LTC2932
Configurable Six Supply
Monitor with Adjustable Reset
Timer and Supply Tolerance
DESCRIPTION
FEATURES
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Simultaneously Monitors Six Supplies
16 User Selectable Combinations of
5V, 3.3V, 3V, 2.5V, 1.8V, 1.5V and
± Adjustable Voltage Thresholds
Guaranteed Threshold Accuracy: ±1.5%
Selectable Supply Tolerances: 5%, 7.5%, 10%,
12.5% Below Monitored Voltage
Reset Disable Pin for Margining Applications
Low Supply Current: 52μA
Power Supply Glitch Immunity
Guaranteed RST for VCC ≥ 1V
High Temperature Operation to 125°C
20-Lead TSSOP Package
APPLICATIONS
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Desktop and Notebook Computers
Multivoltage Systems
Telecom Equipment
Portable Battery-Powered Equipment
Network Servers
Automotive
The LTC®2932 is a configurable supply monitor for systems with up to six supply voltages. One of 16 preset or
adjustable voltage monitor combinations can be selected
using an external resistive divider connected to the mode
select pin. The preset voltage thresholds are digitally
configurable to 5%, 7.5%, 10%, or 12.5% below the
nominal operating voltage. The LTC2932 also features
adjustable inputs with a 0.5V nominal threshold. All six
open-drain voltage comparator outputs are connected to
separate pins for individual supply monitoring.
The reset timeout period is adjustable using an external
capacitor. The RST output is guaranteed to be in the
correct state for VCC down to 1V and may be disabled
during supply margin testing. Each status output has a
weak internal pull-up and may be externally pulled up to
an external voltage.
The 52μA supply current makes the LTC2932 ideal for
power conscious systems and the part may be configured
to monitor less than six inputs.
L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
Protected by U.S. Patents including 6967591, 7119714, 7239251.
TYPICAL APPLICATION
Six Supply Monitor 12V (ADJ),
5V, 3.3V, 2.5V, 1.8V, 1.2V (ADJ)
Voltage Threshold Configuration Table
V1 (V)
V2 (V)
V3 (V)
V4 (V)
V5 (V)
5
3.3
2.5
1.8
ADJ
ADJ
5
3.3
2.5
1.5
ADJ
ADJ
5
3.3
2.5
ADJ
ADJ
ADJ
5
3.3
1.8
ADJ
ADJ
ADJ
5
3.3
1.8
–ADJ
ADJ
ADJ
5
3.3
ADJ
ADJ
ADJ
ADJ
5
3.3
ADJ
–ADJ
ADJ
ADJ
5
3
2.5
ADJ
ADJ
ADJ
V3
5
3
1.8
ADJ
ADJ
ADJ
V4
5
3
ADJ
ADJ
ADJ
ADJ
3.3
2.5
1.8
1.5
ADJ
ADJ
3.3
2.5
1.8
ADJ
ADJ
ADJ
3.3
2.5
1.8
–ADJ
ADJ
ADJ
3.3
2.5
1.5
ADJ
ADJ
ADJ
3.3
2.5
ADJ
ADJ
ADJ
ADJ
3.3
2.5
ADJ
–ADJ
ADJ
ADJ
12V
5V
3.3V
2.5V
SYSTEM
LOGIC
1.8V
1.2V
10k
POWER
GOOD
0.1μF
0.1μF
100k
1% R1
59k
1%
RDIS
V6
VREF
RST
2932 TA01
VPG
GND
R2
40.2k
1%
COMP6
LTC2932
V5
100k
1%
COMP5
COMP4
V2
COMP3
V1
COMP2
124k
1%
COMP1
2150k
1%
T0
T1
CRT
tRST = 94ms
CRT
47nF
V6 (V)
2932fb
1
LTC2932
ABSOLUTE MAXIMUM RATINGS
PIN CONFIGURATION
(Notes 1, 2, 3)
TOP VIEW
V1, V2, V3, V4, V5, V6, VPG ........................ –0.3V to 7V
RST, COMP1-6, T0, T1................................. –0.3V to 7V
CRT, VREF, RDIS ............................–0.3V to (VCC + 0.3V)
Reference Load Current (IVREF) ..............................±1mA
V4 Input Current (–ADJ Mode) ..............................–1mA
RST, COMP1-6 Currents ......................................±10mA
Operating Temperature Range
LTC2932C ................................................ 0°C to 70°C
LTC2932I..............................................– 40°C to 85°C
LTC2932H ..........................................– 40°C to 125°C
Storage Temperature Range...................– 65°C to 150°C
Lead Temperature (Soldering, 10 sec) .................. 300°C
COMP5
1
20 COMP6
V5
2
19 V6
COMP3
3
18 COMP2
COMP1
4
17 COMP4
V3
5
16 V2
V1
6
15 V4
CRT
7
14 VREF
RST
8
13 VPG
T0
9
12 GND
RDIS 10
11 T1
F PACKAGE
20-LEAD PLASTIC TSSOP
TJMAX = 130°C, θJA = 90°C/W
ORDER INFORMATION
LEAD FREE FINISH
TAPE AND REEL
PART MARKING*
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LTC2932F#PBF
LTC2932CF#TRPBF
LTC2932F
20-Lead Plastic TSSOP
0°C to 70°C
LTC2932F#PBF
LTC2932IF#TRPBF
LTC2932F
20-Lead Plastic TSSOP
–40°C to 85°C
LTC2932F#PBF
LTC2932HF#TRPBF
LTC2932F
20-Lead Plastic TSSOP
–40°C to 125°C
Consult LTC Marketing for information on non-standard lead based finish parts. *Temperature grades are identified by a label on the shipping container.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/
This product is only offered in trays. For more information go to: http://www.linear.com/packaging/
ELECTRICAL CHARACTERISTICS
The ● 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
Minimum Internal Operating Voltage
RST, COMPn in Correct Logic State
●
1
V
VCCMINP
Minimum Required for Mode Selection
VCC Rising
●
2.4
V
VCCMINC
Minimum Required for Comparators
VCC Falling
●
2.3
V
VRT50
5V, 5% Reset Threshold
5V, 7.5% Reset Threshold
5V, 10% Reset Threshold
5V, 12.5% Reset Threshold
V1 Input Threshold
●
●
●
●
4.600
4.475
4.350
4.225
4.675
4.550
4.425
4.300
4.750
4.625
4.500
4.375
V
V
V
V
VRT33
3.3V, 5% Reset Threshold
3.3V, 7.5% Reset Threshold
3.3V, 10% Reset Threshold
3.3V, 12.5% Reset Threshold
V1, V2 Input Threshold
●
●
●
●
3.036
2.954
2.871
2.789
3.086
3.003
2.921
2.838
3.135
3.053
2.970
2.888
V
V
V
V
VRT30
3V, 5% Reset Threshold
3V, 7.5% Reset Threshold
3V, 10% Reset Threshold
3V, 12.5% Reset Threshold
V2 Input Threshold
●
●
●
●
2.760
2.685
2.610
2.535
2.805
2.730
2.655
2.580
2.850
2.775
2.700
2.625
V
V
V
V
2932fb
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LTC2932
ELECTRICAL CHARACTERISTICS
The ● 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
VRT25
2.5V, 5% Reset Threshold
2.5V, 7.5% Reset Threshold
2.5V, 10% Reset Threshold
2.5V, 12.5% Reset Threshold
V2, V3 Input Threshold
●
●
●
●
2.300
2.238
2.175
2.113
2.338
2.275
2.213
2.150
2.375
2.313
2.250
2.188
V
V
V
V
VRT18
1.8V, 5% Reset Threshold
1.8V, 7.5% Reset Threshold
1.8V, 10% Reset Threshold
1.8V, 12.5% Reset Threshold
V3, V4 Input Threshold
●
●
●
●
1.656
1.611
1.566
1.521
1.683
1.638
1.593
1.548
1.710
1.665
1.620
1.575
V
V
V
V
VRT15
1.5V, 5% Reset Threshold
1.5V, 7.5% Reset Threshold
1.5V, 10% Reset Threshold
1.5V, 12.5% Reset Threshold
V3, V4 Input Threshold
●
●
●
●
1.380
1.343
1.305
1.268
1.403
1.365
1.328
1.290
1.425
1.388
1.350
1.313
V
V
V
V
VRTA
ADJ, 5% Reset Threshold
ADJ, 7.5% Reset Threshold
ADJ, 10% Reset Threshold
ADJ, 12.5% Reset Threshold
V3, V4, V5, V6 Input Threshold
●
●
●
●
492.5
479.4
466.3
453.1
500.0
486.6
473.3
459.9
507.5
494
480.4
466.8
mV
mV
mV
mV
VRTAN
–ADJ Reset Threshold
V4 Input Threshold
●
–18
0
18
mV
VREF
Reference Voltage
VCC ≥ 2.3V, IVREF = ±1mA, CREF ≤ 1000pF
T0 Low, T1 Low
T0 Low, T1 High
T0 High, T1 Low
T0 High, T1 High
●
●
●
●
1.192
1.160
1.128
1.096
1.210
1.178
1.146
1.113
1.228
1.195
1.163
1.130
0
VPG
Mode Selection Voltage Range
VCC ≥ VCCMINP
●
IVPG
VPG Input Current
VPG = VREF
●
IV1
V1 Input Current
V1 = 5V, IVREF = 12μA (Note 4)
●
IV2
V2 Input Current
V2 = 3.3V
IV3
V3 Input Current
IV4
V
V
V
V
VREF
V
±20
nA
52
75
μA
●
0.8
2
μA
V3 = 2.5V
V3 = 0.55V (ADJ Mode)
●
●
0.52
1.2
±15
μA
nA
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
IV5, IV6
V5, V6 Input Current
V5, V6 = 0.55V
●
±15
nA
ICRT(UP)
CRT Pull-Up Current
VCRT = GND
●
–1.4
–2
–2.6
μA
ICRT(DN)
CRT Pull-Down Current
VCRT = 1.3V
●
10
20
30
μA
ICOMPn
COMPn Pull-Up Current
VCOMPn = GND
●
–2
–6
–12
μA
tRST
Reset Timeout Period
CRT = 1500pF
●
2
3
4
ms
tUV
Vn Undervoltage Detect to RST or
COMPn
Vn Less Than Reset Threshold by More
than 1%
VOL
Voltage Output Low RST, COMPn
ISINK = 3mA, VCC = 3V
ISINK = 100μA, VCC = 1V
●
●
VOH
Voltage Output High RST, COMPn
(Note 5)
ISOURCE = –1μA
●
150
0.15
0.05
V2-1
μs
0.4
0.3
V
V
V
2932fb
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LTC2932
ELECTRICAL CHARACTERISTICS
The ● 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
Digital Inputs T0, T1, RDIS
VIL
T0, T1 Low Level Input Voltage
VCC = 3.3V to 5.5V
●
VIH
T0, T1 High Level Input Voltage
VCC = 3.3V to 5.5V
●
IINTOL
T0, T1 Input Current
T0, T1 = 2V
●
VIL
RDIS Input Threshold Low
VCC = 3.3V to 5.5V
●
VIH
RDIS Input Threshold High
VCC = 3.3V to 5.5V
●
1.6
IRDIS
RDIS Pull-Up Current
VRDIS = 1V
●
–4
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).
0.3VCC
0.7VCC
V
V
±0.1
±1
μA
0.4
V
V
–10
–16
μA
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 output pins RST and COMPn have diode protected 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.
TIMING DIAGRAM
Vn Monitor Timing
Vn
VRT
tUV
tRST
RST
2932 TD
COMPn
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4
LTC2932
TYPICAL PERFORMANCE CHARACTERISTICS
–ADJ Threshold Voltage
vs Temperature
1.010
1.005
1.000
0.995
0.990
0.985
–50 –25
50
25
75
0
TEMPERATURE (°C)
100
VREF vs Temperature
18
1.228
12
1.222
6
1.216
VREF (V)
1.015
THRESHOLD VOLTAGE, VRTAN (mV)
NORMALIZED THRESHOLD VOLTAGES (V/V)
Normalized Threshold Voltages
vs Temperature
0
–6
1.204
–12
1.198
–18
–50 –25
125
50
25
75
0
TEMPERATURE (°C)
100
2932 G01
TYPICAL TRANSIENT DURATION (μs)
300
125°C
IV4 (A)
–1μ
–100n
50
–10n
45
–1n
90°C
25°C
100
125
–100p
–300
–250
–200
–150 –100
V4 (mV)
–50
TA = 25°C
250
200
RESET OCCURS ABOVE CURVE
150
100
50
0
0
0.1
1
10
100
RESET COMPARATOR OVERDRIVE (% OF VRTX)
2932 G05
2932 G04
2932 G06
RST Output Voltage
vs V1, VPG = GND
375
5
TA = 25°C
10k PULL-UP FROM RST TO V1
5
300
RESET OCCURS ABOVE CURVE
225
150
75
RST OUTPUT VOLTAGE (V)
TYPICAL TRANSIENT DURATION (μs)
6
TA = 25°C
Reset Timeout Period
vs Temperature
RESET TIMEOUT PERIOD, tRST (ms)
Transient Duration vs Comparator
Overdrive (V3, V4, V5, V6)
450
4
3
2
1
0
0.1
1
10
100
RESET COMPARATOR OVERDRIVE (% OF VRTX)
2932 G07
125
100
Transient Duration vs Comparator
Overdrive (V1,V2)
–10μ
55
50
75
25
0
TEMPERATURE (°C)
2932 G03
–100μ
V1 = 5V
V2 = 3.3V
65 V3 = 2.5V
V4 = 1.8V
V5 = V6 = 1V
60
50
25
75
0
TEMPERATURE (°C)
1.192
–50 –25
I(V4) vs V4 in Negative
Adjust Mode
70
SUPPLY CURRENT, IV1 (μA)
125
2932 G02
Supply Current vs Temperature
40
–50 –25
1.210
0
0
1
2
3
4
5
V1 (V)
2932 G08
CRT = 1500pF
(SILVER MICA)
4
3
2
1
–50
–25
75
0
25
50
TEMPERATURE (°C)
100
125
2932 G09
2932fb
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LTC2932
TYPICAL PERFORMANCE CHARACTERISTICS
ISINK vs Supply Voltage
(RST, COMPn)
Reset Timeout Period vs CRT
15
TA = 25°C
V1 = 5V
V2 = 3V
125°C
400
12
VOL = 0.4V
100m
ISINK (mA)
RESET TIMEOUT PERIOD tRST (s)
1
500
TA = 25°C
10m
85°C
9
VOL (mV)
10
Voltage Output Low vs Output
Sink Current (RST, COMPn)
VOL = 0.2V
6
300
25°C
200
1m
–40°C
100
3
100μ
10μ
10p
100p
1n
10n
CRT (F)
100n
0
1μ
0
1
3
2
V1 OR V2 (V)
0
4
5
2
0
6
4
ISINK (mA)
2932 G10
8
2932 G11
250
COMPn PROPAGATION DELAY (μs)
TA = 25°C
COMPn = GND
PULL-UP CURRENT (μA)
15
12
9
6
3
0
1
2
3
V2 (V)
4
5
2932 G13
RST Pull-Up Current vs V2
18
TA = 25°C
150
V1, V2
100
50
0
TA = 25°C
15
200
PULL-UP CURRENT (μA)
18
2932 G12
COMPn Propagation Delay vs
Input Overdrive Above Threshold
COMPn Pull-Up Current vs V2
10
V3, V4, V5, V6
12
9
VRT33
VRT30
6
3 VRT25
1000
10
100
INPUT OVERDRIVE ABOVE THRESHOLD (mV)
2932 G14
0
2.0
2.5
3.0
3.5
V2 (V)
4.0
4.5
5.0
2932 G15
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LTC2932
PIN FUNCTIONS
COMP5 (Pin 1): Comparator Output 5. Real-time logic
output with weak 6μA pull-up to V2. Pulls high when V5
is above reset threshold. May be pulled greater than V2
using external pull-up. Leave open if unused.
V5 (Pin 2): Adjustable Voltage Input 5. High impedance
comparator input with 0.5V typical threshold. See
Applications Information for details. Tie to V1 if unused.
COMP3 (Pin 3): Comparator Output 3. Real-time logic
output with weak 6μA pull-up to V2. Pulls high when V3
is above reset threshold. May be pulled greater than V2
using external pull-up. Leave open if unused.
COMP1 (Pin 4): Comparator Output 1. Real-time logic
output with weak 6μA pull-up to V2. Pulls high when V1
is above reset threshold. May be pulled greater than V2
using external pull-up. Leave open if unused.
V3 (Pin 5): Voltage Input 3. Select from 2.5V, 1.8V, 1.5V,
or ADJ. See Applications Information for details. Tie to
V1 if unused.
V1 (Pin 6): Voltage Input 1. Select from 5V or 3.3V. See
Applications Information for details. The greater of V1 or
V2 is also VCC for the device. Bypass this pin to ground
with a 0.1μF (or greater) capacitor.
CRT (Pin 7): Reset Timeout Capacitor. Attach an external
capacitor (CRT) to GND to set a reset timeout of 2ms/nF.
Leaving the pin open generates a minimum delay of
approximately 25μs. A 47nF capacitor generates a 94ms
reset delay time.
RST (Pin 8): Reset Output. Logic output with weak 6μA
pull-up to V2. Pulls low when any voltage input is below
the reset threshold and held low for the configured delay
time after all voltage inputs are above threshold. May be
pulled greater than V2 using external pull-up. Leave open
if unused.
T0 (Pin 9): Supply Tolerance Selection Input. Used in
conjunction with T1 (Pin 11). See Applications Information for tolerance selection chart (Table 2). Choose from
5%, 7.5%, 10% or 12.5%.
RDIS (Pin 10): Digital Input for RST Disable. A low input
on this pin forces RST to V2 (or to the pull-up voltage).
Useful for determining supply margins without issuing a
reset. A weak internal pull-up allows pin to be left open
for normal monitor operation.
T1 (Pin 11): Supply Tolerance Selection Input. Used in
conjunction with T0 (Pin 9). See Applications Information
for tolerance selection chart (Table 2). Choose from 5%,
7.5%, 10% or 12.5%.
GND (Pin 12): Ground.
VPG (Pin 13): Threshold Select Input. Connect to an
external 1% resistive divider between VREF and GND to
select 1 of 16 combinations and/or ±adjustable voltage
thresholds (see Table 1). Do not add capacitance on the
VPG pin.
VREF (Pin 14): Buffered Reference Voltage Output. A
1.210V nominal reference used for the mode selection
voltage (VPG) 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.
V4 (Pin 15): Voltage Input 4. Select from 1.8V, 1.5V, ADJ
or –ADJ. See Applications Information for details. Tie to
V1 if unused and configured for positive voltage.
V2 (Pin 16): Voltage Input 2. Select from 3.3V, 3V or 2.5V.
See Applications Information for details. The greater of V1,
V2 is also VCC for the device. Bypass this pin to ground
with a 0.1μF (or greater) capacitor. All status outputs are
weakly pulled up to V2.
COMP4 (Pin 17): Comparator Output 4. Real-time logic
output with weak 6μA pull-up to V2. Pulls high when V4
is above reset threshold. May be pulled greater than V2
using external pull-up. Leave open if unused.
COMP2 (Pin 18): Comparator Output 2. Real-time logic
output with weak 6μA pull-up to V2. Pulls high when V2
is above reset threshold. May be pulled greater than V2
using external pull-up. Leave open if unused.
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LTC2932
PIN FUNCTIONS
V6 (Pin 19): Adjustable Voltage Input 6. High impedance
comparator input with 0.5V typical threshold. See
Applications Information for details. Tie to V1 if unused.
COMP6 (Pin 20): Comparator Output 6. Real-time logic
output with weak 6μA pull-up to V2. Pulls high when V6
is above reset threshold. May be pulled greater than V2
using external pull-up. Leave open if unused.
BLOCK DIAGRAM
T0
V1
9
T1
BUFFER GAIN
ADJUST
11
POWER
DETECT
VCC
BUFFER
VREF
BANDGAP
REFERENCE
14
V2 V2
V2
VRTA
6μA
V2
6μA
VPG
13
A/D
COMP1
4
V2
6μA
4
COMP2
18
COMP3
3
6μA
V1
6
V2
16
V3
5
RESISTIVE
DIVIDER
MATRIX
4
–
4
+
COMP4
17
V2
CMP1-4
4
6μA
V2
COMP5
1
V4
15
6μA
V5
–
2
COMP6
20
+
V2
CMP5
6μA
VRTA
RST
4
+
CMP6
V6
19
CRT
–
8
ADJUSTABLE
RESET PULSE
GENERATOR
2μA
VCC
22μA
10μA
7
VCC
CRT
RDIS
10
2932 BD
GND
12
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LTC2932
APPLICATIONS INFORMATION
Supply Monitoring
The LTC2932 is a low power, high accuracy configurable
six supply monitoring circuit with six real-time monitor
outputs, a common reset output, a reset disable function
and selectable supply thresholds. An external capacitor
sets the reset timeout period. An external resistive divider
between VREF, VPG and GND selects 1 of 16 possible input
voltage monitor combinations. All six voltage inputs must
be above their predetermined thresholds for the reset not to
be activated. The LTC2932 asserts the reset and comparator outputs during power-up, power-down and brownout
conditions on any one of the voltage inputs.
Power-Up
The greater of V1 and V2 serves as the internal supply
voltage (VCC). On power-up, VCC powers the drive circuits
for the RST pin. This ensures that the RST output will be
low as soon as either V1 or V2 reaches 1V. The RST output
remains low until the part is configured. Once the voltage
thresholds are set, if any of the supply monitor inputs is
below its configured threshold, RST will be a logic low.
Once all the monitor inputs rise above their thresholds,
an internal timer is started and RST is released after the
delay time. If VCC < (V3 – 1.0V) and VCC < 2.4V, the V3
input impedance will be low (10kΩ typical).
Threshold Accuracy
Consider a 5V system with ±5% 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 little
more as explained below). A perfectly accurate supervisor
for this supply generates a reset at exactly 4.75V, however
no supervisor is this perfect. The actual reset threshold
of a supervisor varies over a specified band; the LTC2932
varies ±1.5% 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 specified tolerance band.
NOMINAL
SUPPLY
VOLTAGE
5V
SUPPLY TOLERANCE
MINIMUM
RELIABLE
SYSTEM
VOLTAGE
IDEAL
SUPERVISOR
THRESHOLD
4.75V
±1.5%
THRESHOLD
BAND
–5%
4.675V
–6.5%
4.6V
–8%
REGION OF POTENTIAL MALFUNCTION
Figure 1. 1.5% Threshold Accuracy Improves System Reliability
The LTC2932 has a ±1.5% reset threshold accuracy, so a
“5%” threshold is typically set to 6.5% below the nominal
input voltage. Therefore, a typical 5V, “5%” threshold is
4.675V. The threshold is guaranteed to lie in the band between 4.750V and 4.600V over temperature. The powered
system must work reliably down to the low end of the
threshold band, or risk malfunction before a reset signal
is properly issued.
A less accurate supervisor increases the required system
voltage margin and increases the probability of system
malfunction. The LTC2932’s ±1.5% specification improves
the reliability of the system over supervisors with wider
threshold tolerances.
Monitor Configuration and Tolerance Selection
Select the LTC2932 input voltage combination by placing
the recommended resistive divider from VREF to GND and
connecting the tap point to VPG, as shown in Figure 2.
Table 1 offers recommended 1% resistor values for each
of the 16 modes. The last column in Table 1 specifies
optimum VPG/VREF ratios (± 0.01), when configuring with
a ratiometric DAC.
LTC2932
VREF
VPG
GND
R1
1%
R2
1%
2932 F02
Figure 2. Mode Selection
2932fb
9
LTC2932
APPLICATIONS INFORMATION
Table 2. Tolerance Selection
Table 1. Voltage Threshold Modes*
MODE V1 (V) V2 (V) V3 (V) V4 (V) R1 (kΩ) R2 (kΩ)
VPG
VREF
T0
T1
TOLERANCE (%)
VREF (V)
1.210
Low
Low
5
0
5
3.3
ADJ
ADJ
Open
Short
0.000
Low
High
7.5
1.178
1
5
3.3
ADJ
–ADJ
93.1
9.53
0.094
High
Low
10
1.146
2
3.3
2.5
ADJ
ADJ
86.6
16.2
0.156
High
High
12.5
1.113
3
3.3
2.5
ADJ
–ADJ
78.7
22.1
0.219
4
3.3
2.5
1.5
ADJ
71.5
28
0.281
5
5
3.3
2.5
ADJ
66.5
34.8
0.344
VSUPPLY (V)
VTRIP (V)
R3 (kΩ)
R4 (kΩ)
6
5
3.3
2.5
1.8
59
40.2
0.406
12
11.25
2150
100
7
5
3.3
2.5
1.5
53.6
47.5
0.469
10
9.4
1780
100
8
5
3
2.5
ADJ
47.5
53.6
0.531
8
7.5
1400
100
7
1300
100
Table 3. Suggested 1% Resistor Values for the ADJ Inputs
9
5
3
ADJ
ADJ
40.2
59
0.594
7.5
10
3.3
2.5
1.8
1.5
34.8
66.5
0.656
6
5.6
1020
100
4.725
845
100
3.055
511
100
11
3.3
2.5
1.8
ADJ
28
71.5
0.719
5
12
3.3
2.5
1.8
–ADJ
22.1
78.7
0.781
3.3
13
5
3.3
1.8
–ADJ
16.2
86.6
0.844
14
5
3.3
1.8
ADJ
9.53
93.1
0.906
15
5
3
1.8
ADJ
Short
Open
1
*V5 and V6 are always adjustable (ADJ).
At power-up, once V1 or V2 reaches 2.4V, the monitor
enters a setup period of approximately 150μs. During the
setup time, the voltage on the VPG pin is sampled and the
monitor is configured to the desired input combination. The
comparators are enabled and supply monitoring begins.
Do not add capacitance to the VPG pin.
The two supply tolerance inputs, T0 and T1, configure the
global supply tolerance. Larger tolerances provide more
headroom by lowering the trip thresholds. Table 2 lists the
input combinations for each of the tolerance modes.
3
2.82
464
100
2.5
2.325
365
100
1.8
1.685
237
100
1.5
1.410
182
100
1.2
1.120
124
100
1
0.933
86.6
100
0.9
0.840
68.1
100
*See Figure 3.
Table 4. Suggested 1% Resistor Values for the –ADJ Inputs
VSUPPLY (V)
VTRIP (V)
R3 (kΩ)
R4 (kΩ)
–2
–1.87
187
121
–5
–4.64
464
121
–5.2
–4.87
487
121
–10
–9.31
931
121
–12
–11.30
1130
121
*See Figure 4.
VTRIP
LTC2932
R3
1%
VREF
V3, V4, V5 OR V6
R4
1%
R4
1%
LTC2932
V4
R3
1%
+
–
0.5V
5% TOLERANCE MODE
VTRIP
2932 F03
Figure 3. Setting the Positive Adjustable Trip Point
2932 F04
Figure 4. Setting the Negative Adjustable Trip Point
2932fb
10
LTC2932
APPLICATIONS INFORMATION
Using the Adjustable Thresholds
The reference inputs on the V3 and/or V4 comparators
are set to 0.5V when the positive adjustable modes are
selected (Figure 3). The reference inputs on the V5 and V6
comparators are always set to 0.5V. 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, V6). Calculate
the trip voltage from:
R3 VTRIP = 0.5V • 1+ R4 In the negative adjustable mode, the reference level on the
V4 comparator is connected to ground (Figure 4). The tap
point on an external resistive divider, connected between
the negative voltage being sensed and the VREF pin, is
connected to the high impedance adjustable input (V4).
VREF provides the necessary level shift required to operate
at ground. The negative trip voltage is calculated from:
VTRIP = −VREF •
R3 ; V = 1.210V Nominal
REF
R4
T0, T1 Low (5% Tolerance Mode)
Once the resistor divider is set in the 5% tolerance mode,
there is no need to change the divider for the other tolerance modes (7.5%, 10%, 12.5%) because VREF is scaled
accordingly, moving the trip point in –2.5% increments.
In a negative adjustable application, the minimum value for
R4 is limited by the sourcing capability of VREF (±1mA).
With no other load on VREF, R4 (minimum) is:
1.210V
= 1.210kΩ
1mA
Tables 3 and 4 offer suggested 1% resistor values for various positive and negative supply adjustable applications
assuming 5% monitor thresholds.
Although all six supply monitor comparators have builtin glitch immunity, bypass capacitors on V1 and V2 are
recommended because the greater of V1 or V2 is also the
VCC for the device. Filter capacitors on the V3, V4, V5 and
V6 inputs are allowed.
Power-Down
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
1V. If the bandgap reference becomes invalid (VCC < 2V
typical), the LTC2932 will enter the 150μs setup period
when VCC rises above 2.4V (max).
Selecting the Reset Timing Capacitor
The reset timeout period is adjustable in order to
accommodate a variety of microprocessor applications.
The reset timeout period, tRST, is adjusted by connecting
a capacitor, CRT, between the CRT pin and ground. The
value of this capacitor is determined by:
CRT =
tRST
= 500 [pF / ms] • tRST
2MΩ
Leaving the CRT pin unconnected generates a minimum
reset timeout of approximately 25μs. Maximum reset
timeout 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.
Reset Disable
Under conventional operation, RST and COMPn will go low
when Vn is below its threshold. At any time, the RDIS pin
can be pulled low, overriding the reset operation and forcing
the RST pin high. This feature is useful when determining
supply margins under processor control since the reset
command will not be invoked. The RDIS pin is connected
to a weak internal pull-up to VCC (10μA typical), allowing
the pin to be left open if unused.
2932fb
11
LTC2932
APPLICATIONS INFORMATION
Six Supply Monitor with Hysteresis
The LTC2932 monitors six supply voltages in Figure 5 and
is configured to mode 6 (see Table 1). Supply tolerance
inputs T0 and T1 are tied to RST. As the LTC2932 powers
up, RST is low, which keeps the tolerance at 5%. After all
six inputs exceed their 5% threshold voltages, RST pulls
high. This changes the supply tolerance to 12.5%. If any of
the input voltages drop below the 12.5% threshold level,
reset is asserted. The push button on V6 also allows for
a manual reset when pressed.
Five Supply Power-up Sequencer
In Figure 6, the LTC2932’s real-time COMP outputs are
used to enable DC/DC converters sequentially. The system
is powered by a 12V source.
The system is started when the push-button is pressed and
the LTC2950-1 brings the RUN pin of the LTM4600 high.
Subsequently, the LTM4600 generates a 5V output which
applies power to each of the 4 DC/DC converters.
The LTC2932 is configured to mode 13 and a 12.5%
threshold (see Tables 1 and 2). When the threshold is
reached on V1, COMP1 pulls high. COMP1 then enables
the 3.3V converter first. When the threshold is reached
on V2, COMP2 pulls high and enables the 1.8V converter
next. When all the converters have been enabled and are
good, COMP5 pulls high. RST pulls high 9.4ms after
COMP5. Figure 7 shows the power-up sequence of the
five supplies and the DONE and RST outputs.
If the KILL input on the LTC2950-1 does not receive a logic
high from the RST output within 512ms of initial power-up,
EN pulls low and the LTM4600 is powered down.
In the event that the external 12V supply drops below 9.6V,
COMP6 and RST pull low. The LTC2950-1 then receives
a logic low on the KILL input, which powers down the
LTM4600 and the sequencing circuit.
5V
10k
0.1μF
10k
10k
10k
10k
10k
10k
LTC2932
3.3V
2.5V
1.8V
2150k 1%
12V
1.2V
124k 1%
V1
COMP1
V2
COMP2
V3
COMP3
V4
COMP4
V5
COMP5
V6
COMP6
RST
VREF
R1
59k
1%
T0
GND CRT
PUSHBUTTON
100k
1%
R2
40.2k
1%
100k
1%
*OPTIONAL FOR EXTENDED ESD TOLERANCE
2932 F05
T1
VPG
10k*
SYSTEM
LOGIC
RDIS
CRT
47nF
tRST = 94ms
Figure 5. Six Supply Monitor with Hysteresis
5% Tolerance (Supplies Rising)
12.5% Tolerance (After RST Goes High)
2932fb
12
LTC2932
APPLICATIONS INFORMATION
12V (9.6V THRESHOLD)
LTM4600
VIN
VOUT
5V
5V
RUN
VIN
VIN
LTC2950-1
VIN
INT
PB
LT3028
VOUT 1.8V
1.8V
SYSTEM
LOGIC
LTC3704
VOUT –5.2V
VIN
10k
–5.2V
RUN/UVLO
VIN
10k
3.3V
SHDN
10k
KILL
10k
SHDN
10k
EN
10k
LT3028
VOUT 3.3V
LT3028
VOUT 2.5V
2.5V
SHDN
DONE
12V
SUPPLY
STATUS
COMP1 COMP2 COMP3 COMP4 COMP5 COMP6
2932 F06
V1
10k
0.1μF
365k
1%
487k
1%
1820k
1%
V2
T0
V3
T1
V4
V5
LTC2932
RDIS
V6
RST
100k
1%
100k
1%
121k
1%
VREF
R1
16.2k
1%
R2
86.6k
1%
VPG
CRT
GND
4.7nF
tRST = 9.4ms
Figure 6. Five Supply 12.5% Tolerance Power-Up Sequencer with Pushbutton
2932fb
13
LTC2932
APPLICATIONS INFORMATION
PB
5V
3.3V
2.5V
1.8V
–5.2V
DONE
RST
2932 FO7
Figure 7. Five Supply Power-Up Sequencing (Based on Circuit in Figure 6)
2932fb
14
LTC2932
PACKAGE DESCRIPTION
F Package
20-Lead Plastic TSSOP (4.4mm)
(Reference LTC DWG # 05-08-1650)
6.40 – 6.60*
(.252 – .260)
1.05 p0.10
6.60 p0.10
20 19 18 17 16 15 14 13 12 11
4.50 p0.10
0.45 p0.05
6.40
(.252)
BSC
0.65 BSC
1 2 3 4 5 6 7 8 9 10
RECOMMENDED SOLDER PAD LAYOUT
4.30 – 4.50**
(.169 – .177)
0.09 – 0.20
(.0035 – .0079)
0.50 – 0.75
(.020 – .030)
NOTE:
1. CONTROLLING DIMENSION: MILLIMETERS
MILLIMETERS
2. DIMENSIONS ARE IN
(INCHES)
0.25
REF
1.10
(.0433)
MAX
0o – 8o
0.65
(.0256)
BSC
0.19 – 0.30
(.0075 – .0118)
TYP
0.05 – 0.15
(.002 – .006)
F20 TSSOP 0204
3. DRAWING NOT TO SCALE
*DIMENSIONS DO NOT INCLUDE MOLD FLASH. MOLD FLASH
SHALL NOT EXCEED .152mm (.006") PER SIDE
**DIMENSIONS DO NOT INCLUDE INTERLEAD FLASH. INTERLEAD
FLASH SHALL NOT EXCEED .254mm (.010") PER SIDE
2932fb
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
LTC2932
TYPICAL APPLICATION
Five Supply Adjustable Threshold Monitor with LED Indicators
5V
0.1μF
1k
1k
1k
1k
1k
LTC2932
3.3V
2150k 1%
12V
1.2V
124k 1%
1V
86.6k 1%
V1
COMP1
V2
COMP2
V3
COMP3
V4
COMP4
V5
COMP5
V6
COMP6
RST
VREF
100k
1%
100k
1%
100k
1%
TO SYSTEM RESET
RDIS
CRT
VPG GND
2932 TA02
T0
T1
CRT
47nF
tRST = 94ms
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
LTC1326
Micropower Triple Supply Monitor for 5V/2.5V, 3.3V and ADJ
4.725V, 3.118V, 1V Threshold (±0.75%) and ADJ
LTC1728
Micropower Triple Supply Monitor with Open-Drain Reset
5-Lead SOT-23 Package
LTC2900
Programmable Quad Supply Monitor
Adjustable Reset, 10-Lead MSOP and DFN Packages
LTC2901
Programmable Quad Supply Monitor
Adjustable Reset and Watchdog Timer
LTC2902
Programmable Quad Supply Monitor
Adjustable Reset and Tolerance (5%, 7.5%, 10%, or 12.5%)
LTC2903
Precision Quad Supply Monitor
6-Lead SOT-23 Package
LTC2904-LTC2907
Three-State Programmable Precision Dual Supply Monitor
8-Lead SOT-23 and DFN Packages
LTC2908
Precision Six Supply Monitor (Four Fixed & Two Adjustable)
8-Lead TSOT-23 and DFN Packages
LTC2909
Precision Triple/Dual Input UV, OV and Negative Voltage Monitor
Shunt Regulated VCC Pin, Adjustable Threshold and Reset,
8-Lead SOT-23 and DFN Packages
LTC2910
Precision Octal Positive/Negative Voltage Supply Monitor
16-Lead SSOP and 5mm × 3mm DFN Packages, H-Grade
Temperature Range
LTC2912-LTC2914
Single/Dual/Quad UV and OV Voltage Monitors
Separate VCC Pin, Adjustable Reset Timer,
H-Grade Temperature Range
LTC2915-LTC2918
Single Supply Monitor with 27 Pin-Selectable Thresholds
Manual Reset, Watchdog, TSOT-8/MSOP-10 and
3mm × 2mm DFN Packages, H-Grade Temperature Range
LTC2928
Quad Power Supply Sequencer and Supervisor
Easily Configure Power Management without Software,
36-Lead 5mm × 7mm QFN and SSOP Packages
LTC2930
Configurable Six Supply Monitor with Adjustable Reset Timer,
Manual Reset
3mm × 3mm DFN-12 Package, H-Grade Temperature Range
LTC2931
Configurable Six Supply Monitor with Adjustable Reset and
Watchdog Timers
TSSOP-20 Package, H-Grade Temperature Range,
Individual Supply Comparator Outputs
2932fb
16 Linear Technology Corporation
LT 0408 REV B • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507
●
www.linear.com
© LINEAR TECHNOLOGY CORPORATION 2008
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