LTC2939CMS#PBF [Linear]
LTC2939 - Configurable 6-Supply Monitors with Watchdog Timer; Package: MSOP; Pins: 16; Temperature Range: 0°C to 70°C;
| 型号： | LTC2939CMS#PBF |
| 厂家： | 
Linear |
| 描述： | LTC2939 - Configurable 6-Supply Monitors with Watchdog Timer; Package: MSOP; Pins: 16; Temperature Range: 0°C to 70°C 光电二极管 |
| 文件： | 总20页 (文件大小：238K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LTC2938/LTC2939
Configurable 4- and 6-Supply
Monitors with Watchdog Timer
FEATURES
DESCRIPTION
The LTC®2938/LTC2939 are configurable supply monitors
forsystemswithuptofourorsixsupplyvoltagesthatneed
n
Simultaneously Monitors Four (LTC2938) or Six
Supplies (LTC2939)
n
Sixteen User-Selectable Combinations of 5V, 3.3V,
2.5V, 1.8V, 1.5V, 1.2V and/or Adꢀustable Voltage
Thresholds
Guaranteed Threshold Accuracy: 1.5ꢁ
Adꢀustable Reset and Watchdog Timeout
Low Supply Current: 80μA Typical
Power Supply Glitch Immunity
Guaranteed RST for V > 1V
High Temperature Operation to 125°C
12-Pin 4mm × 3mm DFN or 12-Lead MSOP
(LTC2938) and 16-Lead MSOP Package (LTC2939)
watchdog supervision. One of sixteen preset or adjustable
voltage monitor combinations can be selected using an
external resistive divider connected to the program input.
The preset voltage thresholds are accurate to 1.5ꢀ over
temperature. The LTC2938 and LTC2939 also feature ad-
justable inputs with a 0.5V nominal threshold.
n
n
n
n
n
n
n
The reset and watchdog timeout periods are adjustable
usingexternalcapacitors.Tightvoltagethresholdaccuracy
andglitchimmunityensurereliableresetoperationwithout
false triggering. The RST output is guaranteed to be in the
CC
correct state for V down to 1V. Each status output has
CC
a weak internal pull-up and may be externally pulled up
APPLICATIONS
to a user-defined voltage.
n
Desktop and Notebook Computers
The80μAsupplycurrentmakestheLTC2938andLTC2939
ideal for power conscious systems. The LTC2939 moni-
tors up to six supplies and the LTC2938 monitors up to
four supplies.
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
Protected by U.S. Patents, including 6967591, 7239251, 7119714.
n
Multivoltage Systems
n
Telecom Equipment
Network Servers
Automotive Control Systems
n
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TYPICAL APPLICATION
6-Supply Monitor 12V (ADJ), 5V, 3.3V, 2.5V, 1.8V, 1.2V (ADJ)
Voltage Configuration Table
12V
5V
3.3V
V1 (V) V2 (V) V3 (V) V4 (V) V5 (V) V6 (V)
5
3.3
3.3
3.3
3.3
3.3
2.5
2.5
1.8
1.8
1.8
2.5
2.5
1.8
1.8
1.5
1.2
2.5
2.5
1.8
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
SYSTEM
2.5V
5
LOGIC
1.8V
1.2V
5
1.8
5
5
ADJ
ADJ
1.8
1.8
1.5
2150k 124k
–ADJ
1ꢀ
1ꢀ
3.3
3.3
3.3
3.3
3.3
3.3
3.3
3.3
3.3
3.3
3.3
1.5
ADJ
1.2
V1
V2
V3
V4
V5
V6
WDI
WDO
RST
0.1μF
1.5
1.2
ADJ
ADJ
ADJ
–ADJ
ADJ
–ADJ
ADJ
ADJ
LTC2939
CWT
0.1μF
V
REF
100k
1ꢀ
100k
1ꢀ
R1
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
59k
1ꢀ
V
t
t
= 94ms
= 940ms
PG
RST
WD
CRT
GND
R2
40.2k
1ꢀ
C
WT
47nF
C
RT
47nF
293839 TA01
293839ff
1
LTC2938/LTC2939
ABSOLUTE MAXIMUM RATINGS (Notes 1, 2, 3)
V1, V2, V3, V4, V5, V6, V ......................... –0.3V to 7V
Operating Temperature Range
PG
RST.............................................................. –0.3V to 7V
LTC2939C..................................................... 0°C to 70°C
LTC2939I.................................................. –40°C to 85°C
LTC2939H .............................................. –40°C to 125°C
Storage Temperature Range................... –65°C to 150°C
Lead Temperature (Soldering 10 sec)
CWT, WDO.................................................... –0.3V to 7V
CRT, V , WDI..............................–0.3V to (V + 0.3V)
REF
CC
Reference Load Current (I
).............................. 1mA
VREF
V4 Input Current (–ADJ Mode) ..............................–1mA
RST, WDO Currents ............................................ 10mA
MS Package Only.............................................. 300°C
PIN CONFIGURATION
LTC2938
LTC2938
LTC2939
TOP VIEW
V3
V1
1
2
3
4
5
6
12 V2
11 V4
TOP VIEW
TOP VIEW
1
2
3
4
5
6
7
8
V5
V3
16 V6
15 V2
14 V4
13 NC
1
2
3
4
5
6
V3
V1
CRT
RST
WDO
WDI
12 V2
11 V4
V1
CRT
RST
WDO
WDI
10
9
V
REF
V
PG
13
10
9
V
V
NC
REF
PG
CRT
RST
WDO
WDI
12
11
V
V
REF
PG
8
7
GND
CWT
8
GND
CWT
10 GND
9
CWT
7
MS PACKAGE
12-LEAD PLASTIC MSOP
MS PACKAGE
16-LEAD PLASTIC MSOP
DE PACKAGE
12-LEAD (4mm s 3mm) PLASTIC DFN
T
= 125°C, θ = 130°C/W
T
= 125°C, θ = 110°C/W
JMAX JA
JMAX
JA
T
= 125°C, θ = 43°C/W
JA
JMAX
EXPOSED PAD (PIN 13) PCB GND CONNECTION OPTIONAL
ORDER INFORMATION
LEAD FREE FINISH
LTC2938CDE#PBF
LTC2938IDE#PBF
LTC2938HDE#PBF
LTC2938CMS#PBF
LTC2938IMS#PBF
LTC2938HMS#PBF
LTC2939CMS#PBF
LTC2939IMS#PBF
LTC2939HMS#PBF
TAPE AND REEL
PART MARKING*
2938
PACKAGE DESCRIPTION
TEMPERATURE RANGE
0°C to 70°C
LTC2938CDE#TRPBF
LTC2938IDE#TRPBF
LTC2938HDE#TRPBF
LTC2938CMS#TRPBF
LTC2938IMS#TRPBF
LTC2938HMS#TRPBF
LTC2939CMS#TRPBF
LTC2939IMS#TRPBF
LTC2939HMS#TRPBF
12-Lead (4mm × 3mm) Plastic DFN
12-Lead (4mm × 3mm) Plastic DFN
12-Lead (4mm × 3mm) Plastic DFN
12-Lead Plastic MSOP
2938
–40°C to 85°C
–40°C to 125°C
0°C to 70°C
2938
2938
2938
12-Lead Plastic MSOP
–40°C to 85°C
–40°C to 125°C
0°C to 70°C
2938
12-Lead Plastic MSOP
2939
16-Lead Plastic MSOP
2939
16-Lead Plastic MSOP
–40°C to 85°C
–40°C to 125°C
2939
16-Lead Plastic MSOP
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
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/
293839ff
2
LTC2938/LTC2939
ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C, VCC = 5V unless otherwise specified. (Note 3)
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
1
UNITS
l
l
l
l
l
l
l
l
l
l
l
V
V
V
V
V
V
V
V
V
V
V
Minimum Internal Operating Voltage
Minimum Required for Configuration
5V, 5ꢀ Reset Threshold
3.3V, 5ꢀ Reset Threshold
2.5V, 5ꢀ Reset Threshold
1.8V, 5ꢀ Reset Threshold
1.5V, 5ꢀ Reset Threshold
1.2V, 5ꢀ Reset Threshold
ADJ Reset Threshold
RST in Correct Logic State
V
V
CC
V
Rising
CC
2.6
CCMINP
RT50
RT33
RT25
RT18
RT15
RT12
RTA
V1 Input Threshold
4.600
3.036
2.300
1.656
1.380
1.104
492.5
–18
4.675
3.086
2.338
1.683
1.403
1.122
500
4.750
3.135
2.375
1.710
1.425
1.140
507.5
18
V
V1, V2 Input Threshold
V2, V3 Input Threshold
V2, V3, V4 Input Threshold
V2, V3, V4 Input Threshold
V2, V3, V4 Input Threshold
V3, V4, V5, V6 Input Threshold
V4 Input Threshold
V
V
V
V
V
mV
mV
V
–ADJ Reset Threshold
0
RTAN
REF
Reference Voltage
V
C
> 2.3V, I
REF
=
VREF
1mA,
1.192
1.210
1.228
CC
< 1000pF
l
l
l
l
V
Configuration Voltage Range
V
V
> V
0
V
V
nA
μA
μA
PG
VPG
V1
CC
PG
CCMINP
REF
I
I
I
I
V
PG
Input Current
= V
20
REF
V1 Input Current
V2 Input Current
V3 Input Current
V1 = 5V, I
= 12μA, (Note 4)
80
0.8
125
2
VREF
V2 = 3.3V
V2
l
l
V3 = 2.5V
V3 = 0.55V (ADJ Mode)
0.52
1.2
15
μA
nA
V3
l
l
l
I
V4
V4 Input Current
V4 = 1.8V
V4 = 0.55V (ADJ Mode)
V4 = -0.02V (–ADJ Mode)
0.34
0.8
15
15
μA
nA
nA
l
l
l
l
I
I
I
t
t
, I
V5, V6 Input Current (LTC2939)
CRT Pull-Up Current
V5, V6 = 0.55V
15
–2.6
30
nA
μA
μA
ms
μs
V5 V6
V
V
C
= GND
= 1.3V
–1.4
10
2
–2
20
3
CRT(UP)
CRT(DN)
RST
CRT
CRT
CRT Pull-Down Current
Reset Timeout Period
= 1500pF
4
RT
V Undervoltage Detect to RST
n
V Less Than Reset Threshold V
by
150
UV
n
RTX
More Than 1ꢀ
l
l
l
l
V
Voltage Output Low RST
I
I
I
I
= 2.5mA; V = 3V
0.15
0.05
0.15
0.4
0.3
0.4
V
V
V
V
OL
SINK
CC
= 100μA; V = 1V
SINK
CC
V
V
Voltage Output Low WDO
= 2.5mA; V = 3.3V
CC
OL
SINK
Voltage Output High RST, WDO
(Note 5)
= –1μA; V2 = 3.3V
V2 – 1
OH
SOURCE
l
l
l
I
I
t
CWT Pull-Up Current
CWT Pull-Down Current
Watchdog Timeout Period
WDI Input Threshold
V
V
C
= GND
–1.4
10
–2
20
30
–2.6
30
μA
μA
CWT(UP)
CWT(DN)
WD
CWT
CWT
= 1.3V
= 1500pF
20
40
ms
WT
l
l
l
V
Logic Low
Open
Logic High
0.4
1.1
V
V
V
WDI
(V = 3.3V to 5.5V)
0.7
1.4
0.9
CC
293839ff
3
LTC2938/LTC2939
ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C, VCC = 5V unless otherwise specified. (Note 3)
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
l
l
l
l
I
WDI Input Current
V
WDI
= GND
= 0.7V
= 1.1V
= 5V
–30
μA
μA
μA
μA
WDI
WDI
–10
10
V
V
WDI
WDI
V
30
l
t
WDI Input Pulse Width
V
= 3.3V or 5.5V
2
μs
WP
CC
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.
of supplying the quiescent current, programming (transient) current and
reference load current.
Note 5: The outputs RST and WDO have internal pull-ups to V2 of typically
6μA. However, external pull-up resistors may be used when faster rise
Note 2: All currents into pins are positive, all voltages are referenced to
GND unless otherwise noted.
times are required or for V voltages greater than V2. For V2 configured
to monitor 1.2V, 1.5V, 1.8V and 2.5V supplies, external pull-up resistors
OH
are required to ensure that the output voltage, high, is above the V input
threshold of the external circuit.
IH
Note 3: The greater of V1, V2 is the internal supply voltage (V ).
Note 4: Under static no-fault conditions, V1 will necessarily supply
CC
quiescent current. If at any time V2 is larger than V1, V2 must be capable
TYPICAL PERFORMANCE CHARACTERISTICS
Normalized Threshold Voltages
vs Temperature
–ADJ Threshold Voltage
vs Temperature
VREF vs Temperature
1.015
1.010
1.005
1.000
18
12
6
1.228
1.222
1.216
1.210
0
0.995
0.990
0.985
–6
–12
–18
1.204
1.198
1.192
50
TEMPERATURE (°C)
100 125
50
TEMPERATURE (°C)
100 125
50
TEMPERATURE (°C)
100 125
–50 –25
0
25
75
–50 –25
0
25
75
–50 –25
0
25
75
29389 G01
29389 G02
29389 G03
293839ff
4
LTC2938/LTC2939
TYPICAL PERFORMANCE CHARACTERISTICS
Transient Duration
vs Comparator Overdrive
400
Supply Current vs Temperature
I(V4) vs V4 in –ADJ mode
90
85
80
75
70
–100μ
–10μ
–1μ
V1 = 5V
T
= 25°C
A
V2 = 3.3V
V3 = 2.5V
V4 = 1.8V
V5 = V6 = 1V
350
300
250
200
150
100
50
125°C
RESET OCCURS
ABOVE CURVE
–100n
–10n
–1n
85°C
25°C
0
–100p
50
TEMPERATURE (°C)
100 125
0.1
1
10
100
)
–50 –25
0
25
75
–300 –250 –200 –150 –100 –50
V4 (mV)
0
RESET COMPARATOR OVERDRIVE (ꢀ OF V
RTX
29389 G05
29389 G04
29389 G06
RST Output Voltage vs V1,
Watchdog Timeout Period
vs Temperature
RST Pull-Up Current vs V2
VPG = GND
18
15
12
9
6
36
34
32
30
C
= 1500pF
T
= 25°C
T = 25°C
A
WT
A
(SILVER MICA)
10k PULL-UP FROM RST TO V1
5
V1 = V2
4
3
V
RT33
V
6
RT25
2
1
0
28
26
24
V
RT18
3
V
RT15
V
RT12
0
0.5
1
1.5
3
3.5
4
4.5
5
0
1
2
3
4
5
–50
25
50
75
100 125
2
2.5
–25
0
V2 (V)
V1 (V)
TEMPERATURE (°C)
29389 G07
29389 G08
29389 G09
Reset Timeout Period
vs Temperature
Watchdog Timeout Period vs CWT
Reset Timeout Period vs CRT
100
10
5
4
3
2
10
1
T
= 25°C
C
= 1500pF
A
RT
T = 25°C
A
(SILVER MICA)
1
100m
10m
1m
100m
10m
1m
100μ
100μ
1
10μ
10p
100p
1n
C
10n
(F)
100n
1μ
–50 –25
0
25
50
75 100 125
10p
100p
1n
C
10n
(F)
100n
1μ
TEMPERATURE (°C)
WT
RT
29389 G11
29389 G12
29389 G10
293839ff
5
LTC2938/LTC2939
TYPICAL PERFORMANCE CHARACTERISTICS
Voltage Output Low
ISINK vs Supply Voltage (RST)
vs Sink Current (RST, WDO)
WDI Input Current vs Temperature
15
12
9
500
400
300
200
100
0
20
15
V1 = 5V
V2 = 3V
V
= 5V
T
= 25°C
WDI
A
125°C
V
= 1.1V
WDI
10
V
= 0.4V
OL
85°C
25°C
5
0
V
= 0.2V
OL
6
3
0
–5
–40°C
–10
–15
–20
V
= 0V
WDI
V
WDI
= 0.7V
0
1
2
3
4
5
0
2
4
I
6
8
10
–50
0
25
50
75 100 125
–25
(mA)
TEMPERATURE (°C)
V1 OR V2 (V)
SINK
29389 G15
29389 G13
29389 G14
WDI Input Threshold
vs Temperature
WDO Pull-Up Current vs V2
18
15
1.50
1.25
1.00
0.75
0.50
T
= 25°C
A
WDO = GND
HIGH
OPEN (MAXIMUM)
12
9
6
3
0
LOW
OPEN (MINIMUM)
1
2
3
4
5
–50
0
25
50
75 100 125
TEMPERATURE (°C)
–25
V2 (V)
29389 G17
29389 G16
PIN FUNCTIONS
CRT: Reset Timeout Capacitor. Attach an external capaci- CWT:WatchdogTimeoutCapacitor.Attachacapacitor(C
)
WT
tor (C ) to GND to set a reset timeout of 2ms/nF. A 47nF between CWT and GND to set a watchdog timeout period
RT
capacitor generates a 94ms reset delay time. Leaving CRT of20ms/nF.A47nFcapacitorgeneratesa940mswatchdog
unconnected generates a minimum timeout period of ap- timeout period. Leaving CWT unconnected generates a
proximately 20μs which will vary depending on parasitic minimum timeout period of approximately 200μs which
capacitance on the pin.
293839ff
6
LTC2938/LTC2939
PIN FUNCTIONS
will vary depending on parasitic capacitance on the pin.
Tie CWT to GND to disable the watchdog function.
V : Threshold Select Input. Connect to an external 1ꢀ
PG
resistive divider between V
and GND to select one of
REF
sixteen combinations of voltage thresholds (see Table 1).
Do not add capacitance to the V input.
GND: Device Ground.
PG
NC: No Internal Connection.
V
: Buffered Reference Voltage Output. A 1.210V nomi-
REF
RST: Reset Output. Logic output with weak 6μA pull-up
to V2. Pulls low when any voltage input is below the reset
thresholdandheldlowfortheconfiguredresetdelaytime
after all voltage inputs are above threshold. When the
watchdog timer is enabled but not serviced prior to the
configured watchdog timeout period, RST pulls low for
one reset delay time. May be pulled to greater than V2
using an external pull-up. For V2 configured to monitor
2.5V or below, connect an external pull-up resistor to
the interface logic supply to ensure that the output high
nal reference used for the mode selection voltage (V )
PG
and for the offset of negative adjustable applications. The
buffered reference can source and sink up to 1mA. The
reference can drive a bypass capacitor of up to 1000pF
without oscillation.
WDI: Watchdog Input: A three-state input that controls
the operation of the watchdog timer. Leaving the WDI pin
unconnected disables the watchdog timer while tying it
low or high enables it. While RST is high, a transition
between low and high logic levels (rising or falling edge)
within the watchdog timeout period is required to inhibit
WDO from pulling low and a watchdog initiated reset. A
capacitor attached to CWT sets the watchdog timeout
period. A transition between the low and high logic levels
on the WDI input clears the voltage on the CWT capacitor,
preventing WDO from going low. Once WDO is latched
low,WDImusttransitionbetweenlowandhighlogiclevels
to clear WDO Transitions between open and logic low or
logic high do not clear WDO.
voltage is above the V of the external circuit. Leave
open if unused.
IH
V1: Voltage Input 1. Select from 5V or 3.3V. See the Ap-
plications Information section for details. The greater of
V1 or V2 is also V for the device. Bypass this input to
CC
ground with a 0.1μF (or greater) capacitor.
V2: Voltage Input 2. Select from 3.3V, 2.5V, 1.8V, 1.5V or
1.2V. See the Applications Information section for details.
The greater of V1, V2 is also V for the device. Bypass
CC
this input to ground with a 0.1μF (or greater) capacitor.
WDO:WatchdogOutput.Logicoutputwithweak6μApull-
up to V2. May be pulled greater than V2 using external
pull-up. For V2 configured to monitor 2.5V or below,
connect an external pull-up resistor to the interface logic
supply to ensure that the output high voltage is above the
All status outputs are weakly pulled up to V2.
V3: Voltage Input 3. Select from 2.5V, 1.8V, 1.5V, 1.2V or
ADJ. See the Applications Information section for details.
Tie to V1 if unused.
V of the external circuit. The watchdog timer is enabled
IH
V4: Voltage Input 4. Select from 1.8V, 1.5V, 1.2V, ADJ or
–ADJ.SeetheApplicationsInformationsectionfordetails.
Tie to V1 if unused and configured for positive voltage.
when RST is high. The watchdog output pulls low if the
watchdog timer expires and the output remains low
until set high by the next WDI transition or anytime an
undervoltage condition occurs. A watchdog failure also
triggers a reset event. Leave open if unused.
V5: Adjustable Voltage Input 5 for LTC2939. High imped-
ance comparator input with 0.5V typical threshold. Tie to
V1 if unused.
ExposedPad(DE12packageonly):TheExposedPadmay
be left open or connected to device ground.
V6: Adjustable Voltage Input 6 for LTC2939. High imped-
ance comparator input with 0.5V typical threshold. Tie to
V1 if unused.
293839ff
7
LTC2938/LTC2939
BLOCK DIAGRAM
BUFFER
V1
V2
VREF
BANDGAP
REFERENCE
POWER
DETECT
V
CC
VPG
A/D
V1
V2
V2
4
+
–
6μA
RESISTIVE
DIVIDERS
V3
4
V4
4
RST
ADJUSTABLE
RESET PULSE
GENERATOR
WDFAIL
V5
–
+
0.5V
LTC2939
+
–
V6
2μA
V2
V
CC
22μA
CRT
6μA
GND
WDO
WDFAIL
UV
WATCHDOG
TIMER
WDI
CWT
TRANSITION
DETECT
2μA
V
CC
22μA
293839 BD
293839ff
8
LTC2938/LTC2939
TIMING DIAGRAM
Vn Monitor Timing
V
RT
V
n
t
RST
t
UV
RST
293839 TD01
Reset and Watchdog Timing
V
n
RST
t
t
t
t
t
t
RST
RST
RST
RST
RST
RST
t
RST
t
t
t
t
WD
WD
WD
WD
WDO
WDI
293839 TD02
POWER-ON RESET
FOLLOWED BY RESET
CAUSED BY
WATCHDOG INPUT NOT TOGGLED,
WATCHDOG TIMER EXPIRES, WATCHDOG
OUTPUT PULLS LOW. RESET OUTPUT
PULLS LOW FOR ONE RESET TIMEOUT
PERIOD.
WATCHDOG INPUT NOT
TOGGLED, WATCHDOG
TIMER EXPIRES,
WATCHDOG OUTPUT
PULLS LOW. RESET
OUTPUT PULLS LOW.
WATCHDOG INPUT NOT
TOGGLED, WATCHDOG
TIMER EXPIRES, WATCHDOG
OUTPUT PULLS LOW. RESET
OUTPUT PULLS LOW.
UNDERVOLTAGE EVENT.
WATCHDOG OUTPUT SET
HIGH, WATCHDOG INPUT =
DON’T CARE
WATCHDOG INPUT REMAINS UNTOGGLED,
WATCHDOG OUTPUT REMAINS LOW,
RESET OUTPUT PULLS LOW AGAIN AFTER
ONE WATCHDOG TIMEOUT PERIOD.
WATCHDOG OUTPUT CLEARED BY
UNDERVOLTAGE EVENT.
WATCHDOG OUTPUT NOT
CLEARED BY WATCHDOG
INPUT DURING RESET
TIMEOUT. AFTER RESET
COMPLETED, WATCHDOG
INPUT CLEARS WATCHDOG
OUTPUT.
WATCHDOG OUTPUT
LOW TIME SHORTENED
BY UNDERVOLTAGE
EVENT DURING RESET
TIMEOUT.
293839ff
9
LTC2938/LTC2939
APPLICATIONS INFORMATION
Supply Monitoring
Threshold Accuracy
The LTC2938 and LTC2939 are low power, high accuracy
configurable four (LTC2938) and six (LTC2939) supply
monitoring circuits with reset output and watchdog func-
tions. Both watchdog and reset timeouts are adjustable
usingexternalcapacitors.Single-pinconfigurationselects
oneofsixteeninputvoltagemonitorcombinations.Allfour
(LTC2938) or six (LTC2939) voltage inputs must be above
predetermined thresholds for the reset not to be invoked.
The LTC2938/LTC2939 assert the reset during power-up,
power-down and brownout conditions on any one of the
voltage inputs.
Consider a 5V system with 5ꢀ tolerance. The 5V supply
may vary between 4.75V to 5.25V. System ICs powered by
this supply must operate reliably within this band (and a
littlemoreassubsequentlyexplained).Aperfectlyaccurate
supervisor for this supply generates a reset at exactly
4.75V. However, no supervisor is perfect. The actual reset
threshold of a supervisor varies over a specified band.
The LTC2938/LTC2939 varies 1.5ꢀ around its nominal
threshold voltage (see Figure 1) over temperature.
The reset threshold band and the power supply tolerance
bands should not overlap. This prevents false or nuisance
resets when the power supply is actually within its speci-
fied tolerance band.
Power-Up
The greater of V1 or V2 serves as the internal supply
The LTC2938 and LTC2939 have 1.5ꢀ reset threshold
accuracy, so a 5ꢀ threshold is typically set to 6.5ꢀ below
the nominal input voltage. Therefore, a typical 5V, 5ꢀ
threshold is 4.675V.
voltage (V ). On power-up, V powers the drive circuits
CC
CC
for the RST output. This ensures that the RST output will
be low as soon as V1 or V2 reaches 1V. The RST output
remains low until the part is configured. After configura-
tion, if any one of the supply monitor inputs is below its
configured threshold, RST will be at logic low. Once all
the monitor inputs rise above their thresholds, an internal
timer is started and RST is released after the configured
delay time.
The threshold is guaranteed to lie in the band between
4.750Vand4.600Vovertemperature.Thepoweredsystem
must work reliably down to the low end of the threshold
band, or risk malfunction before a reset signal is properly
issued.
NOMINAL
SUPPLY
VOLTAGE
5V
SUPPLY TOLERANCE
MINIMUM
RELIABLE
SYSTEM
IDEAL
SUPERVISOR
THRESHOLD
VOLTAGE
4.75V
–5ꢀ
1.5ꢀ
THRESHOLD 4.675V
BAND
–6.5ꢀ
4.6V
–8ꢀ
REGION OF POTENTIAL MALFUNCTION
293839 F01
Figure 1. 1.5ꢁ Threshold Accuracy Improves System Reliability
293839ff
10
LTC2938/LTC2939
APPLICATIONS INFORMATION
A less accurate supervisor increases the required system
voltage margin and increases the probability of system
malfunction. The LTC2938 and LTC2939 1.5ꢀ specifica-
tionimprovesthereliabilityofthesystemoversupervisors
with wider threshold tolerances.
Upon power-up, the LTC2938 or LTC2939 enters a con-
figuration period of approximately 150μs during which
the voltage on the V input is sampled and the monitor
PG
is configured to the desired input combination. Do not
add capacitance to the V input. Immediately after
PG
programming, the comparators are enabled and supply
Monitor Configuration
monitoring begins.
Select the LTC2938/LTC2939 input voltage combination
LTC2938/
by placing the recommended resistive divider from V
R1
1ꢀ
LTC2939
REF
to GND and connect the tap point to V , as shown in
PG
V
REF
V
Figure 2.
PG
R2
1ꢀ
GND
Table 1 offers recommended 1ꢀ resistor values for the
various modes. The rightmost column in Table 1 specifies
PG REF
a ratiometric DAC.
293839 F02
optimum V /V ratios ( 0.01), when configuring with
Figure 2. Monitor Programming
Table 1. Voltage Threshold Modes
MODE
0
V1 (V)
5
V2 (V)
3.3
3.3
2.5
2.5
1.8
3.3
3.3
1.8
1.8
1.8
2.5
2.5
1.8
1.5
3.3
1.2
V3 (V)
ADJ
ADJ
ADJ
ADJ
1.5
V4 (V)
ADJ
–ADJ
ADJ
–ADJ
ADJ
ADJ
1.8
R1 (kΩ)
Open
93.1
86.6
78.7
71.5
66.5
59
R2 (kΩ)
Short
9.53
16.2
22.1
28
V
/V
PG REF
0
1
5
0.094
0.156
0.219
0.281
0.344
0.406
0.469
0.531
0.594
0.656
0.719
0.781
0.844
0.906
1
2
3.3
3.3
3.3
5
3
4
5
2.5
34.8
40.2
47.5
53.6
59
6
5
2.5
7
3.3
3.3
3.3
3.3
3.3
3.3
3.3
5
1.5
1.2
53.6
47.5
40.2
34.8
28
8
1.2
ADJ
ADJ
1.5
9
ADJ
1.8
10
11
12
13
14
15
66.5
71.5
78.7
86.6
93.1
Open
1.8
ADJ
–ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
1.8
22.1
16.2
9.53
Short
3.3
ADJ
293839ff
11
LTC2938/LTC2939
APPLICATIONS INFORMATION
Using the Adꢀustable Thresholds
Inanegativeadjustableapplication,theminimumvaluefor
R4 is limited by the sourcing capability of V
( 1mA).
REF
The reference inputs on the V3 and/or V4 comparators are
set to 0.5V when the positive adjustable modes are se-
lected(Figure3). TheLTC2939V5andV6comparatorsare
always in positive adjustable mode with a 0.5V reference.
The tap point on an external resistive divider, connected
between the positive voltage being sensed and ground, is
connected to the high impedance, adjustable inputs (V3,
V4, V5 and V6). Calculate the trip voltage from:
With no other load on V , R4 (minimum) is:
REF
1.210V
= 1.210k
1mA
Tables 2 and 3 offer suggested 1ꢀ resistor values for
various adjustable applications assuming 5ꢀ monitor
thresholds.
Table 2. Suggested 1ꢁ Resistor Values for the ADJ Inputs
⎛
⎞
⎟
R3
R4⎠
VTRIP = 0.5V • 1+
⎜
⎝
V
(V)
V
(V)
R3 (kΩ)
2150
1780
1400
1300
1020
845
R4 (kΩ)
100
100
100
100
100
100
100
100
100
100
100
100
100
100
SUPPLY
TRIP
12
11.25
9.4
V
TRIP
10
8
LTC2938/LTC2939
R3
1ꢀ
7.5
7.5
6
7
V3, V4, V5 OR V6
R4
1ꢀ
5.6
5
4.725
3.055
2.82
2.325
1.685
1.410
1.120
0.933
0.840
3.3
3
511
+
–
0.5V
464
2.5
1.8
1.5
1.2
1
365
293839 F03
237
182
Figure 3. Setting the Positive Adꢀustable Trip Point
124
86.6
68.1
In the negative adjustable mode, the high impedance,
adjustable input on the V4 comparator is connected to
ground (Figure 4). The tap point on an external resistive
divider, connected between the negative voltage being
0.9
Table 3. Suggested 1ꢁ Resistor Values for the Negative
ADJ Inputs
sensed and the V
output, is connected to the high
REF
V
(V)
V
(V)
R3 (kΩ)
1.87
464
R4 (kΩ)
121
SUPPLY
TRIP
impedance adjustable input (V4). V provides the nec-
REF
–2
–1.87
–4.64
–4.87
–9.31
–11.30
essary level shift required to operate at ground. The nega-
–5
121
tive trip voltage is calculated from:
–5.2
–10
–12
487
121
R3
R4
931
121
VTRIP = −VREF
•
; VREF = 1.210V Nominal
1130
121
Although all of the supply monitor comparators have
built-in glitch immunity, bypass capacitors on V1 and V2
are recommended because the greater of V1 or V2 is also
the supply for the device. Filter capacitors on the V3, V4,
V5 and V6 inputs are allowed.
LTC2938/LTC2839
V
REF
R4
1ꢀ
V4
R3
1ꢀ
V
TRIP
293839 F04
Figure 4. Setting the Negative Adꢀustable Trip Point
293839ff
12
LTC2938/LTC2939
APPLICATIONS INFORMATION
Power-Down
impedance. The last method is to continuously drive WDI
between the low and high thresholds.
On power-down, once any of the monitor inputs drops
below its threshold, RST is held at a logic low. A logic low
of 0.4V is guaranteed until both V1 and V2 drop below
Selecting the Watchdog Timing Capacitor
The watchdog timeout period is adjustable and can be
optimized for software execution. The watchdog timeout
1V. If the bandgap reference becomes invalid (V < 2V
CC
typical), the LTC2938/LTC2939 will reconfigure when V
CC
period, t , is adjusted by connecting a capacitor, C
,
rises above 2.4V (max).
WD
WT
between CWT and ground. The value of this capacitor is
Selecting the Reset Timing Capacitor
determined by:
tWD
20MΩ
⎛
⎜
⎞
⎟
pF
⎝ ms⎠
The reset timeout period is adjustable in order to accom-
modateavarietyofmicroprocessorapplications.Thereset
CWT
=
= 50
• tWD
timeout period, t , is adjusted by connecting a capacitor,
RST
LeavingCWTunconnectedgeneratesaminimumwatchdog
timeout period of approximately 200μs. The maximum
watchdog timeout period is limited by the largest available
low leakage capacitor. The accuracy of the timeout period
is affected by capacitor leakage (the nominal charging
current is 2μA) and capacitor tolerance. A low leakage
ceramic capacitor is recommended.
C , between CRT and ground. The value of this capacitor
RT
is determined by:
tRST
2MΩ
⎛
⎜
⎞
⎟
pF
⎝ ms⎠
CRT
=
= 500
• tRST
Leaving CRT unconnected generates a minimum reset
timeout period of approximately 20μs. The maximum
reset timeout period is limited by the largest available low
leakage capacitor. The accuracy of the timeout period is
affectedbycapacitorleakage(thenominalchargingcurrent
is 2μA) and capacitor tolerance. A low leakage ceramic
capacitor is recommended.
Pull-Up Resistors for WDO and RST
The WDO and RST pins provide weak pull-up currents to
V2. This current is typically greater than 6μA when V2 is
greater than 3.3V. The magnitude of the pull-up current
decreases as V2 decreases. For V2 configured to monitor
2.5V,1.8V,1.5Vand1.2Vsupplies,externalpull-upresistors
are required from both pins to the interface logic supply
Watchdog Timer
Thewatchdogcircuittypicallymonitorsamicroprocessor’s
activity. The microprocessor is required to change the
logic state of the WDI input on a periodic basis in order
to clear the watchdog timer. Whenever an undervoltage
condition exists, the watchdog timer is cleared and WDO
is set high. The watchdog timer starts when RST pulls
high. Subsequent edges received on the WDI input clear
the watchdog timer. If uncleared, the watchdog timer
continues to run until it times out. Once it times out,
internal circuitry brings the WDO and RST outputs low.
WDO remains low for at least one reset timeout period
and can then be cleared by a new edge on the WDI input
or anytime an undervoltage condition occurs.
to ensure that the output high voltage is above the V
OH
input threshold of the external circuit. The WDO and RST
pins can be pulled to voltages higher than V2 by external
pull-up resistors.
Watchdog Application
Figure 5 shows a typical application for the LTC2938/
LTC2939. The C timing capacitor adjusts the watch-
WT
dog timeout period for optimal software execution. If
the software malfunctions and the state of the WDI pin
is unchanged before the end of the watchdog timeout
period (t ), the LTC2938/LTC2939 WDO pin is latched
WD
to a low state. At the same time, RST is pulled low to reset
the microprocessor. While RST is low, the WDI pin does
not affect RST or WDO. The system therefore resets for
The watchdog timer may be disabled in three ways. One
methodistosimplygroundCWT.WithCWTheldatground,
any undervoltage event forces WDO high indefinitely. A
second method is to leave the WDI input floating or in high
at least t
.
RST
293839ff
13
LTC2938/LTC2939
APPLICATIONS INFORMATION
After RST returns high, the microprocessor can poll the
state of the WDO pin to determine if the reset was caused
by an undervoltage condition or by a watchdog timeout.
WDO high means that the reset was caused by undervolt-
age since this condition also resets the WDO latch (and
the watchdog timer). If the WDO pin is low, the system
reset was caused by watchdog timeout. The microproces-
sor can then change the state of WDI to clear the WDO
latch. If the microprocessor fails to do so, the LTC2938/
pin. This affects the response of the LTC2938/LTC2939.
When the WDI pin is floated, the watchdog timer is reset
and C is discharged towards ground but WDO remains
WT
unchanged.PuttingWDIinhighimpedancedoesnotaffect
t
. Once RST goes high again, and WDI is driven from
RST
high impedence to a high or low state, the watchdog timer
starts a complete t timeout period. A high-to-low or
WD
low-to-high transition at WDI clears WDO if it was previ-
ously latched low.
LTC2939 will alternate between t
and t
timeout
RST
WD
The RST and WDO pins should not be tied together to
generatethemasterresetsignalsinceawatchdogtimeout
forces RST low together with WDO and the master reset
signal will remain low indefinitely.
and RST will be pulled low for t
after every watchdog
RST
timeout. WDO remains low until the microprocessor flips
the state of WDI.
Some microprocessors force their I/O pins into high
impedance during reset which in turn, floats the WDI
5V
V1
V2
3.3V
0.1μF
0.1μF
2.5V
1.8V
12V
V3
V4
V5
V6
LTC2939
RST
2150k 1ꢀ
WDO
MICROPROCESSOR
124k 1ꢀ
1.2V
WDI
V
REF
R1
59k
1ꢀ
V
GND CRT
CWT
PG
R2
40.2k
1ꢀ
100k
1ꢀ
100k
1ꢀ
C
C
t
t
= 94ms
= 940ms
RT
WT
RST
WD
47nF
47nF
293839 F05
Figure 5. 6-Supply Monitor, 12V (ADJ), 5V, 3.3V, 2.5V, 1.8V, 1.2V (ADJ)
with Watchdog Enabled
293839ff
14
LTC2938/LTC2939
TYPICAL APPLICATIONS
Quad-Supply Monitor (Mode 14) with Watchdog Disabled
5V
V1
V2
3.3V
0.1μF
0.1μF
1.8V
12V
SYSTEM
LOGIC
V3
V4
RST
LTC2938
V
= 11.25V
R3
TRIP
2.15MΩ
1ꢀ
WDO
V
REF
R1
9.53k
1ꢀ
R4
100k
1ꢀ
WDI
CWT
V
PG
GND
CRT
R2
93.1k
1ꢀ
C
RT
47nF
293839 TA02
5V Supply Monitor (Mode 1) with Watchdog Disabled and Unused Inputs Tied High
5V
V1
V2
V3
V4
0.1μF
R3
464k
1ꢀ
LTC2938
SYSTEM
LOGIC
–5V
RST
V
= –4.64V
TRIP
R4
121k
1ꢀ
WDO
V
REF
R1
93.1k
1ꢀ
V
WDI
CWT
PG
GND
CRT
R2
9.53k
1ꢀ
C
RT
47nF
293839 TA03
293839ff
15
LTC2938/LTC2939
TYPICAL APPLICATIONS
Supply and Temperature Monitor (Mode 1, 5V, 3.3V, 28V, –5.2V, 12V, 100°C)
5V
V1
V2
3.3V
10k
1ꢀ
0.1μF
0.1μF
2150k 1ꢀ
467k 1ꢀ
12V
V3
V5
V4
5110k 1ꢀ
28V
LTC2939
–5.2V
SYSTEM
LOGIC
RST
RHYST
280k
1ꢀ
121k
1ꢀ
WDO
V
REF
RBIAS
93.1k
1ꢀ
R1
93.1k
1ꢀ
WDI
CWT
V6
V
GND CRT
PG
RNTC*
470k
R2
9.53k
1ꢀ
C
RT
47nF
100k
1ꢀ
100k
1ꢀ
293839 TA04
*PANASONIC ERTJOEV474J
Buffered VREF to Power High Current Circuits
5V
3.3V
V1
RST
V2
0.1μF
0.1μF
WDO
MICROPROCESSOR
2.5V
1.8V
12V
WDI
V3
V4
V5
V6
LTC2939
2150k 1ꢀ
5V
124k 1ꢀ
1.2V
V
REF
+
R1
59k
1.210V
10mA
LT1809
1ꢀ
V
–
PG
R2
40.2k
1ꢀ
GND
CRT
CWT
100k
1ꢀ
100k
1ꢀ
C
C
WT
47nF
RT
47nF
293839 TAO5
293839ff
16
LTC2938/LTC2939
PACKAGE DESCRIPTION
UE/DE Package
12-Lead Plastic DFN (4mm × 3mm)
(Reference LTC DWG # 05-08-1695)
0.70 p0.05
3.30 p0.05
3.60 p0.05
2.20 p0.05
1.70 p 0.05
PACKAGE OUTLINE
0.25 p 0.05
0.50 BSC
2.50 REF
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED
0.40 p 0.10
4.00 p0.10
(2 SIDES)
R = 0.115
TYP
7
12
R = 0.05
TYP
3.30 p0.10
3.00 p0.10
(2 SIDES)
1.70 p 0.10
PIN 1
TOP MARK
(NOTE 6)
PIN 1 NOTCH
R = 0.20 OR
0.35 s 45o
CHAMFER
(UE12/DE12) DFN 0806 REV D
6
1
0.25 p 0.05
0.75 p0.05
0.200 REF
0.50 BSC
2.50 REF
BOTTOM VIEW—EXPOSED PAD
0.00 – 0.05
NOTE:
1. DRAWING PROPOSED TO BE A VARIATION OF VERSION
(WGED) 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
293839ff
17
LTC2938/LTC2939
PACKAGE DESCRIPTION
MS Package
12-Lead Plastic MSOP
(Reference LTC DWG # 05-08-1668 Rev Ø)
0.889 p 0.127
(.035 p .005)
5.23
(.206)
MIN
3.20 – 3.45
(.126 – .136)
4.039 p 0.102
(.159 p .004)
(NOTE 3)
0.65
(.0256)
BSC
0.42 p 0.038
(.0165 p .0015)
TYP
0.406 p 0.076
(.016 p .003)
REF
12 11 10 9 8 7
RECOMMENDED SOLDER PAD LAYOUT
DETAIL “A”
0o – 6o TYP
3.00 p 0.102
(.118 p .004)
(NOTE 4)
4.90 p 0.152
(.193 p .006)
0.254
(.010)
GAUGE PLANE
0.53 p 0.152
(.021 p .006)
1
2 3 4 5 6
0.86
(.034)
REF
1.10
(.043)
MAX
DETAIL “A”
0.18
(.007)
SEATING
PLANE
0.22 – 0.38
(.009 – .015)
TYP
0.1016 p 0.0508
(.004 p .002)
MSOP (MS12) 1107 REV Ø
0.650
(.0256)
BSC
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
293839ff
18
LTC2938/LTC2939
PACKAGE DESCRIPTION
MS Package
16-Lead Plastic MSOP
(Reference LTC DWG # 05-08-1669 Rev Ø)
0.889 p 0.127
(.035 p .005)
5.23
(.206)
MIN
3.20 – 3.45
(.126 – .136)
4.039 p 0.102
(.159 p .004)
(NOTE 3)
0.50
(.0197)
BSC
0.305 p 0.038
(.0120 p .0015)
TYP
0.280 p 0.076
(.011 p .003)
16151413121110
9
REF
RECOMMENDED SOLDER PAD LAYOUT
3.00 p 0.102
(.118 p .004)
(NOTE 4)
DETAIL “A”
0.254
4.90 p 0.152
(.193 p .006)
(.010)
0o – 6o TYP
GAUGE PLANE
0.53 p 0.152
(.021 p .006)
1 2 3 4 5 6 7 8
0.86
(.034)
REF
1.10
(.043)
MAX
DETAIL “A”
0.18
(.007)
SEATING
PLANE
0.17 – 0.27
(.007 – .011)
TYP
0.1016 p 0.0508
(.004 p .002)
MSOP (MS16) 1107 REV Ø
0.50
(.0197)
BSC
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
293839ff
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.
19
LTC2938/LTC2939
TYPICAL APPLICATION
Quad-Supply Monitor (Mode 14) with Pushbutton Reset
5V
3.3V
1μF
1μF
R3
2.15MΩ
1ꢀ
V2
V4
V1
V3
1.8V
12V
TRIP
V
= 11.25V
CRT
V
REF
LTC2938
R1
9.53k
1ꢀ
RST
WDO
WDI
SYSTEM
LOGIC
10k*
V
PG
C
RT
47nF
GND
C
WT
MANUAL RESET
PUSHBUTTON
R2
93.1k
1ꢀ
R4
47nF
100k
1ꢀ
CWT
293839 TAO6
*OPTIONAL RESISTOR FOR
ADDED ESD PROTECTION
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
LTC2900
Programmable Quad-Supply Monitor
Programmable Quad-Supply Monitor
Programmable Quad-Supply Monitor
Adjustable Reset, 10-Lead MSOP and DFN Packages
Adjustable Reset and Watchdog Timer
LTC2901
LTC2902
Adjustable Reset and Tolerance
LTC2908
Precision 6-Supply Monitor (Four Fixed and Two Adjustable)
8-Lead TSOT-23 and DFN Packages
LTC2930
Configurable 6-Supply Monitor with Adjustable Reset Timer,
Manual Reset
H-Grade Temperature Range, 3mm × 3mm DFN-12 Package
LTC2931
LTC2932
Configurable 6-Supply Monitor with Adjustable Reset and
Watchdog Timers
H-Grade Temperature Range, Individual Supply Comparator
Outputs, TSSOP-20 Package
Configurable 6-Supply Monitor with Individual Comparator
Outputs
Adjustable Reset Timer and Tolerance, Pin-Selectable Tolerance
(5ꢀ, 7.5ꢀ, 10ꢀ or 12.5ꢀ), Reset Disable for Margining,
TSSOP-20 Package
293839ff
LT 0709 • PRINTED IN USA
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
20
●
●
© LINEAR TECHNOLOGY CORPORATION 2009
(408) 432-1900 FAX: (408) 434-0507 www.linear.com
相关型号：
LTC2939IMS#PBF
LTC2939 - Configurable 6-Supply Monitors with Watchdog Timer; Package: MSOP; Pins: 16; Temperature Range: -40°C to 85°C
Linear
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