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LTC2938/LTC2939
Configurable 4- and 6-Supply
Monitors with Watchdog Timer
FEATURES
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 ± Adjustable Voltage
Thresholds
n Guaranteed Threshold Accuracy: ±1.5%
n Adjustable Reset and Watchdog Timeout
n Low Supply Current: 80μA Typical
n Power Supply Glitch Immunity
n Guaranteed RST for VCC > 1V
n High Temperature Operation to 125°C
n 12-Pin 4mm × 3mm DFN or 12-Lead MSOP
(LTC2938) and 16-Lead MSOP Package (LTC2939)
APPLICATIONS
n Desktop and Notebook Computers
n Multivoltage Systems
n Telecom Equipment
n Network Servers
n Automotive Control Systems
DESCRIPTION
The LTC®2938/LTC2939 are configurable supply monitors
for systems with up to four or six supply voltages that need
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 ±1.5% over
temperature. The LTC2938 and LTC2939 also feature ad-
justable inputs with a 0.5V nominal threshold.
The reset and watchdog timeout periods are adjustable
using external capacitors. Tight voltage threshold accuracy
and glitch immunity ensure reliable reset operation without
false triggering. The RST output is guaranteed to be in the
correct state for VCC down to 1V. Each status output has
a weak internal pull-up and may be externally pulled up
to a user-defined voltage.
The 80μA supply current makes the LTC2938 and LTC2939
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.
TYPICAL APPLICATION
6-Supply Monitor 12V (ADJ), 5V, 3.3V, 2.5V, 1.8V, 1.2V (ADJ)
12V
5V
3.3V SYSTEM
2.5V LOGIC
1.8V
1.2V
0.1μF
0.1μF
2150k 124k
1% 1%
100k 100k
1% 1%
V1
V2
V3
V4
V5
V6
VREF
R1
59k
1%
VPG
GND
R2
40.2k
1%
LTC2939
WDI
WDO
RST
CWT
CWT
47nF
tRST = 94ms
CRT tWD = 940ms
CRT
47nF
293839 TA01
Voltage Configuration Table
V1 (V)
5
5
5
5
5
3.3
3.3
3.3
3.3
3.3
3.3
3.3
3.3
3.3
3.3
3.3
V2 (V)
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
V3 (V)
2.5
2.5
1.8
ADJ
ADJ
1.8
1.8
1.5
1.5
1.2
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
V4 (V)
1.8
ADJ
ADJ
ADJ
ADJ
1.5
ADJ
1.2
ADJ
ADJ
ADJ
–ADJ
ADJ
–ADJ
ADJ
ADJ
V5 (V)
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
V6 (V)
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
293839ff
1
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LTC2938/LTC2939
ABSOLUTE MAXIMUM RATINGS (Notes 1, 2, 3)
V1, V2, V3, V4, V5, V6, VPG ......................... –0.3V to 7V
RST.............................................................. –0.3V to 7V
CWT, WDO.................................................... –0.3V to 7V
CRT, VREF, WDI.............................. –0.3V to (VCC + 0.3V)
Reference Load Current (IVREF)..............................±1mA
V4 Input Current (–ADJ Mode) ..............................–1mA
RST, WDO Currents ............................................±10mA
Operating Temperature Range
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)
MS Package Only.............................................. 300°C
PIN CONFIGURATION
LTC2938
TOP VIEW
LTC2938
V3 1
V1 2
CRT 3
RST 4
WDO 5
WDI 6
12 V2
11 V4
10 VREF
13
9 VPG
8 GND
7 CWT
DE PACKAGE
12-LEAD (4mm s 3mm) PLASTIC DFN
TJMAX = 125°C, θJA = 43°C/W
EXPOSED PAD (PIN 13) PCB GND CONNECTION OPTIONAL
TOP VIEW
V3 1
V1 2
CRT 3
RST 4
WDO 5
WDI 6
12 V2
11 V4
10 VREF
9 VPG
8 GND
7 CWT
MS PACKAGE
12-LEAD PLASTIC MSOP
TJMAX = 125°C, θJA = 130°C/W
LTC2939
V5 1
V3 2
V1 3
NC 4
CRT 5
RST 6
WDO 7
WDI 8
TOP VIEW
16 V6
15 V2
14 V4
13 NC
12 VREF
11 VPG
10 GND
9 CWT
MS PACKAGE
16-LEAD PLASTIC MSOP
TJMAX = 125°C, θJA = 110°C/W
ORDER INFORMATION
LEAD FREE FINISH
TAPE AND REEL
PART MARKING*
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LTC2938CDE#PBF
LTC2938IDE#PBF
LTC2938CDE#TRPBF
LTC2938IDE#TRPBF
2938
2938
12-Lead (4mm × 3mm) Plastic DFN
12-Lead (4mm × 3mm) Plastic DFN
0°C to 70°C
–40°C to 85°C
LTC2938HDE#PBF
LTC2938HDE#TRPBF 2938
12-Lead (4mm × 3mm) Plastic DFN
–40°C to 125°C
LTC2938CMS#PBF
LTC2938CMS#TRPBF 2938
12-Lead Plastic MSOP
0°C to 70°C
LTC2938IMS#PBF
LTC2938IMS#TRPBF
2938
12-Lead Plastic MSOP
–40°C to 85°C
LTC2938HMS#PBF
LTC2938HMS#TRPBF 2938
12-Lead Plastic MSOP
–40°C to 125°C
LTC2939CMS#PBF
LTC2939CMS#TRPBF 2939
16-Lead Plastic MSOP
0°C to 70°C
LTC2939IMS#PBF
LTC2939IMS#TRPBF
2939
16-Lead Plastic MSOP
–40°C to 85°C
LTC2939HMS#PBF
LTC2939HMS#TRPBF 2939
16-Lead Plastic MSOP
–40°C to 125°C
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/
2
293839ff
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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
VCC
VCCMINP
VRT50
VRT33
VRT25
VRT18
VRT15
VRT12
VRTA
VRTAN
VREF
VPG
IVPG
IV1
IV2
IV3
Minimum Internal Operating Voltage
Minimum Required for Configuration
5V, 5% Reset Threshold
3.3V, 5% Reset Threshold
2.5V, 5% Reset Threshold
1.8V, 5% Reset Threshold
1.5V, 5% Reset Threshold
1.2V, 5% Reset Threshold
ADJ Reset Threshold
–ADJ Reset Threshold
Reference Voltage
Configuration Voltage Range
VPG Input Current
V1 Input Current
V2 Input Current
V3 Input Current
RST in Correct Logic State
VCC Rising
V1 Input Threshold
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
VCC > 2.3V, IVREF = ±1mA,
CREF < 1000pF
VCC > VCCMINP
VPG = VREF
V1 = 5V, IVREF = 12μA, (Note 4)
V2 = 3.3V
V3 = 2.5V
V3 = 0.55V (ADJ Mode)
l
l
l 4.600
l 3.036
l 2.300
l 1.656
l 1.380
l 1.104
l 492.5
l –18
l 1.192
4.675
3.086
2.338
1.683
1.403
1.122
500
0
1.210
1
2.6
4.750
3.135
2.375
1.710
1.425
1.140
507.5
18
1.228
l0
l
l
l
l
l
VREF
±20
80 125
0.8 2
0.52 1.2
±15
V
V
V
V
V
V
V
V
mV
mV
V
V
nA
μA
μA
μA
nA
IV4 V4 Input Current
V4 = 1.8V
V4 = 0.55V (ADJ Mode)
V4 = -0.02V (–ADJ Mode)
l
0.34 0.8
μA
l ±15 nA
l ±15 nA
IV5, IV6
ICRT(UP)
ICRT(DN)
tRST
tUV
VOL
VOL
VOH
V5, V6 Input Current (LTC2939)
CRT Pull-Up Current
CRT Pull-Down Current
Reset Timeout Period
Vn Undervoltage Detect to RST
Voltage Output Low RST
Voltage Output Low WDO
Voltage Output High RST, WDO
(Note 5)
V5, V6 = 0.55V
VCRT = GND
VCRT = 1.3V
CRT = 1500pF
Vn Less Than Reset Threshold VRTX by
More Than 1%
ISINK = 2.5mA; VCC = 3V
ISINK = 100μA; VCC = 1V
ISINK = 2.5mA; VCC = 3.3V
ISOURCE = –1μA; V2 = 3.3V
l
l –1.4
l 10
l2
–2
20
3
150
l
l
l
l V2 – 1
0.15
0.05
0.15
±15
–2.6
30
4
0.4
0.3
0.4
nA
μA
μA
ms
μs
V
V
V
V
ICWT(UP)
ICWT(DN)
tWD
VWDI
CWT Pull-Up Current
CWT Pull-Down Current
Watchdog Timeout Period
WDI Input Threshold
(VCC = 3.3V to 5.5V)
VCWT = GND
VCWT = 1.3V
CWT = 1500pF
Logic Low
Open
Logic High
l –1.4 –2 –2.6
l 10 20 30
l 20 30 40
l 0.4
l 0.7 0.9 1.1
l 1.4
μA
μA
ms
V
V
V
293839ff
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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
IWDI WDI Input Current
tWP WDI Input Pulse Width
VWDI = GND
VWDI = 0.7V
VWDI = 1.1V
VWDI = 5V
VCC = 3.3V or 5.5V
l
l –10
l 10
l
l2
–30 μA
μA
μA
30 μA
μs
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2: All currents into pins are positive, all voltages are referenced to
GND unless otherwise noted.
Note 3: The greater of V1, V2 is the internal supply voltage (VCC).
Note 4: Under static no-fault conditions, V1 will necessarily supply
quiescent current. If at any time V2 is larger than V1, V2 must be capable
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
times are required or for VOH voltages greater than V2. For V2 configured
to monitor 1.2V, 1.5V, 1.8V and 2.5V supplies, external pull-up resistors
are required to ensure that the output voltage, high, is above the VIH input
threshold of the external circuit.
TYPICAL PERFORMANCE CHARACTERISTICS
Normalized Threshold Voltages
vs Temperature
1.015
1.010
1.005
1.000
0.995
0.990
0.985
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
29389 G01
–ADJ Threshold Voltage
vs Temperature
18
12
6
0
–6
–12
–18
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
29389 G02
VREF vs Temperature
1.228
1.222
1.216
1.210
1.204
1.198
1.192
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
29389 G03
4
293839ff
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TYPICAL PERFORMANCE CHARACTERISTICS
LTC2938/LTC2939
Supply Current vs Temperature
90
V1 = 5V
V2 = 3.3V
V3 = 2.5V
85
V4 = 1.8V
V5 = V6 = 1V
I(V4) vs V4 in –ADJ mode
–100μ
–10μ
–1μ
125°C
80
–100n
85°C
–10n
75
–1n 25°C
70
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
29389 G04
RST Pull-Up Current vs V2
18
TA = 25°C
15
–100p
–300 –250 –200 –150 –100
V4 (mV)
–50 0
29389 G05
RST Output Voltage vs V1,
VPG = GND
6
TA = 25°C
10k PULL-UP FROM RST TO V1
5 V1 = V2
12 4
9
VRT33
6 VRT25
VRT18
3 VRT15
VRT12
0
0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
V2 (V)
29389 G07
3
2
1
0
01
23
V1 (V)
45
29389 G08
Reset Timeout Period
vs Temperature
5 CRT = 1500pF
(SILVER MICA)
4
Watchdog Timeout Period vs CWT
100
TA = 25°C
10
1
3 100m
10m
2
1m
1
–50 –25
0 25 50 75 100 125
TEMPERATURE (°C)
29389 G10
100μ
10p 100p
1n 10n
CWT (F)
100n 1μ
29389 G11
Transient Duration
vs Comparator Overdrive
400
TA = 25°C
350
300
250
200
RESET OCCURS
ABOVE CURVE
150
100
50
0
0.1 1
10 100
RESET COMPARATOR OVERDRIVE (% OF VRTX)
29389 G06
Watchdog Timeout Period
vs Temperature
36
CWT = 1500pF
(SILVER MICA)
34
32
30
28
26
24
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
29389 G09
Reset Timeout Period vs CRT
10
TA = 25°C
1
100m
10m
1m
100μ
10μ
10p 100p
1n 10n
CRT (F)
100n 1μ
29389 G12
293839ff
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