LINER LTC2914IDHC-1 Quad uv/ov positive/negative voltage monitor Datasheet

LTC2914
Quad UV/OV
Positive/Negative
Voltage Monitor
DESCRIPTIO
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FEATURES
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Monitors Four Voltages Simultaneously
Adjustable UV and OV Trip Values
Guaranteed Threshold Accuracy: ±1.5% of
Monitored Voltage over Temperature
Input Glitch Rejection
Monitors up to Two Negative Voltages
Buffered 1V Reference Output
Adjustable Reset Timeout with Timeout Disable
70µA Quiescent Current
Open-Drain OV and UV Outputs
Guaranteed OV and UV for VCC ≥ 1V
Available in 16-Lead SSOP and 16-Lead
(5mm × 3mm) DFN Packages
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APPLICATIO S
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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
Network Servers
Core, I/O Voltage Monitors
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
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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.
TYPICAL APPLICATIO
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
VH1
SEL
VL1
VH2
OV
0.504
27.4k
LTC2914-1
1k
VL2
4.53k
SYSTEM
19.6k
VH3
1k
UV
REF
LATCH
12.4k
4.53k
0.502
0.501
0.500
0.499
0.498
0.497
0.495
–50
1k
VL4
GND
0.503
0.496
VL3
VH4
4.53k
THRESHOLD VOLTAGE, VOUT (V)
P0WER
SUPPLIES
5V
3.3V
2.5V
1.8V
TMR
–25
25
50
0
TEMPERATURE (°C)
75
100
2914 G01
CTMR
22nF
2914 TA01a
TIMEOUT = 200ms
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LTC2914
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ABSOLUTE
AXI U RATI GS
(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
Storage Temperature Range................... –65°C to 150°C
Lead Temperature (Soldering, 10 sec)
SSOP ................................................................ 300°C
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PACKAGE/ORDER I FOR ATIO
TOP VIEW
TOP VIEW
VH1
1
16 VCC
VL1
2
15 TMR
VH2
3
VL2
4
14 SEL
17
13 LATCH
VH3
5
12 UV
VL3
6
11 OV
VH4
VL4
10 REF
7
9
8
GND
VH1
1
16 VCC
VL1
2
15 TMR
VH2
3
14 SEL
VL2
4
13 LATCH
VH3
5
12 UV
VL3
6
11 OV
VH4
7
10 REF
VL4
8
9
DHC PACKAGE
16-LEAD (5mm ´ 3mm) PLASTIC DFN
TJMAX = 150°C, θJA = 43.5°C/W
EXPOSED PAD (PIN 17)
PCB GND CONNECTION OPTIONAL
GND
GN PACKAGE
16-LEAD PLASTIC SSOP
TJMAX = 150°C, θJA = 110°C/W
TOP VIEW
TOP VIEW
VH1
1
16 VCC
VL1
2
15 TMR
VH2
3
VL2
4
VH3
VL3
VH4
VL4
5
6
7
8
14 SEL
17
13 DIS
12 UV
11 OV
10 REF
9
GND
DHC PACKAGE
16-LEAD (5mm ´ 3mm) PLASTIC DFN
TJMAX = 150°C, θJA = 43.5°C/W
EXPOSED PAD (PIN 17)
PCB GND CONNECTION OPTIONAL
VH1
1
16 VCC
VL1
2
15 TMR
VH2
3
14 SEL
VL2
4
13 DIS
VH3
5
12 UV
VL3
6
11 OV
VH4
7
10 REF
VL4
8
9
GND
GN PACKAGE
16-LEAD PLASTIC SSOP
ORDER PART
NUMBER
DHC PART
MARKING*
LTC2914CDHC-1
LTC2914IDHC-1
29141
29141
ORDER PART
NUMBER
GN PART
MARKING
LTC2914CGN-1
LTC2914IGN-1
29141
2914I1
ORDER PART
NUMBER
DHC PART
MARKING*
LTC2914CDHC-2
LTC2914IDHC-2
29142
29142
ORDER PART
NUMBER
GN PART
MARKING
LTC2914CGN-2
LTC2914IGN-2
29142
2914I2
TJMAX = 150°C, θJA = 110°C/W
Order Options Tape and Reel: Add #TR
Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF
Lead Free Part Marking: http://www.linear.com/leadfree/
*The temperature grade is identified by a label on the shipping container. Consult LTC Marketing for parts specified with wider operating temperature ranges.
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LTC2914
ELECTRICAL CHARACTERISTICS
The ● 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
VSHUNT
VCC Shunt Regulator Voltage
ICC = 5mA
●
ICC = 2mA to 10mA
●
MIN
TYP
MAX
6.2
6.6
6.9
UNITS
V
300
mV
ΔVSHUNT
VCC Shunt Regulator Load Regulation
VCC
Supply Voltage (Note 3)
VCCR(MIN)
Minimum VCC Output Valid
DIS = 0V
●
VCC(UVLO)
Supply Undervoltage Lockout
VCC Rising, DIS = 0V
●
1.9
2
2.1
V
ΔVCC(UVHYST)
Supply Undervoltage Lockout Hysteresis
DIS = 0V
●
5
25
50
mV
ICC
Supply Current
VCC = 2.3V to 6V
●
70
100
µA
IVREF = ±1mA
●
0.985
1
1.015
●
492
500
508
mV
●
50
125
500
µs
±15
nA
12.5
ms
VREF
Reference Output Voltage
VUOT
Undervoltage/Overvoltage Voltage Threshold
tUOD
Undervoltage/Overvoltage Voltage Threshold
to Output Delay
IVHL
VHn, VLn Input Current
●
VHn = VUOT – 5mV or VLn = VUOT + 5mV
200
2.3
●
tUOTO
UV/OV Time-Out Period
●
6
VLATCH(IH)
OV Latch Clear Input High
●
1.2
VLATCH(IL)
OV Latch Clear Threshold Input Low
●
CTMR = 1nF
8.5
V
1
V
V
V
●
0.8
V
±1
µA
ILATCH
LATCH Input Current
VDIS(IH)
DIS Input High
VDIS(IL)
DIS Input Low
0.8
V
IDIS
DIS Input Current
VDIS > 0.5V
●
1
2
3
µA
ITMR(UP)
TMR Pull-Up Current
VTMR = 0V
●
–1.3
–2.1
–2.8
µA
ITMR(DOWN)
TMR Pull-Down Current
VTMR = 1.6V
●
1.3
2.1
2.8
VTMR(DIS)
Timer Disable Voltage
Referenced to VCC
●
–180
–270
VOH
Output Voltage High UV/OV
VCC = 2.3V, IUV/OV = –1µA
●
1
VCC = 2.3V, IUV/OV = 2.5mA
VCC = 1V, IUV = 100µA
●
●
VOL
Output Voltage Low UV/OV
VLATCH > 0.5V
VSHUNT
●
1.2
V
●
µA
mV
V
0.1
0.01
0.3
0.15
V
V
Three-State Input SEL
VIL
Low Level Input Voltage
●
VIH
High Level Input Voltage
●
1.4
●
0.7
VZ
Pin Voltage when Left in Hi-Z State
ISEL
SEL High, Low Input Current
ISEL(MAX)
Maximum SEL Input Current
ISEL = ±10µA
SEL Tied to Either VCC or GND
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.
0.4
V
V
1.1
V
●
0.9
±25
µA
●
±30
µA
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.
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LTC2914
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TI I G DIAGRA S
VHn Monitor Timing
VHn
VLn Monitor Timing
VUOT
tUOD
UV
VUOT
VLn
tUOTO
tUOD
1V
OV
tUOTO
1V
2914 TD01
2914 TD02
VHn Monitor Timing (TMR Pin Strapped to VCC)
VHn
VLn Monitor Timing (TMR Pin Strapped to VCC)
VUOT
tUOD
UV
VUOT
VLn
tUOD
tUOD
1V
OV
tUOD
1V
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
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TYPICAL PERFOR A CE CHARACTERISTICS
Specifications are at TA = 25°C, VCC = 3.3V unless otherwise noted.
105
0.504
100
0.503
95
90
0.502
85
0.501
0.500
0.499
65
0.497
60
0.496
55
75
100
2914 G01
6.7
10mA
VCC = 3.3V
6.6
5mA
6.5
2mA
75
70
25
50
0
TEMPERATURE (°C)
VCC = 6V
80
0.498
–25
6.8
VCC (V)
0.505
0.495
–50
VCC Shunt Voltage
vs Temperature
Supply Current vs Temperature
ICC (µA)
THRESHOLD VOLTAGE, VOUT (V)
Input Threshold Voltage
vs Temperature
50
–50
1mA
VCC = 2.3V
6.4
200µA
6.3
–25
0
25
50
TEMPERATURE (°C)
75
100
2914 G02
6.2
–50
–25
0
25
50
TEMPERATURE (°C)
75
100
2914 G03
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LTC2914
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TYPICAL PERFOR A CE 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
VCC (V)
6.55
25°C
6.45
–40°C
85°C
6.35
TYPICAL TRANSIENT DURATION (µs)
REFERENCE VOLTAGE, VREF (V)
1.004
6.65
1.003
1.002
1.001
1.000
0.999
0.998
0.997
0.996
6.25
–2
0
2
6
4
ICC (mA)
8
10
12
0.995
–50
–25
25
50
0
TEMPERATURE (°C)
2914 G04
200
VCC = 6V
100
VCC = 2.3V
UV Output Voltage vs VCC
UV Output Voltage vs VCC
5
VHn = 0.55V
SEL = VCC
VCC
11
4
10
9
8
UV VOLTAGE (V)
0.6
UV VOLTAGE (V)
UV/OV TIMEOUT PERIOD, tUOTO (ms)
300
2914 G06
0.8
CTMR = 1nF
0.4
UV WITH
10k PULL-UP
3
2
0.2
1
UV WITHOUT
10k PULL-UP
7
6
–50
0
25
50
TEMPERATURE (°C)
–25
75
0
100
0.2
0.6
0.8
0.4
SUPPLY VOLTAGE, VCC (V)
0
2914 G07
1.0
VHn = 0.45V
SEL = VCC
4
125°C
UV/OV, VOL (V)
UV AT 150mV
25°C
–40°C
0.6
0.4
UV AT 50mV
1
0
0.2
0
1
3
4
2
SUPPLY VOLTAGE, VCC (V)
5
2914 G10
3
4
2
SUPPLY VOLTAGE, VCC (V)
0
5
10000
0.8
2
1
Reset Timeout Period
vs Capacitance
UV/OV Voltage Output Low
vs Output Sink Current
3
0
2914 G09
UV/OV TIMEOUT PERIOD, tUOTO (ms)
5
0
1.0
2914 G08
UV, ISINK vs VCC
PULL-DOWN CURRENT, IUV (mA)
RESET OCCURS
ABOVE CURVE
400
2914 G05
Reset Timeout Period
vs Temperature
12
500
0
0.1
1
10
100
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
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LTC2914
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PI FU CTIO S
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, 0V 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.
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LTC2914
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BLOCK DIAGRA
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
–
+
+
–
VL4
REF
13
1V
2µA
GND
1V
BUFFER
DIS
LTC2914-2
–
+
0.5V
10
13
1V
LTC2914-1
–
+
+
–
8
LATCH
9
THREE-STATE
POLARITY
DECODER
SEL
14
2914 -1 BD
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LTC2914
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APPLICATIO S I FOR ATIO
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.
V3 INPUT
V4 INPUT
VCC
Positive
Positive
VH3 < VUOT → UV
VL3 > VUOT → OV
VH4 < VUOT → UV
VL4 > VUOT → OV
Open
GND
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
3-Step Design Procedure
LTC2914
+
REF
–
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
+
–
1V
Vn
RC
LTC2914
VHn
+
+
–
RB
RA
–
UVn
+
+
–
RB
0.5V
+
OVn
0.5V
–
–
VLn
–
VHn
OVn
VLn
+
UVn
RC
RA
2914 F02
2914 F01
Vn
Figure 1. 3-Resistor Positive UV/OV Monitoring Configuration
Figure 2. 3-Resistor Negative UV/OV Monitoring Configuration
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LTC2914
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APPLICATIO S I FOR ATIO
For positive supply monitoring, Vn is the desired nominal
operating voltage, In is the desired nominal current through
the resistive divider, VOV is the desired overvoltage trip
point and VUV is the desired undervoltage trip point.
1. Find RA to set the OV trip point of the monitor.
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.
2. Find RB to set the UV trip point of the monitor.
1. Choose RA to obtain the desired OV trip point
RA is chosen to set the desired trip point for the
overvoltage monitor.
V
R A = 0.5V • n
In
VOV
(1)
2. Choose RB to obtain the desired UV trip point
RA = 0.5V • 5V ≈ 45.3k
10µA 5.5V
RB = 0.5V • 5V – 45.3k ≅ 10.2k
10µA 4.5V
3. Determine RC to complete the design.
RC = 5V – 45.3k − 10.2k ≈ 442k
10µA
Negative Voltage Monitor Example
Once RA is known, RB is chosen to set the desired trip
point for the undervoltage monitor.
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.
V
RB = 0.5V • n – RA
In
VUV
1. Find RA to set the OV trip point of the monitor.
(2)
RA = 0.5V • –5V – 1V ≈ 46.4k
10µA –5.5V – 1V
3. Choose RC to Complete the Design
Once RA and RB are known, RC is determined by:
RC =
Vn
– RA – RB
In
2. Find RB to set the UV trip point of the monitor.
(3)
If any of the variables Vn, In, VUV or VOV change, then each
step must be recalculated.
RB = 0.5V • 5V – 1V − 46.4k ≅ 8.45k
10µA 4.5V – 1V
3. Determine RC to complete the design.
RC = –5V – 1V − 46.4k − 8.45k ≈ 549k
10µA
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.
V1
5V ±10%
VCC
5V
VCC
REF
RC
442k
RA
46.4k
VCC
VH1
RB
10.2k
VCC
5V
OV
LTC2914
UV
VL1
RA
45.3k
SEL
GND
2914 F03
Figure 3. Positive Supply Monitor
OV
LTC2914
VH3
UV
VL3
SEL
RB
8.45k
RC
549k
V3
–5V ±10%
GND
2914 F04
Figure 4. Negative Supply Monitor
2914f
9
LTC2914
U
W
U
U
APPLICATIO S I FOR ATIO
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.
⎛
RC • 0.99 ⎞
VUV(MIN) = 0.5V • 0.985 • ⎜ 1+
⎟
⎝ (RA + RB ) • 1.01⎠
and
⎛
RC • 1.01 ⎞
VUV(MAX ) = 0.5V • 1.015 • ⎜ 1+
⎟
⎝ (RA + RB ) • 0.99 ⎠
Once all VH inputs and VCC become valid an internal timer
is started. After an adjustable delay time, UV weakly pulls
high.
For a desired trip point of 4.55V,
Threshold Accuracy
Therefore,
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.
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+
⎝ RA + RB ⎟⎠
RC
=8
RA + RB
VUV(MIN) = 0.5V • 0.985 • ⎛ 1+ 8 0.99 ⎞ = 4.354V
⎝
1.01⎠
and
VUV(MAX ) = 0.5V • 1.015 • ⎛ 1+ 8 1.01⎞ = 4.6500 V
⎝
0.99 ⎠
Glitch Immunity
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.
The two extreme conditions, with a relative accuracy of
1.5% and resistance accuracy of 1%, result in:
2914f
10
LTC2914
U
W
U
U
APPLICATIO S I FOR ATIO
UV/OV Timing
Undervoltage Lockout
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 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.
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
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.
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 pull-up 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.
2914f
11
LTC2914
U
W
U
U
APPLICATIO S I FOR ATIO
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.
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 clears 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)
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 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.
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.
2914f
12
LTC2914
U
TYPICAL APPLICATIO S
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
VCC
SEL
VH1
LTC2914-1
VL1
3
VH2
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
OV
14
11
SYSTEM
UV
12
VL2
REF
13
VH3
LATCH
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
13
LATCH
VL3
VH4
VL4
GND
9
SEL
14
TMR
15
CTMR
2.2nF
TIMEOUT = 20ms
–5V
2914 TA03
2914f
13
LTC2914
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
SEL
VH1
15
TMR
11
OV
VL1
VH2
LTC2914-1
UV
VL2
REF
VH3
14
SYSTEM
12
13
LATCH
VL3
VH4
VL4
GND
9
2914 TA04
2914f
14
LTC2914
U
PACKAGE DESCRIPTIO
DHC Package
16-Lead Plastic DFN (5mm × 3mm)
(Reference LTC DWG # 05-08-1706)
R = 0.115
TYP
5.00 ±0.10
(2 SIDES)
R = 0.20
TYP
0.65 ±0.05
3.50 ±0.05
1.65 ±0.05
2.20 ±0.05 (2 SIDES)
9
3.00 ±0.10 1.65 ± 0.10
(2 SIDES) (2 SIDES)
PIN 1
TOP MARK
(SEE NOTE 6)
PIN 1
NOTCH
PACKAGE
OUTLINE
0.25 ± 0.05
0.50 BSC
0.40 ± 0.10
16
(DHC16) DFN 1103
8
1
0.25 ± 0.05
0.50 BSC
0.75 ±0.05
0.200 REF
4.40 ±0.05
(2 SIDES)
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
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)
.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)
.0532 – .0688
(1.35 – 1.75)
2 3
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 (SSOP) 0204
3. DRAWING NOT TO SCALE
*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
2914f
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
LTC2914
U
TYPICAL APPLICATIO
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
1k
VCC
VH1
SEL
VL1
VH2
OV
510Ω
510Ω
LED
LED
27.4k
4.53k
1k
LTC2914-1
VL2
4.53k
SYSTEM
19.6k
UV
REF
VH3
LATCH
2.05M
1k
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
LTC2901
LTC2902
LTC2903
LTC2904
LTC2905
LTC2906
LTC2907
LTC2908
LTC2909
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
Micropower Triple Supply Monitor with Open-Drain Reset
COMMENTS
4.725V, 3.118V, 1V Threshold (±0.75%)
Adjustable RESET and Watchdog Time-Outs
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
5-Lead SOT-23 Package
Adjustable RESET, 10-Lead MSOP and 3mm x 3mm 10-Lead
DFN Package
Programmable Quad Supply Monitor
Adjustable RESET and Watchdog Timer, 16-Lead SSOP Package
Programmable Quad Supply Monitor
Adjustable RESET and Tolerance, 16-Lead SSOP Package,
Margining Functions
Precision Quad Supply Monitor
6-Lead SOT-23 Package, Ultralow Voltage Reset
Three-State Programmable Precision Dual Supply Monitor
Adjustable Tolerance, 8-Lead SOT-23 Package
Three-State Programmable Precision Dual Supply Monitor
Adjustable RESET and Tolerance, 8-Lead SOT-23 Package
Precision Dual Supply Monitor 1 Selectable and 1 Adjustable Separate VCC Pin, RST/RST Outputs
Precision Dual Supply Monitor 1 Selectable and 1 Adjustable Separate VCC, Adjustable Reset Timer
Precision Six Supply Monitor
8-Lead TSOT-23 and 3mm × 2mm DFN Packages
Precision Dual Input UV, OV and Negative Voltage Monitor
Separate VCC Pin, Adjustable Reset Timer, 8-Lead TSOT-23 and
3mm × 2mm DFN Packages
2914f
16 Linear Technology Corporation
LT 0606 • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507
●
www.linear.com
© LINEAR TECHNOLOGY CORPORATION 2006
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