LINER LTC2912HDDB-1 Single uv/ov voltage monitor Datasheet

LTC2912
Single UV/OV
Voltage Monitor
FEATURES
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■
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■
■
■
■
■
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DESCRIPTION
Monitors Single Voltage
Adjustable UV and OV Trip Values
Guaranteed Threshold Accuracy: ±1.5%
Power Supply Glitch Immunity
Adjustable Reset Timeout with Timeout Disable
29μA Quiescent Current
Open-Drain OV and UV Outputs
Guaranteed OV and UV for VCC ≥ 1V
Available in 8-Lead ThinSOTTM and (3mm × 2mm)
DFN Packages
Three output configurations are available: the LTC29121 has a latch control for the OV output; the LTC2912-2
has an OV and UV output disable feature for margining
applications; the LTC2912-3 is identical to the LTC2912-1
but with a noninverting, OV output.
APPLICATIONS
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The LTC®2912 voltage monitor is designed to detect power
supply undervoltage and overvoltage events. The VL and
VH monitor inputs include filtering to reject brief glitches,
thereby ensuring reliable reset operation without false or
noisy triggering. An adjustable timer defines the duration of
the overvoltage and undervoltage reset outputs which function independently. While the LTC2912 operates directly
from 2.3V to 6V supplies, an internal VCC shunt regulator
coupled with low supply current demand allows operation
from higher voltages such as 12V, 24V or 48V.
Desktop and Notebook Computers
Network Servers
Core, I/O Voltage Monitors
The LTC2912 provides a precise, versatile, space-conscious
micropower solution for voltage monitoring.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
ThinSOT is a trademark of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
Single OV/UV Supply Monitor, 3.3V ±10% Tolerance
Reset Time-Out Period vs Capacitance
10000
3.3V
0.1μF
UV/OV TIMEOUT PERIOD, tUOTO (ms)
POWER
SUPPLY
1000
27.4k
VCC
VH
OV
SYSTEM
LTC2912-1
1k
VL
UV
4.53k
GND
LATCH
TMR
22nF
100
10
2912 TA01a
TIMEOUT = 200ms
1
0.1
1
10
100
TMR PIN CAPACITANCE, CTMR (nF)
1000
2912 G08
2912fa
1
LTC2912
ABSOLUTE MAXIMUM RATINGS
(Note 1)
Terminal Voltages
VCC (Note 3)............................................. –0.3V to 6V
OV, UV, OV ............................................ –0.3V to 16V
TMR ..........................................–0.3V to (VCC + 0.3V)
VH, VL, LATCH, DIS .............................. –0.3V to 7.5V
Terminal Currents
IVCC ....................................................................10mA
IUV, IOV, IOV ........................................................10mA
Operating Temperature Range
LTC2912C ................................................ 0°C to 70°C
LTC2912I.............................................. –40°C to 85°C
LTC2912H .......................................... –40°C to 125°C
Storage Temperature Range
TSOT.................................................. –65°C to 125°C
DFN.................................................... –65°C to 150°C
Lead Temperature (Soldering, 10 sec)
TSOT................................................................. 300°C
PACKAGE/ORDER INFORMATION
TOP VIEW
TOP VIEW
LATCH 1
UV 2
OV 3
GND 4
8 VCC
7 VH
6 VL
5 TMR
TS8 PACKAGE
8-LEAD PLASTIC TSOT-23
TJMAX = 150°C, θJA = 195°C/W
ORDER PART NUMBER
LTC2912CTS8-1
LTC2912ITS8-1
LTC2912HTS8-1
TS8 PART MARKING*
LTCJW
LTCJW
LTCJW
8 LATCH
VCC 1
VH 2
VL 3
9
TMR 4
7 UV
6 OV
5 GND
DDB PACKAGE
8-LEAD (3mm × 2mm) PLASTIC DFN
TJMAX = 150°C, θJA = 76°C/W
EXPOSED PAD (PIN 9) IS GND, CONNECTION TO PCB OPTIONAL
ORDER PART NUMBER
LTC2912CDDB-1
LTC2912IDDB-1
LTC2912HDDB-1
DDB PART MARKING*
LCJZ
LCJZ
LCJZ
TOP VIEW
TOP VIEW
8 VCC
7 VH
6 VL
5 TMR
DIS 1
UV 2
OV 3
GND 4
TS8 PACKAGE
8-LEAD PLASTIC TSOT-23
TJMAX = 150°C, θJA = 195°C/W
ORDER PART NUMBER
LTC2912CTS8-2
LTC2912ITS8-2
LTC2912HTS8-2
TS8 PART MARKING*
LTCJX
LTCJX
LTCJX
VCC 1
VH 2
VL 3
8 DIS
9
TMR 4
7 UV
6 OV
5 GND
DDB PACKAGE
8-LEAD (3mm × 2mm) PLASTIC DFN
TJMAX = 150°C, θJA = 76°C/W
EXPOSED PAD (PIN 9) IS GND, CONNECTION TO PCB OPTIONAL
ORDER PART NUMBER
LTC2912CDDB-2
LTC2912IDDB-2
LTC2912HDDB-2
DDB PART MARKING*
LCKB
LCKB
LCKB
TOP VIEW
TOP VIEW
LATCH 1
UV 2
OV 3
GND 4
8 VCC
7 VH
6 VL
5 TMR
TS8 PACKAGE
8-LEAD PLASTIC TSOT-23
TJMAX = 150°C, θJA = 195°C/W
ORDER PART NUMBER
LTC2912CTS8-3
LTC2912ITS8-3
LTC2912HTS8-3
TS8 PART MARKING*
LTCJY
LTCJY
LTCJY
8 LATCH
VCC 1
VH 2
VL 3
TMR 4
9
7 UV
6 OV
5 GND
DDB PACKAGE
8-LEAD (3mm × 2mm) PLASTIC DFN
TJMAX = 150°C, θJA = 76°C/W
EXPOSED PAD (PIN 9) IS GND, CONNECTION TO PCB OPTIONAL
ORDER PART NUMBER
LTC2912CDDB-3
LTC2912IDDB-3
LTC2912HDDB-3
DDB PART MARKING*
LCKC
LCKC
LCKC
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.
2
2912fa
LTC2912
ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCC = 3.3V, VL = 0.45V, VH = 0.55V, LATCH = VCC unless otherwise
noted. (Note 2)
SYMBOL
VSHUNT
ΔVSHUNT
PARAMETER
VCC Shunt Regulator Voltage
VCC Shunt Regulator Load Regulation
CONDITIONS
MIN
TYP
MAX
ICC = 5mA
●
6.2
6.6
7.2
V
–40°C < TA < 125°
●
6.2
6.6
7.3
V
ICC = 2mA to 10mA
●
200
300
mV
●
VCC
Supply Voltage (Note 3)
VCCR(MIN)
Minimum VCC Output Valid
DIS = 0V
●
VCC(UVLO)
Supply Undervoltage Lockout
DIS = 0V, VCC Rising
●
1.9
ΔVCC(UVHYST)
Supply Undervoltage Lockout Hysteresis
DIS = 0V
●
5
ICC
Supply Current
VCC = 2.3V to 6V
●
VUOT
Undervoltage/Overvoltage Threshold
tUOD
Undervoltage/Overvoltage Threshold to
Output Delay
IVHL
VH, VL Input Current
tUOTO
UV/OV Time-Out Period
2.3
UNITS
VSHUNT
V
1
V
2
2.1
V
25
50
mV
29
70
μA
●
492
500
508
mV
●
50
125
500
μs
●
±15
nA
–40°C < TA < 125°
●
±30
nA
CTMR = 1nF
●
6
8.5
12.5
ms
–40°C < TA < 125°
●
6
8.5
14
ms
1.2
VHn = VUOT – 5mV or VLn = VUOT + 5mV
VLATCH(VIH)
OV Latch Clear Input High
●
VLATCH(VIL)
OV Latch Clear Input Low
●
ILATCH
LATCH Input Current
VLATCH > 0.5V
●
IDIS
DIS Input Current
VDIS > 0.5V
●
1
VDIS(VIH)
DIS Input High
●
1.2
VDIS(VIL)
DIS Input Low
●
ITMR(UP)
TMR Pull-Up Current
V
2
0.8
V
±1
μA
3.3
μA
V
0.8
V
VTMR = 0V
●
–1.3
–2.1
–2.8
μA
–40°C < TA < 125°
●
–1.2
–2.1
–2.8
μA
VTMR = 1.6V
●
1.3
2.1
2.8
μA
2.8
ITMR(DOWN)
TMR Pull-Down Current
–40°C < TA < 125°
●
1.2
2.1
VTMR(DIS)
Timer Disable Voltage
Referenced to VCC
●
–180
–270
VOH
Output Voltage High UV/OV/OV
VCC = 2.3V, IUV/OV = –1μA
●
1
VOL
Output Voltage Low UV/OV/OV
VCC = 2.3V, IUV/OV = 2.5mA
VCC = 1V, IUV = 100μA
●
●
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.
μA
mV
V
0.10
0.01
0.30
0.15
V
V
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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LTC2912
TIMING DIAGRAMS
VL Monitor Timing
VH Monitor Timing
VUOT
VH
tUOD
UV
VUOT
VL
tUOD
tUOTO
OV
1V
tUOTO
1V
2912 TD02
2912 TD01
VH Monitor Timing (TMR Pin Strapped to VCC)
VL Monitor Timing (TMR Pin Strapped to VCC)
VUOT
VH
tUOD
UV
VUOT
VL
tUOD
tUOD
OV
1V
tUOD
1V
2912 TD03
2912 TD04
TYPICAL PERFORMANCE CHARACTERISTICS
Input Threshold Voltage
vs Temperature
VCC Shunt Voltage
vs Temperature
Supply Current vs Temperature
0.505
6.8
45
40
0.503
6.7
10mA
6.6
5mA
6.5
2mA
VCC = 5V
0.502
0.500
0.499
VCC (V)
35
0.501
ICC (μA)
THRESHOLD VOLTAGE, VUOT (V)
0.504
VCC = 3.3V
30
6.4
25
0.498
VCC = 2.3V
0.497
1mA
20
6.3
15
–50
6.2
–50
200μA
0.496
0.495
–50
–25
25
50
0
TEMPERATURE (°C)
75
100
–25
0
25
50
TEMPERATURE (°C)
75
2912 G01
6.75
–40°C
25°C
6.25
–2
0
2
600
400
300
200
VCC
0.6
RESET OCCURS
ABOVE CURVE
500
0.4
UV WITH
10k PULL-UP
0.2
VCC = 6V
UV WITHOUT
PULL-UP
100
VCC = 2.3V
85°C
6
4
ICC (mA)
8
10
12
2912 G04
100
UV Output Voltage vs VCC
UV VOLTAGE (V)
TYPICAL TRANSIENT DURATION (μs)
VCC (V)
6.45
75
0.8
700
6.55
0
25
50
TEMPERATURE (°C)
2912 G03
Typical Transient Duration vs
Comparator Overdrive
6.65
–25
2912 G02
VCC Shunt Voltage vs ICC
6.35
100
50
0.1
1
10
100
COMPARATOR OVERDRIVE PAST THRESHOLD (%)
2912 G05
0
0
0.2
0.6
0.8
0.4
SUPPLY VOLTAGE, VCC (V)
1
2912 G06
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LTC2912
TYPICAL PERFORMANCE CHARACTERISTICS
Reset Time-Out Period
vs Capacitance
UV Output Voltage vs VCC
UV/OV TIMEOUT PERIOD, tUOTO (ms)
VH = 0.55V
SEL = VCC
UV VOLTAGE (V)
4
1000
3
2
1
0
UV, ISINK vs VCC
5
10000
PULL-DOWN CURRENT, IUV (mA)
5
0
1
3
4
2
SUPPLY VOLTAGE, VCC (V)
100
10
1
0.1
5
UV/OV, Voltage Output Low
vs Output Sink Current
12
UV/OV TIMEOUT PERIOD, tOUTO (ms)
25°C
UV/OV, VOL (V)
0.8
–40°C
0.6
0.4
0.2
0
5
10
15
20
IUV/OV (mA)
25
30
1912 G10
PIN FUNCTIONS
2
UV AT 50mV
1
1000
0
1
3
4
2
SUPPLY VOLTAGE, VCC (V)
5
2912 G09
Reset Timeout Period
vs Temperature
1.0
0
UV AT 150mV
3
2912 G08
2912 G07
85°C
4
0
1
10
100
TMR PIN CAPACITANCE, CTMR (nF)
VH = 0.45V
SEL = VCC
CTMR = 1nF
11
10
9
8
7
6
–50
–25
0
25
50
TEMPERATURE (°C)
75
100
2912 G11
(DFN/TSOT Packages)
DIS (Pin 8/Pin 1, LTC2912-2): 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 9, DDB Package): Exposed Pad may
be left open or connected to device ground.
GND (Pin 5/Pin 4): Device Ground.
is cleared. While held high, OV/OV has a similar delay and
output characteristic as UV.
OV (Pin 6/Pin 3, LTC2912-1, LTC2912-2): Overvoltage
Logic Output. Asserts low when the VL input voltage is
above threshold. Latched low (LTC2912-1). Held low for
programmed delay time after VL input is valid (LTC2912-2).
Pin has a weak pull-up to VCC and may be pulled above VCC
using an external pull-up. Leave pin open if unused.
LATCH (Pin 8/Pin 1, LTC2912-1, LTC2912-3): OV/OV
Latch Clear/Bypass Input. When pulled high, OV/OV latch
2912fa
5
LTC2912
PIN FUNCTIONS
(DFN/TSOT Packages)
OV (Pin 6/Pin 3, LTC2912-3): Overvoltage Logic Output.
Asserts high with a weak internal pull-up to VCC when the
VL input is above threshold. Latches high. May be pulled
above VCC using an external pull-up. Leave pin open if
unused.
TMR (Pin 4/Pin 5): 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 7/Pin 2): Undervoltage Logic Output. Asserts low
when the VH input voltage is below threshold. Held low for
a programmed delay time after the VH input is 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 1/Pin 8): 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
should 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.
VH (Pin 2/Pin 7): Voltage High Input. When the voltage
on this pin is below 0.5V, an undervoltage condition is
triggered. Tie pin to VCC if unused.
VL (Pin 3/Pin 6): Voltage Low Input. When the voltage on
this pin is above 0.5V, an overvoltage condition is triggered.
Tie pin to GND if unused.
BLOCK DIAGRAM
1
4
VCC
TMR
VCC
400k
OSCILLATOR
2
UV
–
+
VH
UV PULSE
GENERATOR
DISABLE
UVLO
UVLO
3
+
–
2V
VCC
VCC
400k
–
+
VL
7
OV PULSE
GENERATOR
LTC2912-1
LTC2912-2
OV/OV
6
DISABLE
0.5V
5
GND
LTC2912-3
OV LATCH
CLEAR/BYPASS
+
–
LATCH
8
1V
LTC2912-1, LTC2912-3
1V
DIS
8
+
–
2μA
LTC2912-2
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2912fa
6
LTC2912
APPLICATIONS INFORMATION
Voltage Monitoring
2. Choose RB to obtain the desired UV trip point
The LTC2912 is a low power voltage monitoring circuit
with an undervoltage and an overvoltage input. A timeout
period that holds OV and UV asserted after a fault has
cleared is adjustable using an external capacitor and may
be externally disabled. When configured to monitor a positive voltage Vn using the 3-resistor circuit configuration
shown in Figure 1, VH will be connected to the high side
tap of the resistive divider and VL will be connected to the
low side tap of the resistive divider.
Once RA is known, RB is chosen to set the desired trip
point for the undervoltage monitor.
V
RB = 0.5V • n – RA
In
VUV
3. Choose RC to complete the design
Once RA and RB are known, RC is determined by:
RC =
3-Step Design Procedure
The following 3-step design procedure allows selecting
appropriate resistances to obtain the desired UV and OV
trip points for the voltage monitor circuit in Figure 1.
For 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. 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)
Vn
– RA – RB
In
(3)
If any of the variables Vn, In, VUV or VOV change, then each
step must be recalculated.
Voltage Monitor Example
A typical voltage monitor application is shown in Figure 2.
The monitored voltage is a 5V ±10% supply. Nominal current in the resistive divider is 10μA.
1. Find RA to set the OV trip point of the monitor.
RA = 0.5V • 5V ≈ 45.3k
10µA 5.5V
2. Find RB to set the UV trip point of the monitor.
RB = 0.5V • 5V – 45.3k ≅ 10.2k
10µA 4.5V
Vn
RC
LTC2912
VH
+
+
–
RB
3. Determine RC to complete the design.
–
UV
0.5V
V1
5V ±10%
–
VL
RC = 5V – 45.3k − 10.2k ≈ 442k
10µA
+
OV
VCC
5V
RC
442k
VCC
OV
VH1
RA
RB
10.2k
2912 F01
Figure 1. 3-Resistor Positive UV/OV Monitoring Configuration
LTC2912-1
UV
VL1
RA
45.3k
GND
2912 F02
Figure 2. Typical Supply Monitor
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LTC2912
APPLICATIONS INFORMATION
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 LTC2912 is guaranteed to assert UV low, OV high
(LTC2912-1, LTC2912-2) and OV low (LTC2912-3) under
conditions of low VCC, down to VCC = 1V. Above VCC = 2V
(2.1V maximum), the VH and VL inputs take control.
Once the VH input and VCC become valid an internal timer
is started. After an adjustable delay time, UV weakly pulls
high.
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+
(RA + RB ) • 1.01
and
RC • 1.01 VUV(MAX) = 0.5V • 1.015 • 1+
(RA + RB ) • 0.99 For a desired trip point of 4.5V,
Threshold Accuracy
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.
Both LTC2912 inputs have a relative threshold accuracy
of ±1.5% over the full operating temperature range.
For example, when the LTC2912 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 LTC2912, the UV trip point can be anywhere between
4.433V and 4.567V which is 4.5V ±1.5%.
Likewise, the accuracy of the resistances chosen for RA,
RB and RC can 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
Therefore,
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 = 4.650V
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 LTC2912 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
show a graph of the Transient Duration vs Comparator
Overdrive.
UV/OV Timing
The LTC2912 has an adjustable timeout period (tUOTO) that
holds OV, OV or UV asserted after each fault has cleared.
This delay assures a minimum reset pulse width allowing
settling time for the monitored voltage after it has entered
the “valid” region of operation.
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LTC2912
APPLICATIONS INFORMATION
When the VH input drops below its designed threshold,
the UV pin asserts low. When the input recovers above
its designed threshold, the UV output timer starts. If the
input remains above the designed threshold when the
timer finishes, the UV pin weakly pulls high. However, if
the input falls below its designed threshold during this
timeout period, the timer resets and restarts when the
input is above the designed threshold. The OV and OV
outputs behave as the UV output when LATCH is high
(LTC2912-1, LTC2912-3).
Selecting the UV/OV Timing Capacitor
The UV and OV timeout period (tUOTO) for the LTC2912
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
10pF load 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.
Undervoltage Lockout
When VCC falls below 2V, the LTC2912 asserts an
undervoltage lockout (UVLO) condition. During UVLO, UV
is asserted and pulled low while OV and OV are cleared
and blocked from asserting. When VCC rises above 2V, UV
follows the same timing procedure as an undervoltage
condition on the VH input.
Shunt Regulator
The LTC2912 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 70μA. For VCC voltages higher than
6V, the device operates as a shunt regulator and should
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, select an appropriate
location on the I-V curve shown in the Typical Performance
Characteristics to accommodate any variations in VCC due
to changes in current through RZ.
UV, OV and OV Output Characteristics
The DC characteristics of the UV, OV and 0V pull-up and
pull-down strength are shown in the Typical Performance
Characteristics. 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.
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, OV 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.
2912fa
9
LTC2912
APPLICATIONS INFORMATION
similar timeout period at the output. If LATCH is pulled
low while the timeout period is active, the OV and OV pins
latch as before.
The rise time on the UV, OV and 0V 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, OV
and OV pins:
Disable (LTC2912-2)
tRISE ≈ 2.2 • RPU • CLOAD
The LTC2912-2 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.
where RPU is the pull-up resistance.
OV/OV Latch (LTC2912-1, LTC2912-3)
With the LATCH pin held low, the OV pin latches low
(LTC2912-1) and the OV pin latches high (LTC2912-3)
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 and OV pins behave the same as the UV pin with a
DIS has a weak 2μA (typical) internal pull-down current
guaranteeing normal operation with the pin left open.
TYPICAL APPLICATIONS
Dual UV/OV Supply Monitor, 3.3V ±10% Tolerance
POWER
SUPPLY
48V Supply Monitor (<±10% = Powergood)
3.3V
POWER
SUPPLY
CBYP 0.1μF
RC
27.4k 2
RB
1k
3
48V
CBYP
0.1μF
RZ
200k
1
VCC
OV
VH
LTC2912-1
UV
VL
RA
4.53k
GND
5
LATCH
TMR
4
6
SYSTEM
RC
37.4M 2
7
RB
80.6k 3
8
VCC
OV
VH
LTC2912-2
UV
VL
RA
357k
2912 TA02
GND
CTMR
22nF TIMEOUT = 200ms
RPG
30k
1
5
DIS
TMR
4
6
7
8
POWERGOOD
LED
CTMR
10nF TIMEOUT = 85ms
2912 TA03
Dual UV Supply Monitor, 3.3V, 2.5V, 10% Tolerance
3.3V
POWER
2.5V
SUPPLIES
CBYP 0.1μF
1
RB1
54.9k
2
VCC
VH
TMR 6
OV
LTC2912-2
7
UV
RA1
11k
RB2
39.2k
3
RA2
11k
ROV
10k
4
VL
DIS
GND
RUV
10k
SYSTEM
8
2912 TA04
5
2912fa
10
LTC2912
PACKAGE DESCRIPTION
DDB Package
8-Lead Plastic DFN (3mm × 2mm)
(Reference LTC DWG # 05-08-1702 Rev B)
0.61 ±0.05
(2 SIDES)
3.00 ±0.10
(2 SIDES)
R = 0.115
TYP
5
R = 0.05
TYP
0.40 ± 0.10
8
0.70 ±0.05
2.55 ±0.05
1.15 ±0.05
PACKAGE
OUTLINE
2.00 ±0.10
(2 SIDES)
PIN 1 BAR
TOP MARK
(SEE NOTE 6)
0.25 ± 0.05
0.56 ± 0.05
(2 SIDES)
0.75 ±0.05
0.200 REF
0.50 BSC
2.20 ±0.05
(2 SIDES)
1
(DDB8) DFN 0905 REV B
0.50 BSC
2.15 ±0.05
(2 SIDES)
0 – 0.05
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
4
0.25 ± 0.05
PIN 1
R = 0.20 OR
0.25 × 45°
CHAMFER
BOTTOM VIEW—EXPOSED PAD
NOTE:
1. DRAWING CONFORMS TO VERSION (WECD-1) IN JEDEC PACKAGE OUTLINE M0-229
2. DRAWING NOT TO SCALE
3. ALL DIMENSIONS ARE IN MILLIMETERS
4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE
5. EXPOSED PAD SHALL BE SOLDER PLATED
6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE TOP AND BOTTOM OF PACKAGE
TS8 Package
8-Lead Plastic TSOT-23
(Reference LTC DWG # 05-08-1637)
0.52
MAX
0.65
REF
2.90 BSC
(NOTE 4)
1.22 REF
1.4 MIN
3.85 MAX 2.62 REF
2.80 BSC
1.50 – 1.75
(NOTE 4)
PIN ONE ID
RECOMMENDED SOLDER PAD LAYOUT
PER IPC CALCULATOR
0.22 – 0.36
8 PLCS (NOTE 3)
0.65 BSC
0.80 – 0.90
0.20 BSC
0.01 – 0.10
1.00 MAX
DATUM ‘A’
0.30 – 0.50 REF
NOTE:
1. DIMENSIONS ARE IN MILLIMETERS
2. DRAWING NOT TO SCALE
3. DIMENSIONS ARE INCLUSIVE OF PLATING
0.09 – 0.20
(NOTE 3)
1.95 BSC
TS8 TSOT-23 0802
4. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR
5. MOLD FLASH SHALL NOT EXCEED 0.254mm
6. JEDEC PACKAGE REFERENCE IS MO-193
2912fa
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.
11
LTC2912
TYPICAL APPLICATION
Single UV/OV Supply Monitor with 3.3V ±10%
12V
POWER
SUPPLY
Q1
3.3V
0.1μF
10k
27.4k
SYSTEM
VCC
VH
OV
LTC2912-3
1k
UV
VL
4.53k
GND
LATCH
TMR
2912 TA05
22nF
TIMEOUT = 200ms
RELATED PARTS
PART NUMBER
LTC690
LTC694-3.3
LTC699
LTC1232
LTC1326/
LTC1326-2.5
LTC1536
LTC1726-2.5/
LTC1726-5
LTC1728-1.8/
LTC1728-3.3
LTC1985-1.8
LTC2900
LTC2901
LTC2902
LTC2903
LTC2904
LTC2905
LTC2906
LTC2907
LTC2908
LTC2909
LTC2913
LTC2914
DESCRIPTION
5V Supply Monitor, Watchdog Timer and Battery Backup
3.3V Supply Monitor, Watchdog Timer and Battery Backup
5V Supply Monitor and Watchdog Timer
5V Supply Monitor, Watchdog Timer and Push-Button Reset
Micropower Precision Triple Supply Monitor for 5V/2.5V, 3.3V
and ADJ
Precision Triple Supply Monitor for PCI Applications
Micropower Triple Supply Monitor for 2.5V/5V, 3.3V and ADJ
COMMENTS
4.65 Threshold
2.9V Threshold
4.65 Threshold
4.37V/4.62V Threshold
4.725V, 3.118V, 1V Threshold (±0.75%)
Micropower Triple Supply Monitor with Open-Drain Reset
5-Lead SOT-23 Package
Meets PCI tFAIL Timing Specifications
Adjustable RESET and Watchdog Time-Outs
Micropower Triple Supply Monitor with Open-Drain Reset
Programmable Quad Supply Monitor
5-Lead SOT-23 Package
Adjustable RESET, 10-Lead MSOP and 3mm × 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 TSOT-23 Package, Ultralow Voltage Reset
3-State Programmable Precision Dual Supply Monitor
Adjustable Tolerance, 8-Lead TSOT-23 Package
3-State Programmable Precision Dual Supply Monitor
Adjustable RESET and Tolerance, 8-Lead TSOT-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 (Four Fixed & 2 Adjustable)
8-Lead TSOT-23 and DFN Packages
Prevision Dual Input UV, OV and Negative Voltage Monitor
Separate VCC Pin, Adjustable Reset Timer, 8-Lead TSOT-23 and
DFN Packages
Dual UV/OV Voltage Monitor
Separate VCC Pin, Two Inputs, Adjustable Reset Timer, 10-Lead
MSOP and DFN Packages
Quad UV/OV Positive/Negative Voltage Monitor
Separate VCC Pin, Four inputs, Up To Two Negative Monitors,
Adjustable Reset Timer, 16-Lead TSSOP and DFN Packages
2912fa
12
Linear Technology Corporation
LT 1007 REV A • 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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