LTC2914
Quad UV/OV
Positive/Negative
Voltage Monitor
Description
Features
Monitors Four Voltages Simultaneously
n Adjustable UV and OV Trip Values
n Guaranteed Threshold Accuracy: ±1.5% of
Monitored Voltage over Temperature
n Input Glitch Rejection
n Monitors up to Two Negative Voltages
n Buffered 1V Reference Output
n Adjustable Reset Timeout with Timeout Disable
n 62µA Quiescent Current
n Open-Drain OV and UV Outputs
n Guaranteed OV and UV for V
CC ≥ 1V
n Available in 16-Lead SSOP and 16-Lead
(5mm × 3mm) DFN Packages
n
Applications
The LTC®2914 is a quad input voltage monitor intended for
monitoring multiple voltages in a variety of applications.
Dual inputs for each monitored voltage allow monitoring four separate undervoltage (UV) conditions and four
separate overvoltage (OV) conditions. All monitors share
a common undervoltage output and a common overvoltage output. The LTC2914-1 has latching capability for the
overvoltage output. The LTC2914-2 has functionality to
disable both the overvoltage and undervoltage outputs.
Polarity selection and a buffered reference allow monitoring up to two separate negative voltages. A three-state
input pin allows setting the polarity of two inputs without
requiring any external components. Glitch filtering ensures
reliable reset operation without false or noisy triggering.
The LTC2914 provides a precise, versatile, space-conscious, micropower solution for voltage monitoring.
Desktop and Notebook Computers
n Network Servers
n Core, I/O Voltage Monitors
n
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.
Typical Application
Quad UV/OV Supply Monitor,10% Tolerance, 5V, 3.3V, 2.5V, 1.8V
Input Threshold Voltage
vs Temperature
0.1μF
44.2k
1k
4.53k
0.505
VCC
SEL
VL1
VH2
OV
0.504
VH1
27.4k
LTC2914-1
1k
VL2
4.53k
SYSTEM
19.6k
REF
VH3
1k
UV
LATCH
12.4k
THRESHOLD VOLTAGE, VOUT (V)
P0WER
SUPPLIES
5V
3.3V
2.5V
1.8V
4.53k
0.500
0.499
0.498
0.497
0.495
–50
1k
VL4
GND
0.502
0.501
0.496
VL3
VH4
4.53k
0.503
TMR
–25
25
50
0
TEMPERATURE (°C)
75
100
2914 TA01b
CTMR
22nF
2914 TA01a
TIMEOUT = 200ms
2914fc
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1
LTC2914
Absolute Maximum Ratings (Notes 1, 2)
Terminal Voltages
VCC (Note 3).............................................. –0.3V to 6V
OV, UV.................................................... –0.3V to 16V
TMR...........................................–0.3V to (VCC + 0.3V)
VLn, VHn, LATCH, DIS, SEL....................–0.3V to 7.5V
Terminal Currents
IVCC.....................................................................10mA
Reference Load Current (IREF)............................ ±1mA
IUV, IOV................................................................10mA
Operating Temperature Range
LTC2914C................................................. 0°C to 70°C
LTC2914I..............................................–40°C to 85°C
LTC2914H........................................... –40°C to 125°C
Storage Temperature Range................... –65°C to 150°C
Lead Temperature (Soldering, 10 sec)
SSOP................................................................. 300°C
Pin Configuration
TOP VIEW
TOP VIEW
VH1
1
16 VCC
VH1
1
16 VCC
VL1
2
15 TMR
VL1
2
15 TMR
VH2
3
14 SEL
VH2
3
14 SEL
VL2
4
13 LATCH/DIS
VL2
4
13 LATCH/DIS
12 UV
VH3
5
12 UV
VH3
5
17
VL3
6
11 OV
VL3
6
11 OV
VH4
7
10 REF
VH4
7
10 REF
VL4
8
9
VL4
8
9
GND
GND
GN PACKAGE
16-LEAD PLASTIC SSOP
TJMAX = 150°C, θJA = 110°C/W
DHC PACKAGE
16-LEAD (5mm × 3mm) PLASTIC DFN
TJMAX = 150°C, θJA = 43.5°C/W
EXPOSED PAD (PIN 17)
PCB GND CONNECTION OPTIONAL
Order Information
LEAD FREE FINISH
TAPE AND REEL
PART MARKING*
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LTC2914CDHC-1#PBF
LTC2914CDHC-1#TRPBF
29141
16-Lead Plastic (5mm × 3mm) DFN
0°C to 70°C
LTC2914IDHC-1#PBF
LTC2914IDHC-1#TRPBF
29141
16-Lead Plastic (5mm × 3mm) DFN
–40°C to 85°C
LTC2914HDHC-1#PBF
LTC2914HDHC-1#TRPBF
29141
16-Lead Plastic (5mm × 3mm) DFN
–40°C to 125°C
LTC2914CDHC-2#PBF
LTC2914CDHC-2#TRPBF
29142
16-Lead Plastic (5mm × 3mm) DFN
0°C to 70°C
LTC2914IDHC-2#PBF
LTC2914IDHC-2#TRPBF
29142
16-Lead Plastic (5mm × 3mm) DFN
–40°C to 85°C
LTC2914HDHC-2#PBF
LTC2914HDHC-2#TRPBF
29142
16-Lead Plastic (5mm × 3mm) DFN
–40°C to 125°C
LTC2914CGN-1#PBF
LTC2914CGN-1#TRPBF
29141
16-Lead Plastic SSOP
0°C to 70°C
LTC2914IGN-1#PBF
LTC2914IGN-1#TRPBF
2914I1
16-Lead Plastic SSOP
–40°C to 85°C
LTC2914HGN-1#PBF
LTC2914HGN-1#TRPBF
2914H1
16-Lead Plastic SSOP
–40°C to 125°C
2914fc
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LTC2914
Order Information
LEAD FREE FINISH
TAPE AND REEL
PART MARKING*
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LTC2914CGN-2#PBF
LTC2914CGN-2#TRPBF
29142
16-Lead Plastic SSOP
0°C to 70°C
LTC2914IGN-2#PBF
LTC2914IGN-2#TRPBF
2914I2
16-Lead Plastic SSOP
–40°C to 85°C
LTC2914HGN-2#PBF
LTC2914HGN-2#TRPBF
2914H2
16-Lead Plastic SSOP
–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
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/
Electrical Characteristics
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCC = 3.3V, VLn = 0.45V, VHn = 0.55V, LATCH = VCC, SEL = VCC,
DIS = Open unless otherwise noted. (Note 2)
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
l
6.2
6.6
6.9
–40ºC < TA < 125ºC
l
6.2
ICC = 2mA to 10mA
l
VSHUNT
VCC Shunt Regulator Voltage
ICC = 5mA
ΔVSHUNT
VCC Shunt Regulator Load Regulation
VCC
Supply Voltage (Note 3)
VCCR(MIN)
Minimum VCC Output Valid
DIS = 0V
l
VCC(UVLO)
Supply Undervoltage Lockout
VCC Rising, DIS = 0V
l
1.9
2
ΔVCC(UVHYST)
Supply Undervoltage Lockout Hysteresis
DIS = 0V
l
5
25
50
mV
62
100
µA
1
1.015
V
l
UNITS
V
6.6
7.0
V
200
300
mV
2.3
VSHUNT
V
1
V
2.1
V
ICC
Supply Current
VCC = 2.3V to 6V
l
VREF
Reference Output Voltage
IVREF = ±1mA
l
0.985
–40ºC < TA < 125ºC
l
0.985
1
1.020
VUOT
Undervoltage/Overvoltage Voltage Threshold
l
492
500
508
mV
tUOD
Undervoltage/Overvoltage Voltage Threshold
to Output Delay
l
50
125
500
µs
IVHL
VHn, VLn Input Current
l
±15
nA
–40ºC < TA < 125ºC
l
±30
nA
CTMR = 1nF
l
6
8.5
12.5
ms
–40ºC < TA < 125ºC
l
6
8.5
14
ms
1.2
tUOTO
UV/OV Time-Out Period
VHn = VUOT – 5mV or VLn = VUOT + 5mV
V
VLATCH(IH)
OV Latch Clear Input High
l
VLATCH(IL)
OV Latch Clear Threshold Input Low
l
0.8
V
ILATCH
LATCH Input Current
l
±1
µA
VLATCH > 0.5V
VDIS(IH)
DIS Input High
l
VDIS(IL)
DIS Input Low
l
IDIS
DIS Input Current
VDIS > 0.5V
l
1
ITMR(UP)
TMR Pull-Up Current
VTMR = 0V
l
–40ºC < TA < 125ºC
l
VTMR = 1.6V
–40ºC < TA < 125ºC
ITMR(DOWN)
TMR Pull-Down Current
V
1.2
V
0.8
V
2
3
µA
–1.3
–2.1
–2.8
µA
–1.2
–2.1
–2.8
µA
l
1.3
2.1
2.8
µA
l
1.2
2.1
2.8
µA
2914fc
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3
LTC2914
Electrical Characteristics
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCC = 3.3V, VLn = 0.45V, VHn = 0.55V, LATCH = VCC, SEL = VCC,
DIS = Open unless otherwise noted. (Note 2)
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
VTMR(DIS)
Timer Disable Voltage
Referenced to VCC
l
–180
–270
VOH
Output Voltage High UV/OV
VCC = 2.3V, IUV/OV = –1µA
l
1
VOL
Output Voltage Low UV/OV
VCC = 2.3V, IUV/OV = 2.5mA
VCC = 1V, IUV = 100µA
l
l
MAX
UNITS
mV
V
0.1
0.01
0.3
0.15
V
V
0.4
V
Three-State Input SEL
VIL
Low Level Input Voltage
l
VIH
High Level Input Voltage
l
VZ
Pin Voltage when Left in Hi-Z State
1.4
V
ISEL = ±10µA
l
0.7
0.9
1.1
V
–40ºC < TA < 125ºC
l
0.6
0.9
1.2
V
±25
µA
±30
µA
ISEL
SEL High, Low Input Current
ISEL(MAX)
Maximum SEL Input Current
SEL Tied to Either VCC or GND
l
tPW
Latch Clear Pulse Width
(Note 4)
l
l
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.
2
µs
Note 3: VCC maximum pin voltage is limited by input current. Since the
VCC pin has an internal 6.5V shunt regulator, a low impedance supply that
exceeds 6V may exceed the rated terminal current. Operation from higher
voltage supplies requires a series dropping resistor. See Applications
Information.
Note 4: Guaranteed by design, not subject to test.
2914fc
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LTC2914
timing diagrams
VHn Monitor Timing
VHn
VLn Monitor Timing
VUOT
tUOD
tUOTO
tUOD
1V
UV
VUOT
VLn
tUOTO
1V
OV
2914 TD01
2914 TD02
VHn Monitor Timing (TMR Pin Strapped to VCC)
VHn
VLn Monitor Timing (TMR Pin Strapped to VCC)
VUOT
tUOD
tUOD
tUOD
1V
UV
VUOT
VLn
tUOD
1V
OV
2914 TD03
2914 TD04
NOTE: WHEN AN INPUT IS CONFIGURED AS A NEGATIVE SUPPLY MONITOR, VHn WILL TRIGGER AN OV CONDITION AND VLn WILL TRIGGER A UV CONDITION
typical performance characteristics
Specifications are at TA = 25°C, VCC = 3.3V unless otherwise noted.
Input Threshold Voltage
vs Temperature
75
0.505
6.8
VCC = 5V
70
0.503
65
0.501
0.500
0.499
0.498
60
55
50
0.497
VCC = 3.3V
VCC (V)
0.502
ICC (μA)
THRESHOLD VOLTAGE, VOUT (V)
0.504
–25
25
50
0
TEMPERATURE (°C)
75
100
2914 G01
40
–50
6.7
10mA
6.6
5mA
6.5
2mA
1mA
6.4
VCC = 2.3V
200μA
6.3
45
0.496
0.495
–50
VCC Shunt Voltage
vs Temperature
Supply Current vs Temperature
–25
0
25
50
TEMPERATURE (°C)
100
75
2914 G02
6.2
–50
–25
0
25
50
TEMPERATURE (°C)
75
100
2914 G03
2914fc
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5
LTC2914
Typical Performance Characteristics
Specifications are at TA = 25°C, VCC = 3.3V unless otherwise noted.
Buffered Reference Voltage
vs Temperature
VCC Shunt Voltage vs ICC
6.75
Transient Duration
vs Comparator Overdrive
1.005
700
6.65
VCC (V)
6.55
25°C
6.45
–40°C
85°C
6.35
TYPICAL TRANSIENT DURATION (μs)
REFERENCE VOLTAGE, VREF (V)
1.004
1.003
1.002
1.001
1.000
0.999
0.998
0.997
0.996
6.25
–2
2
0
6
4
ICC (mA)
8
10
12
0.995
–50
–25
25
50
0
TEMPERATURE (°C)
Reset Timeout Period
vs Temperature
8
0.4
UV WITH
10k PULL-UP
0.2
0
100
0.2
0.6
0.8
0.4
SUPPLY VOLTAGE, VCC (V)
0
2914 G07
3
2
85°C
0.6
25°C
–40°C
0.4
0.2
3
4
2
SUPPLY VOLTAGE, VCC (V)
5
2914 G10
3
4
2
SUPPLY VOLTAGE, VCC (V)
0
5
Reset Timeout Period
vs Capacitance
UV AT 50mV
1
1
2914 G09
UV/OV TIMEOUT PERIOD, tUOTO (ms)
UV/OV, VOL (V)
PULL-DOWN CURRENT, IUV (mA)
UV AT 150mV
0
10000
0.8
1
0
1.0
1.0
VHn = 0.45V
SEL = VCC
0
2
UV/OV Voltage Output Low
vs Output Sink Current
4
0
3
2914 G08
UV, ISINK vs VCC
5
VHn = 0.55V
SEL = VCC
1
UV WITHOUT
10k PULL-UP
7
75
VCC = 2.3V
4
UV VOLTAGE (V)
9
VCC = 6V
100
UV Output Voltage vs VCC
0.6
UV VOLTAGE (V)
UV/OV TIMEOUT PERIOD, tUOTO (ms)
11
0
25
50
TEMPERATURE (°C)
200
5
VCC
–25
300
UV Output Voltage vs VCC
CTMR = 1nF
6
–50
400
2914 G06
0.8
10
RESET OCCURS
ABOVE CURVE
2914 G05
2914 G04
12
500
0
1
10
100
0.1
COMPARATOR OVERDRIVE PAST THRESHOLD (%)
100
75
600
0
5
10
15
20
IUV/OV (mA)
25
30
2914 G11
1000
100
10
1
0.1
1
10
100
TMR PIN CAPACITANCE, CTMR (nF)
1000
2914 G12
2914fc
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LTC2914
Pin Functions
DIS (Pin 13, LTC2914-2): Output Disable Input. Disables
the OV and UV output pins. When DIS is pulled high, the
OV and UV pins are not asserted except during a UVLO
condition. Pin has a weak (2µA) internal pull-down to GND.
Leave pin open if unused.
Exposed Pad (Pin 17, DFN Package): Exposed Pad may
be left open or connected to device ground.
GND (Pin 9): Device Ground
LATCH (Pin 13, LTC2914-1): OV Latch Clear/Bypass Input.
When pulled low, OV is latched when asserted. When
pulled high, OV latch is cleared. While held high, OV has
the same delay and output characteristics as UV.
OV (Pin 11): Overvoltage Logic Output. Asserts low when
any positive polarity input voltage is above threshold or
any negative polarity input voltage is below threshold.
Latched low (LTC2914-1). Held low for an adjustable
delay time after all inputs are valid (LTC2914-2). Pin has
a weak pull-up to VCC and may be pulled above VCC using
an external pull-up. Leave pin open if unused.
REF (Pin 10): Buffered Reference Output. 1V reference
used for the offset of negative-monitoring applications.
The buffered reference sources and sinks up to 1mA. The
reference drives capacitive loads up to 1nF. Larger capacitive loads may cause instability. Leave pin open if unused.
SEL (Pin 14): Input Polarity Select Three-State Input.
Connect to VCC, GND or leave unconnected in open state
to select one of three possible input polarity combinations
(refer to Table 1).
TMR (Pin 15): Reset Delay Timer. Attach an external
capacitor (CTMR) of at least 10pF to GND to set a reset
delay time of 9ms/nF. A 1nF capacitor will generate an
8.5ms reset delay time. Tie pin to VCC to bypass timer.
UV (Pin 12): Undervoltage Logic Output. Asserts low when
any positive polarity input voltage is below threshold or
any negative polarity input voltage is above threshold.
Held low for an adjustable delay time after all voltage
inputs are valid. Pin has a weak pull-up to VCC and may
be pulled above VCC using an external pull-up. Leave pin
open if unused.
VCC (Pin 16): Supply Voltage. Bypass this pin to GND with
a 0.1µF (or greater) capacitor. Operates as a direct supply
input for voltages up to 6V. Operates as a shunt regulator for supply voltages greater than 6V and must have a
resistance between the pin and the supply to limit input
current to no greater than 10mA. When used without a
current-limiting resistance, pin voltage must not exceed 6V.
VH1/VH2 (Pin 1/Pin 3): Voltage High Inputs 1 and 2. When
the voltage on this pin is below 0.5V, an undervoltage
condition is triggered. Tie pin to VCC if unused.
VH3/VH4 (Pin 5/Pin 7): Voltage High Inputs 3 and 4. The
polarity of the input is selected by the state of the SEL pin
(refer to Table 1). When the monitored input is configured
as a positive voltage, an undervoltage condition is triggered when the pin is below 0.5V. When the monitored
input is configured as a negative voltage, an overvoltage
condition is triggered when the pin is below 0.5V. Tie pin
to VCC if unused.
VL1/VL2 (Pin 2/Pin 4): Voltage Low Inputs 1 and 2. When
the voltage on this pin is above 0.5V, an overvoltage condition is triggered. Tie pin to GND if unused.
VL3/VL4 (Pin 6/Pin 8): Voltage Low Inputs 3 and 4. The
polarity of the input is selected by the state of the SEL pin
(refer to Table 1). When the monitored input is configured
as a positive voltage, an overvoltage condition is triggered
when the pin is above 0.5V. When the monitored input is
configured as a negative voltage, an undervoltage condition is triggered when the pin is above 0.5V. Tie pin to
GND if unused.
2914fc
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7
LTC2914
Block Diagram
16
15
VCC
1
2
3
4
5
VH1
VL1
VH2
VL2
VH3
TMR
–
+
VCC
400k
OSCILLATOR
UV
–
+
12
UV PULSE
GENERATOR
–
+
VCC
UVLO
+
–
–
+
2V
400k
VCC
OV PULSE
GENERATOR
DISABLE
UVLO
OV
11
–
+
OV LATCH
CLEAR/BYPASS
6
7
VL3
VH4
–
+
LTC2914-1
–
+
+
–
+
–
8
VL4
REF
1V
DIS
1V
13
2μA
GND
1V
BUFFER
13
LTC2914-2
–
+
0.5V
10
LATCH
9
THREE-STATE
POLARITY
DECODER
SEL
14
2914 -1 BD
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LTC2914
applications information
Voltage Monitoring
The LTC2914 is a low power quad voltage monitoring circuit with four undervoltage and four overvoltage inputs. A
timeout period that holds OV or UV asserted after all faults
have cleared is adjustable using an external capacitor and
is externally disabled.
The three-state input pin SEL is connected to GND, VCC or
left unconnected during normal operation. When the pin
is left unconnected, the maximum leakage allowed from
the pin is ±10µA to ensure it remains in the open state.
Table 1 shows the three possible selections of polarity
based on the SEL pin connection.
Each voltage monitor has two inputs (VHn and VLn) for
detecting undervoltage and overvoltage conditions. When
configured to monitor a positive voltage Vn using the
3‑resistor circuit configuration shown in Figure 1, VHn is
connected to the high-side tap of the resistive divider and
VLn is connected to the low-side tap of the resistive divider.
If an input is configured as a negative voltage monitor, the
outputs UVn and OVn in Figure 1 are swapped internally. Vn
is then connected as shown in Figure 2. Note, VHn is still
connected to the high-side tap and VLn is still connected
to the low-side tap.
Table 1. Voltage Polarity Programming (VUOT = 0.5V Typical)
Polarity Selection
The following 3-step design procedure allows selecting
appropriate resistances to obtain the desired UV and OV trip
points for the positive voltage monitor circuit in Figure 1
and the negative voltage monitor circuit in Figure 2. 1%
resistor tolerances are suggested to maintain the ±1.5%
threshold accuracy.
V3 INPUT
V4 INPUT
VCC
Positive
Positive
VH3 < VUOT → UV
VL3 > VUOT → OV
VH4 < VUOT → UV
VL4 > VUOT → OV
Positive
Negative
VH3 < VUOT → UV
VL3 > VUOT → OV
VH4 < VUOT → OV
VL4 > VUOT → UV
Negative
Negative
VH3 < VUOT → OV
VL3 > VUOT → UV
VH4 < VUOT → OV
VL4 > VUOT → UV
Open
GND
3-Step Design Procedure
LTC2914
+
The three-state polarity-select pin (SEL) selects one of three
possible polarity combinations for the input thresholds,
as described in Table 1. When an input is configured for
negative supply monitoring, VHn is configured to trigger an
overvoltage condition and VLn is configured to trigger an
undervoltage condition. With this configuration, an OV condition occurs when the supply voltage is more negative than
the configured threshold and a UV condition occurs when
the voltage is less negative than the configured threshold.
SEL
REF
–
Vn
RC
LTC2914
VHn
–
+
+
–
RB
VLn
RA
UVn
+
–
+
+
–
RB
OVn
VLn
RA
OVn
0.5V
–
+
UVn
RC
2914 F01
Figure 1. 3-Resistor Positive UV/OV Monitoring Configuration
1V
–
VHn
0.5V
+
–
Vn
2914 F02
Figure 2. 3-Resistor Negative UV/OV Monitoring Configuration
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9
LTC2914
Applications Information
For positive supply monitoring, Vn is the desired nominal operating voltage, Ind is the desired nominal current
through the resistive divider, Ina is the resistive divider
current calculated using the 1% resistor RA. VOV is the
desired overvoltage trip point and VUV is the desired
undervoltage trip point.
V1
5V ±10%
RC
442k
RB
10k
RA
45.3k
For negative supply monitoring, to compensate for the 1V
reference, 1V must be subtracted from Vn, VOV and VUV
before using each in the following equations.
RA is chosen to set the desired trip point for the overvoltage monitor.
RA =
0.5V Vn
•
In VOV
(1)
1B. Calculate Ina
Ina =
VCC
VH1
OV
LTC2914
VL1
UV
SEL
GND
2914 F03
Figure 3. Positive Supply Monitor
1A. Find RA to set the OV trip point of the monitor.
1A. Choose RA to obtain the desired OV trip point
VCC
5V
RA =
0.5V 5V
•
≈ 45.3k
10µA 5.5V
1B. Calculate Ina
Ina =
0.5V 5V
•
= 10.034µA
45.3k 5.5V
2. Find RB to set the UV trip point of the monitor.
0.5V Vn
•
R A VOV
RB =
0.5V
5V
•
– 45.3k ≅ 10k
10.034µA 4.5V
2. Choose RB to obtain the desired UV trip point
3. Determine RC to complete the design.
Once RA is known, RB is chosen to set the desired trip
point for the undervoltage monitor.
RB =
0.5V Vn
•
–R A
Ina VUV
(2)
Once RA and RB are known, RC is determined by:
RC =
Vn
–R A –RB
Ina
5V
– 45.3k −10k ≈ 442k
10.034µA
Negative Voltage Monitor Example 1
3. Choose RC to Complete the Design
RC =
(3)
If any of the variables Vn, Ina, Ind, VUV or VOV change, then
each step must be recalculated.
A negative voltage monitor application is shown in Figure 4.
The monitored voltage is a –5V ±10% supply. Nominal
current in the resistive divider is 10µA. For the negative
case, 1V is subtracted from Vn, VOV and VUV.
1A. Find RA to set the OV trip point of the monitor.
Positive Voltage Monitor Example
A positive voltage monitor application is shown in Figure 3.
The monitored voltage is a 5V ±10% supply. Nominal
current in the resistive divider is 10µA.
RA =
0.5V –5V – 1V
•
≈ 46.4k
10µA –5.5V – 1V
1B. Calculate Ina
I no •
0.5V –5V – 1V
•
= 9.947µA
46.4k –5.5V – 1V
2. Find RB to set the UV trip point of the monitor.
10
RB =
0.5V
–5V – 1V
•
− 46.4k ≅ 8.45k
9.947µA –4.5V – 1V
For more information www.linear.com/LTC2914
2914fc
LTC2914
applications information
3. Determine RC to complete the design.
RC =
–5V – 1V
− 46.4k − 8.45k ≈ 549k
9.947µA
2. Calculate RCUV based on the desired undervoltage trip
point of –6V.
RCUV = (R AUV +RBUV )•
VCC
5V
VCC
RB
8.45k
RC
549k
V3
–5V ±10%
VH3
UV
3. Calculate RAOV and Ina
VL3
SEL
LTC2914
R AOV =
GND
2914 F04
Figure 4. Negative Supply Monitor
Negative voltage monitoring applications with wide operating voltage ranges such that:
RBOV =
0.5V – VOV 0.5V – 30 – 1
=
≈ 3.01M
Ina
10.020µA
VCC
5V
1A. Find RAUV and RBUV and let node A be a virtual ground,
which ensures that the diode current will not affect the
voltage monitor threshold accuracy. Let the resistive
divider current Ind = 10µA.
R AUV =
VREF – 0.5V 1V – 0.5V
=
≈ 49.9k
10µA
Ind
R AUV = RBUV
1B. Calculate Ina using the resistor values chosen above.
Ina ≈ 10.020µA
2 • VUV < VOV
create situations where the VH or VL pins exceeds the
–0.3V absolute maximum voltage ratings. To ensure that
the LTC2914 operates within its design specifications,
utilize the equations shown below to determine proper
resistor sizing for the circuit in Figure 5. In the following
example, the undervoltage trip point is –6V. The overvoltage trip point is –30V.
VREF – 0.5V 1V – 0.5V
=
≈ 49.9k
10µA
Ind
4. Calculate RBOV for a desired overvoltage trip point of
–30V.
Negative Voltage Monitoring Example 2
–6V – 1V
≈ 698k
1V
OV
REF
RA
46.4k
(49.9k + 49.9k)•
VUV
=
VREF
Ina =
VREF – 0.5V 1V – 0.5V
=
≈ 10.020µA
R AUV
R AUV
VCC
RAUV
49.9k
D1
RAOV
49.9k
RBOV
3.01M
RBUV
49.9k
A
RCUV
698k
REF
OV
LTC2914
UV
VH3
VL3
SEL
GND
2914 F05
V3
Figure 5. Negative Supply Monitor for Wide Operating Range
Power-Up/Power-Down
As soon as VCC reaches 1V during power-up, the UV output
asserts low and the OV output weakly pulls to VCC.
The LTC2914 is guaranteed to assert UV low and OV high
under conditions of low VCC, down to VCC = 1V. Above VCC
= 2V (2.1V maximum) the VH and VL inputs take control.
Once all VH inputs and VCC become valid an internal timer
is started. After an adjustable delay time, UV weakly pulls
high.
2914fc
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11
LTC2914
Applications Information
Threshold Accuracy
Glitch Immunity
Reset threshold accuracy is important in a supply-sensitive
system. Ideally, such a system resets only if supply voltages
fall outside the exact thresholds for a specified margin.
All LTC2914 inputs have a relative threshold accuracy of
±1.5% over the full operating temperature range.
In any supervisory application, noise riding on the monitored DC voltage causes spurious resets. To solve this
problem without adding hysteresis, which causes a new
error term in the trip voltage, the LTC2914 lowpass filters
the output of the first stage comparator at each input. This
filter integrates the output of the comparator before asserting the UV or OV logic. A transient at the input of the
comparator of sufficient magnitude and duration triggers
the output logic. The Typical Performance Characteristics
section shows a graph of the Transient Duration vs Comparator Overdrive.
For example, when the LTC2914 is programmed to monitor a 5V input with a 10% tolerance, the desired UV trip
point is 4.5V. Because of the ±1.5% relative accuracy of
the LTC2914, the UV trip point is between 4.433V and
4.567V which is 4.5V ±1.5%.
Likewise, the accuracy of the resistances chosen for RA,
RB and RC affect the UV and OV trip points as well. Using the example just given, if the resistances used to set
the UV trip point have 1% accuracy, the UV trip range
is between 4.354V and 4.650V. This is illustrated in the
following calculations.
The UV trip point is given as:
RC
VUV = 0.5V 1+
R A +RB
The two extreme conditions, with a relative accuracy of
1.5% and resistance accuracy of 1%, result in:
RC • 0.99
VUV(MIN) = 0.5V • 0.985 • 1+
(R A +RB ) •1.01
and
RC •1.01
VUV(MAX) = 0.5V •1.015 • 1+
(R A +RB ) • 0.99
For a desired trip point of 4.5V,
RC
=8
R A +RB
Therefore,
0.99
VUV(MIN) = 0.5V • 0.985 • 1+ 8 •
= 4.354V
1.01
and
1.01
VUV(MAX) = 0.5V •1.015 • 1+ 8 •
= 4.650V
0.99
UV/OV Timing
The LTC2914 has an adjustable timeout period (tUOTO) that
holds OV or UV asserted after all faults have cleared. This
assures a minimum reset pulse width allowing a settling
time delay for the monitored voltage after it has entered
the valid region of operation.
When any VH input drops below its designed threshold,
the UV pin asserts low. When all inputs recover above
their designed thresholds, the UV output timer starts. If
all inputs remain above their designed thresholds when
the timer finishes, the UV pin weakly pulls high. However,
if any input falls below its designed threshold during this
time-out period, the timer resets and restarts when all
inputs are above the designed thresholds. The OV output
behaves as the UV output when LATCH is high (LTC2914-1).
Selecting the UV/OV Timing Capacitor
The UV and OV timeout period (tUOTO) for the LTC2914
is adjustable to accommodate a variety of applications.
Connecting a capacitor, CTMR, between the TMR pin and
ground sets the timeout period. The value of capacitor
needed for a particular timeout period is:
CTMR = tUOTO • 115 • 10–9 (F/s)
The Reset Timeout Period vs Capacitance graph found in
the Typical Performance Characteristics shows the desired
delay time as a function of the value of the timer capacitor
that must be used. The TMR pin must have a minimum of
10pF or be tied to VCC. For long timeout periods, the only
limitation is the availability of a large value capacitor with
2914fc
12
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LTC2914
applications information
low leakage. Capacitor leakage current must not exceed
the minimum TMR charging current of 1.3µA. Tying the
TMR pin to VCC bypasses the timeout period.
Undervoltage Lockout
When VCC falls below 2V, the LTC2914 asserts an undervoltage lockout (UVLO) condition. During UVLO, UV is
asserted and pulled low while OV is cleared and blocked
from asserting. When VCC rises above 2V, UV follows the
same timing procedure as an undervoltage condition on
any input.
Shunt Regulator
The LTC2914 has an internal shunt regulator. The VCC pin
operates as a direct supply input for voltages up to 6V.
Under this condition, the quiescent current of the device
remains below a maximum of 100µA. For VCC voltages
higher than 6V, the device operates as a shunt regulator
and must have a resistance RZ between the supply and
the VCC pin to limit the current to no greater than 10mA.
When choosing this resistance value, choose an appropriate
location on the I-V curve shown in the Typical Performance
Characteristics section to accommodate variations in VCC
due to changes in current through RZ.
UV and OV Output Characteristics
The DC characteristics of the UV and OV pull-up and
pull-down strength are shown in the Typical Performance
Characteristics section. Each pin has a weak internal
pull-up to VCC and a strong pull-down to ground. This arrangement allows these pins to have open-drain behavior
while possessing several other beneficial characteristics.
The weak pull-up eliminates the need for an external pullup resistor when the rise time on the pin is not critical.
On the other hand, the open-drain configuration allows
for wired-OR connections and is useful when more than
one signal needs to pull down on the output. VCC of 1V
guarantees a maximum VOL = 0.15V at UV.
At VCC = 1V, the weak pull-up current on OV is barely turned
on. Therefore, an external pull-up resistor of no more
than 100k is recommended on the OV pin if the state and
pull-up strength of the OV pin is crucial at very low VCC.
Note however, by adding an external pull-up resistor, the
pull-up strength on the OV pin is increased. Therefore, if
it is connected in a wired-OR connection, the pull-down
strength of any single device must accommodate this
additional pull-up strength.
Output Rise and Fall Time Estimation
The UV and OV outputs have strong pull-down capability.
The following formula estimates the output fall time (90%
to 10%) for a particular external load capacitance (CLOAD):
tFALL ≈ 2.2 • RPD • CLOAD
where RPD is the on-resistance of the internal pull-down
transistor, typically 50Ω at VCC > 1V and at room temperature (25°C). CLOAD is the external load capacitance
on the pin. Assuming a 150pF load capacitance, the fall
time is 16.5ns.
The rise time on the UV and OV pins is limited by a 400k
pull-up resistance to VCC. A similar formula estimates the
output rise time (10% to 90%) at the UV and OV pins:
tRISE ≈ 2.2 • RPU • CLOAD
where RPU is the pull-up resistance.
OV Latch (LTC2914-1)
With the LATCH pin held low, the OV pin latches low
when an OV condition is detected. The latch is cleared by
raising the LATCH pin high. If an OV condition changes
while LATCH is held high, the latch is bypassed and the
OV pin behaves the same as the UV pin with a similar
timeout period at the output. If LATCH is pulled low while
the timeout period is active, the OV pin latches as before.
Disable (LTC2914-2)
The LTC2914-2 allows disabling the UV and OV outputs via
the DIS pin. Pulling DIS high forces both outputs to remain
weakly pulled high, regardless of any faults that occur on
the inputs. However, if a UVLO condition occurs, UV asserts and pulls low, but the timeout function is bypassed.
UV pulls high as soon as the UVLO condition is cleared.
DIS has a weak 2µA (typical) internal pull-down current
guaranteeing normal operation with the pin left open.
2914fc
For more information www.linear.com/LTC2914
13
LTC2914
typical applications
Quad UV/OV Supply Monitor, 10% Tolerance, 5V, 3.3V, 2.5V, 1.8V
5V
3.3V
2.5V
1.8V
P0WER
SUPPLIES
CBYP 0.1μF
16
RC1
44.2k
RB1
1k
1
RC2
27.4k
2
3
RA1
4.53k
RB2
1k
RA2
4.53k
4
10
RC3
19.6k
RB3
1k
5
RC4
12.4k6
7
RA3
4.53k
RB4
1k 8
RA4
4.53k
VCC
SEL
VH1
LTC2914-1
VL1
OV
VH2
UV
14
11
SYSTEM
12
VL2
REF
VH3
LATCH
13
VL3
VH4
VL4
GND
TMR
9
15
2914 TA02
CTMR
22nF TIMEOUT = 200ms
Dual Positive and Dual Negative UV/OV Supply Monitor,
10% Tolerance, 5V, 3.3V, –5V, –3.3V
5V
P0WER
SUPPLIES
3.3V
CBYP 0.1μF
16
RC1
44.2k
RB1
1k
1
RC2
27.4k
2
3
RA1
4.53k
RB2
1k
4
10
RA2
4.53k
RA3
4.64k
RB3
845Ω
5
RA4
4.64k 6
7
RC3
54.9k
RB4
768Ω 8
RC4
37.4k
–3.3V
VCC
VH1
VL1
VH2
OV
LTC2914-1
VL2
UV
11
12
REF
SYSTEM
VH3
LATCH
VL3
VH4
VL4
GND
9
SEL
13
14
TMR
15
CTMR
2.2nF
TIMEOUT = 20ms
–5V
2914 TA03
14
For more information www.linear.com/LTC2914
2914fc
LTC2914
typical applications
Triple UV/OV Supply Monitor Powered from 48V, 10% Tolerance, 48V, 5V, 2.5V
48V
P0WER
SUPPLIES
RZ
8.25k
5V
2.5V
CBYP 0.1μF
16
RC1
475k
RB1
1k
1
RC2
44.2k
2
3
RA1
4.53k
RB2
1k
RA2
4.53k
4
RC3
19.6k
RB3
1k
10
5
6
7
RA3
4.53k
8
VCC
VH1
SEL
15
TMR
11
OV
VL1
VH2
LTC2914-1
UV
VL2
REF
VH3
14
LATCH
SYSTEM
12
13
VL3
VH4
VL4
GND
9
2914 TA04
2914fc
For more information www.linear.com/LTC2914
15
LTC2914
Package Description
Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings.
DHC Package
16-Lead Plastic DFN (5mm × 3mm)
(Reference LTC DWG # 05-08-1706 Rev Ø)
5.00 ±0.10
(2 SIDES)
R = 0.20
TYP
0.65 ±0.05
3.50 ±0.05
PIN 1
TOP MARK
(SEE NOTE 6)
1.65 ±0.05
2.20 ±0.05 (2 SIDES)
9
3.00 ±0.10
(2 SIDES)
PIN 1
NOTCH
8
0.75 ±0.05
0.200 REF
4.40 ±0.05
(2 SIDES)
1
0.25 ±0.05
0.50 BSC
(DHC16) DFN 1103
4.40 ±0.10
(2 SIDES)
0.00 – 0.05
BOTTOM VIEW—EXPOSED PAD
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
NOTE:
1. DRAWING PROPOSED TO BE MADE VARIATION OF VERSION (WJED-1) IN JEDEC
PACKAGE OUTLINE MO-229
2. DRAWING NOT TO SCALE
3. ALL DIMENSIONS ARE IN MILLIMETERS
0.40 ±0.10
16
1.65 ±0.10
(2 SIDES)
PACKAGE
OUTLINE
0.25 ± 0.05
0.50 BSC
R = 0.115
TYP
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
GN Package
16-Lead Plastic SSOP (Narrow .150 Inch)
(Reference LTC DWG # 05-08-1641 Rev B)
.189 – .196*
(4.801 – 4.978)
.045 ±.005
16 15 14 13 12 11 10 9
.254 MIN
.009
(0.229)
REF
.150 – .165
.229 – .244
(5.817 – 6.198)
.0165 ±.0015
.150 – .157**
(3.810 – 3.988)
.0250 BSC
RECOMMENDED SOLDER PAD LAYOUT
1
.015 ±.004
× 45°
(0.38 ±0.10)
.007 – .0098
(0.178 – 0.249)
2 3
.0532 – .0688
(1.35 – 1.75)
4
5 6
7
8
.004 – .0098
(0.102 – 0.249)
0° – 8° TYP
.016 – .050
(0.406 – 1.270)
NOTE:
1. CONTROLLING DIMENSION: INCHES
INCHES
2. DIMENSIONS ARE IN
(MILLIMETERS)
.008 – .012
(0.203 – 0.305)
TYP
.0250
(0.635)
BSC
GN16 REV B 0212
3. DRAWING NOT TO SCALE
4. PIN 1 CAN BE BEVEL EDGE OR A DIMPLE
*DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH
SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
**DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD
FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE
2914fc
16
For more information www.linear.com/LTC2914
LTC2914
Revision History
(Revision history begins at Rev B)
REV
DATE
DESCRIPTION
PAGE NUMBER
B
10/10
Added tPW and Note 4 to Electrical Characteristics section
C
12/13
Updated equations and added Negative Voltage Monitoring Example 2 to Applications Information section
Corrected LATCH/DIS label in Pin Configuration section
4
9-13
2
2914fc
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.
For more
information
www.linear.com/LTC2914
17
LTC2914
Typical Application
Quad UV/OV Supply Monitor with LED Undervoltage and Overvoltage Indicator
and Manual Undervoltage Reset Button, 10% Tolerance, 12V, 5V, 3.3V, 2.5V
P0WER
SUPPLIES
12V
5V
3.3V
2.5V
0.1μF
44.2k
VCC
VH1
SEL
510Ω
510Ω
LED
LED
27.4k
1k
VL1
VH2
4.53k
1k
VL2
4.53k
SYSTEM
OV
LTC2914-1
19.6k
UV
REF
VH3
1k
LATCH
2.05M
VL3
VH4
4.53k
100k
10k
VL4
GND
TMR
2914 TA06
CTMR
22nF TIMEOUT = 200ms
MANUAL
RESET BUTTON
(NORMALLY OPEN)
Related Parts
PART NUMBER
LTC1326/
LTC1326-2.5
LTC1726-2.5/
LTC1726-5
LTC1727-2.5/
LTC1727-5
LTC1728-1.8/
LTC1728-3.3
LTC1728-2.5/
LTC1728-5
LTC1985-1.8
LTC2900
DESCRIPTION
Micropower Precision Triple Supply Monitor for 5V/2.5V, 3.3V
and ADJ
Micropower Triple Supply Monitor for 2.5V/5V, 3.3V and ADJ
COMMENTS
4.725V, 3.118V, 1V Threshold (±0.75%)
Micropower Triple Supply Monitor with Open-Drain Reset
Individual Monitor Outputs in MSOP
Micropower Triple Supply Monitor with Open-Drain Reset
5-Lead SOT-23 Package
Micropower Triple Supply Monitor with Open-Drain Reset
5-Lead SOT-23 Package
Micropower Triple Supply Monitor with Push-Pull Reset
Programmable Quad Supply Monitor
LTC2901
LTC2902
Programmable Quad Supply Monitor
Programmable Quad Supply Monitor
LTC2903
LTC2904
LTC2905
LTC2906
LTC2907
LTC2908
LTC2909
Precision Quad Supply Monitor
Three-State Programmable Precision Dual Supply Monitor
Three-State Programmable Precision Dual Supply Monitor
Precision Dual Supply Monitor 1 Selectable and 1 Adjustable
Precision Dual Supply Monitor 1 Selectable and 1 Adjustable
Precision Six Supply Monitor
Precision Dual Input UV, OV and Negative Voltage Monitor
5-Lead SOT-23 Package
Adjustable RESET, 10-Lead MSOP and 3mm × 3mm 10-Lead DFN
Package
Adjustable RESET and Watchdog Timer, 16-Lead SSOP Package
Adjustable RESET and Tolerance, 16-Lead SSOP Package,
Margining Functions
6-Lead SOT-23 Package, Ultralow Voltage Reset
Adjustable Tolerance, 8-Lead SOT-23 Package
Adjustable RESET and Tolerance, 8-Lead SOT-23 Package
Separate VCC Pin, RST/RST Outputs
Separate VCC, Adjustable Reset Timer
8-Lead TSOT-23 and 3mm × 2mm DFN Packages
Separate VCC Pin, Adjustable Reset Timer, 8-Lead TSOT-23 and
3mm × 2mm DFN Packages
Adjustable RESET and Watchdog Time-Outs
2914fc
18
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
For more information www.linear.com/LTC2914
(408) 432-1900 ● FAX: (408) 434-0507
●
www.linear.com/LTC2914
LT 1213 REV C • PRINTED IN USA
LINEAR TECHNOLOGY CORPORATION 2006
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