preventing toggling
of the reset output in most cases, it is not effective at
preventing nuisance resets due to short glitches (due to
load transients or other effects) on a valid supply.
Topreventnuisanceresets, thesupervisorthresholdmust
be guaranteed to lie outside the power supply tolerance
band. To ensure that the threshold lies outside the power
supplytolerancerange,thenominalthresholdmustlieout-
side that range by the monitor’s accuracy specification.
Toreducesensitivitytotheseshortglitches,thecomparator
hasadditionalanti-glitchcircuitry.Anytransientattheinput
of the comparator needs to be of sufficient magnitude and
duration t before it can change the monitor state.
UV
All 27 of the selectable thresholds have the same relative
threshold accuracy of 1.5% of the programmed nominal
input voltage (over the full operating temperature range).
Considertheexampleofmonitoringa5Vsupplywitha10%
tolerance. The nominal threshold internal to the LTC2917
is 11.5% below the 5V input at 4.425V. With 1.5% ac-
curacy, the trip threshold range is 4.425V 75mV over
temperature (i.e. 10% to 13% below 5V). The monitored
system must thus operate reliably down to 4.35V or 13%
below 5V over temperature.
The combination of the reset timeout and anti-glitch cir-
cuitry prevents spurious changes in output state without
sacrificing threshold accuracy.
Adjustable Input
When the monitor threshold is configured as ADJ, the
internal comparator input is connected to the pin without
a resistive divider, and the pin is high-impedance. Thus,
any desired threshold may be chosen by attaching VM to
a tap point on an external resistive divider between the
monitored supply and ground, as shown in Figure 1.
Glitch Immunity
The above discussion is concerned only with the DC
value of the monitored supply. Real supplies also have
relatively high-frequency variation, from sources such as
loadtransients,noise,andpickup.Thesevariationsshould
not be considered by the monitor in determining whether
a supply voltage is valid or not. The variations may cause
spurious outputs at RST, particularly if the supply voltage
is near its trip threshold.
V
MON
R2
–
+
VM
R1
+
0.5V
–
29178 F01
Figure 1. Setting the Trip Point Using
the Adjustable Threshold.
29178f
10
LTC2917/LTC2918
APPLICATIONS INFORMATION
10000
1000
100
10
The reference input of the comparator is controlled by the
tolerance pin. The external resistive divider should make
the voltage at VM = 0.5V when the supply is at nominal
value. The actual threshold of VM accounts for the sup-
ply tolerance of 1.5% guaranteed over the full operating
temperature range. The resulting tolerances are –6.5%,
–11.5%, –16.5% which correspond to 0.468V, 0.443V,
0.418V respectively.
1
Typically, the user will pick a value of R1 based on accept-
able current draw. Current used by the resistor divider will
be approximately:
0.1
0.001 0.01
0.1
1
10
100 1000
RT PIN CAPACITANCE, C (nF)
RT
29178 F02
0.5V
I
⎛
⎞
R1=
Figure 2. Reset Timeout Period vs RT Capacitance
RST Output Characteristics
⎜
⎝
⎟
⎠
Recommended range of R1 is 1k—1M. Higher values of
resistance exacerbate the degradation of threshold ac-
curacy due to leakage currents.
The DC characteristics of the RST pull-down strength
are shown in the Typical Performance Characteristics
section. RST is an open-drain pin and thus requires an
external pull-up resistor to the logic supply. RST may be
If the nominal value of the supply being monitored is
V
, then
NOM
pulled above V , providing the voltage limits of the pin
CC
are observed.
R2 = R1(2V
– 1)
NOM
The open-drain of the RST pin allows for wired-OR con-
nection of several LTC2917/LTC2918’s.
Resistor tolerances must be taken into account when
determining the overall accuracy.
Watchdog
Selecting the Reset Timing Capacitor
LTC2917-A/LTC2918-A
The reset timeout period can be set to one of two fixed
internal timers or set with a capacitor in order to accom-
modate a variety of applications. Connecting a capacitor,
A standard watchdog function is used to ensure that the
system is in a valid state by continuously monitoring
the microprocessor’s activity. The microprocessor must
toggle the logic state of the WDI pin periodically (within
upper boundary) in order to clear the watchdog timer. If
timeout occurs, the LTC2917-A/LTC2918-A asserts RST
low for the reset timeout period, issuing a system reset.
Once the reset timeout completes, RST is released to go
high and the watchdog timer starts again.
C , between the RT pin and ground sets the reset timeout
RT
period,t .Thefollowingformulaapproximatesthevalue
RST
of capacitor needed for a particular timeout:
C
= t
• 110 [pF/ms]
RST
RT
For example, using a standard capacitor value of 2.2nF
would give a 20ms timeout.
Figure 2 shows the desired reset timeout period as a
function of the value of the timer capacitor.
Duringpower-up,thewatchdogtimerremainsclearedwhile
RST is asserted low. As soon as the reset timer times out,
RST goes high and the watchdog timer is started.
Leaving RT open with no external capacitor generates a
reset timeout of approximately 400μs. Shorting RT to V
generates a reset timeout of approximately 200ms.
CC
29178f
11
LTC2917/LTC2918
APPLICATIONS INFORMATION
LTC2917-B/LTC2918-B
Manual Reset (LTC2918 Only)
For applications in which reliability is even more critical,
theLTC2917-B/LTC2918-Bimplementsawindowedwatch-
dog function by adding a lower boundary condition to the
standard watchdog function. If the WDI input receives a
falling edge prior to the watchdog lower boundary, the
part considers this a watchdog failure, and asserts RST
low (releasing again after the reset timeout period as
described above). The LTC2917-B/LTC2918-B WDI input
only responds to falling edges.
The LTC2918 includes the MR pin for applications where a
manualresetisdesired. MRisinternallypulledup, making
it ready to interface with a push button with no external
componentsrequired.AssertingMRlowwhenRSTishigh
initiates a reset, resulting in RST being asserted low for
the reset timeout time.
Shunt Regulator
The LTC2917 and LTC2918 contain an internal 6.2V shunt
regulator on the V pin to allow operation from a high
CC
Setting the Watchdog Timeout Period
voltage supply. To operate the part from a supply higher
The watchdog timeout period is adjustable and can be
optimized for software execution. The watchdog timeout
period is adjusted by connecting a capacitor between WT
and ground. Given a specified watchdog timeout period,
the capacitor is determined by:
than 5.7V, the V pin must have a series resistor, R ,
CC CC
to the supply. See Figure 3. This resistor should be sized
according to the following equation:
VS(MAX) −5.7V
VS(MIN) −7V
250μA
≤RCC
≤
5mA
C
= t • 13.8 [nF/s]
WD
WT
where V
and V
are the operating minimum
S(MAX)
S(MIN)
For example, using a standard capacitor value of 0.047μF
would give a 3.4s watchdog timeout period.
and maximum of the supply.
As an example, consider operation from an automobile
battery which might dip as low as 10V or spike to 60V. We
must then pick a resistance between 10.86k and 12k.
Leaving WT open with no external capacitor generates
a timeout of approximately 3.2ms. Shorting WT to V
CC
generates a timeout of approximately 1.6s. Connecting
WT to GND disables the watchdog function.
(V
= 10.64V)
TRIP
12V
3.3V
R2
1.15M
R
R
PU
10k
CC
11k
C
BYPASS
0.1μF
V
CC
V
CC
LTC2917
μP
VM
RST
WDI
RST
I/O GND
SEL1
SEL2
TOL
R1
49.9k
29178 F03
GND WT
RT
C
C
RT
WT
Figure 3. 12V Supply Monitor Powered From 12V, Utilizing
the Internal Shunt Regulator with 3.3V Logic Out
29178f
12
LTC2917/LTC2918
TYPICAL APPLICATIONS
1V Supply Monitor with Windowed Watchdog Timeout
and Internal Timers Selected
12V Supply Monitor with 20ms Reset Timeout and 3.4s
Watchdog Timeout, with 3.3V Logic Out
3.3V
3.3V
C
C
BYPASS
0.1μF
R
R
PU
10k
BYPASS
PU
0.1μF
10k
V
V
V
V
CC
CC
CC
CC
LTC2917-B
μP
LTC2917-A
μP
1V
12V
VM
RST
WDI
RST
I/O GND
VM
RST
WDI
RST
I/O GND
SEL1
SEL1
SEL2
TOL
29178 TA02
29178 TA03
SEL2
TOL
GND WT
RT
GND WT
RT
C
C
RT
0.0022μF
3.3V
t
t
t
= 1.6s
WT
WDU
WDL
RST
0.047μF
= 50ms
= 200ms
9V, –15% Tolerance Supply Monitor
with 1.8V Logic Out
1.8V
C
R
BYPASS
PU
0.1μF
10k
9V
R2
866k
V
V
CC
CC
LTC2917-A
μP
VM
RST
WDI
RST
I/O GND
SEL1
SEL2
TOL
29178 TA04
R1
51.1k
GND WT
RT
C
C
RT
WT
29178f
13
LTC2917/LTC2918
TYPICAL APPLICATIONS
3.3V, –10% Tolerance Supply Monitor
with Disabled Watchdog
1.8V, –5% Supply Monitor with Manual Reset
3.3V
1.8V
C
C
BYPASS
0.1μF
R
R
PU
10k
BYPASS
PU
0.1μF
10k
V
V
V
CC
V
CC
CC
CC
LTC2917
RST
WDI
μP
LTC2918
μP
VM
RST
VM
RST
WDI
RST
I/O GND
SEL1
GND
SEL1
SEL2
MR
29178 TA06
29178 TA07
SEL2
TOL
10k*
GND WT RT
GND
WT
RT
C
MANUAL RESET
PUSH BUTTON
RT
C
C
RT
WT
*OPTIONAL RESISTOR RECOMMENDED TO EXTEND ESD TOLERANCE
1.5V Supply Monitor with Tolerance Control for Margining,
–5% Operation with –15% Margining
3.3V
C
R
BYPASS
PU
0.1μF
10k
V
CC
V
CC
LTC2917
μP
1.5V
VM
RST
RST
I/O
SEL1
SEL2
WDI
TOL
I/O GND
–15% –5%
29178 TA08
GND
WT
C
RT
C
WT
RT
29178f
14
LTC2917/LTC2918
PACKAGE DESCRIPTION
MS Package
10-Lead Plastic MSOP
(Reference LTC DWG # 05-08-1661)
3.00 0.102
(.118 .004)
(NOTE 3)
0.497 0.076
(.0196 .003)
10 9
8
7 6
REF
3.00 0.102
(.118 .004)
(NOTE 4)
4.90 0.152
(.193 .006)
DETAIL “A”
0.254
0.889 0.127
(.035 .005)
(.010)
0° – 6° TYP
GAUGE PLANE
1
2
3
4 5
0.53 0.152
(.021 .006)
5.23
3.20 – 3.45
(.206)
0.86
(.034)
REF
1.10
(.043)
MAX
(.126 – .136)
MIN
DETAIL “A”
0.18
(.007)
0.50
(.0197)
BSC
0.305 0.038
(.0120 .0015)
TYP
SEATING
PLANE
0.17 – 0.27
(.007 – .011)
TYP
0.1016 0.0508
(.004 .002)
RECOMMENDED SOLDER PAD LAYOUT
0.50
(.0197)
BSC
MSOP (MS) 0307 REV E
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
DDB Package
10-Lead Plastic DFN (3mm × 2mm)
(Reference LTC DWG # 05-08-1722 Rev Ø)
R = 0.115
0.64 0.05
(2 SIDES)
0.40 0.10
10
3.00 0.10
(2 SIDES)
TYP
R = 0.05
6
TYP
0.70 0.05
2.55 0.05
1.15 0.05
2.00 0.10
(2 SIDES)
PIN 1 BAR
TOP MARK
PIN 1
R = 0.20 OR
(SEE NOTE 6)
0.25 × 45°
PACKAGE
OUTLINE
0.64 0.05
(2 SIDES)
CHAMFER
5
1
(DDB10) DFN 0905 REV Ø
0.25 0.05
0.25 0.05
0.75 0.05
0.200 REF
0.50 BSC
0.50 BSC
2.39 0.05
(2 SIDES)
2.39 0.05
(2 SIDES)
0 – 0.05
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
BOTTOM VIEW—EXPOSED PAD
NOTE:
1. DRAWING CONFORMS TO VERSION (WECD-1) IN JEDEC PACKAGE OUTLINE M0-229
2. DRAWING NOT TO SCALE
3. ALL DIMENSIONS ARE IN MILLIMETERS
4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE
5. EXPOSED PAD SHALL BE SOLDER PLATED
6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE TOP AND BOTTOM OF PACKAGE
29178f
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 representa-
tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
15
LTC2917/LTC2918
TYPICAL APPLICATION
Dual Supply Monitor (1.8V and 12V) with Manual Reset
1.8V
C
C1
0.1μF
R
BYPASS
PU
0.1μF
10k
V
CC
V
V
CC
CC
LTC2916
RST
LTC2917-B
μP
VM
12V
VM
RST
WDI
RST
I/O GND
SEL1
SEL1
SEL2
TOL
29178 TA10
SEL2
MR
GND
RT
1.8V
GND WT RT
MANUAL RESET
PUSH BUTTON
1.8V
RELATED PARTS
PART NUMBER
LTC690
DESCRIPTION
COMMENTS
5V Supply Monitor, Watchdog Timer and Battery Backup
3.3V Supply Monitor, Watchdog Timer and Battery Backup
4.65V Threshold
2.9V Threshold
LTC694-3.3
LTC1232
LTC1326
LTC1536
LTC1726
LTC1727
LTC1728
LTC2900
LTC2901
LTC2902
LTC2903
LTC2904
LTC2905
LTC2906
LTC2907
LTC2908
LTC2909
LTC2910
LTC2912
LTC2913
LTC2914
LTC2915
LTC2916
5V Supply Monitor, Watchdog Timer and Push-Button Reset 4.37V/4.62V Threshold
Micro Power Precision Triple Supply Monitor
4.725V, 3.118V, 1V Threshold ( 0.75%)
Meets PCI tFALL Timing Specifications
Precision Triple Supply Monitor for PCI Applications
Micro Power Triple Supply Monitor for 2.5V/5V, 3.3V and ADJ Adjustable RESET and Watchdog Time-Outs
Micro Power Triple Supply Monitor with Open-Drain Reset
Micro Power Triple Supply Monitor with Open-Drain Reset
Programmable Quad Supply Monitor
Individual Monitor Outputs in MSOP
5-Lead SOT-23 Package
Adjustable RESET, 10-Lead MSOP and 3mm × 3mm 10-Lead DFN
Adjustable RESET and Watchdog Timer, 16-Lead SSOP Package
Adjustable RESET and Tolerance, 16-Lead SSOP Package, Margining
6-Lead SOT-23 Package, Ultra Low Voltage Reset
Adjustable Tolerance, 8-Lead SOT-23 Package
Programmable Quad Supply Monitor
Programmable Quad Supply Monitor
Precision Quad Supply Monitor
3-State Programmable Precision Dual Supply Monitor
3-State Programmable Precision Dual Supply Monitor
Adjustable RESET and Tolerance, 8-Lead SOT-23 Package
Precision Dual Supply Monitor 1 Selectable and 1 Adjustable Separate V Pin, RST/RST Outputs
CC
Precision Dual Supply Monitor 1 Selectable and 1 Adjustable Separate V Pin, Adjustable Reset Timer
CC
Precision Six Supply Monitor (Four Fixed and 2 Adjustable)
Precision Triple/Dual Input UV, OV
8-Lead SOT-23 and DDB Packages
2 ADJ Inputs
Octal Positive/Negative Voltage Monitor
16-Lead SSOP and 5mm × 3mm DFN Packages
8-Lead TSOT and 3mm × 2mm DFN Packages
10-Lead MSOP and 3mm × 3mm DFN Packages
16-Lead SSOP and 5mm × 3mm DFN Packages
10-Lead MSOP and 3mm × 2mm DFN-10 Packages
Manual Reset, 10-Lead MSOP and 3mm × 2mm DFN-10 Packages
Single UV/OV Voltage Monitor, Adjustable UV and OV
Dual UV/OV Voltage Monitor
Qual UV/OV Positive/Negative Voltage Monitor
Single Supervisor with 27 Selectable Thresholds
Single Supervisor with 9 Selectable Thresholds
29178f
LT 0907 • PRINTED IN USA
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
16
●
●
© LINEAR TECHNOLOGY CORPORATION 2007
(408) 432-1900 FAX: (408) 434-0507 www.linear.com
相关型号:
LTC2918IMS-A1#TRPBF
LTC2918 - Voltage Supervisor with 27 Selectable Thresholds and Watchdog Timer; Package: MSOP; Pins: 10; Temperature Range: -40°C to 85°C
Linear
LTC2918IMS-B1#TRPBF
LTC2918 - Voltage Supervisor with 27 Selectable Thresholds and Watchdog Timer; Package: MSOP; Pins: 10; Temperature Range: -40°C to 85°C
Linear
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