LTC2910
1
2910fc
TYPICAL APPLICATION
FEATURES
APPLICATIONS
DESCRIPTION
Octal Positive/Negative
Voltage Monitor
The LTC®2910 is an octal input voltage monitor intended
for monitoring multiple voltages in a variety of applications. Each input has a nominal 0.5V threshold, featuring
1.5% tight threshold accuracy over the entire operating
temperature range. Glitch fi ltering ensures reliable reset
operation without false or noisy triggering.
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.
The LTC2910 provides a precise, versatile, space-conscious, micropower solution for voltage monitoring.
Octal Supply Monitor, 10% Tolerance, 12V, 5V (x2), 3.3V (x2), 2.5V, 1.8V, 1.2V
■
8 Low Voltage Adjustable Inputs (0.5V)
■
Guaranteed Threshold Accuracy: ±1.5%
■
Input Glitch Rejection
■
Pin Selectable Input Polarity Allows
Negative and OV Monitoring
■
Buffered 1V Reference Output
■
Adjustable Reset Timeout with Timeout Disable
■
50μA Quiescent Current
■
Open Drain RST and RST Outputs
■
Guaranteed RST and RST for VCC ≥ 1V
■
Available in 16-Lead SSOP and 16-Lead
(5mm × 3mm) DFN Packages
■
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.
Typical Transient Duration
vs Comparator Overdrive
RSTRSTGND
V8 V7 V6 V5 V4 V3 V2 V1
LTC2910
TMR
V
CC
1nF
TIMEOUT = 8.5ms
DIS SEL
226k
0.1μF
88.7k54.9k39.2k24.9k12.7k88.7k54.9k
11k
11k 11k 11k 11k 11k 11k 11k
12V
5V
3.3V
2.5V
1.8V
1.2V
5V
3.3V
2910 TA01
POWER
SUPPLIES
SYSTEM
COMPARATOR OVERDRIVE PAST THRESHOLD (%)
0.1
400
TYPICAL TRANSIENT DURATION (μs)
500
600
700
1 10 100
2910 TA01b
300
200
100
0
VCC = 6V
RESET OCCURS
ABOVE CURVE
VCC = 2.3V
LTC2910
2
2910fc
PACKAGE/ORDER INFORMATION
ELECTRICAL CHARACTERISTICS
ABSOLUTE MAXIMUM RATINGS
Terminal Voltages
V
CC
(Note 3) ............................................. –0.3V to 6V
RST, RST ................................................ –0.3V to 16V
TMR ..........................................–0.3V to (V
CC
+ 0.3V)
Vn, DIS, SEL ......................................... –0.3V to 7.5V
Terminal Current
I
VCC
....................................................................10mA
Reference Load Current (I
REF
) ...........................±1mA
I
RST/RST
..............................................................10mA
(Note 1, 2)
16
15
14
13
12
11
10
9
17
1
2
3
4
5
6
7
8
V
CC
TMR
SEL
DIS
RST
RST
REF
GND
V1
V2
V3
V4
V5
V6
V7
V8
TOP VIEW
DHC16 PACKAGE
16-LEAD
(
5mm × 3mm) PLASTIC DFN
T
JMAX
= 150°C, θJA = 43.5°C/W
EXPOSED PAD (PIN 17) PCB GND CONNECTION OPTIONAL
GN16 PACKAGE
16-LEAD PLASTIC SSOP
1
2
3
4
5
6
7
8
TOP VIEW
16
15
14
13
12
11
10
9
V1
V2
V3
V4
V5
V6
V7
V8
V
CC
TMR
SEL
DIS
RST
RST
REF
GND
T
JMAX
= 150°C, θJA = 110°C/W
ORDER PART NUMBER DHC16 PART MARKING* ORDER PART NUMBER GN16 PART MARKING*
LTC2910CDHC
LTC2910IDHC
LTC2910HDHC
2910
2910
2910
LTC2910CGN
LTC2910IGN
LTC2910HGN
2910
2910I
2910H
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 identifi ed by a label on the shipping container.
The ● denotes the specifi cations which apply over the full operating
temperature range, otherwise specifi cations are at TA = 25°C. VCC = 3.3V, Vn = 0.55V, SEL = VCC, DIS = OPEN unless otherwise noted.
(Note 2)
Operating Temperature Range
LTC2910C ................................................ 0°C to 70°C
LTC2910I.............................................. –40°C to 85°C
LTC2910H .......................................... –40°C to 125°C
Storage Temperature Range
SSOP, DFN .......................................... –65°C to 150°C
Lead Temperature (Soldering, 10 sec)
SSOP ................................................................ 300°C
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
V
SHUNT
VCC Shunt Regulator Voltage ICC = 5mA
●
6.2 6.6 6.9 V
–40°C < T
A
<125°C
●
6.2 6.6 7.0 V
ΔV
SHUNT
VCC Shunt Regulator Load Regulation ICC = 2mA to 10mA
●
200 300 mV
V
CC
Supply Voltage
●
2.3 V
SHUNT
V
LTC2910
3
2910fc
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
V
CC(MIN)
Minimum VCC Output Valid DIS = 0V
●
1V
V
CC(UVLO)
Supply Undervoltage Lockout VCC Rising, DIS = 0V
●
1.9 2 2.1 V
ΔV
CC(UVHYST)
Supply Undervoltage Lockout Hysteresis DIS = 0V
●
52550 mV
I
CC
Supply Current VCC = 2.3V to 6V
●
50 100 μA
V
REF
Reference Output Voltage I
VREF
= ±1mA
●
0.985 1 1.015 V
–40°C < T
A
< 125°C
●
0.985 1 1.020 V
V
RT
Vn Input Voltage Threshold
●
492 500 508 mV
t
PROP
Vn Input Threshold to Output Delay Vn = VRT – 5mV
●
50 125 500 μs
I
VN
Vn Input Current
●
±15 nA
–40°C < T
A
< 125°C
●
±30 nA
t
RST
Reset Timeout Period C
TMR
= 1nF
●
6 8.5 12.5 ms
–40°C < T
A
< 125°C
●
6 8.5 14 ms
V
DIS(VIH)
DIS Input Threshold Voltage High
●
1.2 V
V
DIS(VIL)
DIS Input Threshold Voltage Low
●
0.8 V
I
DIS
DIS Input Current V
DIS
> 0.5V
●
123 μA
I
TMR(UP)
TMR Pull-Up Current V
TMR
= 0V
●
–1.3 –2.1 –2.8 μA
–40°C < T
A
< 125°C
●
–1.2 –2.1 –2.8 μA
I
TMR(DOWN)
TMR Pull-Down Current V
TMR
= 1.6V
●
1.3 2.1 2.8 μA
–40°C < T
A
< 125°C
●
1.2 2.1 2.8 μA
V
TMR(DIS)
Timer Disable Voltage Referenced to V
CC
●
–180 –270 mV
V
OH
Output Voltage High RST/RST VCC = 2.3V, I
RST/RST
= –1μA
●
1V
V
OL
Output Voltage Low RST/RST VCC = 2.3V, I
RST/RST
= 2.5mA
V
CC
= 1V, I
RST
= 100μA
●
0.1
0.01
0.3
0.15
V
V
Three-State Input SEL
V
IL
Low Level Input Voltage
●
0.4 V
V
IH
High Level Input Voltage
●
1.4 V
V
Z
Pin Voltage when Left in Hi-Z State I
SEL
= ±10μA
●
0.6 0.9 1.1 V
–40°C < T
A
< 125°C
●
0.6 0.9 1.2 V
I
SEL
SEL High, Low Input Current
●
±25 μA
I
SEL(MAX)
Maximum SEL Input Current SEL tied to either VCC or GND
●
±30 μA
ELECTRICAL CHARACTERISTICS
The ● denotes the specifi cations which apply over the full operating
temperature range, otherwise specifi cations are at TA = 25°C. VCC = 3.3V, Vn = 0.55V, SEL = VCC, DIS = OPEN unless otherwise noted.
(Note 2)
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2: All currents into pins are positive; all voltages are referenced to
GND unless otherwise noted.
Note 3: V
CC
maximum pin voltage is limited by input current. Since the
V
CC
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.
LTC2910
4
2910fc
TIMING DIAGRAM
t
PROP
t
RST
2910 TD01
Vn V
RT
RST
RST
1V
1V
t
PROP
t
RST
2910 TD02
Vn V
RT
RST
RST
1V
1V
t
PROP
t
PROP
2910 TD03
Vn V
RT
RST
RST
1V
1V
t
PROP
t
PROP
2910 TD04
Vn V
RT
RST
RST
1V
1V
Vn Positive Monitor Timing
Vn Negative Monitor Timing
Vn Positive Monitor Timing (TMR strapped to VCC)
Vn Negative Monitor Timing (TMR strapped to VCC)
LTC2910
5
2910fc
SUPPLY VOLTAGE, VCC (V)
0
RST VOLTAGE (V)
3
4
5
4
2910 G09
2
1
0
123
5
Vn = 0.55V
SEL = V
CC
TEMPERATURE (°C)
–50
6
RST/RST TIMEOUT PERIOD, t
RST
(ms)
7
8
9
10
12
–25 0 25 50
2910 G07
75 100
11
C
TMR
= 1nF
SUPPLY VOLTAGE, VCC (V)
0
RST VOLTAGE (V)
0.4
0.6
0.8
2910 G08
0.2
0
0.2 0.4 0.6
1.0
0.8
V
CC
RST WITH
10k PULL-UP
RST WITHOUT
10k PULL-UP
ICC (mA)
–2 0
6.25
V
CC
(V)
6.45
6.75
268
2910 G04
6.35
6.65
6.55
41012
25°C
–40°C
85°C
TEMPERATURE (°C)
–50
0.995
REFERENCE VOLTAGE, V
REF
(V)
0.997
0.999
1.001
–25 0 25 50
2910 G05
75
1.003
1.005
0.996
0.998
1.000
1.002
1.004
100
COMPARATOR OVERDRIVE PAST THRESHOLD (%)
0.1
400
TYPICAL TRANSIENT DURATION (μs)
500
600
700
1 10 100
2910 G06
300
200
100
0
VCC = 6V
RESET OCCURS
ABOVE CURVE
VCC = 2.3V
TEMPERATURE (°C)
–50
0.495
THRESHOLD VOLTAGE, V
RT
(V)
0.497
0.499
0.501
–25 0 25 50
2910 G01
75
0.503
0.505
0.496
0.498
0.500
0.502
0.504
100
TEMPERATURE (°C)
–50 50 75–25 25
I
CC
(μA)
40
35
50
45
0
2910 G02
100
65
60
55
VCC = 5V
VCC = 3.3V
VCC = 2.3V
TEMPERATURE (°C)
–50
6.2
V
CC
(V)
6.3
6.4
6.5
6.6
6.8
–25 0 25 50
2910 G03
75 100
6.7
200μA
1mA
2mA
5mA
10mA
TYPICAL PERFORMANCE CHARACTERISTICS
Input Threshold Voltage vs
Temperature Supply Current vs Temperature
VCC Shunt Voltage vs
Temperature
VCC Shunt Voltage vs I
CC
Buffered Reference Voltage vs
Temperature
Transient Duration vs Comparator
Overdrive
Reset Time-Out Period vs
Temperature RST Output Voltage vs V
CC
RST Output Voltage vs V
CC
Specifi cations are at TA = 25°C and VCC = 3.3V
unless otherwise noted. (Note 2)
LTC2910
6
2910fc
TMR PIN CAPACITANCE, C
TMR
(nF)
10
RST/RST TIMEOUT PERIOD, t
RST
(ms)
100
1000
10000
0.1 10 100 1000
2910 G12
1
1
SUPPLY VOLTAGE, VCC (V)
0
PULL-DOWN CURRENT, I
RST
(mA)
3
4
5
4
2910 G10
2
1
0
123
5
Vn = 0.45V
SEL = V
CC
RST AT 150mV
RST AT 50mV
I
RST/RST
(mA)
0
0
RST/RST, V
OL
(V)
0.2
0.4
0.6
0.8
1.0
5101520
2910 G11
25 30
85°C
–40°C
25°C
PIN FUNCTIONS
DIS (Pin 13): Output Disable Input. Disables the RST and
RST output pins. When DIS is pulled high, the RST and
RST 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
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.
RST (Pin 11): Open-Drain Reset Logic Output. Asserts
high when any positive polarity input voltage is below
threshold or any negative polarity input voltage is above
threshold. Held high for an adjustable delay time after all
voltage inputs are valid. Pin has a weak pull-up to V
CC
and
may be pulled above V
CC
using an external pull-up. Leave
pin open if unused.
RST (Pin 12): Open-Drain Inverted Reset 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 V
CC
and may be pulled above V
CC
using an external pull-up.
Leave pin open if unused.
SEL (Pin 14): Input Polarity Select Three-State Input.
Connect to V
CC
, 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 (C
TMR
) 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 V
CC
to bypass timer.
V1-V6 (Pin 1, 2, 3, 4, 5 & 6): Voltage Inputs 1 through 6.
When the voltage on this pin is below 0.5V, a reset condition is triggered. Tie pin to V
CC
if unused.
V7-V8 (Pin 7 & 8): Voltage Inputs 7 and 8. The polarity
of the input is selected by the state of the SEL pin (refer
TYPICAL PERFORMANCE CHARACTERISTICS
RST, I
SINK
vs V
CC
RST/RST Voltage Output Low vs
Output Sink Current
Reset Timeout Period vs
Capacitance
Specifi cations are at TA = 25°C and VCC = 3.3V
unless otherwise noted. (Note 2)
LTC2910
7
2910fc
BLOCK DIAGRAM
PIN FUNCTIONS
to Table 1). When the monitored input is confi gured as a
positive voltage, a reset condition is triggered when the
pin is below 0.5V. When the monitored input is confi gured as a negative voltage, a reset condition is triggered
when the pin is above 0.5V. Tie pin to V
CC
if unused and
confi gured as a positive supply. Tie pin to GND if unused
and confi gured as a negative supply.
V
CC
(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.
–
+
–
+
–
+
–
+
–
+
–
+
–
+
–
+
–
+
V1
V2
V3
V4
V5
V6
2910 BD
REF
BUFFER
V
CC
RESET DELAY
TIMER
OSCILLATOR
THREE-STATE
POLARITY
DECODER
RST
V
CC
RST
400k
2μA
1
16 15
2
3
4
5
6
10
GND
9
DIS
13
11
12
14
V7
7
V8
8
–
+
1V
0.5V
1V
V
CC
2V
UVLO
SEL
V
CC
TMR
DISABLE
400k
LTC2910
8
2910fc
APPLICATIONS INFORMATION
Voltage Monitoring
The LTC2910 is a low power octal voltage monitoring
circuit with eight individual undervoltage monitor inputs.
A timeout period that holds a reset after all faults have
cleared is adjustable using an external capacitor and is
disabled, by tying TMR to V
CC
.
Each voltage monitor is compared to a fi xed 0.5V reference
for detecting undervoltage conditions. When confi gured
to monitor a positive voltage V
m
, the application is con-
nected as shown in Figure 1. For negative inputs V
m
is
connected as shown in Figure 2. R
A
is now connected to
the REF pin and R
B
remains connected to the monitored
voltage V
m
.
Using the confi gurations in Figures 1 and 2, a UV condition will result when the magnitude of the voltage at V
m
is less than its designed threshold.
Polarity Selection
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 confi gured for
negative supply monitoring, a reset condition occurs when
the supply voltage is less negative than the confi gured
threshold.
The three-state input pin SEL is connected to GND, V
CC
, 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.
2-Step Design Procedure
The following 2-step design procedure allows selecting
appropriate resistances to obtain the desired UV trip point
for the positive voltage monitor circuit in Figure 1 and the
negative voltage monitor circuit in Figure 2.
For positive supply monitoring, V
m
is the desired nominal
operating voltage, I
m
is the desired nominal current through
the resistive divider, and V
UV
is the desired undervoltage
trip point.
For negative supply monitoring, to compensate for the 1V
reference, 1V must be subtracted from V
m
and VUV before
using each in the following equations.
1. Choose R
A
to obtain the desired UV trip point
R
A
is chosen to set the desired trip point for the
undervoltage monitor.
R
V
V
V
A
m
UV
=
05.
I
•
m
(1)
Figure 1. Positive UV Monitoring Confi guration Figure 2. Negative UV Monitoring Confi guration
Table 1. Voltage Polarity Programming (VRT = 0.5V Typical)
SEL V7 INPUT V8 INPUT
V
CC
Positive
V7 < VRT → UV
Positive
V8 < VRT → UV
Open Positive
V7 < VRT → UV
Negative
V8 > VRT → UV
GND Negative
V7 > VRT → UV
Negative
V8 > VRT → UV
2910 F01
R
B
R
A
V
m
UVn
LTC2910
+
–
–
+
Vn
0.5V
2910 F02
R
A
R
B
REF
Vn
V
m
0.5V
UVn
+
–
–
+
–
+
1V
+
–
LTC2910
LTC2910
9
2910fc
APPLICATIONS INFORMATION
2. Choose RB to complete the design
Once R
A
is known, RB is determined by:
R
V
R
B
m
A
= −
I
m
(2)
If any of the variables V
m
, Im, or VUV change, then both
steps must be recalculated.
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.
1. Find R
A
to set the UV trip point of the monitor.
R
V
µA
V
V
k
A
= ≈
05105
45
56 2
.
•
.
.
2. Determine RB to complete the design.
R
V
µA
kk
B
= −≈
5
10
56 2 499.
Negative Voltage Monitor Example
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 V
m
and VUV.
1. Find R
A
to set the UV trip point of the monitor.
R
V
µA
VV
VV
k
A
=
−
−
≈
05
10
51
45 1
54 9
.
•
–
–.
.
2. Determine RB to complete the design.
R
VV
µA
kk
B
=
−
−≈
–.51
10
57 6 549
Power-Up/Down
As soon as V
CC
reaches 1V during power up, the RST output
asserts low and the RST output weakly pulls to V
CC
.
The LTC2910 is guaranteed to assert RST low and RST high
under conditions of low V
CC
, down to VCC = 1V. Above VCC
= 2V (2.1V maximum) the Vn inputs take control.
Once all inputs and V
CC
become valid, an internal timer is
started. After an adjustable delay time, RST pulls low and
RST weakly pulls high.
Threshold Accuracy
Reset threshold accuracy is important in a supply sensitive
system. Ideally, such a system would reset only if supply
Figure 3. Positive Supply Monitor
2910 F03
R
B
449k
R
A
56.2k
5V ± 10%
RST
RST
SEL
V7
V
CC
5V
GND
LTC2910
Figure 4. Negative Supply Monitor
2910 F04
R
A
54.9k
R
B
549k
–5V ± 10%
RST
RST
SEL
REF
V7
V
CC
5V
GND
LTC2910
LTC2910
10
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voltages fell below the exact threshold for a specifi ed margin. All LTC2910 inputs have a relative threshold accuracy
of ±1.5% over the full operating temperature range.
For example, when the LTC2910 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 LTC2910, the UV trip point is between 4.433V and
4.567V which is 4.5V ±1.5%.
The accuracy of the resistances chosen for R
A
and RB affect
the UV trip point 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
VUV= 0.5V • 1+
R
B
R
A
The two extreme conditions, with a relative accuracy of
1.5% and resistance accuracy of 1%, result in
V
UV(MIN)
= 0.5V •0.985 • 1+
R
B
• 0.99
R
A
• 1.01
and
V
UV(MAX)
= 0.5V •1.015 • 1+
R
B
• 1.01
R
A
• 0.99
For a desired trip point of 4.5V,
R
B
R
A
= 8
Therefore,
V
UV(MIN)
= 0.5V •0.985 • 1+ 8•
0.99
1.01
= 4.354V
and
V
UV(MAX)
= 0.5V •1.015 • 1+ 8•
1.01
0.99
= 4.650V
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 LTC2910 lowpass fi lters
the output of the fi rst stage comparator at each input.
This fi lter integrates the output of the comparator before
asserting the reset output logic. A transient at the input
of the comparator of suffi cient magnitude and duration
triggers the output logic. The Typical Performance Characteristics section shows a graph of the Transient Duration
vs. Comparator Overdrive.
RST/RST Timing
The LTC2910 has an adjustable timeout period (t
RST
) that
holds RST and RST 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 input drops below its designed threshold, the
RST pin asserts low and the RST pin asserts high. When
all inputs recover above their designed thresholds, the
reset delay timer starts. If all inputs remain above their
designed thresholds when the timer fi nishes, the RST
pin weakly pulls high and the RST pin strongly pulls low.
However, if any input falls below its designed threshold
during this timeout period, the timer resets and restarts
when all inputs are above the designed thresholds.
Selecting the Reset Timing Capacitor
The reset timeout period (t
RST
) for the LTC2910 is adjustable to accommodate a variety of applications. Connecting
a capacitor, C
TMR
, between the TMR pin and ground sets
the timeout period. The value of capacitor needed for a
particular timeout period is:
C
TMR
= t
RST
• 115 • 10–9 (F/s)
The Reset Timeout Period vs. Capacitance graph found
in the Typical Performance Characteristics section shows
APPLICATIONS INFORMATION
LTC2910
11
2910fc
the desired delay time as a function of the value of the
timer capacitor. The TMR pin must have a minimum of
10pF or be tied to V
CC
. 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 V
CC
bypasses the timeout period.
Undervoltage Lockout
When V
CC
falls below 2V, the LTC2910 asserts an
undervoltage lockout (UVLO) condition. During UVLO, RST
is asserted and pulled low and RST is pulled high. When
V
CC
rises above 2V, RST and RST follow the same timing
procedure as an undervoltage condition on any input.
Shunt Regulator
The LTC2910 has an internal shunt regulator. The V
CC
pin
operates as a direct supply input for voltages up to 6V.
In this range, the quiescent current of the device remains
below a maximum of 100μA. For V
CC
voltages higher than
6V, the pin functions as a shunt regulator and must have a
resistance R
Z
between the supply and the VCC pin to limit
the current to no greater than 10mA.
When selecting this resistance value, choose an appropriate
location on the I-V curve shown in the Typical Performance
Characteristics to accommodate any variations in V
CC
due
to changes in current through R
Z
.
RST/RST Output Characteristics
The DC characteristics of the RST and RST pull-up and
pull-down strength are shown in the Typical Performance
Characteristics. Each has a weak internal pull-up to V
CC
and
a strong pull-down to ground. This arrangement allows
each pin to have open-drain behavior while possessing
several other benefi cial characteristics. The weak pull-up
eliminates the need for an external pull-up resistor when
the rise time on this pin is not critical. On the other hand,
the open drain confi guration allows for wired-OR connections and is useful when more than one signal needs to
pull down on the RST or RST lines. V
CC
of 1V guarantees
a maximum V
OL
= 0.15V.
At V
CC
= 1V, the weak pull-up current on RST is barely
turned on. Therefore, an external pull-up resistor of no more
than 100k is recommended on the RST pin if the state and
pull-up strength of the RST pin is crucial at very low V
CC
.
Note however, by adding an external pull-up resistor, the
pull-up strength on the RST 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 RST and RST outputs have strong pull-down capability. The following formula estimates the output fall time
(90% to 10%) for a particular external load capacitance
(C
LOAD
):
t
FALL
≈ 2.2 • RPD • C
LOAD
where RPD is the on-resistance of the internal pull-down
transistor, typically 50Ω at V
CC
> 1V, and at room tem-
perature (25°C). C
LOAD
is the external load capacitance
on the pin. Assuming a 150pF load capacitance, the fall
time is 16.5ns.
The rise time on the RST and RST pins is limited by a
400k internal pull-up resistance to V
CC
. A similar formula
estimates the output rise time (10% to 90%) at the RST
and RST pins:
t
RISE
≈ 2.2 • RPU • C
LOAD
where RPU is the pull-up resistance.
Disable
The LTC2910 allows disabling the RST and RST outputs
via the DIS pin. Pulling DIS high forces both outputs to
remain unasserted, regardless of any faults that occur
on the inputs. However, if a UVLO condition occurs, RST
asserts and pulls low, RST asserts and pulls high, but the
timeout function is bypassed. RST pulls high and RST pulls
low 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.
APPLICATIONS INFORMATION
LTC2910
12
2910fc
TYPICAL APPLICATIONS
Eight UV Supply Monitor, 10% Tolerance, 12V, 5V (x2), 3.3V (x2), 2.5V, 1.8V, 1.2V
16
RSTRSTGND
V8 V7 V6 V5 V4 V3 V2 V1
LTC2910
TMR
V
CC
C
TMR
1nF
TIMEOUT = 8.5ms
DIS SEL
C
BYP
0.1μF
RA8
11k
RA7
11k
RA6
11k
RA5
11k
RA4
11k
RA3
11k
RA2
11k
RA1
11k
12V
5V
3.3V
2.5V
1.8V
1.2V
5V
3.3V
2910 TA02
POWER
SUPPLIES
SYSTEM
14111213915
87654321
RB1
226k
RB2
88.7k
RB3
54.9k
RB4
39.2k
RB5
24.9k
RB6
12.7k
RB7
88.7k
RB8
54.9k
Six Positive and Two Negative UV Supply Monitor, 10% Tolerance,
12V, 5V, 3.3V, 2.5V, 1.8V, 1.2V, –5V, –3.3V
16
RSTRSTGND
V8 V7 V6 V5 V4 V3 V2 V1
LTC2910
TMR
V
CC
C
TMR
22nF
TIMEOUT = 200ms
DIS SEL
C
BYP
0.1μF
12V
5V
3.3V
2.5V
1.8V
1.2V
–3.3V
–5V
2910 TA03
POWER
SUPPLIES
SYSTEM
14111213915
87
REF
10654321
RB7
11k
RB8
54.9k
RA8
107k
RA7
11k
RA6
11k
RA5
11k
RA4
11k
RA3
11k
RA2
11k
RA1
11k
RB1
226k
RB2
88.7k
RB3
54.9k
RB4
39.2k
RB5
24.9k
RB6
12.7k
LTC2910
13
2910fc
TYPICAL APPLICATIONS
Six UV and One OV/UV Supply Monitor, 10% Tolerance,
12V, 5V, 3.3V (x2), 2.5V, 1.8V, 1.2V
RA8
4.53k
RA7
1k
RA6
11k
RA5
11k
RA4
11k
RA3
11k
RA2
11k
RA1
11k
C
BYP
0.1μF
16
RSTRSTGND
V8 V7 V6 V5 V4 V3 V2 V1
LTC2910
TMR
V
CC
C
TMR
1nF
TIMEOUT = 8.5ms
DIS SEL
12V
5V
3.3V
2.5V
1.8V
1.2V
3.3V
2910 TA04
POWER
SUPPLIES
SYSTEM
14111213915
87654321
RB1
226k
RB2
88.7k
RB3
54.9k
RB4
39.2k
RB5
24.9k
RB6
12.7k
RB7
27.4k
Six UV Supply Monitor Powered from 48V, 10% Tolerance,
48V, 5V, 3.3V, 2.5V, 1.8V, 1.2V
RA6
11k
RA5
11k
RA4
11k
RA3
11k
RA2
11k
RA1
11k
C
BYP
0.1μF
16
RSTRSTGND
V8 V7 V6 V5 V4 V3 V2 V1
LTC2910
TMR
V
CC
V
CC
DIS SEL
48V
5V
3.3V
2.5V
1.8V
1.2V
2910 TA05
POWER
SUPPLIES
SYSTEM
14111213915
87654321
R
Z
8.25k
RB1
953k
RB2
88.7k
RB3
54.9k
RB4
39.2k
RB5
24.9k
RB6
12.7k
LTC2910
14
2910fc
TYPICAL APPLICATIONS
Eight UV Supply Monitor with Manual Reset Button, 10% Tolerance,
12V, 5V (x2), 3.3V (x2), 2.5V, 1.8V, 1.2V
RA7
11k
RA6
11k
RA5
11k
RA4
11k
RA3
11k
RA2
11k
RA1
11k
C
TMR
22nF
TIMEOUT = 200ms
MANUAL
RESET BUTTON
(NORMALLY OPEN)
16
RSTRSTGND
V8 V7 V6 V5 V4 V3 V2 V1
LTC2910
TMR
V
CC
DIS SEL
C
BYP
0.1μF
RA8
110k
R
PB
10k
12V
5V
3.3V
2.5V
1.8V
1.2V
5V
3.3V
2910 TA06
POWER
SUPPLIES
SYSTEM
14111213915
87654321
RB1
226k
RB2
88.7k
RB3
54.9k
RB4
39.2k
RB5
24.9k
RB6
12.7k
RB7
88.7k
RB8
549k
LTC2910
15
2910fc
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.
GN16 (SSOP) 0204
12
3
4
5
678
.229 – .244
(5.817 – 6.198)
.150 – .157**
(3.810 – 3.988)
16
15
14
13
.189 – .196*
(4.801 – 4.978)
12 11 10
9
.016 – .050
(0.406 – 1.270)
.015
± .004
(0.38 ± 0.10)
× 45°
0° – 8°
TYP
.007 – .0098
(0.178 – 0.249)
.0532 – .0688
(1.35 – 1.75)
.008 – .012
(0.203 – 0.305)
TYP
.004 – .0098
(0.102 – 0.249)
.0250
(0.635)
BSC
.009
(0.229)
REF
.254 MIN
RECOMMENDED SOLDER PAD LAYOUT
.150 – .165
.0250 BSC.0165 ±.0015
.045 ±.005
*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
INCHES
(MILLIMETERS)
NOTE:
1. CONTROLLING DIMENSION: INCHES
2. DIMENSIONS ARE IN
3. DRAWING NOT TO SCALE
GN Package
16-Lead Plastic SSOP (Narrow .150 Inch)
(Reference LTC DWG # 05-08-1641)
3.00 ±0.10
(2 SIDES)
5.00 ±0.10
(2 SIDES)
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
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
BOTTOM VIEW—EXPOSED PAD
1.65 ± 0.10
(2 SIDES)
0.75 ±0.05
R = 0.115
TYP
R = 0.20
TYP
4.40 ±0.10
(2 SIDES)
18
169
PIN 1
TOP MARK
(SEE NOTE 6)
0.200 REF
0.00 – 0.05
(DHC16) DFN 1103
0.25 ± 0.05
PIN 1
NOTCH
0.50 BSC
4.40 ±0.05
(2 SIDES)
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
1.65 ±0.05
(2 SIDES)
2.20 ±0.05
0.50 BSC
0.65 ±0.05
3.50 ±0.05
PACKAGE
OUTLINE
0.25 ± 0.05
DHC Package
16-Lead Plastic DFN (5mm × 3mm)
(Reference LTC DWG # 05-08-1706)
PACKAGE DESCRIPTION
LTC2910
16
2910fc
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507
●
www.linear.com
© LINEAR TECHNOLOGY CORPORATION 2006
LT 1007 REV C • PRINTED IN USA
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Eight UV Supply Monitor with LED Indicator, 10% Tolerance,
12V, 5V (x2), 3.3V (x2), 2.5V, 1.8V, 1.2V
510μΩ
V
CC
16
RSTRSTGND
V8 V7 V6 V5 V4 V3 V2 V1
LTC2910
TMR
V
CC
1nF
TIMEOUT = 8.5ms
DIS SEL
0.1μF
11k
11k 11k 11k 11k 11k 11k 11k
12V
5V
3.3V
2.5V
1.8V
1.2V
5V
3.3V
2910 TA07
POWER
SUPPLIES
SYSTEM
14111213915
87654321
226k88.7k54.9k39.2k24.9k12.7k88.7k54.9k
TYPICAL APPLICATION
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